CNC Chatter: Still Babysitting Your Cuts?

Do you accept CNC chatter as a necessary evil that must be manually addressed in the machine shop? Certainly there are some basic best practices that go a long way in preventing this profit-drainer. Even better, there’s new CNC control technology that takes the guesswork out of the trial and error process typically used to dial down the chatter.

Start with the Basics

Following are some of the techniques commonly used to combat CNC chatter. Use these guidelines to establish a good foundation:

1. Choose the Right Toolholder - Standard toolholder shanks using side-lock, double-angle collets, and standard ER collets do not provide the accuracy or stiffness needed for high performance machining. Better options are toolholder shanks that incorporate face and taper contact (e.g. Big-Plus^®) coupled with high accuracy toolholding to provide precision and rigidity. This type of holder engages the precision ground face of the spindle with simultaneous contact with the taper, which provides the additional rigidity required, and also aids in damping. All tooling should be evaluated for balancing, which provides improvements in surface finish even at lower RPMs.
2. Cutting Tool Selection  - Cutting tools can greatly influence CNC chatter. Considerations include correct substrate, geometry, coating and length-diameter ratio. Programmers often gravitate to using the largest tool that can “fit,” but that may not be the ideal tool size. Incorporating multiple tools with variable flute geometries is an effective way to reduce vibrations.
3. Proper Workholding - If the part is not properly secured, the part itself can vibrate and induce chatter. There are many excellent systems available to clamp your work pieces. Criteria to look for include high precision, high clamping force, ease of use and flexibility (allowing use across multiple machine tool platforms).
4. Machine Maintenance - If you’re trying to hold fine finishes and tight tolerances on a poorly maintained machine, you’ll need to overcome mechanical challenges well beyond the issues listed here. Keep your equipment on a regular maintenance schedule to ensure the best performance.

Machining Navi M-i: New Intelligent CNC Control Technology

The basics listed above can correct many causes of chatter, but there are limitations to these methods. Okuma offers a new CNC control technology that goes beyond the basics. Okuma’s Intelligent Technologies are “smart control systems” that navigate processes and eliminate potentials for costly surface finish problems. One of Okuma’s Intelligent Technologies is Machining Navi M-i, designed to reduce chatter. Machining Navi M-i takes the guesswork out of the trial and error process typically used to find the correct spindle speed, allowing the cutting tool and machine tool to continuously operate at the highest performance.

Machining Navi M-i uses the Okuma THINC^®-OSP control and vibration sensors to monitor vibration and automatically adjust spindle speed. No longer does an operator need to babysit a cut. With Intelligent Technology in place, your shop can be more profitable and gain a competitive advantage.

Watch Machining Navi in action – check out the video on this page. Got comments or questions about your chatter solutions? Send them our way and we’ll tackle your challenge.

Kyle Klaver is 5-Axis and Pallet System Product Specialist, Okuma America Corporation