In slow wire processing, we often face a series of problems such as wire breakage, reduced efficiency, abnormal precision, and cutting deformation. How to deal with these problems correctly often involves key details, and these details are often the tacit secrets of the masters, and they will not teach them all easily. This article will present you with various common problems in actual production and share master-level solutions.
01
What should I do if the wire breaks during slow wire processing?
Wire breakage is one of the most common problems in slow wire processing. When encountering broken wires, be careful not to adjust parameters blindly. On the contrary, the possible reasons for the broken wire should be carefully judged based on the processing conditions at that time, and then corresponding measures should be taken in a targeted manner.
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1) The upper surface of the cut parts has large fluctuations
Countermeasures: The upper surface of the cut parts has large fluctuations. The upper and lower water nozzles cannot be processed, and the high-pressure water cannot be flushed effectively, resulting in wire breakage. This situation occurs during rough machining. You can avoid wire breakage by reducing the discharge energy. Prioritize the reduction of the discharge power P value. When the wire is still broken after a large reduction, consider reducing the discharge current I. Lowering P will reduce some Processing efficiency, but reducing the discharge current will significantly reduce the processing efficiency.
2) Inability to effectively flush with high pressure
In 1), it is also the type that cannot achieve effective high-pressure flushing, but that is determined by the workpiece, and we cannot change the workpiece. In actual processing, there are many inefficiencies in high-pressure flushing that can be improved artificially. For example, if the distance between the upper nozzle and the upper surface of the workpiece is too large, this situation is wrong. The distance between the upper nozzle and the upper surface of the workpiece should be reduced as much as possible. For example, when processing a flat plate, the distance should be controlled to about 0.1mm; in addition, check Check whether the upper and lower water nozzles are damaged. If damaged, please replace them in time.
3) Improper electrical parameters
Countermeasures: Please carefully check whether the selected discharge parameters are correct, whether the wrong workpiece height, wrong electrode wire type, etc. are selected; if the discharge parameters themselves are not stable enough, they can be improved by reducing the P value and reducing the pulse discharge energy; in the parameters If the tension value is too large, the electrode wire will be broken and the wire tension will be reduced, especially in taper processing; if the wire speed is too low during rough processing, it will cause wire breakage. Adjust if necessary.
4) Quality issues of electrode wire and workpiece materials
Countermeasures: The quality of the electrode wire used is not good, the coils are overlaid, oxidized, etc. You should replace it with high-quality electrode wire; reduce the P and I values until the wire is broken.
5) The conductive block is severely worn or too dirty; the wire guide part is too dirty, causing wire scraping.
Countermeasures: Check the wear, surface roughness (oxidation), and connection condition of the conductive block and brush; clean, rotate or replace the conductive block; clean the guide wire components
6) The thread movement is unstable and the balance wheel vibrates greatly.
Countermeasures: Wire fluctuation. Use a tensiometer to check the tension of the electrode wire and make adjustments.
7) The waste wire in the waste wire barrel overflows and comes into contact with the machine tool or the ground, causing a short circuit.
Countermeasures: Put the overflowing waste silk back into the waste silk barrel, and clean the waste silk barrel in time.
02
What should I do if the slow wire processing efficiency is low?
1) No veneer processing, which reduces the P and I values
Countermeasures: Adjust the Z axis and try to process as close as possible. When the P value or I value must be reduced, it should be moderate and cannot be reduced too much.
2) Improper electrical parameters
Countermeasures: According to the processing requirements, select a reasonable process sequence file; check whether the ACO adaptive function is selected. When the cutting state is stable, you can cancel ACO; when there are many corners, the machine tool will use the corner strategy, and the corner strategy can be appropriately reduced according to the processing accuracy requirements. .
3) The workpiece is deformed and cannot be repaired by trimming; when repairing the mold, the main cutting speed is not limited and the repair speed is slow.
Countermeasures: Reasonably arrange the process to reduce material deformation; when repairing the mold, set a reasonable speed limit value for the main cutting to avoid being too fast and not cutting the allowance in place.
4) Main cutting efficiency is lower than before
Countermeasures: Carry out timely maintenance on machine tools. It is necessary to check whether the cooling water of the conductive block is normal; check whether the guide wheel rotates flexibly; whether the take-up wheel is normal; check the tension and speed of the wire, and readjust it if necessary; check and clean the guide nozzle and the conductive block.
03
How to prevent temperature differences from causing errors in slow wire processing?
1) The temperature range to ensure working accuracy for high-precision slow wire processing is 20±1º. If this condition cannot be reached, the most important condition is to control the temperature fluctuation range, which is preferably not to exceed ±3º.
2) Before working, the parts should be soaked or rinsed in the working fluid for a period of time, and then aligned and processed, which will help ensure accuracy.
3) Larger parts are best completed in one start-up. If the processing is stopped for a long time (such as one night), it will be difficult to ensure the processing accuracy. If the downtime during one processing exceeds two hours, water should be flushed for more than half an hour before continuing to process to reduce errors caused by temperature differences.
04
How to prevent cutting deformation when processing punches?
In actual production and processing, due to the residual stress deformation inside the workpiece blank and the thermal stress deformation caused by discharge, the threading hole should be processed first for closed cutting to avoid deformation caused by open cutting as much as possible.
If closed form cutting cannot be performed due to the size of the workpiece blank, for square blank parts, attention should be paid to selecting the cutting route (or cutting direction) during programming. The cutting route should be conducive to ensuring that the workpiece is always in the same coordinate system as the fixture (clamping support frame) during the processing process and avoids the influence of stress deformation. The clamp is fixed on the left end, and cutting is performed in counterclockwise direction from the left side of the gourd-shaped punch. The entire blank is divided into left and right parts according to the cutting route. As the material connecting the left and right sides of the blank becomes smaller and smaller as it is cut, the right side of the blank gradually separates from the clamp and cannot resist the internal residual stress and deforms, and the workpiece also deforms. If cutting in a clockwise direction, the workpiece remains on the left side of the blank, close to the clamping part. Most of the cutting process keeps the workpiece and the fixture in the same coordinate system, which results in better rigidity and avoids stress deformation. Generally speaking, a reasonable cutting route should arrange the cutting section that separates the workpiece from the clamping part at the end of the total cutting program, that is, the pause point (support part) should be left close to the clamping end of the blank.
05
What is the cutting process for high-precision multi-hole concave templates?
Before the high-precision multi-hole concave template is processed by slow wire cutting, the template has been cold processed and hot processed, and large residual stress has been generated internally. The residual stress is a relatively balanced stress system. When a large amount of waste is removed by wire cutting, Stress is released as equilibrium is disrupted. Therefore, when the template is processed by wire cutting, due to the effect of the original internal stress and the influence of the processing thermal stress generated by spark discharge, non-directional and irregular deformation will occur, making the subsequent cutting thickness uneven, affecting the Improve the processing quality and processing accuracy.
In response to this situation, for templates that require relatively high precision, 4 cuts are usually used. In the first cutting, the waste material of all the holes is cut off. After taking out the waste material, the automatic shifting function of the machine tool is used to complete the second, third and fourth cuttings. a cut for the 1st time, take the scrap → b cut for the 1st time, take the scrap → c cut for the 1st time, take the scrap →… → n cut for the 1st time, take the scrap → a cut for the 2nd time → b cut for the 2nd time → …→n cutting for the 2nd time→a cutting for the 3rd time→…→n cutting for the 3rd time→a cutting for the 4th time→…→n cutting for the 4th time, the processing is completed. This cutting method allows enough time for each hole to release the internal stress after processing, can minimize the mutual influence and trace deformation of each hole due to different processing sequences, and better ensure the processing size of the template. Accuracy. However, the processing time is too long, the number of wire threadings is large, and the workload is large, which increases the manufacturing cost of the template. In addition, the machine tool itself will also creep as the processing time increases and the temperature fluctuates. Therefore, based on actual measurement and comparison, if the processing accuracy of the template allows, the first unified processing can be used to keep the scrap unchanged, and the subsequent 2, 3, and 4 times can be combined for cutting (i.e., a cuts the second After the 3rd and 4th cuts without shifting or removing the wires→b→c…→n), or omit the 4th cut and make 3 cuts. After measurement, the shape and size basically meet the requirements after cutting. This not only improves production efficiency but also reduces labor, thus also reducing the manufacturing cost of the template.
06
How to arrange long-term unmanned operation of multi-cavity parts?
(1) For some multi-cavity parts with relatively large cutting workload, they can be processed at night with unmanned operation, which can save costs and increase the utilization rate of machine tools. Multiple cavities must set their own pause allowances, leaving a section uncut to ensure that the parts do not fall off. The remaining contours are cut multiple times to meet the processing requirements. When the pause allowance position is reached, the machine tool automatically cuts the wire and moves to the next step. At the position of the wire threading hole in the cavity, the machine tool automatically threads the wire and then continues processing. The processes of wire cutting, shifting, wire threading, and processing are performed multiple times until all cavities are processed. In this way, there will be no material core falling during the cutting process, and no personnel intervention is required. Cutting and picking up materials will be carried out with the intervention of personnel to complete the processing of the paused section. In order to ensure the smooth progress of automatic wire threading during processing, the diameter of the wire threading hole should be as large as possible.
(2) For the processing of multiple small cavities, since the material core is relatively small, it is inconvenient to set the dwell amount, and short circuits are prone to occur. The coreless cutting method can be used to achieve the purpose of leaving the machine unattended.
