There are six techniques to maintain strict tolerance requirements in the processing of CNC precision parts. CNC machining machinists love to see something like this:+/- 0.005 ". Five thousandths of an inch is a training for any good machinist - they might as well close their eyes and polish it. However, those jobs are more demanding. Add another zero, and now you have: 0.0005". Holding five tenths of you is a completely different story. This is the difference between the thickness of human hair and white blood cells. When it comes to strict tolerances, here are some suggestions to keep your part specifications.
Spindle preheating and preheating procedures can help maintain strict tolerances during machining.
1. The spindle warms up to maintain severe tolerances
Run a warm-up program - Although this is the standard program for most CNC machining, consider running something more laborious. A typical procedure only warms up the spindle, which is critical to applying grease to prevent premature bearing wear. However, you also need to allow the internal components to reach a stable operating temperature to cope with thermal expansion. Now, if you only want to maintain strict tolerance on the Z axis, all this is correct, but if you combine the spindle preheating with the machine tool movement on all axes, it will help to go further. Allow the machine to run for 10-20 minutes, all part movements allow the parts to reach the desired temperature, and will help mitigate the effects of thermal expansion during milling. In any case, at the end of the warm-up, ensure that all tools are accurately measured and that strict tolerances are maintained.
Tool selection may be a factor in maintaining tight tolerances. Use rough machining tools for "rough machining" to reduce the wear of finishing tools and maintain accuracy.
2. Selection of tools to maintain tight tolerance
Choose your tools carefully - when dealing with these intolerable tolerances, be sure to adapt to your tools. You need to ensure that you have specific tools for roughing and finishing so that the roughing tool can withstand wear, while the finishing tool only saves the last process, thus ensuring a repeatable process for creating accurate parts.
Before machining to the exact size, the gauge pin can be used to measure the undersized parts.
3. Compensation for strict tolerance
Compensate your tools - tool manufacturers are not perfect, so their tools are a little tolerant. They know that if you want to use their tools to do something, you will be more happy if the size of the reduced function is too large rather than too large. It's like a haircut: you can take more rest, but you can't put it back. Knowing this, you need to make sure that the first thing you do when setting up a precise job is to dial your actual tool diameter. You can do this in many ways, but my preferred method is to mill a feature and then use accurate tools to verify dimensions. Easy - If you insert a 0.236 inch tool into a 0.250 inch hole and only a 0.248 inch measuring pin can be inserted, your tool size will be reduced by 0.001 inch (because the size on each side is not small enough, use a half value).
Temperature will affect accuracy due to heat growth. Therefore, please pay attention to your environment and machine location.
4. Temperature to maintain tight tolerance
Thermal stability - This is one of the most important things on the list, because it can make a huge difference that you may not even notice. Please note the location of your machine. Is it near the window, and if so, does the sun shine on it at certain times of the day? Is the air conditioning system started in the afternoon and cooled in the cabin? Are your materials stored in a stuffy warehouse and then in a cold 68 ° environment? These seem innocent, but they will cause huge trouble in your process. Thermal expansion or contraction of milling machines or cutting materials may make a big difference in your processing. Put them all in lock - keep your machines and materials in a temperature controlled climate, free from the influence of sunlight, and you will reap rewards - consistent in your process.
Club testing and regular calibration of your machine will help maintain tight tolerances.
5. Calibration to maintain tight tolerance
Calibrate your device - When you've done all the above, but all you need is * that * more stringent, consider calling the manufacturer. After a machine is built, it will be transported, dropped from the truck, moved stably, and used for thousands of hours. Things will be transferred and solved. This is unavoidable. Fortunately, there are several pieces of equipment, whether granite blocks or Renishaw Ballbar, that can help to run the reins on the tight machine to help maintain tolerance. We like to have a club test and adjust it as part of the annual maintenance, so that you can keep a close relationship with the accuracy of the machine. In addition, performing these annual services ensures that the bearings are tight and lubricated, that the belts are properly tensioned, and that the drive motors operate well - all of which are important factors for precision machining machines.
The linear scale increases machine accuracy and consistency and maintains strict tolerances.
6. Linear scale used to maintain tight tolerance
If everything fails, steelyard- If you have completed all the work on this list and are still working hard, it may be time to consider using a linear ruler to obtain the machine. Your typical CNC machine tool will use the drive motor encoder as the main method to track its absolute position, but this may be caused by the defect or temperature difference of the ball screw. Linear rulers change all this - usually factory installed, they consist of two main parts - the ruler and the reading head. In short - the scale is like a high-precision scale that can be read by a machine, constantly comparing and adjusting the deviation. On our M10Pro, this can achieve 25% more stringent positioning tolerance, improve repeatability by 20%, and reduce backlash by 85%.