Wobble or wave cutting issue

[Tech_Marco]

When doing cutting for small circle or small section area, waves or wobble is always happening on certain machine. It seems to me that if the machine is in large format like 1200x900 or bigger and with linear guide, it is hard to avoid that from happening if cutting speed is over 50mm/s.

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Here are a few things you may do to eliminate or minimize the wobbles.

1) Adjust belt tension on both X and Y. Make sure that the belts tension on the Y is balance. I used a 'tension scale' or 'pressure scale' to do the job.
2) After belt tension adjust, move the gantry to the far end, either side is fine. Then, loose up the axial coupling (both side) so that the Y motor is free to move without engaging with the gantry. Slide the gantry from one end to another end without Y motor is turning. Make sure that the gantry touch the rail stopper at the same time. If not, you may have rail alignment. Slide the gantry back to the original starting point, then tide the coupling firm enough without escaping.
3) Adjust the belt tension (motor to the 2:1 reduction gear) . Not to loose but not too much. Firm but with a little flexible.
4) Clean the rail with a cloth then spray lubricant .
5) Test the art work again. Sometimes change the direction of cutting make a huge difference.
6) Update the firmware (I have a latest firmware upgrade for X7 and it helps a lot!)


Marco

[SWMS]

I have this same problem on my large machine, especially on small intricate cuts


I'd just like to add something else, you can also get whats called chatter. This is the vibration of the motors going in to the frame. Try all that Marco advised first and if its still like that it could be that.


You need to put a balance on the back of your stepper motor ( you can buy them or make them ) or you could use a shim to isolate the motor from the body. I tried the shim option ( although I prefer the balance option ) and my machine is much quieter. All CNC and lathes etc, have chatter in them and it can be an engineers nightmare.

The final option I have been looking in to is larger stepper motors or steppers and and drivers with feedback for the following reasons.

If the machine you bought is engineered to be just good enough you may find your gantry carriage is a little too heavy for the steppers, so they can't make it accelerate and decelerate quick enough on small intricate cuts. There isn't enough torque, as if you increase the micro steps the talk reduces.

Larger steppers have more torque and you can put in more micro steps and have higher torque So, say upgrade from a Nema 17 to a Nema 23.

You could try steppers and drivers with feedback, so they know if they have missed a step.

I haven't tried this yet, I am just tying to sort out backlash and chatter.

Cheers