Hello Guest it is May 16, 2021, 02:31:46 PM

Author Topic: Help with Offsets  (Read 3347 times)

0 Members and 1 Guest are viewing this topic.

Help with Offsets
« on: June 10, 2008, 12:22:22 PM »
Hey so I am fairly new to Mach 3 and am using the program to create a machine that rotates a bracket in 2 dimensions while applying a gasket to the outer edge.  Basically, the a axis is set as rotational and linear movement is in the x axis.  The b axis is set up to feed the gasket out as the bracket rotates.  The problem I am having is that with each run of the cycle, the b axis is accumulating some sort of offset, and when it passes 360 degrees, the offset rolls back around to begin the 360 count.  This is bad because it causes the B motor to wastefully feed material as it trys to reset itself.  My question is, is there any way to set up the b axis so it will feed a set length of material for infinite runs without having to reset itself.  To rephrase, is there any sort of G code i can use to make this b axis forget that it just moved a set number of units?

Thanks
Danny a

Offline Chaoticone

*
  • *
  •  5,626 5,626
  • Precision Chaos
    • View Profile
Re: Help with Offsets
« Reply #1 on: June 10, 2008, 01:32:26 PM »
Danny, Have you tried checking, unchecking Rot Rollover in general config. mid lower section of page?

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: Help with Offsets
« Reply #2 on: June 10, 2008, 02:04:39 PM »

"Danny, Have you tried checking, unchecking Rot Rollover in general config. mid lower section of page?"


i have tried a dry run with the rotational rollover unchecked....this would be perfect except it also affects the a axis, which i want to reset at 360.....is there anyway to single out that rollover for just the b axis?

Re: Help with Offsets
« Reply #3 on: June 10, 2008, 02:22:15 PM »

"Danny, Have you tried checking, unchecking Rot Rollover in general config. mid lower section of page?"


i have tried a dry run with the rotational rollover unchecked....this would be perfect except it also affects the a axis, which i want to reset at 360.....is there anyway to single out that rollover for just the b axis?

 **I realized before that i had dismissed this solution too readily....i went back and reprogramed my G code so the a axis angles continued beyond 360 and then shut off the rotational rollover>>>>SUCCESS!!

The only issue with this fix is an increased homing time....and since we are trying to set this up for mass production....I am still going to try for other alternatives, such as reprograming using incremental units....i'll keep you informed as to how its going, but thanks for the solution, its the first big break ive had in weeks
 
 
 

Offline Chaoticone

*
  • *
  •  5,626 5,626
  • Precision Chaos
    • View Profile
Re: Help with Offsets
« Reply #4 on: June 10, 2008, 03:05:39 PM »
Quote
The only issue with this fix is an increased homing time....and since we are trying to set this up for mass production....I am still going to try for other alternatives, such as reprograming using incremental units....i'll keep you informed as to how its going, but thanks for the solution, its the first big break ive had in weeks

This could be fixed with a limit switch, dog, and a little VB I think. I have sent you a personal message.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: Help with Offsets
« Reply #5 on: June 11, 2008, 12:27:36 PM »
Ok, so I revised my G code in 2 different ways based on the suggestions above.

A) In this fix, I programmed using absolute movements with the rotational rollover shut off.  This required continuing angular measurements beyond 360>>>a355 a360 a365 a370 etc...
This is a good fix, but does require changes to the home switch of the a axis which i am unsure of...

B) In this fix, I programmed using incremental movements....this also fixed the problem, and i was able to leave the rotational rollover option enabled....As a result i will probably use this as my permanent fix as opposed to reconfiguring the homing limits..

Using option B, i came across another question...
I set my code up like this for movements
g91 g01 a5 x1 b1
g91 g01 a5 x1.3 b0.7
etc......

My question comes about from the idea of the modal g code
The way i understand it, g90 and g91 are saying whatever follows this code will be in either absolute or incremental units...
So g91 g01 will say "move at feed rate in incremental units by......"
Is this right?
Also, do i have to repeat the g91 g01 for every move?
I found when i did not include the g01 command, the movement was very jerky....

Still Learning.....
Danny A