CN1169652C - Control method of workpiece surface concave-convex shape during ball-end milling cutter machining - Google Patents

Abstract

The invention discloses a method for controlling the concave-convex shape of the surface of a workpiece during ball-end milling cutter processing, which belongs to the field of mechanical processing technology. For the CNC milling machine without circumferential positioning function, the present invention controls the cutting edge phase difference of the milling cutter during processing by controlling the moving distance of the milling cutter of the CNC milling machine under the condition of constant spindle speed and moving speed, thereby obtaining ideal processing The surface is uneven. Adopting the method of the present invention can obtain the regular concave-convex pattern of the machined surface. For the machined surface, the service life of the surface can be extended, the frictional resistance of the surface can be reduced, and the surface roughness can be reduced. Especially when the phase difference of the blade is 0°, the surface roughness It will reach the minimum value, which is 30% to 40% lower than the irregular surface roughness.

Description

Control method of workpiece surface concave-convex shape during ball-end milling cutter machining

technical field

The invention relates to a method for controlling the concave-convex pattern on the surface of a workpiece, in particular to a method for controlling the concave-convex pattern on the surface of the workpiece when a ball-end milling cutter is used, and belongs to the field of mechanical processing technology.

Background technique

In CNC milling, in order to improve the processing efficiency, while continuously increasing the spindle speed, the feed rate is also continuously increased, that is, the feed rate per revolution of the spindle is increased (hereinafter referred to as the feed rate per spindle revolution) as "feed rate"). The feed rate used in cutting abroad sometimes even reaches 0.4-0.5 mm/rev. After literature search, it was found that Zhao Minming and others wrote an article in "Journal of the Society of Precision Engineering" (Japan), 1998, 64 (12) 1826-1830, "5-axis Yuboyiruendomiru machining ni おける surface roughness generation mechanism (using ball end milling cutter The generation mechanism of surface roughness during 5-axis NC machining)", the paper proposes that if a ball end milling cutter is used, and when the feed rate of the spindle is large, the processing surface of the machining method so far will behave in the direction of the spindle feed The pits are connected one by one, and from the direction of intermittent feeding, the pits are staggered and arranged in disorder, that is to say, the concave-convex shape of the processed surface is irregular. Such a surface not only has a high surface roughness, but also has poor surface contact performance.

The difference ( i - i _-1 ) between the phase angle  _i of a certain edge of the milling cutter at the starting position of the i-th feed and the phase angle  _{i -1} of the previous feed is called the blade phase difference , represented by _i . The literature also proves through theoretical analysis and computer simulation that the "blade phase difference" at each feed is the main factor affecting the arrangement of concave-convex patterns on the machined surface. The pits that change according to the law of large-small-large-small appear in the feed direction, which is the result of the rotation eccentricity of the spindle during the machining process. If the rotation eccentricity of the spindle is small, the size of the pits in the feed direction will tend to be the same. If the blade phase difference can be properly controlled during processing, a uniform and regular concave-convex pattern will be processed, and the processed surface will have the advantages of prolonging the service life and reducing surface friction and roughness. However, the CNC milling machines used in actual processing generally do not have the function of circumferential positioning, that is to say, the phase difference of the blade for each feed cannot be set during the processing.

Contents of the invention

The purpose of the present invention is to fill up the vacancy in the prior art, and provide a method for controlling the concave-convex shape of the workpiece surface during processing with a ball end milling cutter. For a CNC milling machine without circumferential positioning function, control The phase difference of the cutting edge during processing results in an ideal concave-convex pattern on the processed surface. The present invention is realized through the following technical scheme, and the method of the present invention is as follows: the phase difference of the cutting edge is determined by the rotating speed of the main shaft, the moving speed and the moving distance of the milling cutter during the machining process. For the CNC milling machine without circumferential positioning function, under the condition of constant spindle speed and moving speed, by controlling the moving distance of the milling cutter of the CNC milling machine, the phase difference of the cutting edge of the milling cutter during processing is controlled, so as to obtain the ideal unevenness of the processed surface appearance.

The method of the present invention is further described as follows:

During the machining process, the milling cutter completes a cycle movement trajectory: the milling cutter first feeds the distance L _a , during this feeding process, the milling cutter cuts the workpiece, and then the milling cutter lifts up the distance L _b and retreats the distance L _c . Move the feed line distance L _d to the side, and then drop the distance L _e , assuming that the starting point of the milling cutter is A and B during the two feeds, then the moving distance between A and B is L _a mm, L _b mm, L _c mm, L _d mm and L _e mm, when the moving speed of the milling cutter in these five moving segments is v _a mm/min, v _b mm/min, v _c mm/min, v _d mm/min and v _e mm/min, when the spindle speed is n revolutions/min,

The time T required by the milling cutter between two feeds is:

The number of revolutions of the milling cutter between two feeds is:

M＝T·n＝M ₁ ·M ₂ (rotation) (2)

The number of revolutions M of the milling cutter is a positive real number, and the fractional part _M2 is the phase difference of the same cutting edge during two feeds.

Therefore, the phase difference ω of the blade during two feeds is:

ω＝360×M ₂ (°) (3)

From the above, it can be seen that under the condition that the spindle speed n and the feed speed v _a , v _b , v _c , v _d and v _e are constant, by adjusting the moving distance of the milling cutter L _a , L _b , L _c , L _d and L _e can adjust the phase difference ω of the cutting edge during the machining process, and as a result, the required concave-convex pattern of the machined surface can be obtained.

The milling machine adopted in the method of the present invention is a high-precision numerically controlled milling machine. If the numerically controlled milling machine used cannot move correctly according to the set spindle speed and feed speed, even if the moving distance of the milling cutter is adjusted according to the aforementioned method, the desired result may not be obtained. To be concave and convex. Therefore, the CNC milling machine used must be of high precision.

By adopting the method of the invention, regular concave-convex patterns on the processed surface can be obtained. This has the following three advantages for the machined surface: (1) Extend the service life of the surface: if the surface is the surface of the mold, it can make the surface of the mold more uniform when combined, thus increasing the wear resistance of the surface of the mold and prolonging the life of the surface. Service life; (2) Reduce the frictional resistance of the surface: If the surface is a guide rail surface, in addition to increasing the uniformity of bonding, these pits can also be used to store lubricating oil and reduce the frictional resistance of the guide rail; (3) Reduce surface roughness : When the cutting conditions are exactly the same, the surface roughness of uniform and regular concave-convex patterns is smaller than that of irregular concave-convex patterns, especially when the phase difference of the cutting edge is 0°, the surface roughness will reach the minimum value, which is higher than that of irregular concave-convex patterns. The surface roughness is reduced by 30% to 40%.

Description of drawings

Fig. 1 is a schematic diagram of the working principle of the present invention.

Detailed ways

As shown in Figure 1, in actual processing, since the feed distance L _a , retraction distance L _c and feed distance L _d of the milling cutter 1 are fixed, only the tool lift distance L _b and feed distance can be used. The tool distance L _e is used to adjust the moving distance of the milling cutter, and the tool lift distance L _b is equal to the tool feed distance L _e , that is to say, the desired concave-convex shape can be obtained by adjusting the tool lift distance.

Material of workpiece 2: brass; material of milling cutter 1: solid carbide, radius of milling cutter 1 is 5 mm; cutting depth of 0.2 mm; spindle speed n=250 rpm; inclination angle of milling cutter 1 is 15°; Feed speed v _a =v _b =v _c =v _d = _ve =250 mm/min; L _a =L _c =100 mm, L _d =0.5 mm.

(a) When L _b ＝L _e ＝0.750 mm, the blade phase difference ω＝0° is obtained from the formula (1) - formula (3). According to the actual processing results, the pits on the processing surface correspond neatly. The roughness of the machined surface is minimal.

(b) When L _b = L _e = 0.875 mm, the phase difference ω=90° of the blade is obtained from the formula (1) - formula (3). According to the actual processing results, the pit on the processing surface has a misalignment forward, The surface roughness is larger than that of the blade phase difference ω=0°.

(c) When L _b ＝L _e ＝1.000 mm, the blade phase difference ω＝180° is obtained from the formula (1) - formula (3). According to the actual processing results, the arrangement of the pits is just right when the front and rear feeds are twice on the contrary. That is to say, when the previous arrangement is "big → small → large → small", the next time is the arrangement of "small → large → small → large". Of course, when there is no eccentricity in the main shaft, the pits will be of the same size. At this time, the concave-convex pattern with the blade phase difference ω=180° is the same as the concave-convex pattern with ω=0°.

(d) When L _b = L _e = 1.125 mm, the phase difference of the blade is ω = 270° obtained from formula (1) - formula (3). According to the actual processing results, there is a displacement of the pit on the processing surface backward.

Claims (2)

1. A method for controlling the concave-convex shape of the workpiece surface during ball-end milling cutter processing, which is characterized in that for a CNC milling machine without circumferential positioning function, under the condition that the spindle speed and moving speed are constant, by controlling the CNC milling machine milling cutter (1 ) to control the edge phase difference of the milling cutter (1) during processing, so as to obtain an ideal concave-convex pattern on the processed surface. 2. The processing method according to claim 1, characterized in that the method is specifically as follows: during the processing, the milling cutter (1) completes a cycle of movement trajectory: the milling cutter (1) first feeds the distance L _a , and then mills The cutter (1) lifts up the distance L _b , retracts the distance L _c , moves to the side the feed distance L _d , and then falls the distance L _e . Let the starting point of the milling cutter (1) be A and B during the two feeds, Then the moving distance between A and B is the sum of L _a mm, L _b mm, L _c mm, L _d mm and L _e mm, when the moving speed of the main shaft in these five moving segments is v _a mm/min , v _b mm/min, v _c mm/min, v _d mm/min n and v _e mm/min, when the spindle speed is n revolutions/min, The time T required by the milling cutter (1) between two feeds is: $T=\frac{L_a}{v_a}+\frac{L_B}{v_b}+\frac{L_c}{v_c}+\frac{L_d}{v_d}+\frac{L_e}{v_e}$ (minute) The number of revolutions that the milling cutter (1) turns between two feeds is: M＝T·n＝M ₁ .M ₂ (turn) The number of revolutions M that the milling cutter (1) has turned is a positive real number, wherein the fractional part _M2 is the phase difference of the same cutting edge during two feedings. The phase difference ω of the blade during two feeds before and after is: ω＝360×M ₂ (°) Under the condition that the spindle speed n and the feed speed v _a , v _b , v _c , v _d and v _e are constant, by adjusting the moving distances L _a , L _b , L _c , L _d and L _e , can adjust the phase difference ω of the blade during the machining process, and as a result, the desired concave-convex pattern of the machined surface can be obtained.