CN104808581A - Compensation processing method for complicated face-type curved surface manufacture - Google Patents

Abstract

The invention provides a compensation processing method for complicated face-type curved surface manufacture, a processing lathe used by the method is provided with an in-situ measuring head. The method is as follows: performing the processing path design to the to-be-processed workpiece ideal model; processing the to-be-processed workpiece, performing the offline surface shape measurement after detaching the processed workpiece, and obtaining the surface shape error of the to-be-processed device; re-installing the to-be-processed workpiece on the processing lathe, and obtaining the position relation between the to-be-processed workpiece and the lathe processing coordinate system with the help of the in-situ measurement mode, namely the rotation matrix R and the translation matrix T; using the obtained rotation matrix R and translation matrix T to perform the coordinate conversion to the to-be-processed workpiece ideal model, obtaining new processing model after overlapping the surface shape error of the to-be-processed device, and performing the processing path design to the new processing model; and processing again. The method is capable of achieving the error compensation processing after the complicated face-type curved surface offline measurement.

Description

The compensation job operation that a kind of Surfaces of Unusual Shape curved surface manufactures

Art

The invention belongs to the Surfaces of Unusual Shape part by numerical control processing in advanced manufacture field, the manufacture of optical surface Free-form Surface Parts, relate to the high precision manufacture of Surfaces of Unusual Shape device.

Background technology

Surfaces of Unusual Shape curved surface refers to have the complex-curved arbitrarily of specific function, and it does not generally have the symmetrical feature of revolution, has the deformation of more face than traditional surface of revolution, therefore, it is possible to provide more design freedom for deviser and open one's minds.But Surfaces of Unusual Shape is manufacture process brings certain difficulty.Such as, in order to control higher machining precision in process, need to measure device, and carry out the compensation processing of mismachining tolerance according to measurement data.But because Surfaces of Unusual Shape curved surface does not have axis of symmetry and reference field, be difficult to after off-line measurement again playback in existing Cutter coordinate system by machinery adjustment.And because face type is complicated, small playback error can cause larger machining deviation amount.Design specialized fixture or extra reference point is generally needed to assist the adjustment of again playbacking.In addition, also have a kind of method to be adopt in-situ measuring method, namely measuring system is installed on machining tool, after process finishing, realizes the measurement of face shape error when not unloading device, thus avoid the difficult problem again playbacked.But because in-situ measurement system is placed oneself in the midst of in system of processing, the reaction of the error of lathe self not out, thus can not complete reacting processing error, is unfavorable for that machining precision controls.Therefore, need the high precision method for homing proposing a kind of simple possible badly, realize again playbacking after Surfaces of Unusual Shape curved surface device offline is measured and then compensating processing.

Summary of the invention

The present invention is intended to design the method for homing in a kind of Surfaces of Unusual Shape Machining of Curved Surface, ensures that Surfaces of Unusual Shape curved surface device is after lathe unloading, high-precisionly can be re-installed in lathe, thus realizes the processing of the error compensation after Surfaces of Unusual Shape curved surface off-line measurement.Technical scheme of the present invention is as follows:

The compensation job operation that Surfaces of Unusual Shape curved surface manufactures, the machining tool that the method adopts is equipped with in site measurement head, and method is as follows:

(1) machining path design is carried out to workpiece to be machined ideal model;

(2) workpiece to be machined is processed, carry out off-line surface shape measurement after being unloaded by workpiece after processing, obtain the face shape error of processed device;

(3) workpiece to be machined is re-installed in machining tool, and obtains the position relationship between workpiece to be machined and machine tooling coordinate system by site measurement mode, be i.e. rotation matrix R and translation matrix T;

(4) use the rotation matrix R obtained and translation matrix T to carry out coordinate transform to workpiece to be machined ideal model, and obtain new processing model after superposing the face shape error of processed device, machining path design is carried out to new processing model;

(5) again process, repeat (2)-(5) step until face shape error meets the demands.

Preferably, described in step (3) to obtain the process of the position relationship between workpiece to be machined and machine tooling coordinate system by site measurement mode as follows:

1) by site measurement head, point-to-point measurement is carried out to workpiece to be machined surface, obtain a series of measurement point p _i;

2) set initial rotation matrix R and translation matrix T, measurement point is carried out the conversion of six degree of freedom, set up the measurement data after adjustment and model data q _ithe minimum evaluation function of distance, the optimum using optimization algorithm to carry out rotation matrix R and the conversion of translation matrix T solves;

3) optimum solution of the rotation matrix R obtained after solving and the conversion of translation matrix T is the position relationship between workpiece to be machined and machine tooling coordinate system.

Step 2 wherein), the optimization algorithm of employing can be Gauss – Newton optimization algorithm or Levenberg – Marquardt optimization algorithm.

The present invention is directed to Surfaces of Unusual Shape high precision processing problems, propose the integrated compensation job operation in conjunction with off-line measurement and in-situ measuring method.Achieve by site measurement head and ressemble device high precision position location, and directly generate compensation machining path by the evolution of processing model, thus avoid the complicated processes needing complicated positioning fixture and equipment adjustment.

Again the playback method of assembling of the high precision of Surfaces of Unusual Shape device proposed by the invention is also used to many-sided.Such as, for the curved surface of large rise difference, consider the factor of working (machining) efficiency, need to consider that substep carries out roughing and finishing respectively on different machining tool, and by the playback of rough machined device degree of precision on high-accuracy machining tool, effectively to control unnecessary processing capacity, just need again to be installed location to Surfaces of Unusual Shape device.

Accompanying drawing explanation

Fig. 1 processing flow chart of the present invention

Measurement point and ideal model corresponding relation after Fig. 2 (a) playback

The deviate of measurement point and ideal model after Fig. 2 (b) playback

Embodiment

Fig. 1 is process flow diagram of the present invention.Carry out machining path design according to Surfaces of Unusual Shape curved surface device model, unload from lathe after device fabrication and carry out off-line measurement, obtain face shape error.Whether whether then ressemble on lathe by device, the installation of this process is random, need not pay close attention to consistent with the position before unloading.In site measurement head is utilized to measure the device after reinstalling, the position relationship both before and after being determined by the coupling of measurement data and ideal model.Here position relationship adopts rigid body translation matrix to describe, i.e. rotation matrix R and translation matrix T.General processed curved surface coordinate system is consistent with Cutter coordinate system.As long as determine again to be installed, the offset relation of rear curved surface and index plane type, just can determine the position relationship between Cutter coordinate system.Then after identical evolution (i.e. rotation matrix R and translation matrix T) being carried out to Surfaces of Unusual Shape surface model, and after adding face shape error, carry out the redesign of machining path, thus compensate processing.

In above treatment step, the position relationship between processed device and Cutter coordinate system is the six-freedom motion of a rigid body, i.e. rotation matrix R and translation matrix T.And the instrument of the offset relation of determine again to be installed rear curved surface and ideal model is the in-situ measurement system that can carry out surface shape measurement.Be processed as example with three axle ultra-precise cuttings, in typical optics Surfaces of Unusual Shape Machining of Curved Surface mode, in-situ measurement system is placed on machining tool, before processing, is guaranteed unanimously by adjustment between its surving coordinate system and Cutter coordinate system.The counterweight rear curved surface that is newly installed is measured, and obtains a series of measurement of curved surface point p _i, by solving the matching relationship of measurement of curved surface point and ideal model, the relation R of determine again to be installed rear curved surface and ideal model under surving coordinate system and T.The solving of matching relationship of measurement of curved surface point and ideal model is a vital step, and it is an optimization process.Measurement data p _ibe considered to rigid body, carry out rotation R and translation T convert whole optimizing and revising in process.Evaluation function setting principle in optimization adjustment is the measurement data p ' after adjustment _i=Rp _i+ T and ideal model data q _idistance minimum,

$F_{\mathrm{obj}}=\min \underset{R,T}{\mathrm{\Σ}}{\left|\right|{\mathrm{Rp}}_i+T-q_i\left|\right|}^2=\min \underset{R,T}{\mathrm{\Σ}}{\left|\right|p_i^{\′}-q_i\left|\right|}^2---\left(1\right)$

The method solving such problem is a lot, can adopt Gauss – Newton or Levenberg – Marquardt optimization algorithm etc.

At present, most of high-precision numerical control machine is all equipped with in-situ measurement system, is generally contact type measurement head, can realize carrying out point-to-point measurement operation to measurement component face type, is the important tool in the art of this patent.

In specific implementation process, to shape of a saddle Surfaces of Unusual Shape curved surface device (face type equation z=(x/51.3736) ²-(y/51.3736) ²) carrying out processing compensation experiment, curved surface bore is 40mm.After first time processing, opposite type utilizes off-line measurement device measuring, its face shape error peak-to-valley value is 4.047 μm, the in site measurement head using machining tool to carry afterwards is measured, evenly acquire 49 measurement points during measurement, solve by Levenberg – Marquardt optimization algorithm and determine its position relationship.Then again curved surface is measured again, sampling number increases to 309, these measurement points to be carried out after conversion directly according to position relationship and ideal model compares, comparative result as shown in Figure 2, can find out measurement point and ideal model consistance fine, and error deviation is about 4.495 μm, and the face shape error of off-line measurement is at an order of magnitude.Demonstrate the algorithm again playbacked and there is good precision and effect.After processing, its face shape error reaches 1.482 μm after compensating again.

Claims (3)

1. a compensation job operation for Surfaces of Unusual Shape curved surface manufacture, the machining tool that the method adopts is equipped with in site measurement head, and method is as follows:

(1) machining path design is carried out to workpiece to be machined ideal model;

(2) workpiece to be machined is processed, carry out off-line surface shape measurement after being unloaded by workpiece after processing, obtain the face shape error of processed device;

(3) workpiece to be machined is re-installed in machining tool, and obtains the position relationship between workpiece to be machined and machine tooling coordinate system by site measurement mode, be i.e. rotation matrix R and translation matrix T;

(4) use the rotation matrix R obtained and translation matrix T to carry out coordinate transform to workpiece to be machined ideal model, and obtain new processing model after superposing the face shape error of processed device, machining path design is carried out to new processing model;

(5) again process, repeat (2)-(5) step until face shape error meets the demands.

2. compensation job operation according to claim 1, is characterized in that, described in step (3) to obtain the process of the position relationship between workpiece to be machined and machine tooling coordinate system by site measurement mode as follows:

1) by site measurement head, point-to-point measurement is carried out to workpiece to be machined surface, obtain a series of measurement point p _i;

2) set initial rotation matrix R and translation matrix T, measurement point is carried out the conversion of six degree of freedom, set up the measurement data after adjustment and model data q _ithe minimum evaluation function of distance, the optimum using optimization algorithm to carry out rotation matrix R and the conversion of translation matrix T solves;

3) optimum solution of the rotation matrix R obtained after solving and the conversion of translation matrix T is the position relationship between workpiece to be machined and machine tooling coordinate system.

3. compensation job operation according to claim 2, is characterized in that, step 2) in, the optimization algorithm of employing can be Gauss – Newton optimization algorithm or Levenberg – Marquardt optimization algorithm.