The processing process of the machining center
In the mold factory, CNC machining centers mainly process key mold components such as mold kernels, inserts, and copper pins. The quality of the mold core and inserts directly determines the quality of the formed part of the mold. The quality of copper processing directly constrains the impact of EDM processing. The key to ensuring the quality of CNC machining is preparation before processing. For this position, in addition to having rich machining experience and mold knowledge, good communication should also be paid attention to in work, especially with the production team and colleagues.
Table of Contents
- The process of CNC machining
- Precautions before processing
- Precautions for clamping workpieces
- Precautions for clamping tools
- Precautions for correcting and aligning workpieces
- Precautions during processing
- Precautions after processing
- Differentiation of processing accuracy requirements
- Organization of the workplace
- 1) Reading drawings and program sheets.
- 2) Transfer the corresponding program to the machine tool.
- 3) Check program heads, cutting parameters, etc.
- 4) Determination of machining dimensions and allowances in the previous process of the workpiece.
- 5) Reasonable clamping of workpieces.
- 6) Accurate alignment of workpieces.
- 7) Accurate establishment of workpiece coordinates.
- 8) Selection of reasonable cutting tools and cutting parameters.
- 9) Reasonable clamping of cutting tools.
- 10) Safe trial cutting method.
- 11) Observation of the processing process.
- 12) Adjustment of cutting parameters.
- 13) Problems during the processing and timely feedback from corresponding personnel.
- 14) Inspection of workpiece quality after processing.
Precautions before processing
- 1) For new molds, the machining drawings should meet the requirements, and the data should be clear; The machining drawing of the new mold must have the supervisor’s signature, and all machining drawing columns have been filled in.
- 2) The workpiece has a qualified identification from the quality department.
- 3) After receiving the program order, check whether the workpiece reference position is consistent with the drawing reference position.
- 4) review each requirement on the program sheet, and confirm if the requirements of the program and drawings are consistent. If there are any issues, they must be resolved together with the programmer and production team.
- 5) Based on the material and size of the workpiece, determine the rationality of the programmer’s selection of cutting tools for rough or smooth cutting programs. If the application of cutting tools is found to be unreasonable, immediately notify the programmer to make corresponding changes to improve processing efficiency and workpiece processing accuracy.
Precautions for clamping workpieces
- 1) When clamping the workpiece, it is important to pay attention to the position of the clamp and the appropriate extension length of the nut and bolt on the pressure plate. Additionally, the screw should not be pushed against the bottom when locking the corner.
- 2) Copper cylinders are generally processed with locking plates. Before starting the machine, the number of cuts on the program sheet should be checked to ensure consistency, and the screws for closing the plates should be checked for tightness.
- 3) For situations where multiple pieces of copper are collected on a single board, the direction should be checked for correctness and whether each copper material interferes during processing.
- 4) According to the shape of the program diagram and the data of the workpiece size, it is necessary to note that the writing method for the workpiece size data is XxYxZ. At the same time, if there are any loose part diagrams, it is necessary to check whether the graphics on the program diagram match those on the loose part diagram, pay attention to which direction is facing out, and the swing of the X and Y axes.
- 5) When clamping the workpiece, it is necessary to verify whether the size of the workpiece meets the size requirements of the program sheet. If there is a spare part diagram, it is necessary to verify whether the size of the program sheet is the same as that of the spare part diagram.
- 6) The workbench and bottom of the workpiece should be cleaned before installing the workpiece on the machine. The machine tool table and workpiece surface should be pushed off with an oilstone to remove burrs and damaged areas.
- 7) When coding, ensure the code is not damaged by a knife and communicate with the programmer if necessary. At the same time, if the bottom is square, the code must be aligned with the square’s position to achieve a balanced force.
- 8) When using a vise for clamping, it is necessary to understand the machining depth of the tool to prevent the clamped position from being too long or too short.
- 9) The screw must be inserted into the T-shaped block and not only a portion of the thread. When connecting the screw, the upper and lower screws must each use half of the joint thread. The nut thread on the pressure plate must be fully used, and not only a few threads should be inserted.
- 10) When determining the depth of Z, it is necessary to see the position of the program’s single hit number and the data of the highest point of Z. After inputting the data into the machine tool, it must be checked again.
- 1) The tool should be securely clamped and not too short in the handle.
- 2) Before each cutting process, it is necessary to check whether the tool meets the requirements. The length of the cutting process should be determined based on the machining depth indicated in the program sheet, which should generally be slightly longer than the machining depth value of 2mm, and consideration should be given to whether the tool handle collides.
- 3) When encountering situations where the machining depth is very deep, you can communicate with the programmer and use the method of twice drilling the tool as appropriate, that is, first drilling half to 2/3 of the length and then drilling longer when the machining reaches a deeper position, which can improve the machining efficiency.
- 4) When using an extended cable nipple, it is particularly important to understand data such as the depth of the tool and the required length.
- 5) Before installing the cutting head on the machine, its taper fitting position should be wiped clean with a cleaning cloth, and the corresponding position of the machine tool sleeve should also be cleaned to avoid iron filings on the fitting surface, affecting accuracy and damaging the machine tool.
- 6) Usually, the tool length is adjusted using the tip-to-tip method (in special cases, the tool is adjusted in the middle of the tool), and the instructions on the program sheet should be carefully checked during tool adjustment.
- 7) When the program is interrupted or needs to be re-aligned, attention should be paid to whether the depth can be aligned with the front. Generally, the height can be increased by 0.1mm first and adjusted according to the situation.
- 8) For rotary retractable cutting heads, if water-soluble cutting fluid is used, they should be soaked in lubricating oil for several hours every half month for maintenance, which can lubricate the internal components of the cutting head and prevent wear.
Precautions for correcting and aligning workpieces
- 1) When dragging the workpiece, it is necessary to pay attention to the verticality, flatten one side, and then drag the vertical edge.
- 2) When dividing the workpiece, it must be verified twice.
- 3) After dividing and counting, the center position should be checked based on the external dimensions provided in the program sheet and the dimensions on the spare parts diagram.
- 4) All workpieces must be centered using the centering method, and the zero position on the edge of the workpiece must also be centered using the centering method before moving to the edge, ensuring that the margin on both sides is consistent. If unilateral data retrieval is necessary for special circumstances, it must be confirmed by the production team again before passing. After completing the unilateral counting, remember the radius of the rod in the compensation loop.
- 5) The zero input of the workpiece center must be the same as the three-axis center in the workstation computer diagram.
Precautions during processing
- 1) 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.
- 2) The most important aspect of machining is the first tool, as careful operation and verification can reveal whether there are errors in tool length compensation, tool diameter compensation, program, speed, etc., to avoid damaging the workpiece, tool, and machine tool.
- 3) Try cutting the program as follows:
- a) The first point is to raise the height to a maximum of 100mm and use your eyes to check if it is correct;
- b) Control the “fast moving” 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 travel and program are correct;
- e) After restarting the machine, place one hand on the pause button, ready to stop at any time, and control the feed speed 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 smooth and stable cutting process, adjust each control back to its normal state.
- 4) After entering the program name, use a pen to copy back the program name on the screen, and then check with the program sheet. When opening the program, check whether the tool diameter size 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. It is prohibited to fill in the file name and tool diameter afterward or beforehand.
- 5) In principle, NC technicians must stay when the workpiece is roughened. If it is necessary to leave when changing tools or assisting in adjusting other machine tools, please ask other NC team members or come back regularly for inspection.
- 6) When making medium light, NC technicians should pay special attention to the area that is not touched during rough cutting to prevent the tool from colliding with this area.
- 7) Program cutting. If the program is interrupted during processing and running from scratch wastes too much time, the team leader and programmer should be notified to modify the program and cut off the parts that have already been run.
- 8) Program exception. If there is an abnormal situation in the program and you are unsure, you can lift it, observe its process, and then decide on the next action.
- 9) The speed and rotation speed provided by the programmer during the machining process can be adjusted by the NC technician according to the situation. However, special attention should be paid to the speed of small copper parts when exposed to rough conditions to avoid the loosening of the workpiece due to oscillation.
- 10) During the machining process of the workpiece, the NC technician should check with the spare parts diagram to see any abnormalities. Once any discrepancies are found, the machine must be immediately shut down, and the team leader must be notified to verify if there are any errors.
- 11) When using tools longer than 200mm for machining, attention must be paid to issues such as allowance, feed depth, speed, and running speed to avoid tool oscillation. At the same time, the running speed of the corner position should be controlled.
- 12) For the requirements on the program sheet to test the diameter of the cutting tool, the operator must be serious and responsible and record the tested diameter. If it exceeds the tolerance range, it should be immediately reported to the team leader or replaced with a new tool.
- 13) When the machine tool is in automatic operation or available, the operator should go to the workstation to understand the remaining machining programming situation and prepare and grind appropriate tools for the next machining backup to avoid a shutdown.
- 14) Technological errors are the main reasons for wasting time: incorrect use of inappropriate tools, scheduling errors in processing, wasting time in locations that do not require processing or noncomputer processing, improper use of processing conditions (such as slow speed, empty cutting, dense tool path, slow feed, etc.). When these events occur, they can be contacted through programming or other means.
- 15) During the machining process, attention must be paid to the wear of the cutting tools, and the cutting particles or tools should be replaced appropriately. After replacing the cutting particles, attention should be paid to whether the adjacent boundaries of the machining match.
Precautions after processing
- 1) Confirm that each program and instruction required by the program sheet has been completed.
- 2) After the processing is completed, it is necessary to check whether the appearance of the workpiece meets the requirements and conduct a self-inspection of the workpiece size based on the loose part diagram or process diagram to detect errors promptly.
- 3) Check if there are any abnormalities in the various positions of the workpiece, and if there are any questions, notify the NC team leader.
- 4) For larger workpieces to be removed from the machine, the team leader, programmer, and production team leader should be notified.
- 5) When removing workpieces from the machine, pay attention to safety, especially when removing larger workpieces; protect the workpieces and the NC machine.
Differentiation of processing accuracy requirements
- 1) Mold core and insert block.
- 2) Copper Duke.
- 3) Avoid empty positions at the support head holes of the ejector pin plate.
- 4) Eliminating the phenomenon of vibrating knife lines.
- 1) Measurable dimensions must be strictly inspected after processing.
- 2) When processing for a long time, it is necessary to consider the loss of cutting tools, especially at the sealing position and other cutting edges.
- 3) Should use new hard alloy cutting tools as much as possible.
- 4) Determine the energy-saving modulus after polishing based on processing requirements.
- 5) Confirmation of production, quality, and other quality after processing.
- 6) Control tool loss during sealing position processing according to processing requirements.
- 1) Confirm the homework situation for each shift, including processing conditions, mold conditions, etc.
- 2) Confirm if the equipment is working properly during work hours.
- 3) Other handover and confirmation, including drawings, program sheets, tools, measuring tools, fixtures, etc.
Organization of the workplace
- 1) Execute according to 5S requirements.
- 2) Tools, measuring tools, fixtures, workpieces, etc., are classified and neatly placed.
- 3) Cleaning of machine tools.
- 4) Cleanliness of the workplace floor.
- 5) Returning processed, idle, and measuring tools to the warehouse.
- 6) The processed workpiece shall be sent to the inspection or corresponding department.