Small Circle problem

[supman]

I am having problem cutting a 12mm circle. the machine is cutting the circle in two arcs as pic shows. you can here the machine as it makes the small circle. it does not sound like it is in a smooth constant motion unlike. big circles are no problem, the machine cuts in a smooth motion for the complete circle.

I have attached G Code for 12mm Circle Just in Case. I have just cut this out of the file as I had quite a few shapes in the NC file as a test to see how the machine preformed. All worked fine except that small Circle. Any suggestions?

 

[cncnutz]

Hi Supman,

The photo looks a little like backlash but your description sound like lost steps. The issue is occurring on the X axis assuming the photo is orientated correctly. Notice the flats on the circle sides and there is a notch on the left side of the bottom circle.

Check your couplers and belts to make sure they are tight and not slipping. (Not sure what type of drive system you are using)

Share a screen print of your X & Y axis settings. If your acceleration is set too high it will cause lost steps.

Cheers Peter

 

[supman]

X Axis is Left to Right Y Axis is Top to Bottom

One circle was cut CW the other was CCW. I did increase the acceleration from 300 to 400 (didn't make any difference that was noticeable). I also cut a 100mm * 100mm Square which was done in a nice and smooth operation. Also a 102mm Circle with the same result. measurements one those were also good too.

 

[cncnutz]

Hi Supman

The acceleration looks reasonable though increasing acceleration makes things worse not better on a machine That cannot handle it.

The way to test if the acceleration is the problem is to slow it down to maybe 100 and see if it cuts correctly. It's like a car, you cannot go from 0 -100 instantly. You need to accelerate smoothly.

The Gcode looks ok with the circle made up of 4 arcs. What version software are you using and are you G2 or G3?

If you share the Gcode file I can machine the hole and see how it runs and show the result I get. I'm too busy / lazy to type out the code manually. ;-)

Cheers Peter

 

[supman]

G3 is the controller. Software Version v3.45. Serial No. G3-5758.

I can try later slowing down the acceleration. the machine used to cut small holes no problem with old controller. when I ran the attached file below it cut all shapes good except small holes, so I thought the backlash should not be a problem as that associates itself with mechanical deficiency. (or at least that is how I understand it)

 

[cncnutz]

Hi Supman

I cut your sample file and it came out correctly. Photo below.

I notice that your software version is out of date. It should be 3.46.1 though this is not your problem. I would look for something mechanical myself.

Cheers Peter

PS. If you want to share the screen on Masso press CRTL +P and it will copy the screen to the flash drive for you.

 

[supman]

Cheers for the test cut out. your test cut out certainly went better than mine.

OK can you point us in the right direction regarding checking out for a mechanical problem

Also what do you mean by "share the screen" is CTRL+P just a print screen?

 

[breezy]

@supman,

OK can you point us in the right direction regarding checking out for a mechanical problem

Go to Peter's YouTube page "CNCNUTZ" and search for a video on backlash, that will give you a good insight what to look for and how to compensate for backlash that can't be adjusted out.

Also follow Peter's suggestion to reduce acceleration to a low value and test, then adjust up by small percentage and test again, keep repeating this until your cutting results deteriorate, then go back to the previous setting. This way you tune MASSO to your motor / driver combination for best performance.

Also what do you mean by "share the screen" is CTRL+P just a print screen?

Instead of taking a photo of your screen, which can cause distortion / reflections etc. Use CTRL + P which will do a screen dump to your USB stick as a BMP file that you can then upload.

Regards,

Arie.

 

[supman]

Ok I finally get back to machine and while checking for possible free play / backlash I have noticed on my X Axis that one motor has holding torque and one does not. would this contribute to the problem of having with irregular shape holes?

 

[cncnutz]

It sure will SUPMAN and then some.

All stepper motors should have holding torque. It's the only thing they are really good at.

Cheers Peter

 

[supman]

Just an update. after helpful replies and following Gecko troubleshooting flowchart for the G203V driver found and fixed problem.

ROOKIE mistake forgot to plug connector into one motor oops! now works fine (surprisingly). of course also did have to change motor direction on one side of Axis as they are "counter rotating" so to speak.

THANKS

 

[cncnutz]

Glad you got it sorted.

I assume your axis is Rack or belt drive and allowed the motor on one side of the axis to drag the other side around making it look like it was working.

Bet it works much better now.

Cheers Peter