In mould factories, CNC machining centres are mainly used for the processing of key parts of moulds such as die kernels, inserts and copper males. The quality of the mould insert and inserts directly determines the quality of the moulded part. The quality of the copper male processing directly constrains the impact of EDM processing. For CNC machining quality assurance, the key lies in the preparation before processing, for this position, in addition to having rich processing experience and mould knowledge, we should also pay attention to good communication in the work, especially with the production team and colleagues' communication.
Process of NC machining
1) Reading of drawings and program sheets
2) Transfer of the corresponding program to the machine
3) Checking the program head, cutting parameters, etc.
4) Determination of machining dimensions and allowances for the workpiece in the previous process
5) Proper clamping of the workpiece
6) Accurate setting of the workpiece
7) Accurate establishment of workpiece coordinates
8）The selection of reasonable tool and cutting parameters
9) Reasonable clamping of the tool
10）Safe test cutting method
11）Observation of the machining process
12) Adjustment of cutting parameters
13) timely feedback of problems and corresponding personnel during processing
14) Inspection of the quality of the workpiece after machining
▌ Precautions before machining
1）For new moulds, the processing diagram should meet the requirements and the data should be clear; the processing diagram for new moulds should have the signature of the supervisor and the columns of the processing diagram have been filled in.
2）The workpiece has a qualified mark from the quality department.
3）After receiving the procedure sheet, check whether the workpiece datum position is consistent with the drawing datum position.
4) Read each requirement on the program sheet and check that the program is consistent with the drawing's requirements. If there is a problem, you must work with the programmer and production team to solve the problem.
(5) According to the material of the workpiece and its size, judge the reasonableness of the tool chosen by the programmer to open the coarse or bare tool program. If the application of the tool is found to be unreasonable, the programmer should be informed immediately to make corresponding changes in order to improve the machining efficiency and the machining accuracy of the workpiece.
▌ Precautions for clamping workpieces
1) When clamping the workpiece, pay attention to the position of the code boy and the right length of the nut bolt protruding from the pressure plate, in addition, when locking the corner boy, the screw should not top the bottom.
2) The brass is generally processed by locking the plate, so you should check the number of openings on the program sheet to make sure it matches before you go on the machine, and check whether the closing screws are tightened.
3) For the case of a board receiving multiple pieces of copper, check whether the direction is correct and whether there is interference in the processing of each copper material.
4) Clamp workpieces according to the shape of the diagram in the program sheet and the data of the workpiece dimensions, it must be noted that the workpiece dimensions are written as XxYxZ.
5) When clamping the workpiece, check whether the size of the workpiece conforms to the size requirements of the program sheet, and check whether the size of the program sheet is the same as the size of the bulk drawing if there is a bulk drawing.
6) The workpiece should be cleaned on the table and the bottom of the workpiece before it is put on the machine. The machine table and workpiece surface should be oiled and pushed off the burrs and bumps.
7) When coding yardage, ensure that the yardage is not touched by the knife, and communicate with the programmer if necessary. At the same time, if the bottom pad is square, the code must be aligned with the position of the pad square to achieve the purpose of balanced force.
8) When using a vise to clamp, the depth of the tool must be understood to prevent the clamped position being too long or too short.
9) Screws must be included in the T-block, not just a part of the thread, if you need to connect the screws, the upper and lower screws must each use half of the thread of the joint, the thread of the nut on the pressure plate must be used completely, not just a few threads.
10) When fixing the Z depth number, check the position of the number of touches in the program sheet and the data of the highest point of Z. After inputting the data into the machine tool, check again.
▌ Precautions for clamping tools
(1) The tool should be clamped securely and not too short in the toolholder.
(2) Each time before the tool should be checked whether the tool meets the requirements, the length of the tool should be determined according to the processing depth of the program sheet instructions, generally should be slightly longer than the processing depth value of 2mm and to consider whether the toolholder collision.
(3) When you encounter a deep machining depth, you can communicate with the programmer and use the method of two tool lengths, i.e. half to 2/3 of the length first, and then a longer length when machining to a deeper position, which can improve the machining efficiency.
(4）When using the extension nozzle, especially you should understand the depth of the tool, the required tool length and other data.
(5）Before installing the tool head on the machine, its taper with the position, should be clean cloth wipe clean, the corresponding position of the machine tool set is also clean, to avoid with the surface of the iron chips affect the accuracy and damage to the machine tool.
(6）Usually use the tool tip to the tool length (special case with the tool in the case of the tool), check the instructions of the program sheet carefully when the tool is set.
(7）When the program is interrupted or the line must be re-tooled, attention should be paid to whether the depth can be connected with the front, in general, can first adjust 0.1mm line, and then adjusted according to the situation.
(8）Rotary collection type of cutter head, such as the use of water-soluble cutting fluid, should be used every half month with lubricant immersion for a few hours for maintenance, so that the internal parts of the cutter head have lubrication does not wear.
▌ Attention to the correction of the workpiece
(1) The workpiece must pay attention to the verticality when dragging the table, dragging a flat side, and then dragging the vertical side.
(2）When dividing the workpiece, the workpiece must be divided twice for verification.
(3) After the centreing process, the centreing should be checked against the dimensions provided in the program sheet and the dimensions on the drawing of the loose part.
(4) All workpieces must be split using the splitting method, and the zero position on the side of the workpiece must also be split using the splitting method and then moved to the side, ensuring that the margin is the same on both sides. In exceptional cases where a single side must be taken, the production team must confirm this again before passing. After taking the number on one side, compensate for the radius of the centering bar.
(5) The zero input of the workpiece centre must be the same as the centre of the three axes of the workstation computer chart.
▌ Notes on the machining process
(1) in the workpiece top surface margin is too large, with a large knife manual gong to the margin, remember not to gong deep.
(2) The most important processing is the first cut, because if you operate carefully and check it, you can know whether the cutter length, cutter diameter, program, speed, etc. are wrong to avoid damage to the workpiece, tool and machine tool.
(3) Test cut the program in the following way.
(a) Raise the first point to a maximum height of 100mm and use the eye to feel if it is correct.
(b) Control the "quick shift" to 25% and the feed to 0%.
(c) Pause the machine when the tool is close (approx. 10 mm) to the machined surface.
(d) Check that the remaining travel and program are correct.
(e) After starting the machine again, 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, the machine can be stopped again, and the remaining travel of the Z-axis must be checked.
(g) After the cutting line is smooth and stable, adjust the controls back to the normal state.
(4）After entering the program name, copy the program name on the screen with a pen and check it against the program sheet. When opening the program, check that the tool diameter size in the program matches the program sheet and fill out the file name and tool diameter size in the machinist's signature field on the program sheet immediately, not afterwards or in advance.
(5) In principle, the NC technician must not leave the workpiece while it is being roughened. In the event of a tool change or assistance with other machines, etc., if he must leave, he must ask another NC team member or return at regular intervals to check.
(6) When doing the centre light, the NC technician should pay special attention to the area that is not opened when roughing, to prevent the tool from hitting this area.
(7) Program cutting. If the program is interrupted in the middle of processing and too much time is wasted, the team leader and the programmer should be informed to modify the program and cut off the part that has already passed.
(8) Program abnormalities. If there is an abnormality in the program and you are not sure, you can lift the program to observe the process and then decide on the next step.
(9) The NC technician can adjust the line speed and rotation speed provided by the programmer during the machining process according to the situation. However, special attention should be paid to the fact that the line speed should not be turned on too fast when the small copper pieces are open and rough, in order to avoid loosening of the workpiece due to oscillation.
(10) During the machining of the workpiece, the NC technician should check with the bulk drawing to see if there are any abnormalities, and if the two do not match, he must immediately stop the machine and inform the team leader to check if there are any errors.
(11) When machining with tools longer than 200mm, attention must be paid to the margin and the depth of tool entry speed, travel speed and other issues, in order to avoid swinging the tool, while the travel speed of the corner position should be controlled.
(12) For the program list requires the detection of the diameter of the tool, the operator must be responsible, while the diameter of the test will be recorded, out of tolerance, should be immediately reflected to the team leader or change the tool.
(13) When the machine is in automatic operation or free, the operator should go to the workstation to understand the remaining machining programming, prepare and grind the appropriate tool to the next processing backup to avoid downtime.
(14) Process errors are the main cause of wasted time: incorrect use of unsuitable tools, incorrect machining sequence, wasted time in positions that do not require machining or non-computerised machining, use of inappropriate machining conditions (too slow, empty tool, too dense tool path, too slow feed, etc.), the above events can occur in the programming and other links.
(15) During machining, attention must be paid to the wear of the tool, and the tool should be replaced appropriately, and after replacing the tool, attention should be paid to whether the machined joint boundary matches.
Contact: Jacky Wang
Phone: +86 14714816052
Tel: +86 14714816052
Email: [email protected]
Add: Floor 1, Shixi Industrial area, Canton, Guangdong, China. 510288