Surface finish issues can be a profit killer for moldmakers today. One of the most common causes is chatter caused by vibrations during the cutting process of the CNC drilling machine. This can lead to higher costs, delayed deliveries, or even lost orders due to poor quality. Additionally, vibration can cause uneven tool wear, resulting in poor surface finish, inconsistent geometry and reduced tool life.
Chatter is caused by the natural frequency of the cutting tool. It can be triggered by many process conditions: tool holder, tool tool, part fixation and machine conditions. Often, operators try to cope by combining multiple solutions, some of which may not be possible due to part geometry or machine limitations. Fortunately, there are new technologies available today that can eliminate chatter during cutting.
Here are some commonly used techniques to combat tremors. Use these guidelines to create a good foundation for optimizing your mold making process:
1. The right tool holder: Ordinary tool holders (side locks, double angle chucks and standard ER chucks) cannot provide the precision or stiffness required for high-performance machining. A better option is a holder that combines face and taper contact to provide high precision and rigidity. This type of shank engages the precision ground face of the spindle while in contact with the taper, which provides the extra rigidity needed and also helps with damping. All tools should be evaluated for balance, and surface finish can be improved even at lower RPMs.
2. Selection of cutting tools: cutting tools will greatly affect the chatter. Considerations include the correct substrate, geometry, coating and aspect ratio. Programmers generally tend to use the largest tool they can hold, but this may not be the ideal tool size. Combining multiple tools with variable groove shapes is an effective way to reduce vibration.
3. Correct clamping: If the part is not fixed correctly, the part itself may vibrate and cause tremor. There are many excellent systems for clamping your workpieces. Criteria to look for include high accuracy, high clamping force, ease of use and flexibility (allowing for use on multiple CNC drilling machine platforms).
4. CNC drilling machine maintenance: If you want to maintain a good finish and tight tolerances on a poorly maintained CNC drilling machine, you will need to overcome mechanical challenges other than those listed here. Keep your equipment regularly maintained to ensure optimum performance.
5. Control solutions: The above methods can correct some of the causes of chattering, but these methods have limitations. Another approach is to use new control technology (intelligent control systems) to navigate the process and eliminate potentially expensive surface preparation issues. One such technology is designed to eliminate chatter and guesswork from the trial-and-error process often used to find the correct spindle speed, allowing cutting tools and CNC drilling machines to run continuously at peak performance. It uses a single-processor smart CNC and vibration sensors to monitor chatter noise and automatically adjust spindle speed. The operator no longer has to take care of the incision. With this technology, your shop can be more profitable and gain a competitive advantage.
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