Need Help!- Chatter vibration issues

[Designsync]

Hi,

I've just completed my home built MDF CNC router. My design is loosely based on 'www.buildyourcnc.com' design with a few changes here and there.

My first cut was into MDF and the vibration marks showed up immediately. I then tried a clear plastic cut (as attached) and still showed vibration.

This was cutting very slowly at around 8"/minute and I also tried upto 50"/minute which showed no difference. I varied the cutting speed from between 11,000-32,000rpm, nothing seemed to make any difference.

The distance between the router mount and the collet is 3", therefore router mount to tip of router bit is about 4". Is this distance too long? All axis movement are rock solid with no play at all.

The router cuts well when used freehand so that rules out any offset collet/router bit issues.

As you can see the sign looks OK from a distance but up close it's shocking. Has anyway resolved a similar issue. Any advise welcome.

Cheers
Iain

[cncspear]

The pattern suggests a large oscillation which would indicate that your gantry is flexing. You might want to try lowering your acceleration ramp and your instantaneous start speed. Since you are starting and stopping in very short segments you are constantly accelerating and decelrating which upsets your gantry and causes it to oscillate. Machines without much rigidity and mass are very susceptible to flexing and vibrations.

As a test, plunge into a sacrificial piece of material and allow it to come to a complete stop at that depth. Then route a straight line from there for a good distance, say 20 inches. Take a look at the cut quality from start to finish of the line. You might notice that the oscillations or chattering is most pronounced at the very beginning of the cut and will diminish as it goes along the line. You may even notice some curviness at the beginning of the line which means the machine is flexing under the cutting forces.

For a sign building I would recommend you buy or build a more rigid machine to obtain cleaner cuts.

Gil

[Shinosky]

Designsync,
I am in the final stages of building my router and saw something similar to what you are experiencing. I use Mach3 and it turned out that CV (constant velocity) was turned off in the control. By re enabling it it smoothed out the movement