In mold factories, CNC machining centers are primarily used to process important mold components such as mold cores, inserts, and copper pins. The quality of the mold core and inserts directly affects the quality of the molded part. Similarly, the quality of copper processing directly affects the impact of EDM processing. The key to ensuring the quality of CNC machining lies in the preparation before machining. For this role, it is essential to have rich machining experience and mold knowledge, as well as the ability to communicate effectively with the production team and colleagues.
The process of CNC machining
- Reading drawings and program sheets
- Transfer the corresponding program to the machine tool
- Check program header, cutting parameters, etc
- Determination of machining dimensions and allowances on workpieces
- Reasonable clamping of workpieces
- Accurate alignment of workpieces
- Accurate establishment of workpiece coordinates
- The selection of reasonable cutting tools and cutting parameters
- Reasonable clamping of cutting tools
- Safe trial cutting method
- Observation of the machining process
- Adjustment of cutting parameters
- Problems during the processing and timely feedback from corresponding personnel
- Inspection of workpiece quality after processing
Precautions before processing
- New mold machining drawings need to meet specific requirements and must be clear. The supervisor’s signature is required on the machining drawing, and all columns must be completed.
- The workpiece needs to be approved by the quality department.
- Upon receiving the program order, verify if the workpiece reference position matches the drawing reference position.
- Carefully review each requirement on the program sheet and ensure consistency with the drawings. Any issues should be addressed in collaboration with the programmer and production team.
- Evaluate the rationality of the cutting tools selected by the programmer based on the workpiece’s material and size for rough or light cutting programs. If any unreasonable tool applications are identified, promptly notify the programmer to make necessary changes to enhance machining efficiency and workpiece accuracy.
Precautions for clamping workpieces
- When clamping the workpiece, ensure the clamp is positioned correctly with the appropriate extension length of the nut and bolt on the pressure plate. Additionally, do not push the screw to the bottom when locking the corner.
- Copper is typically processed by locking plates. Prior to starting the machine, verify the number of cuts on the program sheet for consistency, and check the tightness of the screws for closing the plates.
- For situations where multiple pieces of copper material are collected on one board, double-check the correct direction and possible interferences during processing.
- Consider the shape of the program diagram and the data on the workpiece size. Note that the workpiece size data should be represented as XxYxZ. If a loose part diagram is available, ensure that the graphics on the program diagram align with those on the loose part diagram, paying attention to the outward direction and the swing of the X and Y axes.
- When clamping the workpiece, confirm that its size meets the requirements of the program sheet. Verify if the size of the program sheet matches that of the loose part drawing, if applicable.
- Prior to placing the workpiece on the machine, clean the workbench and the bottom of the workpiece. Use an oilstone to remove any burrs and damaged areas from the machine tool table and the workpiece surface.
- During coding, prevent the code from being damaged by the cutter, and communicate with the programmer if necessary. If the base is square, ensure that the code is aligned with the square’s position to achieve force balance.
- When using pliers for clamping, understand the machining depth of the tool to avoid clamping that is too long or too short.
- Ensure that the screw is fully inserted into the T-shaped block, and use the entire thread for each upper and lower screw. Fully engage the threads of the nut on the pressure plate and avoid only inserting a few threads.
- When determining the depth of Z, carefully verify the position of the single stroke number in the program and the highest point of Z. After inputting the data into the machine tool, double-check for accuracy.
Precautions for clamping tools
- Always securely clamp the tool and ensure the handle is not too short.
- Before each cutting process, check that the tool meets the requirements. The length of the cutting process should slightly exceed the machining depth value by 2mm as indicated on the program sheet, and consider the tool holder to avoid collision.
- In cases of very deep machining depth, consider communicating with the programmer to use the method of twice drilling the tool. Initially, drill half to 2/3 of the length and then drill longer when reaching a deeper position to improve machining efficiency.
- When using an extended cable nipple, understand the blade depth and required blade length.
- Before installing the cutting head on the machine, wipe the taper fitting position and corresponding position of the machine tool sleeve clean to avoid iron filings affecting accuracy and damaging the machine tool.
- Adjust the tool length using the tip-to-tip method; carefully check the program sheet instructions during tool adjustment.
- When interrupting the program or requiring realignment, ensure that the depth can be aligned with the front. Generally, raise the line by 0.1mm first and adjust it as needed.
- For rotary retractable cutting heads using water-soluble cutting fluid, immerse them in lubricating oil for several hours every half month for maintenance to prevent wear.
Precautions for correcting and aligning workpieces
- When moving the workpiece, make sure it is vertical, flatten one side, then move the vertical edge.
- When cutting the workpiece, double-check the measurements.
- After cutting, verify the center based on the dimensions in the program sheet and the parts diagram.
- All workpieces must be centered using the centering method. The zero position on the edge of the workpiece should also be centered before cutting to ensure consistent margins on both sides. In special cases when one-sided cutting is necessary, approval from the production team is required. After one-sided cutting, remember the radius of the rod in the compensation loop.
- The zero point for the workpiece center must match the three-axis center in the workstation computer diagram.
Processing precautions
- When there is too much margin on the top surface of the workpiece and the margin is manually removed with a large knife, remember not to use a deep gong.
- The most important aspect of machining is the first tool, as careful operation and verification can determine whether there are errors in tool length compensation, tool diameter compensation, program, speed, etc., to avoid damaging the workpiece, tool, and machine tool.
- Try cutting the program in the following way:
a) The first point is to raise the height by a maximum of 100mm, and check with your eyes if it is correct;
b) Control the “fast movement” to 25% and the feed to 0%;
c) When the tool approaches the machining surface (about 10mm), pause the machine;
d) Check if the remaining itinerary and program are correct;
e) After restarting, place one hand on the pause button, ready to stop at any time, and control the feed rate with the other hand;
f) When the tool is very close to the workpiece surface, it can be stopped again, and the remaining travel of the Z-axis must be checked.
g) After the cutting process is smooth and stable, adjust all controls back to normal state.
- After entering the program name, use a pen to copy the program name from the screen and ensure it matches the program sheet. When opening the program, check if the tool diameter size in the program matches the program sheet, and immediately fill in the file name and tool diameter size in the signature column of the processor on the program sheet.
- NC technicians are not allowed to leave when the workpiece is roughened. If changing tools or assisting in adjusting other machine tools, invite other NC team members or arrange regular inspections.
- When working with Zhongguang, NC technicians should pay special attention to areas where rough cutting is not performed to avoid tool collisions.
- If the program is interrupted during processing and running from scratch wastes too much time, notify the team leader and programmer to modify the program and cut off the parts that have already been run.
- In case of a program exception, lift it up to observe the process and decide on the next action when unsure of the abnormal situation in the program.
- The line speed and speed provided by the programmer during the machining process can be adjusted by the NC technician according to the situation. Pay special attention to the speed of small copper pieces when exposed to rough conditions to avoid workpiece loosening due to oscillation.
- During the machining process of the workpiece, check with the loose part diagram to see if there are any abnormal conditions. If a discrepancy is found between the two, immediately shut down the machine and notify the team leader to verify if there are any errors.
- When using tools longer than 200mm for cnc machining and manufacturing, pay attention to allowance, feed depth, speed, and running speed to avoid tool oscillation. Control the running speed of the corner position.
- Take the requirements on the program sheet to test the diameter of the cutting tool seriously and record the tested diameter. If it exceeds the tolerance range, report it immediately to the team leader or replace it with a new tool.
- When the machine tool is in automatic operation or has free time, go to the workstation to understand the remaining machining programming situation, prepare and grind appropriate tools for the next machining backup, to avoid shutdown.
- Process errors lead to wasting time: incorrect use of inappropriate cutting tools, scheduling errors in processing, wasting time in positions that do not require processing or are not processed by computers, improper use of processing conditions (such as slow speed, empty cutting, dense tool path, slow feed, etc.). Contact them through programming or other means when these events occur.
- During the machining process, pay attention to the wear of the cutting tools, and replace the cutting particles or tools appropriately. After replacing the cutting particles, check whether the machining boundary matches.
Precautions after processing
- Check that every program and instruction listed on the program sheet has been completed.
- After processing, verify if the workpiece complies with the requirements and conduct a self-inspection of the workpiece size according to the loose part diagram or process diagram to promptly identify errors.
- Examine for any irregularities in the workpiece at various positions. If you have any queries, inform the NC team leader.
- Inform the team leader, programmer, and production team leader when removing larger workpieces from the machine.
- Exercise caution when removing workpieces from the machine, especially larger ones, and ensure the protection of both the workpiece and the NC machine.
Differentiation of processing accuracy requirements
Smooth surface quality:
- Mold core and inlay block
- Copper Duke
- Avoid empty spaces at the top pin plate support hole and other locations
- Eliminating the phenomenon of shaking knife lines
Precision size:
1) Make sure to thoroughly check the dimensions of the processed items for accuracy.
2) When processing for extended periods, take into account potential wear and tear on cutting tools, especially at the sealing position and other cutting edges.
3) Preferably use new hard alloy cutting tools at Jingguang.
4) Calculate the energy-saving ratio after polishing according to cnc processing requirements.
5) Verify production and quality after processing.
6) Manage tool wear during sealing position processing according to processing requirements.
Taking over the shift
- Confirm the status of homework for each shift, including processing conditions, mold conditions, etc.
- Ensure proper functioning of the equipment during work hours.
- Other handover and confirmation, including drawings, program sheets, tools, measuring tools, fixtures, etc.
Organize the workplace
- Execute tasks according to 5S requirements.
- Organize cutting tools, measuring tools, fixtures, workpieces, and tools neatly.
- Clean the machine tools.
- Keep the workplace floor clean.
- Return processed tools, idle tools, and measuring tools to the warehouse.
- Send processed workpieces for inspection by the relevant department.
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Post time: Jul-09-2024