Industry Information

What are the mechanical problems with unstable dimensions in CNC machining?

1. Poor surface finish of the workpiece
The reasons for this phenomenon are mostly that the tool tip is damaged and not sharp enough; the machine is unstable or resonates and crawls; the titanium machining technology is not perfect. You can change or re-grind the tool, and re-process the tool; adjust the flat temperature of the machine tool; change the worn carriage guide rail and screw ball, add lubricating oil, choose a suitable cutting fluid; and use a higher spindle as much as possible Speed to solve.

2. Workpiece taper size head phenomenon
This problem occurs because the machine is not stable; when turning the long shaft, the workpiece material is too hard, which causes the tool to eat a large amount, which causes the tool to give up. In addition, the tailstock thimble is not concentric with the spindle. Use level gauges to adjust the level of the machine tool, and reliably fix it to increase its rigidity; select cutting technology and feed rate must be fair, compared to see the tool; and adjust the tailstock of the machine tool, these methods can eliminate the taper of the workpiece.

3. The size of the workpiece is large or small
The screw rod and bearing wear caused by the long-term work of the machine tool carriage; the long-term use of the tool post causes the repeated positioning accuracy to be prohibited. These are the worst causes of the small size of the workpiece. When encountering this kind of problem, you should first check the repeatable positioning accuracy of the carriage. The method is to edit a fixed cycle program in the system, and then place the dial indicator against the bottom of the tool post for measurement. If it is a problem with the screw and bearing, answer Adjust the screw gap and change the new bearing; then use the same method to check the repeat positioning accuracy of the tool holder and the accuracy of the workpiece after machining, and guide the starting point of the program; if there is no problem with the above, check whether the spindle of the machine tool is correct There is a fault, change the spindle bearing.

4. The axial size of the workpiece differs greatly
This is mostly caused by the fact that the positioning speed is too fast, the drive and the electromechanics cannot keep up with the rhythm; the carriage screw and the bearing are too tight and jam; the tool post cannot lock the tool, the programming head and tail have no response or the tool compensation is not prohibited ; The system electronic gear ratio or step angle is set incorrectly. The solution is to adjust the positioning speed appropriately to make the equipment run at the rated frequency; adjust the gap between the screw and bearing; check whether the turbine and worm inside the tool holder are worn; improve the program and machining technology; and adjust the electronic gear and step The parameters of the distance angle, etc.

5. The machining arc size is not in place
This is because of resonance of machine tool components; unfair machining technology and parameter settings, excessive feed speed, which makes arc machining out of step; too loose or too tight lead screw to cause out of step; and timing belt wear. The operator needs to reverse the frequency of the resonant component; set a fair titanium machining technology and reduce the feed speed by an appropriate amount; adjust the screw gap and change the synchronization belt to solve this problem.

6. Mass production occasionally exhibits out-of-tolerance workpieces
Possible reasons include unstable clamping or dimensional changes; interference with the CNC system, etc. The clamping method should be adopted to improve the workpiece, increase the firmness of the clamping, and minimize possible dimensional changes; discharge the electromagnetic interference from the outside and the inside, and affect the normal operation of the CNC system. For example, the strong electric cable that will have strong electric field interference is isolated from the weak electric signal signal line, and anti-interference absorbing capacitance is added and shielded wire isolation is adopted.

7. The size of each process increases or decreases
This phenomenon occurs because of programming errors; system parameters and configuration are not fair; mechanical transmission parts have regular periodic changes. It is necessary to locate the dial indicator at the starting point of the program, and check whether the carriage returns to the starting point after the program ends, so as to check whether the program instructions are executed in accordance with the requested trajectory; modify the unfair system parameters and configurations; also check the machine tool transmission section Whether the parts are damaged, whether the gear coupling is uniform, and the faults that periodically change are eliminated.

8. The size changes caused by the system are not chaotic
The main reason for this problem is that the system is damaged or the parameter setting is not fair, or it is interfered by the outside; the impedance between the system and the driver is not matched or the signal transmission is abnormal; the working voltage is unstable, etc.

After confirming that the system is not damaged, the operator needs to adjust the cutting speed appropriately, check whether the pulse generation signal is lost or added; ensure that the ground wire is connected reliably, install anti-interference absorption capacitors at the titanium machining pulse output contacts of the driver, and select the appropriate Type of capacitor; check whether the signal connection line between the system and the driver is reliable, and whether it has a shielding function; install voltage regulator equipment.

Leave a Reply