Background technology
General little cutting-in, low feeding and the high rotating speed of adopting of single-point diamond turning processing, to guarantee nano level surface roughness, but material is removed and the surperficial very complexity of mechanism that forms in the process, at present, in single-point diamond turning processing in the surface roughness Study on Forecast, the basic thought of setting up shaggy Forecasting Methodology based on cutting theory is based under certain assumed condition theoretical roughness of surface and cutter is superposeed with relative vibration between workpiece, and there is following problem in existing Forecasting Methodology:
1, the relative vibration between cutter and workpiece is in lathe idle running and do not carry out predicting under the machining condition, so it can not be reflected in the relative vibration information between cutter and workpiece in the actual processing really.
2, material behavior and the cutting parameter influence to vibrating that does not have consideration to be cut to cutter and workpiece.
3, the calculating of theoretical roughness of surface is considered from geometric point of view purely, but in the actual working angles, because complicated variations such as the elasticity that material takes place recovery and plastic deformation, the height of the residual region of the reflection reality that the theoretical roughness of surface that calculates from geometric angle can not be correct purely.
4, do not consider that material behavior and cutting parameter recover elasticity in the working angles and the influence of plastic deformation.
Because the existence of the problems referred to above, the predicated error of existing Forecasting Methodology is bigger, and the predicated error of Ra value is about 10%.
Summary of the invention
The present invention has the bigger problem of surface roughness Forecasting Methodology error now for solving, and then proposes the Forecasting Methodology of surface roughness in a kind of single-point diamond turning processing.
The present invention addresses the above problem the technical scheme of being taked to be: the establishment step of the Forecasting Methodology of a kind of single-point diamond turning machined surface roughness of the present invention is as follows:
Step 1, choose typical workpiece for measurement material, change feeding rotating speed, the speed of mainshaft and back engagement of the cutting edge contrived experiment scheme, on ultra-precision machine tool, carry out single-point diamond machining experiment in advance;
Step 2, the surface outline curves that adopts the prediction of contact pin type contourgraph to process typical workpiece for measurement;
Step 3, extract the process amplitude information of relative vibration between cutter and workpiece from the testing result of machined surface, the amplitude information of relative vibration obtains by the following method between described cutter and workpiece:
Step 3 (one), according to the surface outline curves and the data that detect, outermost with the processing work end face is that radial diameter maximum place is that initial point is set up X, Z coordinate system, extract point of a knife and radially representing in the actual process the relative reflection of vibrating radially between cutter and workpiece with respect to the profile of workpiece, X-direction is the tool feeding direction, Z-direction is a cutter cutting-in direction, and then radially the number of cutter profile is:
Wherein L is for radially detecting length, and s is the amount of feeding of cutter revolution, and the number that extracts data from the detection curve of machined surface also is N;
Coordinate is x on the X-axis of step 3 (two), extraction data
i=x
1+ (i-1) Δ x=x
1+ (i-1) s (2), i=1 wherein, 2 ..., N, thus the point of a knife coordinate data that can obtain extracting is (x
i, Z
i(x
i)), the contour curve of relative vibration is between the cutter that extracts from machined surface and workpiece: Z
m(x
i)=Z
i(x
i)-min (Z
i(x
i)) (3), i=1 wherein, 2 ..., N-1, the surface roughness that the contour curve of above-mentioned relative vibration causes:
I=1 wherein, 2 ..., N;
Step 3 (three), the relative vibration equivalence between cutter and workpiece is simple harmonic oscillation, the equation of establishing its simple harmonic oscillation is:
Its discretization can be obtained:
Δ x=1/40f wherein, i=1,2 ..., N, N=L/ Δ x, the surface roughness that then equivalent simple harmonic oscillation causes is:
The relative vibration equivalence is that two to vibrate the surface roughness that causes identical for the principle of simple harmonic oscillation between cutter and workpiece, i.e. Ra
h=Ra
m(8);
Equivalent amplitude is found the solution in step 3 (four), through type (4), (7) and (8)
Value,
Be in the actual processing amplitude information of relative vibration between cutter and workpiece;
Step 4, calculate expansion ratio, expansion ratio is the ratio that expands the height of the residual region after the effect and do not expand the residual region height of effect, promptly
H in the formula
RiBe the residual height of i tool margin after expanding effect on the finished surface, H
cBe the theoretical residual height that does not expand the effect tool margin, i=1 wherein, 2 ..., n;
Step 5, calculate the contour curve expand finished surface after the effect, the height that expands tool margin residual region in the contour curve of finished surface after the effect is H
cSP;
Step 6, find corresponding equivalent amplitude by the particular process material and the speed of mainshaft, thereby obtain the equivalence oscillating curve relatively between cutter, workpiece, the equivalence between cutter, workpiece oscillating curve relatively is:
Step 7, by matlab software the relative oscillating curve of equivalence in the contour curve that expands finished surface after the effect in the step 5 and the step 6 being superposeed to obtain new surface outline curves, new curve is carried out the data processing calculate surface roughness.
The invention has the beneficial effects as follows: the present invention extracts the relative vibration information of cutter and Tool Room from machined surface, and consideration bulking effect his-and-hers watches The surface roughness affected, the notion of expansion ratio is proposed, thereby effectively improved the precision of prediction of surface roughness, the consensus forecast error of Ra value is 5.1%.
Description of drawings
Fig. 1 extracts nose profile curve and data from machined surface, Fig. 2 is that (a represents to take place the finished surface after elasticity is recovered to bulking effect his-and-hers watches The surface roughness affected, b represents to take place the finished surface after plasticity flows, c representation theory finished surface), Fig. 3 is the theoretical finished surface (amount of feeding of s-revolution, R-cutter radius of corner, Rt-is the residual height of tool margin ideally), Fig. 4 is the flow chart of Roughness Model, Fig. 5 is the ideal surfaced under the machined parameters among the embodiment one, Fig. 6 is the detection surface of NiP, Fig. 7 is the detection surface of Cu, Fig. 8 is to be 1000r/min in the speed of mainshaft, back engagement of the cutting edge is 2 μ m, under the different feed speeds, (dotted line is a predicted value in the contrast of caluclate table surface roughness and real surface roughness, solid line is a predicted value), Fig. 9 is to be 1000r/min in the speed of mainshaft, feed speed is 40mm/min, under different back engagement of the cutting edge, (dotted line is a predicted value in the contrast of caluclate table surface roughness and real surface roughness, solid line is a predicted value) Figure 10 is that outermost with the processing work end face is that radial diameter maximum place is that initial point is set up X, (wherein A is a cutting direction to the Z coordinate system, B is a direction of feed, C is a cutter, workpiece vibrates relatively, D is a workpiece, and E is a diamond cutter).
The specific embodiment
The specific embodiment one: shown in Fig. 1-10, the establishment step of the described a kind of single-point diamond turning machined surface roughness Forecasting Methodology of present embodiment is as follows:
Step 1, choose typical workpiece for measurement material, change feeding rotating speed, the speed of mainshaft and back engagement of the cutting edge contrived experiment scheme, on ultra-precision machine tool, carry out single-point diamond machining experiment in advance;
Step 2, the surface outline curves that adopts the prediction of contact pin type contourgraph to process typical workpiece for measurement;
Step 3, extract the process amplitude information of relative vibration between cutter and workpiece from the testing result of machined surface, the amplitude information of relative vibration obtains by the following method between described cutter and workpiece:
Step 3 (one), according to the surface outline curves and the data that detect, outermost with the processing work end face is that radial diameter maximum place is that initial point is set up X, Z coordinate system, extract point of a knife and radially representing in the actual process the relative reflection of vibrating radially between cutter and workpiece with respect to the profile of workpiece, X-direction is the tool feeding direction, Z-direction is a cutter cutting-in direction, and then radially the number of cutter profile is:
Wherein L is for radially detecting length, and s is the amount of feeding of cutter revolution, and the number that extracts data from the detection curve of machined surface also is N;
Coordinate is x on the X-axis of step 3 (two), extraction data
i=x
1+ (i-1) Δ x=x
1+ (i-1) s (2), i=1 wherein, 2 ..., N, thus the point of a knife coordinate data that can obtain extracting is (x
i, Z
i(x
i)), the contour curve of relative vibration is between the cutter that extracts from machined surface and workpiece: Z
m(x
i)=Z
i(x
i)-min (Z
i(x
i)) (3), i=1 wherein, 2 ..., N-1, the surface roughness that the contour curve of above-mentioned relative vibration causes:
I=1 wherein, 2 ..., N;
Step 3 (three), the relative vibration equivalence between cutter and workpiece is simple harmonic oscillation, the equation of establishing its simple harmonic oscillation is:
Its discretization can be obtained:
Δ x=1/40f wherein, i=1,2 ..., N, N=L/ Δ x, the surface roughness that then equivalent simple harmonic oscillation causes is:
The relative vibration equivalence is that two to vibrate the surface roughness that causes identical for the principle of simple harmonic oscillation between cutter and workpiece, i.e. Ra
h=Ra
m(8);
Equivalent amplitude is found the solution in step 3 (four), through type (4), (7) and (8)
Value,
Be in the actual processing amplitude information of relative vibration between cutter and workpiece;
Step 4, calculate expansion ratio, expansion ratio is the ratio that expands the height of the residual region after the effect and do not expand the residual region height of effect, promptly
H in the formula
RiBe the residual height of i tool margin after expanding effect on the finished surface, H
cBe the theoretical residual height that does not expand the effect tool margin, i=1 wherein, 2 ..., n;
Step 5, calculate the contour curve expand finished surface after the effect, the height that expands tool margin residual region in the contour curve of finished surface after the effect is H
cSP;
Step 6, find corresponding equivalent amplitude by the particular process material and the speed of mainshaft, thereby obtain the equivalence oscillating curve relatively between cutter, workpiece, the equivalence between cutter, workpiece oscillating curve relatively is:
Step 7, by matlab software the relative oscillating curve of equivalence in the contour curve that expands finished surface after the effect in the step 5 and the step 6 being superposeed to obtain new surface outline curves, new curve is carried out the data processing calculate surface roughness.
The software of matlab described in the present embodiment is main in the face of science is calculated, the high-tech computer software of visual and interactive program design by U.S. mathworks company issue.
The specific embodiment two
At rotating speed is 1000r/min, back engagement of the
cutting edge 2 μ m, and feed speed is under the condition of 25mm/min, for NiP, extracts relative vibration amplitude information
Be 5nm,, extract relative vibration amplitude information for Cu
Be 15nm, by
Calculate equivalence vibration relatively;
Shown in Fig. 5-7, calculate expansion ratio SP, under this processing conditions, the expansion ratio SP of NiP is 1.3, the expansion ratio SP of Cu is 0.65, calculates the contour curve that expands finished surface after the effect;
The superpose line data processing calculating of going forward side by side of the contour curve that will expand finished surface after the effect by matlab software and the relative vibration of equivalence can be predicted the outcome, predict the outcome with actual result to such as Fig. 8 and Fig. 9;
Shown in Fig. 8-9, NiP and Cu process under the same conditions, identical lathe, identical cutter, identical machined parameters, different places are properties of materials, and actual processing result all has certain departing from for theoretical value, and main cause just is that bulking effect has changed the size of theoretical roughness of surface, under the identical condition, the surface roughness of NiP and Cu differs bigger, and this shows in the surface roughness Forecasting Methodology, must consider the influence of bulking effect.