Author Topic: Steps (chugging) around radius.  (Read 3149 times)

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Offline AkPirate

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Steps (chugging) around radius.
« on: April 28, 2009, 08:51:16 PM »
I am wondering if any one can help, or point me to a post that covers my problem.  I am running Mach3, using Vcarve and Aspire.  I am using a solsylva machine with 18 tpi, 200 step motors, hobby cnc pro board. CV is on, backlash is off, and I have tuned my motors the best I can.  I am only able to run at about 30 to 35 ipm.  My problem is that all of my radius' have tool marks on them.  The machine seems to chug or jerk around.  It runs great in a straight line.  My recent, more detailed projects have needed a lot of clean up.  Not what I was looking forward to in a cnc..    Thanks, James.    ???

Offline SteinarN

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Re: Steps (chugging) around radius.
« Reply #1 on: April 29, 2009, 01:44:09 AM »
When you look at your G-code, does your arcs consists of many short straight lines or many short arcs?

Have a look on here http://www.machsupport.com/forum/index.php/topic,11310.msg71822.html#msg71822

And here http://www.machsupport.com/forum/index.php/topic,11310.msg71911.html#msg71911

Offline jimpinder

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Re: Steps (chugging) around radius.
« Reply #2 on: April 29, 2009, 11:46:12 AM »
Have you tried to do anything manually - e.g. a G2 or a G3 move. This is an arc (or circle) generated by Mach, and is a recognised CNC move. I think your will find your machine will do that properly.

Most CAD/Cam programs  do not generate arcs or curves at all, they are all straight lines - short straight lines - and this is probably what is causing the marks on your  workpiece.

Also check that the backlash on your machine is non-existant, or is at least compenstated, becasue every time the axis changes direction, backlash occurs, and again, marks your work.

Lastly try to ensure that your machine is on constant velocity, not absolute stop. In constant velocity Mach computes the acceleration into the next line as it is slowing down the present line, and strikes a level between the two. In absolute stop, Mach completes one line, i.e. slows to a stop, before accelerating into the next line. This will make the short straight lines all the more apparent.
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Offline AkPirate

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Re: Steps (chugging) around radius.
« Reply #3 on: April 30, 2009, 01:58:28 PM »
I have not tried any manual moves.  Not sure how.  Until recent my parts have been small.  Larger parts seem to have bigger marks.  CV is on.  Backlash off.  Not sure where to set CV numbers on settings page.  It does seem to go one direction at a time instead of combining X and Y movement together.   My original set up I could draw a square with a diagonal line with a pen and it looked great.  I will have to try it again.  ???  James 

Offline ger21

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Re: Steps (chugging) around radius.
« Reply #4 on: April 30, 2009, 06:40:37 PM »
Are you using the "Arcs" post?
Gerry

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Offline AkPirate

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Re: Steps (chugging) around radius.
« Reply #5 on: May 07, 2009, 07:55:47 PM »
Yes, Mach Arcs inch.  Only other is the ATC, and I believe that is for Auto Tool Changer.  Right?  I have been super busy and have not gotten to the machine.  Tonight I will be trouble shooting.  Thanks, James.