FR2480960A1 - METHOD FOR DIGITAL CONTROL OF A MACHINE TOOL - Google Patents

Abstract

A. DIGITAL CONTROL PROCEDURE FOR A MACHINE-TOOL. B. ORDERING PROCESS CHARACTERIZED IN THAT ALL THE DATA NECESSARY TO CALCULATE THE MOVEMENT OF THE TOOLS USING SEVERAL INPUT BUFFER MEMORIES ARE ENTERED INTO A CALCULATION UNIT, THE MACHINING DATA IS SUCCESSIVELY CALCULATED USING THE DATA AND THE CALCULATIONS ARE TRANSFERRED INTO THE MACHINING BUFFER MEMORY. C. THE INVENTION CONCERNS NUMERICALLY CONTROLLED MACHINE TOOLS.

Description

The present invention relates to a method of controlling a machine-

  in which the movement of the machine is calculated automatically by introducing the shape of the machining and the final dimensions of the workpiece and the machining conditions using the keys of a caliber forming part of the control panel, the machine being ordered

  in zo-c-ion the result of these calculations.

  Known machines with digital control sound,

classified into three types.

  In the first type of machines, all the control data is introduced via perforated strips. In the second type, the data is introduced by

a keyboard.

  In the third type, real machining is performed

  and record the resulting data.

  The first two types require a detailed program of the movement of the device to be controlled using a particular digital coding; it takes a lot of work and time to prepare the punched tapes and has

  difficulties in adjusting the tools.

  In the third type, the skill of the user who actually does the work greatly influences subsequent operations and there are many disadvantages in the control so that this type of machines is not widely used. The present applicant has already proposed a device described in US Pat. No. 4,033,206 to overcome the drawbacks of known solutions. This device is characterized by the fact that the data is introduced by means of digital switches and not by bands, the number of input phases is reduced.

  of data and simplify the input operations.

  For this, the device allows-utrer machining data of the shape and finish of the shape as well as the dimensions to be given to the blank and the machining conditions as well as the

  replication mode of the tool that are the conditions set.

  This type of device solves all the problems

disadvantages of the prior art.

  The present invention aims to improve the

crrcradC of such a device.

248096O

  For this purpose, the invention relates to a control method characterized in that records the data necessary for the machining work in a microcomputer by reducing them to the minimum necessary for the machining of the shape and the finish of the form , while the various data actually needed during the execution of the work, such as the path of movement of the tool during coarse finishing and the path of movement of the tool during final finishing, are successively calculated using data stored in a microcomputer, the data processing associated with! various pieces being made with a

minimum amount of recorded data.

  The control method according to the invention makes it possible to introduce in a simple manner data concerning the shape of the finish and the dimensions, this recording being done in the microcomputer which automatically calculates the coarse machining dimension and the coarse finish for

  perform the corresponding operations.

  The control method according to the invention makes it possible to make the machining of complex shape having concave parts

  and convex parts, and this in a simple way.

  The invention also relates to a method according to which the machining data intended to be introduced into the computer are corrected automatically according to the shape of the cutting edge of the machining tool, for

perform this machining.

  According to another characteristic, the invention relates to

  is a process that allows the operator to use the calculator to decide whether the shape of the cutting edge of the tool and the shape of the machining of the workpiece for which the data is

  introduced in the calculator, are appropriate or not.

  According to the method, two successive machining operations with two types can be performed precisely.

  tools with different beak diameter.

  It is thus possible to facilitate the control of devices of this type, to make this command more

  accurate and improve the features.

  The present invention will be described in more detail with the aid of the accompanying drawings, in which: FIG. 1 is an example of a control panel for introducing the data necessary for machining according to the invention. FIG. 2 is a block diagram of an installation according to the invention; FIG. 3 shows the shape of the tip of a tool; FIGS. 4a-4e show various phases of a

  process in which the CPU calculator prepares a record

  very machining based on the data provided by the buffer

input.

  - Figure 5 is an example of the shape of the machining

  a machine working by copy.

  - Figure 6 shows how to find the rough finishing line from the shape of the finishing machining

on a copy machine.

  - Figure 7 shows a linear interpolation of a

copy machine.

  - Figure 8 shows the calculation of an intersection

a copy machine.

  Fig. 9 is a flowchart showing how to prepare a data set for coarse finishing during any machining step of a copying machine. - Figure 10 shows how to find the line of

  coarse finish on a copy machine.

  FIG. 11 is a flowchart showing how to prepare a data set for coarse machining on

a copy machine.

  - Figure 12 gives an example of a form of machining

of a cylindrical piece.

  - Figure 13 gives an example of a form of machining

open of a cylindrical part.

  FIG. 14 represents an example of a single-pass concave machining form for a cylindrical part according to FIG.

the invention.

  FIG. 15 shows a diagram of movement instructions of a tool for coarse machining of a cylindrical part. FIG. 16 is a geometric view showing how to find the starting point of coarse machining for a cylindrical part in the case of a concave shape at a

  only one passes for a conical part.

  FIG. 17 is a geometric view showing how to find the rough machining end of a cylindrical part in the case of a conical part. FIG. 18 is a geometric view showing how to find the coarse machining start point of a cylindrical part in the case of a concave part to a single

pass on a convex circle.

  FIG. 19 is a geometric view showing how to find the end of coarse machining on a

  cylindrical piece in the case of a convex part.

  FIG. 20 is a geometric view showing how to find the starting point of a coarse machining of a cylindrical part in the case of a concave part to a single

pass, on a concave circle.

  FIG. 21 is a geometrical figure showing how to find the end of coarse machining of a part

  cylindrical in the case of a concave part.

  - Figure 22 is a flowchart showing the application of

  a coarse machining control method of a part

  cylindrical in the case of a single pass concave portion.

  FIGS. 23 and 24 show the application of a cutting path for a coarse machining tool obtained by

  the coarse machining control method of a cylindrical part

  according to the flow chart of Figure 22.

  FIG. 25 is a flowchart showing a coarse machining control method of a cylindrical part

in the case of an open party.

  FIG. 26 shows a machining shape corresponding to a concave part with a single pass, making it possible to execute a coarse machining control of a cylindrical part during

  of a single phase according to the invention.

  - Figures 27, 28 show an interference between a

  tool and a form of machining, making machining impossible.

  - Figure 29 shows a known interpolation process

  used in cases of the impossibility of machining.

  - Figures 30 - 35 show the application of the method

of the invention to various forms.

  - Figure 36 is a flow chart that leads to the

  decision of the impossibility of machining.

  - Figure 37 is another flow chart that leads

  the decision of impossible machining.

  - Figure 38 gives an example of a form of machining with data entry in a control device. FIG. 39 is an enlarged view of

  the cutting edge of a tool used in lathes.

  - Figure 40 shows a machined part without compensation

the radius of the nozzle of the tool.

  - Figures 41, 42 show machined parts with

  compensation of the radius of the nozzle of the tool.

  FIGS. 43 and 44 show two successive phases executed using two types of tools according to the method

  Knife compensation tool.

  FIGS. 45, 46, 47 and 49, 50 show two successive phases executed using two types of tools according to FIG.

  control method of the invention.

  - Figure 48 is a flowchart showing the

  control method according to the invention.

  DESCRIPTION OF VARIOUS PREFERENTIAL EMBODIMENTS

  FIG. 1 shows an example of a control panel of a control device implementing the digital control method according to the invention, showing the situation

  the invention in a very comprehensible manner.

  Reference 2 relates to the keys provided on the control panel 1, to determine the shape to be machined on the lathe; reference 3 relates to indicator lights to indicate to the user the type of data needed according to the shape of the machining provided by the keys. Keys and indicator lamps carry indications in the appropriate languages. The ten digit 4 keys are used

  to introduce numerical values according to the indica-

  witness lights 3. A touch of

  Table 5 is used for the microcomputer to output the start operation signal. The set key 6 is used to record data in the microcomputer after the input of the data using the keys 2 or 4. Key 7 "function as before" is used when

6 2480960

  the following piece has a predetermined shape, so complex that it is necessary to introduce the machining data into the microcomputer, in certain phases rather than at a given moment and when the numerical values indicated by the indicator lamps 3 which light up at the moment in which to enter the data for the nth minor machining phase are the same numerical values for the same product as during the phase

  of management (ie, in the case of the act of

  Numeric daters introduced for the same product, during (n-1) machining phase, are guided and concuremment such quantities are displayed on an indicator device 16 which will be described later. Reference 8 relates to the correction key used to correct the data that comes

  to be fixed; reference 9 relates to an erase key

  all data used to erase all data entered into the microcomputer; the reference relates to an erase key of a machining phase, to erase the data entered in the microcomputer and

  which correspond to a machining phase.

  Reference 11 relates to a program key

  used to give calculation and recording instructions

  various data necessary for the order

  of the machine after entering the data

  cessaires; reference 12 relates to an operating mode switch used to ensure the transition between manual operation and automatic operation of the lathe reference 13 relates to a part switch used to read the data part on different workpieces,

  these data being registered in advance and corresponding to

  lay at the workpiece at this time, to allow automatic machining of the workpiece. Reference 14 relates to indicator lamps indicative of the state of the lathe; the reference

  concerning indicator lamps indicative of abnormal situations

  males, at the level of one of the different devices; the reference

  reference 16 concerns an indicator indicating the quantities of

  In addition, there is provided a group of switches shown in the right-hand part of FIG. 1, which serve to control the lathe by hand.

  The present invention relates to a method of

7 '2480960

  of a numerically controlled macr

such mly. of gold.

  I.a figure 2 is an overall diagram of a circuit

  for the implementation of a control method according to the

  vePt.on; in this diagram, the microcomputer 17 comprises a central processing unit CPU 18, a read-only memory 19, the

  input buffers 20 and a set of machining buffers 21.

  The turn 22 is the microcomputer 17 by the inter = -

  - 23 - for machine tools with control

  numerically (still loosely called NC machines).

  There are N input buffers 20 and the data of the cortical part are fed into each input buffer.

  c by setting the input switch that will be described later.

  quently. The data to be entered in each buffer of

  20 are classified into common data and phase data for each phase of machining. The

  common data concern the original position (for

  dex *, one-it) the finishing tolerance and, as

  As shown in FIG. 3, the cutoff angle, the outlet angle 2 ') of the y-profile and the radius of the spout or tip of the tool

  po.r a given tool number. Phase data

  include the shape of the machining, the X and 7 coordinates of a cut point, the X and Z coordinates of a starting point, the X and Z coordinates of an end point or end point , the radius R of a corner, the degree of cut, the number m of the finishing tool, the number of the tool

  coarse machining m ', the speed of rotation N and the vi-

  In addition, if the shape of the workpiece is too complex to introduce data relating to

  this form of machining at the instant of the control of the switching

  setting of the data entry 25 can be entered

  to obtain these data step by step. Each input buffer 20

  saves data up to n

  swimming. The assembly of machining pads 21 consists of a finishing pad, a coarse finishing pad and a coarse machining pad. The data relating to the path of

  movement of a tool during finishing machining, the

  mid-movement of the tool 'during rough finishing

  and the path of movement of a tool during rough machining

  data calculated by the unit CPU 18 on the basis of the dornnes introduced dal-s the ta': pon whole D., peIv-.n be introduced in the dif r-ts-ts tampuos of 1'en- -nbi. 2 !. Besides, there is only one in e. h! It is therefore possible to use any number of input buffers 20 so that, in each case, the type of coin to be used can be changed. the database previously stored in the input buffer associated with the device, cane, e7 causes the re-registration of these data! 21. Reference 2 refers to a room changeover switch designating a

  particular buffer among the N input buffers 20 in the

  which data should be recorded or read. The reference

  reference 25 relates to the data setting switch

  used to insert data into the data buffer.

  The reference 26 relates to an input data correction switch used to correct the data that has just been introduced by the input data adjustment switch.

  25. Reference 27 relates to an erase switch to-

  input data to delete all data

  introduced in the input buffers 20. Reference 28

  identifies the machining data preparation switch used to control the CPU 18 and calculate on the basis of the data recorded in the input buffer 20 as well as to record the data obtained in the set 21. These

  different switches are provided on the board

  (21) and are connected to the microcomputer 17 via a

switch reading face 29.

  Figures 4a-4e schematize the method of pre-

  paration of the assembly of the machining buffers 21 for a datum of a particular machining phase, selected from the data recorded in the input buffers 20 by manipulating

  input data adjustment switch 25.

  Figure 4a shows the basic shape obtained during

  introduced into the input buffer 20, the data cor-

  corresponding to the shape of the machining at the starting point T at the end point F and at the radius R. After inputting the data of the basic form into the input buffer 20, the data switch is depressed. machining 28 then the CPU 18 calculates the center P of the arc of the circle, the sormet F

9 2480960

  of the arc and the point of contact d between the slope (tangent) and

  the bow (Figure 4b). Among the angles of cut (m, & m 'of the

  Finishing tool m and roughing tool m ', one designates the advance, the smallest of which is called ok, and the cutting exit angles n m, i 3 m' of the finishing tool m and

  the roughing tool m ', the smallest of which is called / 3.

  The points of intersection b and e are calculated from d,

  and / to find a form of machin

  carried out on the spot at the beginning of

  lable. The radius of the spout is then trimmed along the radius rm of the finishing tool m (FIG. 4c) and the path a ', b', c ', d', K ', e', f ', P' the actual movement of the finishing tool m is calculated so that by machining one obtains the shape of Figure 4b. In addition, the radius of the arc changes from R to rm. Then prepare the finishing pad. As represented in FIG. 4d, the radius of the tip of the tool is compensated by the radius rm 'of the roughing tool and a path a ", b", c ", d", K ", e is calculated. ", f", P "of provisional movements of the roughing tool for machining, to arrive at the form calculated in Figure 4b and change the radius of the arc from R to rmn. Furthermore, with the finishing tolerance Y, the coarse machining points a '", b"', c ', ", K', el ', f"', Pl ", P" "are calculated from path of movement of the tool

  roughing m 'to prepare the coarse finishing pad.

  Finally, as shown in FIG. 4e, the coarse machining points Gi, Hi, Ji are calculated giving the finishing tolerance i from the coarse finishing points to prepare the coarse finishing pad. In addition, when this rough machining is done by reciprocating the roughing tool m 'is carried out n times as shown in Figure 4e, we do not search every time points Hi, Ji,

  Gi and they are not recorded in the coarse finishing pad.

  IESO; instead we only record Hi, Gi, Ji

  first time in the coarse finishing pad and then

  that the calculator passes on the next phase, it does the

  successive calculations according to the data of the pre-

  give and save the results in the final buffer.

  to update the contents of this buffer; In these circumstances, it is sufficient

  memory capacity to arrive at an infinite number of

-'-: 2480960

  coarse machining tools. The operation described above is given in the list below. Machining buffer Input buffer (for each machining step)

  1 TamTpon Buffer Tampon

  % for each case finite finish machinaze) Machining form X (T (a) X (a ') X a ") X (G1) Z (T) Z (a') Z (a '") X (Gi) X (A) x (b') X (b '' ') Z (Gi) Z (A) Z (b') Z (b '' ') X: IHii X (F') ) X (c ') X (c' ") Z (Hi) Z (F) Z (c ') Z (c'") X fJJl) RX (d ') X (d' ') Z (Ji)) Z (d ') Z (d ") m X (K') X (K '') m 'Z (K') Z (K '") NX (e') X (e "') VZ (e) ') Z (e' ") x (f ') x f'") z (f ') z (f' ") X (P) x (P '")

Z (P ') Z (P' ")

R-rm X (P ""))

Z (P "")

  R-rm 'n 1l 2480960 As soon as the CPU 18 calculates on the basis of the data recorded in the input buffer

  to complete the assembly 21, the lathe is automatically

  tically by the data of the assembly 21 and the workpiece is machined to the predetermined shape. If only a minimum amount of data necessary for the machining in the input buffer 20 is stored and the c: e-n c-displacement of the tool required for the machining effect is calculated each time by the CPU unit 18 on the

  base of the data applied to the input-20 buffer; the result

  The state of the calculations is recorded in the set 21. According to this installation, the indicated list shows that the content stored in the input buffer 20 is considerably reduced and as it suffices for a single machining buffer set 21, whatever the number of input buffers 20, one can record a large number of parts machining forms in

  microcomputer 17, at the same time.

  To increase the storage capacity of each input buffer 20 can be provided a separate CPU unit for the detection of the job number, in addition to the CPU 18 to prepare the assembly 21 on the basis of the data applied to the input buffer 20, the CPU unit which detects the part number being connected to the input buffer 20. If an instruction transfer of the CPU unit 18 is performed in the CPU number detection unit piece, the data stored in the input buffer 20 is transferred to the CPU 18. The memory can thus be increased in

  the limits of what is allowed for the CPU unit of de-

  part number, regardless of the capacity in

addresses of the CPU 18.

  The foregoing description shows that in the

  given above, the data needed to machine a part

  can register using a memory capacity, mini-

  which allows "'to record at the same time in the micro-

  calculator, the data necessary for machining an erand number of parts. It follows that in a workshop manufacturing small series, very diverse, when you want to repeatedly manufacture a limited number of parts, it is necessary

  to save the data concerning the parts in the micro-

  computer. By proceeding in this way it is possible to carry out

  na4e of u: _;:? - C particular by actuating simplf-2rrT] t.s

  Also, read the appropriate codes for this part.

  it is not necessary to re-record the data each

  once you change. of pirce, as was necessary; this increases the yield.

  Moreover, when you have to record in the micro-

  the data corresponding to a particular room, it is necessary to introduce a minimum of data, which facilitates

  considerably this introduction. Although the shape of the

  If the workpiece is sufficiently complex to exceed the number of machining steps allowed by an input buffer, this problem is solved by entering the number of the part into several input tamDons. In this way, it is possible to

  to treat a number n of machining phases, permitted by a tamper

  input multiplied by the number of input buffers N (i.e., n x N) by simply manipulating the coin change switch and the readiness switch

machining stamp.

  A process for preparing the machining stamp 21 envisaged above will be described below by taking as an example a copying machine processing a complex shape having concave portions and convex portions as shown.

in Figure 5.

  As described above, each input buffer has a memory portion for storing a set of cut data Yx, É z, a set of machining tolerances Lx, Lz, a set of finishing tolerances 6 x, 6 z and a point of

  cut T regardless of the number of machining phases. (The suffi-

  xes x and z correspond to the components x and z). The finishing pad has a memory section for recording a machining shape, a start point A, an end point F, a center point P, a radius R and other elements (including speed

  of rotation and advance) for each machining phase.

  The coarse finishing pad has the same organization

than the finishing pad.

  The coarse finishing pad has a portion of memory to record a set of finishing tolerances

  coarse machining t xi, 6 zi, a starting point for

  A, a finishing point Fi and a central point of cut Pi, irrespective of the number

of machining phases.

  The input data described above relates to elements concerning the machining shape, the dimensions of

finish and the input buffer.

  The model of the machining form is divided into four parts, namely a straight line, a convex arc and a concave arc. When the outline of the finishing shape of a part breaks down into a combination of straight lines, arcs

  convex and concave arc, the corresponding data are

  straight lines along the coordinates of the starting point and the end point and the coordinates of the starting and ending points as well as the radius of curvature of the arc

concave or convex.

  The coordinates are expressed by taking the right origin of the part, the Z axis corresponding to the axis of the part and the X axis being perpendicular to the previous axis. This process

* makes it possible to directly use the finishing machining dimensions

the room.

  A practical example of input data from a

  machining shape model and finishing machining dimensions

  The contour will be divided as follows in FIG. 5. The contour is divided starting at the left end into a straight line, a convex arc and a concave arc, and the data for the various machining steps are entered as follows. : 2 0 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

  - - - - - - - - - - - - - - - - --____

  Phase Mdl Point of Point 0h of machining Mpart of arrival Radius 1 - Straight line A1 F1 2 Convex arc A F2 R2 3 Straight line A3 F3 4 Concave arc A4 F4 R4 Straight line A5 F5 6 Convex arc - A6 F6 R6 7 Arc convex A7 F7 R7 8 Concave arc A8 F8 R8 9 Straight line A9 F9 Starting from the entry point, the CPU 2 calculates the machining shape, starting point, end point, center point, radius and other elements (including rotational speed and feedrate) for each machining phase; The results are saved in the finishing buffer. In

  function of such data, the CPU 2 decides whether to

  think the tip of the cutting tool and whether the machining paths of the adjacent machining phases are continuous or not; the resulting data is saved as a travel path for the finishing tool for finishing machining to ensure

continuous control of the machining.

  When the preparation of the machining data of all the machining phases of the input tamon is completed,

  the next step is to prepare the data for the

swimming rough finish.

  Under these conditions, the path of movement of the coarse finishing machining tool is such that it is offset from the path of movement of the finishing machining tool by a distance corresponding to the finishing tolerance. We

  can thus have a shape by connecting an infinite number of rec-

  tangles defined by the X and Z coordinates of the position components as well as the finishing tolerances 6 x9 z next

  the finishing line (see Figure 6).

  As the shape of the machining during each machining phase is the same as the shape of the finish, the way

  to find the coarse finishing dimension at the heart of each

  that machining phase will be described below. The way to find the coarse machining point is the same for each machining phase during a given machining operation (for example Nth machining phase) if the starting point of the finishing corresponds to AN, the point d arrival at FN and the central point

  at PN and if the starting point of the coarse finishing corresponds to

  corresponds to AN ', the point of arrival at F N and the central point at P', the coarse finishing point is represented N

  by the finishing point to which the final tolerance is added

  tion. We obtain: X (AN ') = X (AN) + x X (FN'> = X (FN) + x X (PN ') = X (PN) x

Z (AN ') = Z (AN) + S

  Z (FN ') = Z (FN) + z Z (PN') Z (PN) + z In these relations, the plus or minus signal preceding g is determined so that the sign is more for X (AN) X (FN), and

  that the sign is less for the inequality X (AN)> X (FN).

  When the calculations are made according to the rule above, in the case of a shape such as that of Figure 7, with a starting point X (AN) for the Nth machining phase which is less than or equal to the point of arrival X (FN) and with a starting point X (AZ) which for the preceding machining phase is greater than the arrival point X (FNI), there is a shift of the point of contact between these two phases machining. Point

  finish of the coarse finish fFN ') is given by the

  following mules: X (FN ') = X (FN) + x Z (FN') = Z (FN) + z but the starting point of the coarse finishing (AN l,) for the (Ni) phase of machining is given by the following formulas: X (AN_1 ') = X (AN_1) + 6xZ (AN-') Z (AN-1) z Thus the points (FN ') and (AN_') have the same coordinate X, but the ordinate Z-is separated from 2 z be AN1 = FN) Thus in the case:

X (AN) - X (FN)

  X (An_l)> X (Fn-1) the difference between the contact point during the two machining phases can be suppressed and it is possible to arrive at a continuous command by interpolating according to a

connecting line (FN ') and (AN1').

  In addition, this difference at the point of contact occurs in the case of Figure 8. It is thus:

X (AN)) X (FN)

  X (AN_) -X (FN-1), X (FN ') = X (FN) +4 x Z (FN') = Z (FN) -Z X (ANI ') = X (AN1) + x Z (AN-1 ') = Z (AN-1) + z.

  In this case, the points (FN ') and (AN1')

  range from 2 Gz (', AN1 = FN).

  Then, the intersection between the straight line (or arc) (AN ') -) (FN') and the arc (or straight line) (AN _ ') - => (F 1') is calculated by the installation who makes up the bow using

  the intersection as a point of contact.

  This intersection can easily be calculated

  from the equation of the coarse finishing line corresponding to

  laying at the Nth machining phase and the equation of the line of

  coarse finish for the (N-1) th machining phase.

  In the other cases than the two described above (FIGS. 7, 8), there is no such difference between the contact points, so that it is not necessary to provide compensation. In summary, the flow chart for the calculations of the different points of the Nth rough finishing machining is that shown in Figure 9; the same flow chart is used sequentially for all the machining steps and the results are stored in the coarse finishing buffer. In addition, in the flowchart of FIG. 9, for N = 1, it is indicated that

  the previous machining step (N - 1) does not exist and the results

  previous calculations are stored in the buffer of

coarse finish.

  Such quantities stored in the coarse finishing pad indicate the main points of the coarse finishing line for machining coarse finish and

  the moment of the rough, real finishing machining, the interpolation

  Linear or curved interpolation are made between adjacent points, following the shape (straight or curved) to obtain

  continuous contour machining data.

  The preparation of the rough machining stamp will be

described below.

  In the case, the term "rough machining" or "roughing" concerns the machining of a rough blank, until one reaches the rough finishing line and the part

  cut or removed is usually called "tolerance".

  In this invention, the tolerance is defined as the curve obtained by connecting an infinite number of rectangles determined by L, L on the finishing line (as shown in Figure 10) the set encompassing the tolerance

  between the finishing line and the coarse finishing line.

  The amount of cutting and machining tolerance & z. sz are derived from the relationship LX / Lz = Sx / & Z = & x / Yz on the basis of initially entered tolerances Lx, L, Yx degree of cutting and finishing tolerance ix The tolerance dimension L along the axis X x can be set according to the draft part of maximum tolerance used as standard. Even if there are some variations in the actual tolerability between the parts of the individual blanks or in a given value, there is no

  difficult because it is only a rough machining.

  In particular because the tolerance is chosen according to the finishing line which is the shape or the final machining curve, this way of proceeding does not influence the precision

machining of the piece.

  As rough machining is performed by gradually cutting the blank from the outside and passing

  at the coarse finishing line, the quantity removed, the name

  The number of repetitions of coarse machining operations is such that if the tolerance is divided by the quantity removed or the quantity cut off, a quotient (integer) and a remainder are obtained; the rest is added to the cut quantity for the rough machining time. First, we will describe how to find

  each time the path of the tool for rough machining.

  This can be considered in the same way as to find the coarse finishing line from the finish line described above. Thus, the finishing point AN of the flowchart of FIG. 9 is taken as the coarse finish point AN 'and the finishing tolerances s as coarse finishing tolerances & xi 6 i. However, the rough finish tolerances xi 'zi of a quantity corresponding to

  the quantity cut for each coarse machining.

  In practical terms, referring to the

  gram of FIG. 11, the path of the tool for the first rough machining is calculated according to the starting instruction

  machining. For this purpose, we subtract the finite tolerances

  ix, i input tolerances L, L, then subtract from the result the quantities for cuts ex 'Wz The next step is to decide if the quantities xi', & Zi are each equal to or less than 0. If both answers are yes, liisinage ends; if both answers

  are, for the machining phase N used as the machining phase

  final swim n ', we take the starting points X (Ai), Z (A.), the points of arrival X (Fi), Z (Fi), and the central points X (P), Z (Pi ) for rough machining from this nth machining phase. When the coarse machining start point (Ai) and the coarse machining end point (F.) are obtained for the nth machining step, the roughing tool (A) is moved to (F.). If the phase N is the phase 1, we go to the section (T) and if the machining phase N is different from 1, we advance the machining phase on the next machining phase namely N which is replaced by N - 1; and we look for the starting point of roughing (A.), the point of arrival of roughing (F.) and the central point (Pi) for this phase

  machining, this operation being repeated until for N = 1.

  In rough machining (roughing) the coarse machining buffer has a memory capacity corresponding only to one machining phase, so that the tool is removed each time and re-entered in the memory for further processing.

machining.

  As soon as the first coarse machining is completed in this way, the second coarse machining is started. At this point, the coarse finishing tolerances Exi ', zi are obtained by removing the cut quantities Y' CY The coarse machining is repeated until the coarse finishing tolerances i xi '9zi are such that xi i and & zi In practice, according to FIG. 5, the path of movement of the tool for the upper line is machined starting at the right while searching for the starting points.

  end and center, until the tool reaches the end

  left, then the tool returns to the cutting point T and finally the second rough machining is performed in the same way. Finally, the quantity corresponding to the remainder of the cutting quantity division ("N z) is cut off by the coarse finishing machining until the coarse finish line is reached and the quantity corresponding to the finishing tolerance by doing the finishing machining for

finish the job.

  In the method described above, one can perform a copy machining of a complex structure having concave and convex portions on a numerically controlled machine tool, by simply introducing into the machine the dimension of

  finishing machining since the calculator then calculates

  the coarse finishing dimension and the roughing dimension. This reduces the number of manual inputs to be made by the operator as well as unnecessary movement.

  of the tool, which results in a very efficient machining.

  The way to prepare the assembly 21 of the machining buffers will be described using a rough machining example

  of a cylindrical piece on a lathe.

  As described above according to the invention, it is possible

  automatically machine a piece to give it a com-

  such as that shown in FIG. 12, by rough machining, then rough finishing machining and

  finally to a finishing machining; for that, we introduce simple-

  the common data including the original position (for attaching a tool), the finishing tolerance 6 and the cutting angle d as well as the rear angle of cut P and the radius of the point r associated with a predetermined number of the tool as well as the data of the machining phase such as the shape of the machining, the X and Z coordinates of the cutting point, the X and Z coordinates of the starting point, the X and Z coordinates of the point the cutting radius of a wedge (fillet) R and the cut quantity Y, the number m of the finishing tool, the number m 'of the roughing tool, the speed of rotation N, and the speed of advance V. The assembly 21 comprises a finishing pad, a coarse finishing pad and a machining pad

  coarse or roughing, to record data relating to

  the size of the finished machining, the size of the coarse finishing machining and the coarse or rough machining. The coarse machining buffer is provided so that data can be recorded relating to the machining shape, starting point A, end point F. center point P, radius R, cutting amount Y, the starting point of roughing M and other parameters (including the speed of rotation and the speed of advance) for each machining phase

  as shown below.

  Coarse machining stamp Machining phase êl2me -2m1 Machining form Starting point

X (A), Z (A)

Arrival point

X (F), Z (F)

Central point

X (P) - Z (P)

  Radius R Cutting size y Starting point M roughing Other parameters Other parameters one concave pass convex circle

(100, 200)

(150, 200)

(100, 250)

  n_me The finishing pad is made of the same

  way that the roughing buffer.

  The coordinates of the starting point, etc., are expressed using the rectangular coordinate system, the origin being at one end of a blank the axis of rotation of the outline constituting the Z axis and the X axis being perpendicular Z-axis. The magnitudes of the starting point, end point, center point, finishing buffer and finishing pad

  coarse, are calculated and stored according to the size

  The number of the machining phases described above is given in FIG. 12. The first machining phase is between points 1 and 2, the second phase between the two machining phases described in FIG. points 2 and 3 etc; the final machining phase is between the points 9 and 10. According to FIG. 12, the operation is divided into 9 machining phases; the starting point of each machining phase is calculated and in the case of a machining form and an arc

-------------------- L.

  for each part of the blank, the center point is calculated

and it is recorded in the buffer.

  The roughing buffer registers the preceding roughing point Gi-i which precedes by one, the starting point of roughing Gi, the finishing point Hi and the roughing point Ji as is indicated below. Thus using such a buffer, there is a memory capacity, sufficient to record data preceding a machining phase that is to say four points, which

  regardless of the number of machining phases.

Roughing buffer

  --------------------------------------------__________-_________

  Starting point of roughing of previous unit X (Gi-1) Starting point of roughing X (Gi), Z (Gi) Finishing point of roughing X (Hi), Z (Hi) Return point of roughing X (Ji), Z (Ji) Coarse or rough machining can be classified according to the two machining forms, namely an open form like that of FIG. 13 or a concave shape to a

  only one passes as shown in Figure 14.

  In addition, the schema of the instructions for moving

  The tool in a rough machining (roughing) is fixed as shown in Figure 15 so that the path from Gi-1 to Gi allows fast forwarding for the open form and a cutting speed for the unidirectional concave shape ; for the path between points Gi and Hi, the cutting speed is used for both types; for the path between the points

  Hi and Ji, we use fast return for both types.

  If one calculates successively the coordinates

  Z and X of Gi, Hi and Ji, one can obtain a rough machining.

  The calculation procedure will be described below. The following relation must be obtained

  X (Gi) = X (Gi-1) -9 (t size of cut).

X (Hi) = X (Gi)

  X (Ji) = X (Gi) + a (fixed value, given 0.1-0.5 mm).

Z (Ji) = Z (Gi).

  For this reason, the only difficulty concerns Z (Gi) and Z (Hi) which can be found in the following way depending on the form to be machined Form to be machined Z (Gi) Open form Z (Gi) = Z (A _) + b (b = O0 -5mm) Concave form at Z (Gi) = Z (A) - Z (A) Z <F) X (A) -X (Gi) - at a ZG pass (P) -R2X (A) -X (F) Convex Circle Z (Gi) = Z (P) -y R -% X (P) -X (Gi) 3 2 to a PassR2 P - XG -6 Concave Circle Z (Gi) = Z (P) + R2- 2

_____ Z G) = () + R ____________ _

  has a pass In these formulas A is the starting point of n

  the final machining phase (right end).

  Machining form Z (Hi) Conical Z (Hi) = Z (A) X (A) X (A) -X (Gi) + Convex circle Z (Hi) = Z (P) + R2 {X (P) X (Gi) 2 + Convex circle Z (Hi) = Z (P) + 1R-IX (P) -X (Gi) 3 2 + s Concave circle Z (Hi) = Z (P) -R2-X (P) ) -X (Gi) + Thus, we can find Z (Gi) of a concave cone with a single pass, from the coordinates Z and X of the point

  taper (A) and end point (F) for the final

  The reason for taking into account this finishing tolerance is that the tool should not cut into the rough finishing machining path. during roughing, to smooth finish resulting from coarse finishing machining although this is not absolutely necessary. In addition, Z (Hi) of the single-pass concave part can be calculated in the same way as above.

Figure 17.

  Moreover, as for Z (Gi) of the convex circle, the Z and X coordinates, namely Z (P) and X (P) of the central point, can be calculated from the starting point of the arc and the arrival point. of it and the radius R, the calculation being done

as shown in Figure 18.

  Similarly, we calculate Z (Hi) for the concave circle

  as shown in Figure 19.

  Z (Gi) of a convex circle is calculated as shown in Fig. 20 and Z (Hi) as shown

in Figure 21.

  Therefore, for a given machining form, with a start point A, an end point F, a central point

  arc P, an arc radius R, a cutting quantity Y, a tolerance of

  6 and the X coordinate (Gi-1) of the roughing point which precedes one unit, it is possible to

to calculate Z (Gi) and Z (Hi).

  As for A, F, P, R, and g, it suffices to give the number of the machining phase N to the finishing finishing buffer. So after all, just give the number of the machining phase N for the coarse finishing pad and

X (G-l).

  The number N of the machining phase for Z (Gi) or Z (Hi) can be given sequentially and the number of the phase

  machining for others is chosen.

  Figure 22 shows such a flow chart.

  The starting point of the roughing X (M) for all the machining phases of the coarse finishing pad of FIG. 22 can be canceled in advance as for the starting point of roughing (Gi-1) which precedes a unit; this can be done at one time, just give the end point (F1) of the first machining phase for the buffer of

  coarse finish. This is why X (Gi-1) = X (F1).

  As for the phase number of NUsage N, the

  roughing begins at the final machining stage N = n.

  The quantities X (Gi), Z (Gi), X (Gi),

X (Ji) and Z (Hi).

  Then, we give the machining phase number which

  preceded by a unit N '= n - 1 and Z (Ni) is calculated.

  In this case, if the two coordinates of X for I pointd. X (AN ') and for the end point X (FN') of the Nli'ine machining phase, are smaller than X (Gi), we have the number of the machining phase which precedes a unit and this machining phase number which will give X (A) or X (F) greater than X (Gi) '

is chosen for the calculation of Z (Hi).

  If the number (N'-l) of the machining phase, which -

  This machining step is preceded by one unit and does not include a roughing point X (MN, _), so X (MNi-) = X (Gi-1) is recorded in the coarse finishing buffer. (X (M)

  for all the machining phases is cleared in advance).

  The following decision concerns the end of the sidings

  wise; if the roughing is completed, machining proceeds to the next N-1 phase number and the X (MN) value is recorded

as corresponding to X (G-1).

  If the operation is not complete, an instruction

  is sent to move the Gi-a Hi-4 Ji tool, but by comparison

  reason with the cases shown in Figures 23 and 24, it is necessary that after the displacement on X (Gi-l) + a in the direction of the axis X, we go to Z (Gi) + X <Gi-l ) -X (Oi) + a tg (t - 3)

  in the direction of the Z axis, for the first time.

  This means that in the case of FIG. 23, the number of machining phases for the coarse machining buffer is equal to 4; the first machining phase with starting point A1 and end point F1, we move to the second machining phase with as starting point A2 and as finishing point F2, then to the third machining phase as starting point A3 and as finishing point F3, then at the fourth machining stage with starting point A4 and end point F4 as starting point. The roughing is started at the final machining phase or fourth phase. In this case, Gi, Hi, J1 are calculated according to the process shown in FIGS. 16 and 17; G2 is deduced from G1 according to the method of Figure 16; H2 is found from the process of Figure 19 etc. In the case of Figure 23, the starting point of the roughing, the end point and the return point for the third machining phase are suffixed "i", which gives Gi, Hi, Ji; these points can be calculated by the method already described. However, the starting point of roughing X (Gi-1) of the machining phase which precedes a unit that of Gi was the starting point of roughing X (NN ,, 1).

  in pr-t [that X (Gi) of Figure 23 corresponds to X (Gi-1).

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  According to Fig. 23, an instruction is used to move the tool to X (Gi-1) + a, ie X (G1) + a in the direction of the X axis, and then to X (Gi-1) -X (Gi) + a Z (Gi) (G) + 0+ in the direction of the Z axis. Tg (δ -3) The magnitude ((Figure 3) is the angle of cutting output of the tool and is introduced as input, in advance

in the control device.

  When calculating the roughing start point Ji, the roughing finishing point Hi and the roughing return point Ji for the roughing phase From the sizes of the starting points and the finishing points of the various phases of machining recorded in the coarse finishing buffer, the instruction is issued only if Gi, Hi, Ji can be calculated for the first moment of each phase

  machining for coarse finishing pad.

  In the case of FIG. 24, the coarse finishing buffer records A1 and F1 respectively as starting point and as finishing point for the first machining phase A2, F2 are respectively recorded as starting point and as point of departure. arrival for the second phasedusage and A3, F3 are respectively recorded as the starting point and as the end point of the third machining phase. Under these conditions, the number of machining phase is equal to 3. The first point X (Gi-1) of the third machining phase is given by X (Gi-1) = X (Fi) of the flow chart. of Figure 22 and the point G1 for n = 3 derives from the process shown in Figure 16. H1 is obtained according to Figure 17 and (Ji) is obtained as follows J (1) = X (G1) + a and Z (J1) = Z (G1). G2 is found from the start point A2 and the end point F2 of the second machining step according to the method of FIG. 16; H2 is found according to the method of FIG. 17. Under these conditions, as for the movement of the tool for the point X (Gi-1), namely X (G-2) moves the tool from the point J1 to the X (Gi-l) + a in the direction of the X axis. However, in fact X (Gi-1) is X (Ii) and X (G1) + a corresponds to X (Ji). So for the passage from J1 to X-- 2_1), there is no movement in the direction of the X axis (because this movement is not necessary) and the tool moves only in the direction of the Z axis to move to the point Z (G2) + X (G) -X (G2) + a, namely Z (G2 1) In the case of the point tg (P - 3 2

  G3, as this is the second moment of the second phase of

  swimming (and that there is no such movement) the tool goes directly

from point J2 to G3.

  When the roughing is completed in the manner described Gi -> Hi - Ji, X (Gi) is transferred to X (Gi-1) in the roughing buffer and the recording of Gi, Hi is deleted.

  and Ji in the roughing buffer.

  The value X (Gi-1) is given and the roughing

  is done during the calculation of Gi, Hi and Ji next.

  LO As the content of the roughing buffer is progressively updated as just indicated, it is possible to have a memory of very low capacity and which

  can receive an unlimited number of times of roughing.

  Moreover, in the case of an open form, we have Z (Gi) = Z (An) + b (with b = at O, 1-Smm, and An as the starting point of the last machining phase). ), it is enough only

to calculate Z (Hi).

  The number of the machining phase can be obtained in the case sequentially starting from the first phase

O machining.

  As shown in Figure 5, the flowchart

  to the calculations is very simple in the case by comparison

  with the concave single-pass curve described above.

  The combination of the two types, that is to say of a single pass concave part and of an open part in the case of roughing processes, makes it possible to machine

very complex shapes.

  In addition, according to the invention, a form of machining given by the points A, B, C, D, K, E, F, (Figure 26) can be sided in one operation. If the installation is such that one can record X (M ') to be used separately from X (M) within a machining phase, one can make the calculations in a machining phase in using a computer program

  wherein X (M) of Figure 22 is replaced by X (M ').

  Thanks to this, it is possible to machine cormplex forms with concave and convex parts and this by a simple input operation, which improves considerably

  the advantages of digital towers of this type.

  The following description relates to a procedure [p, .r-

  r ;. 't', *., l 'r) u vet a (f) orm. l ,, I'.t u; t r.

  Machined using the lathe using a tool of predefined shape, for example, to cut the vertical wall portion 30a of a workpiece 30.

  (FIG. 27) using a cutting tool 40 whose cutting angle est is equal to or less than 90 ', if the tool 40 moves from right to left, depending on the final dimension of the piece 30, tool 40 meets with

  difficulties in removing the vertical wall 30a.

  Moreover, in the case of a part 30 having a concave part 30b (FIG. 28), to cut the vertical wall 30c at the initial end, the cutting tool 40 whose end angle of cut P is smaller or equal to 90 meets difficulties.

  To overcome these difficulties, a process consists of

  it would be for the operator to compensate the input quantities around the definitive dimension of the part taking into account the shape of the cutting tool used, by introducing this shape; another method would be to cut towards the point of entry 0 at a fixed angle 9, without taking into account the shape of the

  the tool and the final shape of the piece (Figure 29). Toute-

  There is a very large variety of cutting tool shapes, so that the first method of offsetting the input variables leads to very complex input operations and may cause errors; the second cutting method according to a fixed pattern has limits according to

the final shape of the piece.

  The present invention consists of classifying the various tools used on the towers, according to their shape, using code numbers, to record them in a fixed manner in the memory section of the numerically controlled lathe, to introduce the data of the tools to be used. in a machining data preparation section with a code number and retrieving the recorded data corresponding to a particular tool. The classification of the tools by shape is based on the cutting angle θ and the cutting exit angle γ of each tool (Figure 3); these quantities are classified according to code numbers as indicated in the table below:

Board

Code I <3e 0 93 30c'3 0

1,930 50

2,450,450

3,600,600

4 -750 150

93 0 370

6 93 0 520

7 93 0 930

  It is desirable that the digit numbers used in the code numbers are small. The input method is to use the functional keys of the keyboard. According to the invention, described above, the shapes to be machined and the cutting variables are introduced in digital representation and as indicated by the final dimension provided on the plans; the introduction is done in the section

  to prepare the machining data using the keys func-

  of the control panel keypad.

  The machining data preparation section automatically calculates the optimum path of the tool, from the tool code number, entered, the machining pattern diagram and the cutting quantity to prepare the data.

machining.

  Machining shapes are classified in straight line, inclined line, convex circle, concave circle, concave circle

  a single pass etc and the corresponding functional keys

  are provided on the control panel so that the

  The controller can order them to introduce the diagram. Furthermore,

  each key is identified by one or more corresponding words.

  The diagrams are characteristic of any form of machining and can be applied to any complex shape. In the same way as for the cutting size, the axial dimension of the part as well as its radius, and the end surface

  of the reference document, are introduced in

digitalisation.

  In practice, we take for the axis Z, the axis of the

  part and for the X axis, an axis included in the end surface

  the room; the starting point and the end point for the machining position are measured from the end surface of the workpiece; the quantities measured represent coordinates along the X axis and the magnitudes of the radius

  definitive at the point of departure and the point of arrival of the posi-

  Machining are Z-axis coordinates. For example, as shown in FIG. 30, when machining a concave curve, following a pass, the key of a single-pass concave curve is used to introduce the shape to be machined; the dimension or axial length k separating the end surface S from the machining starting point A and the radius r at the point A are introduced as input signals as well as the cutting quantity, the axial length m of the surface. end S of the workpiece to the machining end point F and the radius r at the point F and the radius t in the cavity between A and F. As a result, the machining data preparation section record the form to be machined as follows: X coordinate of point A is Xr, and its coordinate Z is Zk X coordinate of point B is Xt, and its coordinate Z is -Zk X coordinate of point C is Xt, and its coordinate Z is -Zm X coordinate of the point F is Xr, and its coordinate Z is -Zm X coordinate of the point F is Xr, and its coordinate Z is -Zm The machining data preparation section thus calculates the optimum path of the tool following the form to

  machine and the code number of the tool.

  In this calculation, the comparison is made with the cutting exit angle (of the tool as well as BCF which is compared with the angle of the tool.) Si - ABC and t - BCF are less than (and ci, it is decided that it is not necessary to compensate and the data of the path of the tool is prepared with machining data such as A -> B- C - F. Thus, for 1t-t ABC and it- 4 BCF equal to r that A o is greater than P and iS, we compensate points B and C as follows:

* L4 AB'B = (3 3 = (3.

  BC'F = o4- 30 = Qie The angle of 3 gives room to avoid interference with the tool and this angle can be a minimum

irreductible, not limited to 3.

  The coordinate C of point B 'is the same and only

  its Z coordinate is compensated in the following way

-K - (r -) side.

  Moreover, the coordinate X of the point C 'is the same and only the coordinate Z is compensated as follows -m + (r - t) cot' So, if't <ABC <(A it is not compensated if the - <ABC 2 t3 is compensated if t- BCF 4th, is not compensated if '(BCF - is compensated If there is compensation, the path of the tool is the following one

A- B '-> C'- F.

  The same procedure is performed if, as shown

  in FIG. 31, there is a conical or inclined portion

  a concave single-pass curve and if, as

  in figure 32, there is a convex circle inside

  from the concave part to a single pass.

  According to FIG. 31, the path of the machining form is introduced by means of the keys serving for a concave part with a single pass and an inclined part; the cutting quantity is introduced by introducing the information A (XA7 ZA)

  B (XB, ZB), C (XC, ZC), D (XD, ZD), and F (XF 'ZF).

  By proceeding in this way, the comparison described above for B, C and D is made. In the case of FIG. 31, points B and D are compared and the angle at point C is

  less than i, no compensation is made.

  Point B is compensated for its Z coordinate, of

  way to move this point to point B '.

  The Z coordinate of point B 'is calculated as

follows ZB - (XA - XB) cot / 3 '.

  We compensate the point D for moving it to the point D 'and its X coordinate is the following: XD (ZF - Zc) tg c' + XF (XD -) XD XC + (ZD - Zc) tgc 'The coordinate Z is the following: 3 2 -ZC (XD-XF) + ZFXF-XC) + (ZF-ZC) zF ____ XD XC + (ZE, - ZC) -t In addition, in FIG. 32, the machining diagram is introduced by the keys of a concave curve to a single

  passes and a convex circle; the cutting quantity is inserted

  inserting the data A (X Ar ZA) r B (XB, ZB), C (XC, ZC)

  D (XD, ZD), F (XF, ZF) and the radius R of the arc.

  In the case, we compensate in the same way the point B to pass it to the point BI and we compensate the

points C and D as follows.

  We first compare the angle of the tangent to the circle at point C to the angle of cut Q> 1. of the tool as described above and if this angle is equal to or greater than c,

  compensate for the point to move it to Cs.

  As for the point C ', we find the tangent of the angle arc ok' and the intersection between this tangent and the line segment BC so as to automatically calculate the

coordinates of the CI point.

  As for the point D, we find the intersection D 'between a line of angle ô \ passing through the point F and the arc, as compensation point and we compute the coordinates of this point. This is why, according to FIG. 32, the path of the tool A --- 4 C '---> D' -> F which constitutes the machining data is obtained. In the case of a concave circle, we make the

  same way a comparison and a compensation.

  As described above, one can automatically correct

  tically the machining shapes according to the tools that have

  different cutting angles and performs the machining.

  In addition, the invention makes it possible to decide whether the shape of the cutting edge provided by the input code of the tool makes it possible to cut a form of machining, introduced into the machine, if this cutting is impossible. , the operator is informed by

  the control device of the machining preparation section.

  This operation will be described more

detailed below.

  For example, as shown in FIG. 33, to cut a tilt shape of angle X and gold at the conditions 4 4 and t4 tC, the circuit informs that the selection of

the tool is not correct.

  By machining a convex circle like the one

  34, similar information is given if the angle of the tangent at the initial end is greater than

  Where the angle of the tangent at the end of arrival is greater than

with (.

  For the machining of a concave circle as shown in Fig. 35, similar information is provided if the tangent at the initial end is greater than r and if

  the one at the end is greater than

  The above decisions are made by the provision

  control of the data preparation section

  machining according to the flow chart of Figure 36.

  When an instruction to find a toolpath is issued at the end of the input of the tool code number and the form to be machined, the decision begins and is

made for each form to be machined.

  First of all in the case of the inclined part of FIG. 33, if the coordinates of points A, B, C and D are the following ones A (XAI ZA), B (XB, ZB), C (X, Z0) and D (Xfil Zi), and if the gradient of ago of the line segment AB is tgra = (XA - XB) / - (ZB - Z), and only if this angle is equal to or greater than tg <i we have an error representation; in case

  otherwise, the circuit decides that there is no error. The grading

  if tg% of the line segment CD is tg x = (XD - Xc) / - (zD ZC) and only if this gradient is equal to or greater than tget ', it is decided that there is an error; otherwise, the circuit decides

that there is no mistake.

  In addition, the above description concerns the cases

  line segment gradients that are taken into account.

  However, if this is not taken into account, the error can be displayed by deciding whether the cutting angle J% and the cutting exit angle (interfering with each other as shown by

the flowchart in Figure 37.

  Indeed, in the case of machining a workpiece having portions inclined in two places such as the

  line segments AB and CD in Figure 33, we examine separately

  the inclined parts. The gradient tg a- of the inclined part corresponding to the line segment AB is given by tgO = (XA - XB) / (ZA ZB) Only if tg Or tg ('and - tg a- = tgc', the circuit decides that there is an error;

  otherwise, he decides that there is no mistake.

  The gradient tg of the inclined part corres

  laying on the CD segment is equal to tg = (Xc - XD) / (Zc - ZD).

  Only in this case, if tg) tgb 'and if -tg = tg.', The circuit decides that there is an error; if not, he decides

that there is no mistake.

  In the case of a convex circle (Figure 34), if the coordinates of the points A and B are given by A (XA, ZA) and AB (XB, ZB) and if the radius of the arc is equal to R, the gradient tg 'of the tangent at the point A is equal to tgl' = - (ZR-ZA) / (XA-XR)

RA A R

  and only if tgt 'is greater than tgj &, the circuit decides that there is an error; if not, he decides that there is no mistake. The gradient tgo- 'of the tangent at point B is

  equal to tg- '= - (ZB-ZR) / (XB-XR); only if tg g 'is greater than

  the circuit decides that there is an error;

  otherwise, the circuit decides that there is no error.

  In the circuit of a concave circle (Figure 35), if the coordinates of the points A and B are A (XA, ZA) and B (XB, ZB) and if the radius of the arc is equal to R, the gradient tg "of the tangent at point A is equal to tgt" = - (ZR RA) / (XA - XR); only if tgt "is greater than tg P ', the circuit decides that there is an error and if it does not, it decides that there is no error." The gradient tgO- "of the tangent at point B is equal at tgo- "= (ZB-ZR) / (XB-XR) and only if tgar" is greater than tgo ', the circuit decides that there is an error; if not,

he decides that there is no mistake.

  If X and Z are the coordinates of the center of the arc and are calculated automatically by the control device of the machining data preparation section, the calculated values are given by the following formula: XR = {a + d ( a - b) + rq / (d2 + 1) (In this formula the double sign means that there is the sign (-) for a convex circle and the sign (+) for a concave circle.

2480960

  ZR d-X + a q = la + d (a R b) 1 2 (d2 + 1) (2a2 + b2 _ C _ 2ab) a = XA-X

A B

b = ZA - Z

A B

  c = R (convex or concave radius of curvature of a circle, input quantity)

d = (XA - XB) / (ZB ZA).

  As described above, according to the invention, it suffices that the operation introduces the code number of Ig tool

  to use as well as the size of the machining; then, the

  Positive control automatically corrects the shape of the

  swimming that suits the tool. Moreover, we can detect

  data entry errors, which reduces the workload of the

  and allows high precision numerical control machining

if we.

  The compensation method of the moving path

  of the tool according to the radius of the tip of the tool will be

described below.

  In general to machine a piece for example of

  cylindrical shape and give it a shape such as that

  felt in Figure 38 using a lathe whose motion

  is controlled numerically, the operator introduces generally

  the X and Z coordinates of the cutting point T, of the starting point A and of the finishing point F in the control device comprising a microcomputer 17. Then, the microcomputer described above calculates the path of the displacement of the tool

  for roughing, coarse finishing machining and machining

  Finishing swim, based on lap data and controls based on the results of the calculations. For example in the case of finishing machining, the circuit calculates the coordinates of the points a and f from the data and commands of the finishing tool so that the cutting edge of the tool is

  move on the line through points a, A, Fp f.

  In this context, it should be noted that the cutting edge of the lathe tool does not have a ridge vertex

  but this tool is rounded as shown in Figure 39.

  To adjust the movement of movement of the tool m according to the method described above, it is necessary to choose a certain point of

  the cutting edge as a set point. For this, generally-

  According to Fig. 39, the fictitious cutting edge W for each tool is determined based on the radius r of the tip and this fictitious edge is set so that it moves on the line connecting the points a, A, F , f which are calculated by the microcomputer. Controlling the movement of the tool m using such imaginary cutting edge W presents no difficulty for the areas between the points a and A and between the points F and f. However, in the region between points A and F, on the inclined surface (or conical) the actual cutting edge of the tool m moves along a dotted line (Figure 40) and does not cut the hatched portion. Thus, according to the known solutions (FIG. 41), a method of correcting the radius of the tip of the tool is used; according to this method, the path c-% d described by the imaginary cutting edge W is calculated as the actual cutting edge moves between the points A and F on the inclined surface; this calculation is done from the X coordinates of the cutting point T, the starting point A and the end point F as well as the radius r of the tip of the tool to adjust the fictitious cutting edge W of the tool m to move it along a path through points a, c, d and f, and properly machine the inclined surface. The coordinates X and Z of the points c and d are calculated in the following way:

  If the X and Z coordinates of point A are

  the X and Z coordinates of the point F being equal to X (F) and Z (F) respectively, the X and Z coordinates of the point T are respectively equal to X (T) and Z (T) and if the radius

  the tip of the tool is equal to r, we have the following relationships

  v: X (a) = X (A) Z (a) = Z (T) X (c) = X (A) f2> 3 Xr {Z (A) -Z (F) + X (F) -X (A) (Z (A) -Z (F)) 2X-F) -X (A)) 2}

Z (c) = Z (A) -

X (F) - X (A)

  rr) + (X (F) -X (A "2 - = r - Z (A) -Z (F) + X (F) -X (A) - v (Z (A) -Z (Ffl2 + (X (F) -X (A>) 23 X (d) = X (F) - -_

Z (A) - Z (F)

Z (d) = Z (F) X (f) = X (T)

Z (f) = Z (F).

  Moreover, to machine a shape in which the inclined surfaces meet as in FIG.

  facilitate the description of two adjacent machining phases,

  one of the left side with respect to the axis of the part is called the first machining phase and the other second machining phase) the path a - d l - f 1 of the cutting edge is determined.

  imagination using the same method as that described above.

  above, using the data entered into the machine namely the X and Z coordinates of the cutting point T1, the starting point A1 and the arrival point F1 and the radius r of the tool. The path a2-c2 f2 'of the dummy cutting edge can be determined using the same method as described.

  above, using the input data, namely the coordinates

  X and Z of the T2 cutting point, the starting point A2 and the

  arrival point F2 and the radius r of the tip of the tool.

  The intersection Y between the extension of the line segment a1'-d1 and the line segment c2-f2 is then determined from the data of the two paths; then after deleting the previously determined starting point a1 'of the first machining phase and the finishing point f 2 of the second machining phase, the point Y is set as the new starting point a1 of the first phase of machining. machining and the end point f2 of the second machining phase. This moves the imaginary cutting edge of tool m along the path passing through the points

  a2, c2, f2, ai, d1 and fl for machining the workpiece to the desired shape.

  However, if the tool m. of the first machining phase and the tool m2 of the second machining phase are not the same tools and if the rays, r2 of the tip are different from each other, and if the want to machine a part having inclined surfaces which meet, the implementation of the method for obtaining chenin fictitious cutting edge would result that comna shown in Figure 43, the tool m2 would not move to the point of arrival corresponding to the second machining phase but leave uncut the hatched part inside the machining contour,

  overflowing with this hatched party.

  Therefore, the present invention uses the following method to determine the fictitious cutting edge displacement path, which path is necessary to cut during the second machining step using two types.

38 2480960

  tool having different tip radii.

  It is assumed that the tool mi of the second machining phase is used for the first and second phases as shown in FIGS. 45 and 48. It is further assumed that the radius r of the tip of the tool is equal Thus, according to the known methods, the displacement paths a2-c2 -f2 'and a1-d -f of the dummy cutting edge of the tool m2 are determined, which paths are necessary to cut off the using the m2 tool in the first and second machining phases; the displacement path a '-diff f is recorded in a temporary memory buffer of the microcomputer and the path of movement a2-c2-f2' in the normal buffer of the microcomputer. The shape (straight line, curve or incline) to be cut during each machining phase is determined using the data entered in the microcomputer, then we decide whether to find the intersection between the path of displacement of the dummy cutting edge during the first machining step and the cutting edge moving path for the second machining step. If necessary, the intersection Y between the extension of the line segment a1'-d1 and the line segment c2 f 2 'is determined on the basis of the data recorded in the provisional buffer and the normal buffer and the data of the point. f2 'arrival for the second machining phase, in the normal buffer, are deleted; point Y is recorded as new point f2 for the second

machining phase.

  Then, as shown in FIG. 46, it is assumed that the tool m1 of the first machining tool is used for

  first and second machining phases and we take r = r1.

  The paths of displacement a2- c2- f2 'and a1- d1 _f1 of

  the fictitious cutting edge of the tool mi, necessary for the machining

  of the ml tool in the first and second phases of

  are determined by the same process as in the example

  known as described above; after deleting the contents of the drum

  In the provisional manner of the microcomputer, the path of movement a2-c2-f2 'in the temporary buffer is determined while the path of movement at e-d1 f1 is stored in the normal buffer. The shape to be machined for each phase is determined

  machining using the data entered into the micro-

  calculator and it is decided whether it is necessary to find

  section between the path of movement of the cutting edge

  fictitious of the first phase of machining and the path of

  the fictitious cutting edge of the second machining phase.

  If necessary, the intersection Y between the extension of the line segment a1 '-d and the line segment C2-f2' is determined using the data recorded in the provisional buffer and the data recorded in the normal buffer; after erasing the data of the starting point a1 'of the first machining phase in the normal buffer, the point Y is recorded as the new starting point a1 of the first machining phase. In this way, we complete the recording of the displacement path al7-d-fl of the cutting edge Ictive of the first machining phase and the path of displacement a2 c = f2 of the fictitious cutting plate of the second stage of machining as shown in Figure 47. It is then sufficient to control the lathe for the dummy cutting edge of the second tool m2 moves along the path a2 c2- f2 and the cutting edge of the first tool m1 moves along the path all- d7 -f to perform precise machining with two tools with different peak radii in two phases

consecutive machining.

  In addition, in the foregoing description, the tool

  has been described as moving from right to left in each machining phase, that is, the starting point of each machining phase is on the right and the point

  arrival is on the left; in the case of a tool moves

  from left to right, the starting point is

  as the point of arrival and the point of arrival as a point

departure.

  Moreover, even in the case of the combination of an arc and an inclined curve or two arcs to be machined during two consecutive machining phases with two tools having different peak radii (FIG. and 50), the path of displacement ao ei f1 of the cutter is determined.

  fictitious of the first phase of machining and the path of

  a2 ^ if2 of the fictitious cutoff of the second machining phase using the same process as described above

  to precisely machine the workpiece to a given shape.

Claims (1)

R E V E N D I C A T I 0 N   A method of controlling a machine tool with a numerical control   to perform a copy machining process according to the-   all the data necessary for the control are introduced into the control device to prepare the machining data, the introduction being done using the keys of a keyboard of the control panel, characterized in that assimilates the shape to be machined to a continuous contour comprising in combination   simple shapes, each of which is machined in each phase of   travels thus machining during n machining phases by starting at one end of the form and ending at the other end, each phase corresponding to a simple shape, the starting point, the end point, the central point, the radius, etc ... of each machining step being calculated and the results recorded in a finishing buffer to form the instruction data for moving the finishing tool while the   coarse finish, the point of arrival, the central point   tral, the radius of each machining phase are calculated for each machining phase with a finishing tolerance that depends on the   simple form by adding the quantities recorded in the drum.   finishing for each machining phase, the results of the calculations serving as instruction data for moving the tool for rough finishing, and subtracting the cutting quantity during each machining phase from the tolerance of machining to obtain the coarse finishing tolerance which is then added to the value stored in the coarse finishing pad, starting successively at the last machining step so as to calculate the starting point of roughing the finishing point , the center point, the radius, etc., the results of the calculations being recorded in the roughing buffer, with update for   each machining phase to execute the roughing, this roughing   sizing being repeated a number of times equal to the quotient obtained by dividing the machining allowance by the size of the cut, coarse finishing machining being performed if the division   give a rest, then perform finishing machining.