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Author Topic: Need help with basic understanding  (Read 16129 times)

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Re: Need help with basic understanding
« Reply #20 on: February 20, 2011, 09:08:57 AM »
Yeah, I do see the tiny little offsets on it in the images.

I just reduced the acceleration from 500 all the way down to 50, and it didn't make any difference.

Cheers,
Dan

Offline ger21

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Re: Need help with basic understanding
« Reply #21 on: February 20, 2011, 09:19:46 AM »
Any chance the pen is moving?
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html

Offline RICH

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Re: Need help with basic understanding
« Reply #22 on: February 20, 2011, 09:23:11 AM »
I think both I and Gerry have shown you that it is not a code problem.
I don't need to try a different program or run the program as the backplot overlays exactly onto the original file.
I believe you have a problem with you machine. It may be your plotting device, axis, setup etc.....so the quicker you accept that fact
the sooner you will define and solve the problem.
RICH
Re: Need help with basic understanding
« Reply #23 on: February 20, 2011, 09:26:11 AM »
Well, it's actually a laser, as its only temporarily setup, it has the potential to move. I did try setting home on the machine to a different position, just to make sure it wasnt a certain section of the machine, but got the same thing. I will secure the laser down better tomorrow and give it another try.

I never said it could have been bad axis setup or an option somewhere in mach3, but there are no pointers that my steppers are skipping or belt is slipping.

Offline ger21

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Re: Need help with basic understanding
« Reply #24 on: February 20, 2011, 09:29:25 AM »
Quote
but there are no pointers that my steppers are skipping or belt is slipping

Probably 9 out of 10 (or more) people that have these types of issues always find out in the end that it's their machine. And most always want to point to the software first.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Need help with basic understanding
« Reply #25 on: February 20, 2011, 09:39:04 AM »
Well, how would I go about checking if they are skipping steps or the belt is slipping? I've tightened the belts enough that they have minimal sag, maybe it needs to be even tighter? My steppers have a fair bit of torque, it takes a fair bit of effort to stop them, so i'd be surprised if they were the problem.

Offline RICH

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Re: Need help with basic understanding
« Reply #26 on: February 20, 2011, 09:49:29 AM »
Make note of your current steps per unit. Go to the Settings Tab and use the axis calibration in the lower left corner of the page. Do a command via MDI line to move each axis one way and then the reverse. That will check your steps per unit.
You can also try different velocity and accelration settings, start low and just double the value until the calibrated steps per unit do not agree anymore with DRO displayed.That will give you an indication of when your starting to skip. That's why Gerry suggested you cut your velocity in half.

Let us know how you make out.

BTW, You can loose steps due to belt tension and you would not know it, but the amount  would be small, don't want to dwell on the belt.
RICH

Offline ger21

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Re: Need help with basic understanding
« Reply #27 on: February 20, 2011, 11:41:04 AM »
I wasn't implying that the motors are losing steps. My guess is that the laser is moving. I was just telling you why we tend to look there first.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Need help with basic understanding
« Reply #28 on: February 20, 2011, 12:39:53 PM »

Ive been generating gcode in various software, however sometimes the software will output the Y coordinates in the - values, and sometimes it won't.

I didn't see that anyone addressed this so I'll take a shot.  If you're laser homes to the left, for instance, and the table is set up so the a G0 Y1 moves the laser 1 unit to the right, then G0 Y0 would move it to the left one unit.  This assumes you're O,O origin is at the lower left of the drawing.  If origin is in the middle of the drawing, for example, and you start at the lower left of the drawing, left hand moves that go past the 0,0 origin will be negative numbers.

 


« Last Edit: February 20, 2011, 01:26:49 PM by Overloaded »
Re: Need help with basic understanding
« Reply #29 on: February 20, 2011, 09:40:05 PM »
Yeah, I understand why it could go into the -s now. Originally I didn't have a solid software to test with, so my gcode was all over the place. Now that I know sketchup works OK (Unless the machine isn't the problem), it makes sense that the machine draws it in the exact same spot as you did in sketchup.

I'll mount the laser on it properly when I get home and try it again.