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Software or Mechanical Problem
« on: March 27, 2009, 12:50:59 PM »
I am having some issues with a cnc router running Mach3. Lets see if I can explain this properly.
It all started cutting a circle in a piece of UHMW. When I was done the circle measured out of round by .025 / .03 travelling along X axis.. I started to investigate & was doing searches on the web & here at CNC Zone. I made some adjustments in Mach3 & started doing some tests.

I ended up ataching a 12" digital caliper on my x axis, opened it all the way. I jogged the axis until it started to move the caliper. I thened zeroed the caliper. I went into the MDI screen & zeroed the x axis. I then plunged into the material .125 deep & did a move, lets say 10.000 with a .500 end mill. I checked the travel on the Mach screen & it read 9.9996. I read my caliper & it read 10.000. I then preceded to measure the the cut. It was exactly .025 short or 9.975.

If I cut a square or circle, it is always off that amount on the x axis but dead on with the y axis. I have no significant backlash on any axis, for sure not .025.

I have had help from the manufacturer, Vortech Routers. They have gotten me through a few problems, but this one is still kicking my ass. Any help would be greatly appreciated.

Offline Graham Waterworth

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Re: Software or Mechanical Problem
« Reply #1 on: March 27, 2009, 12:57:25 PM »
If you cut a slot that is 5" long is the error half as much?

If YES its a steps per issue

If NO then its backlash/loose component

Graham
Without engineers the world stops
Re: Software or Mechanical Problem
« Reply #2 on: March 27, 2009, 01:10:47 PM »
No to your question Graham. The error is consistantly between .025 / .030 on anything I cut,

btw I had an oops
my measure ment on the 10.000 inch move with a .500 endmill was 10.475. The 10" inpass with the total diameter of the endmill, minus the .025 I am off

sorry.

I was thinking my steps per was accurate being that I made the 9.9996 move & my digital scale read 10.000. .0005 over 10.000 seemed to be accurate enough. With that being said, is the axis calibration tool in the settings screen accurate. This is what I used to set my steps per. Also thanks for the quick reply.
If you cut a slot that is 5" long is the error half as much?

If YES its a steps per issue

If NO then its backlash/loose component

Graham

« Last Edit: March 27, 2009, 01:33:12 PM by ynnek »

Offline RICH

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Re: Software or Mechanical Problem
« Reply #3 on: March 27, 2009, 02:14:14 PM »
I never used the axis calibration feature, but, another user i know just recently tried it out and said
it worked like a charm.

RICH

Offline Graham Waterworth

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Re: Software or Mechanical Problem
« Reply #4 on: March 28, 2009, 05:06:25 AM »
1.  If the error is a constant amount no matter what distance you have moved, you have backlash or a loose component.

2.  If the error changes as the distance moved changes you have step count error, the amount is proportional to the distance moved.

Backlash or a loose component is a constant error (within reason) it jerks one way and stops then the axis moves, reverse the direction and the component moves the other way then stops and the machine continues on its way.

If your error is constant then you have the first problem.

Look for loose blocks, belts, screws, anchor plates etc.

Graham
Without engineers the world stops
Re: Software or Mechanical Problem
« Reply #5 on: March 25, 2010, 11:57:10 AM »
I've got the same problem or a similar problem. My router will cut complete cirlcles, squares, etc. perfectly. But when I try to cut an open arch it ends up + or - 0.200" short. If I tell the machine to move 75 inches it moves 75 inches. I've checked the math in the code and it's what you'd expect. This will drive you nuts!!! How can the machine accurately step off everything else, but then consistently step off short during certain action. I also have a milling machine that I use the same program and it performs all actions perfectly. As for backlash wouldn't it show up in all the other cuts also? I'm certain that there is not .020" backlash in the router, much less .200". Please help if you have figured anything out.

Phillip
Re: Software or Mechanical Problem
« Reply #6 on: March 25, 2010, 02:11:20 PM »
I've got the same problem or a similar problem.
Phillip

Phillip unless you have the exact same problem it would be best to start your own thread

ynnek

IF you had some flex in the machine AND your cutter was dull it would measure consistently undersize

Phil
The Good Thing About Mach3, Is It's very Configurable

The Bad Thing About Mach3, Is It's Too Configurable

Offline Graham Waterworth

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Re: Software or Mechanical Problem
« Reply #7 on: March 28, 2010, 12:56:18 PM »
Hi Phillip,

post your code here and hi-light the problem area in the code.

Graham
Without engineers the world stops
Re: Software or Mechanical Problem
« Reply #8 on: March 28, 2010, 03:32:59 PM »
Graham I was sure that the error wasn't in the code. The math looked right. I do think the problem is resolved. Andrew @ Machmotion had me change the CV angle from 75 degrees to 45 degrees (in config/general config). I don't understand what that did, but it seems to have corrected the problem.

I see your posts constantly as I read along on this forum, and I think that's awesome. Glad your on here to try and help so many people!

Phillip
Re: Software or Mechanical Problem
« Reply #9 on: April 02, 2010, 03:15:46 PM »
help, some how locked myself out of config. how do you unlock?