Thread: CNC chattering badly

You are calling it 'chatter' but I suspect that it something else.

Chatter is a term normally used for a situation where the tools reaction forces can override the machines rigidity and ability to control the tool. It can arise if there is slop in the slideways or drive mechanism. Your explanation of the problem suggests that you believe that this is not the issue. This is confirmed by the fact that the issue remains when you do an 'air cut' with the same job that creates the problem in a true cut.

I suspect that the issue is poor tuning of the stepper drivers, drivers programmed for too many micro steps causing them to buzz excessively, or the stepper power supply current limiting while trying to drive multiple motors simultaneously, resulting in the motors not perfectly following commands. Does a finished cut look correct, or does it look like it was chewed out by a mouse? If it doesn't have a smooth circumference, it is possible that the motors are missing steps.

I have a basic understanding of steppers, servos, drivers, and power supplies, but no background with the system you are using, so I can't offer better corrective advice, and will leave that to those experienced with the systems you are using.

Thanks for this helpful reply, malb. I have slowed the feed rate of the cutter down to 30mm/ min, and that has reduced the ‘chatter’ a lot, a d the circles are a lot better quality in terms of shape and diameter.. Low speed is Good for circles cutting, ridiculously slow for straight line cutting.
Will get hold of a larger 24V power supply with 10A capacity and try it out

Originally Posted by Dengue

I have slowed the feed rate of the cutter down to 30mm/ min

Ummm....are you missing a zero there? Going that slow will burn up your cutter edges very quickly

Unless your cutter is out of balance it should not be the RPM of the spindle if the noise still occurs while doing an air cut like you mentioned earlier , try an air cut with the cutter and spindle collet removed.

Nope, 30 mm/min is correct. that is why I use cheap Chinese cutters whilst learning this CNC machine So far have only broken a 1.5mm cutter.

Hi all, problem solved. The original controller for the 3040 CNC machine with a 500W 24 V DC spindle motor has two PCBs, one for voltage to drive the spindle and three stepper motors, and one for controlling the steppers. This latter board has failed, so a mate installed an Arduino controller. The problem with the shaking and crunching and rocking of the spindle was due to TOO MUCH CURRENT. By adjusting the current supply from zero to where the noise started, he was able to set the current supply to the spindle. It now runs quietly and on mdf runs 300mm/min ( so far) without any problems, and the Celtic knot is done perfectly, on MDF and on acrylic.
Thanks to everyone for their help and suggestions, they are very much appreciated