CN1418758A - Working method of linear cutting high precision double plane runin different plane - Google Patents

Abstract

The present invention provides a double-plane interpolation non-aniplanar machining method, and the correspondent control software also is designed according to said method. For upper surface and undersurface of workpiece to be machined it can respectively make drawing, interpolation and calculation so as to ensure the uniformity of upper surface and undersurface machining speed. Said method can be used for machining control of workpiece cone linear cutting, can raise its machining accuracy and cutting efficiency.

Description

High-precision double-plane interpolation different-plane machining method for wire cutting

Technical field

The method belongs to the wire cutting numerical control processing technology in a computer numerical control (CNC) system.

Background technique

Multi-axis linkage different-surface machining technology is an important development direction of computer numerical control. At present, the technical level of domestic wire-cut CNC machine tools is still relatively high in terms of machinery, and the cutting accuracy of large-taper molds has also been greatly improved. However, the development of control technology is relatively lagging behind. Although most domestic control systems can support four-axis linkage processing, the accuracy is good when processing taper workpieces with the same shape on the upper and lower surfaces, but the effect is not ideal when processing different-surface workpieces with different sizes and shapes on the upper and lower surfaces. If the requirements are not met, even the arc becomes a broken line. The root cause is that the control method has shortcomings. For example, there are currently two commonly used methods for wire cutting taper processing: ①The stepping angle follow-up method; ②UV proportional follow-up method. Its working principle is basically to use the same model, that is, only interpolation control is performed on the lower plane of the workpiece, and the upper plane of the workpiece is followed. For the lower plane, due to the direct interpolation control, the machining accuracy is higher; however, the error of the upper surface is equal to the sum of β times the original upper surface machining error and the lower surface error, resulting in a greatly reduced machining accuracy of the upper surface.

There is also a third taper processing control method for wire cutting CNC machine tools, that is, the four-dimensional trajectory linear linkage method. Although this third processing control method can process workpieces with different surfaces, the accuracy error is added to the original basis and comes from the linearization calculation of the arc, which further reduces the processing accuracy, and the number of entire curve processing programs after linearization If it is too large, it is not easy to improve efficiency.

Contents of the invention

The present invention aims at the deficiencies of the current high-precision machining control methods of wire cutting, and proposes a dual-plane interpolation and different-plane machining method, which can respectively draw, interpolate and calculate the upper surface and the lower surface of the workpiece to be processed, ensuring It ensures the uniform processing speed of the upper and lower surfaces, and greatly improves the processing accuracy and cutting efficiency.

The technical solution adopted by the present invention to solve its technical problems is:

(1) Draw the graphics of the upper surface and the lower surface of the workpiece respectively, and correspond to each segment;

(2) Perform interpolation according to the graphics of the upper and lower surfaces of the workpiece in the corresponding segment—two-plane interpolation. In the interpolation process, whether it is an interpolation step on the upper plane of the workpiece or a step on the lower plane, it must be converted into the number of feed steps of the XY carriage and UV carriage;

(3) When performing proportional conversion, the feed of the upper and lower surfaces is based on a μ, so the feed of XY and UV has decimals in addition to the integer part, and the decimals are accumulated. When the decimal is full of one μ, it is supplemented. Give;

(4) In the corresponding section of the upper and lower planes, the coordination function is properly selected to achieve the uniform processing speed of the upper and lower surfaces. In this way, the shape and size of the workpiece processed are consistent with the drawing, and the side transition is smooth, meeting the high-precision requirements.

We designed and produced corresponding control software according to the method of double-plane interpolation and different-plane machining. It has been proved by practice that using this method to control the processing of workpiece taper wire cutting overcomes the shortcomings of the original processing method and greatly improves the processing accuracy and cutting efficiency. In addition, the machining accuracy of the upper and lower planes is also high when machining different surfaces of the workpiece.

Description of drawings

Figure 1 is a schematic diagram of wire cutting CNC machining process. A hardware control card is inserted into the existing microcomputer, and the processing control software sends XY and UV four-axis control signals through the control card. After the signal is amplified and processed, it drives the stepping motor of the machine tool to work, so that the XY and UV carriages on the machine tool work as Relative movement, that is, the relative movement between the workpiece and the molybdenum wire. In addition, a high-frequency power supply is added between the workpiece and the molybdenum wire, and the workpiece is cut by the electric spark discharge between them.

Figure 2 is a schematic diagram of the interpolation calculation method for the lower surface.

Figure 3 is a schematic diagram of the upper surface interpolation calculation method.

Detailed ways

The control software realizes the wire-cut EDM through the hardware control card and the drive power supply. The implementation process of the control software is as follows: 1. According to the workpiece drawing, draw different two-dimensional graphics on the upper and lower parts of the workpiece and mark the corresponding relationship. 2. The XY plane and UV plane form their respective processing programs. 3. Coordinated interpolation function for upper and lower surfaces

(a) Selection of coordination function

In the process of processing, in the corresponding sections of the upper surface and the lower surface, the interpolation feed should be carried out evenly according to a certain proportional relationship, and finally the upper and lower corresponding sections can be fed at the same time.

Define the following five parameters:

S _is the total number of interpolation feeds on the upper surface;

_Under S is the total number of interpolation feeds for the lower surface;

_Sup ' is the number of interpolation feed steps on the current upper surface;

S_下' is the number of interpolation feed steps for the current lower surface;

S _J is the total number of interpolation steps between the upper and lower surfaces (S _J = S _up + S _down )

即S_下S_上’-S_上S_下’＞0，则应该进行下表面的插补进给。因此，可以设协调函数为F_S＝S_下S_上’-S_上S_下’，来控制上下表面的插补进给的按比例进行。During processing, if the That is, S _lower S _upper' -S _upper S _lower '=0, it can ensure that the interpolation feed of the upper and lower surfaces is carried out evenly in proportion, if

That is, S _lower S _upper' -S _upper S _lower '>0, then the interpolation feed of the lower surface should be performed. Therefore, the coordination function can be set as F _S =S _lower S _upper' -S _upper S _lower ' to control the proportionality of the interpolation feed of the upper and lower surfaces.

When F _S ≥ 0, the interpolation feed of the lower surface;

When F _S <0, the upper surface interpolation feed.

(b) Calculation of coordination function

After one step of interpolation on the lower surface,

S _next '←S _next '+1

S _down S _up' -S _up (S _down '+1)=S _down S _up' -S _up S _down' -S _up

That is, the calculation formula of F _S is: F _S ←F _S -S When the _upper surface is interpolated for one step,

_Sup '← _Sup '+1

S _down (S _up '+1)-S _up, S _down '=S _down, S _up' -S _up , S _down '+S _down

That is, the calculation formula of F _S is: F _S ← F _S + _S 4. Lower surface interpolation calculation

When interpolating the feed of the lower surface, the position of the intersection point between the electrode wire and the upper surface should be kept unchanged, as shown in Figure 2, the feed amount of the lower surface is ΔD, and the feed amount of the electrode wire driven by the XY carriage is ΔX, UV The feed rate of the electrode wire driven by the carriage is ΔU. According to the geometric relationship, the feed rate of the XY carriage and UV carriage can be calculated by the following formula:

ΔX＝ΔD×(h+ _H )/h

ΔU=ΔD× _Hup /h (the direction of ΔU is opposite to the direction of ΔX). Considering that the movement of the XY carriage is actually the movement of the workpiece, the position of the UV carriage and the workpiece are also moving relative to each other. Therefore, in the direction of ΔU (in the opposite direction to ΔX) plus the displacement of ΔX, that is

          ΔU = ΔU + ΔX5. Upper surface interpolation calculation

When the upper surface is interpolated to feed, the position of the intersection point between the electrode wire and the lower surface should be kept unchanged, as shown in Figure 2(b), the feed amount of the upper surface is set to ΔD, and the XY carriage drives the electrode wire to advance The feeding amount ΔX, the feeding amount of the electrode wire driven by the UV carriage is ΔU. According to the geometric relationship, the feed amount of the XY carriage and the UV carriage can be calculated by the following formula:

ΔX=ΔD×H/ _h

ΔU=ΔD×(h+ _H )/h+ΔX6. Error processing

The feed rate of XY carriage and UV carriage is the result obtained according to the proportional formula, not necessarily an integer value. But the actual number of feed steps can only be represented by integers, so during the feed process, the decimal places of the feed must be accumulated and processed.

For example, H _down = 37.5mm, h = 32mm, H _up = 53.5mm, when the lower surface is interpolated one step, that is, ΔD = 1μ:

ΔX=ΔD×(h+ _H )/h=1μ×(32+37.5)/32=2.172μ

   ΔU＝ΔD×Hup/h+ΔX＝1μ×5.35/32+2.172μ＝3.844μ

At this time, the XY carriage feeds 2μ in the X direction, and the UV carriage feeds 3μ in the U direction. After the XY carriage and the UV carriage alternately feed, the remaining feed amounts of 0.172μ and 0.844μ are respectively added to the X direction. and the error register in the U direction, and judge whether the value in the error register is greater than 1μ, if the condition is met, then advance one step in the X direction or U direction accordingly, and subtract 1μ from the error register, if it is less than 1μ, continue For the following interpolation feed, the error must be accumulated after each feed, and the value of the error register must be judged to decide whether to feed. In this way, the error range can be controlled within 1μ. After this treatment, not only the speed of processing is improved, but also the precision of processing can be improved.

Claims (2)

1. a line cuts high accuracy biplane interpolation antarafacial processing method, it is characterized in that: in the corresponding section of last lower plane, suitably selecting coordination function to carry out interpolation calculates to realize the even of upper and lower surface process velocity, concrete drafting, interpolation, calculating and processing method are: (a) draw the figure of workpiece surface and lower surface respectively, and the segmentation correspondence;

(b) in corresponding section respectively the figure by the upper and lower surface of workpiece carry out interpolation, in the interpolation process, no matter be one step of plane interpolation on the workpiece, still one step of lower plane interpolation, all will be its conversion feeding step number that is XY planker and UV planker;

(c) carrying out ratio when conversion, is to be unit with μ of upper and lower surface feeding, so the feeding step number of XY and UV except integer part, also has decimal, its decimal place is accumulated processing, replenishes feeding when the full μ of decimal.

2. line cutting high accuracy biplane interpolation antarafacial processing method according to claim 1, it is characterized in that above-mentioned processing method sends the four spool control signals of software to XY and UV by control card, signal is handled the work of rear drive lathe stepper motor through amplifying, thereby makes XY on the lathe, UV planker do relative motion.

Images