CNC Knowledge: Here are all the slow thread processing techniques that the masters don’t teach you!

When processing wire slowly, we often encounter a series of problems such as wire breakage, reduced efficiency, abnormal precision and cutting deformation. How to properly solve these problems often involves key details, and these details are often the unspoken secrets of the masters, and they will not learn them all easily. This article will introduce you to various common problems in real production and share master-level solutions.

01 What should I do if the old thread breaks during slow thread processing?
Wire breakage is one of the most common problems during slow wire processing. When encountering broken wires, be careful not to adjust settings blindly. On the contrary, the possible causes of wire breakage should be carefully evaluated according to the processing conditions at that time, and then corresponding measures should be taken in a targeted manner.

1) The upper surface of the cut pieces has large fluctuations
Countermeasures: The upper surface of the cut pieces 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. Give priority to reducing the P value of discharge power. When the wire is still broken after large reduction, consider reducing the discharge current I. Lowering P will reduce. some processing efficiency, but reducing the discharge current will greatly reduce the processing efficiency.
2) Inability to flush effectively at high pressure
In 1), it is also the type that cannot achieve effective high pressure flushing, but is determined by the workpiece, and we cannot change the workpiece. In actual treatment, there are many inefficiencies of high-pressure flushing that can be improved artificially. For example, if the distance between the upper nozzle and the upper surface of the part is too large, this situation is incorrect. The distance between the upper nozzle and the upper surface of the workpiece should be reduced as much as possible. When processing a flat plate, the distance should be controlled at about 0.1mm. Additionally, check whether the upper and lower water nozzles are damaged. If they are damaged, please replace them in time.
3) Incorrect electrical settings
Countermeasures: Please carefully check whether the selected discharge parameters are correct, 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. pulse discharge energy; in the settings. If the voltage value is too large, the electrode wire will be broken and the wire tension will be reduced, especially during taper processing, if the wire speed is too low during coarse processing, it will cause wire runoff; break. Adjust if necessary.
4) Quality problems of electrode wire and workpiece materials
Countermeasures: The quality of the electrode wire used is not good, the coils are overlapped, oxidized, etc. You need to replace it with high quality electrode wire; reduce the P and I values ​​until the wire is broken.
5) The conductor block is very worn or too dirty; the thread guide part is too dirty, causing the thread to scratch.
Countermeasures: Check the wear, surface roughness (oxidation) and connection condition of the conductor block and brush; clean, rotate or replace the driver block; clean the guide wire components;
6) The movement of the wire is unstable and the pendulum vibrates strongly.
Countermeasures: Wire fluctuation. Use a tension meter to check the tension of the electrode wire and make adjustments.
7) The waste wire in the waste wire barrel overflows and contacts the machine tool or ground, causing a short circuit.
Countermeasures: Return the overflowing waste silk to the waste silk barrel and clean the waste silk barrel in time.
02 What should I do if the efficiency of slow yarn processing is low?
1) No plating treatment, which reduces P and I values
Countermeasures: Adjust the Z axis and try to process as close as possible. When the P value or I value needs to be reduced, it should be moderate and cannot be reduced too much.
2) Incorrect electrical settings
Countermeasures: According to the processing requirements, select a reasonable process sequence file; check if the ACO adaptive function is selected. When the cutting state is stable, you can cancel the 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 precision requirements.
3) The part is deformed and cannot be repaired by cutting; when repairing the mold, the main cutting speed is not limited and the repair speed is slow.
Countermeasures: reasonably organize 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 margin in place.
4) The main cutting efficiency is lower than before
Countermeasures: Perform timely maintenance on machine tools. It is necessary to check whether the cooling water of the driver block is normal; check whether the guide wheel rotates smoothly; if the receiving wheel is normal; check and readjust if necessary; clean the guide nozzle and the conductor block.
03How to prevent temperature differences from causing errors during slow wire processing?
1) The temperature range ensuring working precision for slow processing of high precision wire is 20±1°. If this condition cannot be achieved, the most important condition is to control the temperature fluctuation range, which should preferably not exceed ±3°.
2) Before working, the parts should be soaked or rinsed in the working fluid for a period of time, then aligned and processed, which will help ensure accuracy.
3) It is better to make larger pieces in one start. If treatment is stopped for a long time (for example overnight), it will be difficult to ensure treatment accuracy. If the downtime during a treatment exceeds two hours, the water should be flushed for more than half an hour before continuing the treatment to reduce errors caused by temperature differences. 04How to avoid cutting deformation during punch processing?
In actual production and processing, due to the residual stress deformation inside the workpiece blank and the thermal stress deformation caused by discharge, the thread hole should be processed first for a closed cutting to avoid deformation caused by open cutting as much as possible.
If closed shape cutting cannot be performed due to the size of the blank, for square blanks, attention should be paid to the selection of the cutting route (or cutting direction) when of programming. The cutting route should ensure that the workpiece is always in the same coordinate system as the fixture (clamping support frame) during the processing process and avoid the influence of stress deformation . The pliers are attached to the left end and cutting is done counterclockwise 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 withstand the stress internal residual and deforms, and the part also deforms. If you cut clockwise, the workpiece remains on the left side of the blank, near the clamping part. Most of the cutting process keeps the part and fixture in the same coordinate system, resulting in better rigidity and avoiding stress deformation. . Generally speaking, a reasonable cutting route should arrange the cutting section that separates the workpiece from the workpiece at the end of the total cutting program, i.e. the break point (part of support) should be left near the clamping end of the blank. . 05What is the cutting process of high precision multi-hole concave jig?
Before the high-precision multi-hole concave jig was processed by slow wire cutting, the jig was cold and hot processed, and large residual stress was generated internally. Residual stress is a relatively balanced stress system. waste is eliminated by wire cutting. Constraints are released when balance is disrupted. Therefore, when the jig is processed by wire cutting, due to the effect of the original internal stress and the influence of processing thermal stress generated by spark discharge, non-directional deformation and irregular will occur, making the subsequent cutting thickness uneven, affecting Improve processing quality and precision.
In response to this situation, for jigs that require relatively high precision, 4 cuts are generally used. During the first cut, the waste from all holes is cut off. After removing the waste, the automatic moving function of the machine tool is used to complete the second, third and fourth cuts. a cut for the 1st time, take the debris → b cut for the 1st time, take the debris → c cut for the 1st time, take the debris →… → n cut for the 1st time, take the debris → a cut for the 2nd time → b cut for the 2nd time → …→n cut for the 2nd time→a cut for the 3rd time→…→cut for the 3rd time→cut for the 4th time→…→cut for the 4th time, the treatment is completed. This cutting method allows each hole enough time to release internal stress after processing, can minimize the mutual influence and trace the deformation of each hole due to different processing sequences, and better guarantee the processing size of the model. However, the processing time is too long, the number of threadings is large, and the workload is large, which increases the manufacturing cost of the template. In addition, the machine tool itself also fluctuates as the processing time increases and the temperature fluctuates. Therefore, based on the actual measurements and comparisons, if the processing accuracy of the template allows, the first unified processing can be used to keep the scraps unchanged, and the following 2, 3 and 4 steps can be combined for the cutting (i.e. cut the second after the 3rd and 4th cuts without moving 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, thereby also reducing the manufacturing cost of the model.
06How to organize 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 reduce costs and increase the utilization rate of machine tools. Multiple cavities must set their own break tolerances, leaving a section uncut to ensure parts don’t fall out. The remaining contours are cut several times to meet the processing requirements. When the pause tolerance position is reached, the machine tool cuts automatically. thread and move on 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 cutting, moving, threading and processing the wire are carried out several times until all cavities are processed. In this way, no material cores will fall during the cutting process and no personnel intervention will be necessary. The cutting and collection of materials will be carried out with the intervention of staff, and the processing of the paused section will be completed. In order to ensure that the automatic threading of the thread runs smoothly during processing, the diameter of the thread threading hole should be as large as possible.
(2) For the processing of multiple small cavities, because the core of the material is relatively small, it is inconvenient to adjust the stay amount, and short circuits are likely to occur. The coreless cutting method can be used to achieve the goal of leaving the core. machine without supervision.