Hello Guest it is May 14, 2021, 10:18:20 PM

Author Topic: My machine is not repeating  (Read 3269 times)

0 Members and 1 Guest are viewing this topic.

My machine is not repeating
« on: October 07, 2008, 10:13:25 PM »
Hi I need some ideas. My machine is not repeating. I have a 3 axis router table, two of the three axis are like grid shifting. I used the auto cal. to set the units (imperial units), but it keeps moving .001 to the positive every time it change direction. The cutter comes out of the wood after it goes up and down a bunch of times.        Thanks Louie
Re: My machine is not repeating
« Reply #1 on: October 07, 2008, 10:19:19 PM »
That sounds like a timing problem on the DIR signal.  You should try changing the pulsewidth.  If you're using a BOB, it could indicate there is excessive delay through the BOB on the DIR signal, so when there is a change of direction, the first step in the new direction is taken before your stepper driver sees the DIR line change.  The solution there is to either find a faster BOB output to use, or get a better BOB.  What BOB are you using?

Regards,
Ray L.
Regards,
Ray L.
Re: My machine is not repeating
« Reply #2 on: October 07, 2008, 11:10:55 PM »
Ray thank you for your reply. The BOB I have is a CNC4PC C1-parallel port interface card. I tried to increcse the Dir pulse to 5 but it did not change. do you thing I need a different BOB.   
       Thank louie
                           
Re: My machine is not repeating
« Reply #3 on: October 07, 2008, 11:55:45 PM »
Louie,
   I'm not familiar with the C1, but I have a C11, and I know the early ones used fast optos only for the step signals, and slow optos for all the others.  On mine, the slow ones were REALLY slow.  The current C11 uses fast optos for all signals, and works much better.  I'd suggest you look at your board, and determine the revision level, the contact Arturo at CNC4PC, describe your problem, and suggest this might be the problem.  At a minimum, he can tell you which are the faster outputs.  Are you using the outputs he recommends?
   One thing you can try, to determine if this is the problem, is to connect one axis connecting the DIR signal through the output you normally use for the STEP of another axis, and see if that one axis now works correctly.  If it does, then I think you have a smoking gun.

Regards,
Ray L.
Regards,
Ray L.
Re: My machine is not repeating
« Reply #4 on: October 08, 2008, 05:45:36 PM »
Hi Ray I tried moving the DIR signal wire to the Z Axis to a stepper output and we had no change.
So I tried moving the Y Axis wires (the one that works OK) to the Z Axis outputs at the BOB and moved the Y Axis wires to the Z Axis at the BOB. Now the Y Axis which is on the Z Axis outputs at the BOB still works OK.The Z Axis which is on the Y Axis outputs at the BOB still is moving .001 to the positive direction every direction change. Looking at the two test it looks to me that the problem is in my drives not picking up the DIR signal quick enough at the change of direction. I would like to thank you for your ideas and a look at this from a new direction.

Thanks Louie
Re: My machine is not repeating
« Reply #5 on: October 08, 2008, 06:08:04 PM »
Hi Ray I tried moving the DIR signal wire to the Z Axis to a stepper output and we had no change.
So I tried moving the Y Axis wires (the one that works OK) to the Z Axis outputs at the BOB and moved the Y Axis wires to the Z Axis at the BOB. Now the Y Axis which is on the Z Axis outputs at the BOB still works OK.The Z Axis which is on the Y Axis outputs at the BOB still is moving .001 to the positive direction every direction change. Looking at the two test it looks to me that the problem is in my drives not picking up the DIR signal quick enough at the change of direction. I would like to thank you for your ideas and a look at this from a new direction.

Thanks Louie

Louie,

    That is very odd indeed.  What motor controllers are you using?

Regards,
Ray L.
Regards,
Ray L.
Re: My machine is not repeating
« Reply #6 on: October 08, 2008, 09:19:44 PM »
The drives I am trying to use are Allen Bradley Ultra series 100 servo Drive two 1398-DDM-005 and
one 1398-DDM-019. The 019 is working OK. It's the older of the three units. The 005 units are not behaving. I have them set up for a (External Step/Direction Interface via TTL Differential Line Drivers). These Drives have an auto tune But I think I need to go deeper to get them working right.
     Louie