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Author Topic: MPG motion and following error help needed!  (Read 7590 times)

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MPG motion and following error help needed!
« on: May 08, 2013, 01:05:32 PM »
I have a setup using a DSPMC/IP and am having troubles with MPG motion.   When set to 10 thou per step, if the encoder MPG is turned to fast, or quick change from one direction to another, following errors consistently occur.  No following errors are occurring with rapids or feedrates.

It is as if the MPG is electronically geared to the motor at 10 thou per step, completely ignoring any and all velocity/acceleration limits. I see Mach3 has MPG velocity limits but the DSP plugin seems to ignore these values?   Really hoping to find a simple fix to this.  Or have I missed something?

Thanks in advance!

Re: MPG motion and following error help needed!
« Reply #1 on: May 10, 2013, 08:54:54 AM »
I cant believe no one else has not seen this issue?  I have a 1991 Haas in the shop and you can grab the MPG handwheel, give it a hard spin and you can see the axis lag significantly behind the mpg wheel, because the motors (motion commands) are limited within acceleration and velocity limits.   Doing the same on my 2013 mach3/DSPMC rebuild causes annoying following errors because of the way the mpg ----> motion is calculated within the DSPMC.   

Can I work around this by either increasing the following error to a dangerous value (ie 50800 which gives me 1 full inch of following error) ONLY when MPG mode is active?   Returning to 3000 for MFE when MPG is not active?     Is there a DSP macro accessibility to this parameter?

Or can I connect the MPG to a serial or parallel port using Mach3 to read the mpg position and and generate the motion command?  I think this may not be possible with the DSPMC plugin active.........

Would love to solve this.

Offline Chaoticone

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Re: MPG motion and following error help needed!
« Reply #2 on: May 10, 2013, 11:53:58 AM »
Have you asked the folks that make the DSPMC?  I'm just thinking out loud here so take it with a grain of salt.......  they would be the only ones that can modify their plugin.

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: MPG motion and following error help needed!
« Reply #3 on: May 10, 2013, 02:36:24 PM »
Thanks Chaoticone, I did, and finally got a response this afternoon.... (I know I am a little impatient  :P

Hopefully this will be implemented soon.   I still am surprised that no one else has encountered a similar issue?  To all the other DSPMC users, what has been your MPG experience?   

Thanks again.
Re: MPG motion and following error help needed!
« Reply #4 on: May 10, 2013, 04:33:49 PM »
My experience has been that I don't use an MPG just yet. Itis on thelistof things to do however.

Mike

Thanks Chaoticone, I did, and finally got a response this afternoon.... (I know I am a little impatient  :P

Hopefully this will be implemented soon.   I still am surprised that no one else has encountered a similar issue?  To all the other DSPMC users, what has been your MPG experience?   

Thanks again.
We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.

Offline Chaoticone

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Re: MPG motion and following error help needed!
« Reply #5 on: May 10, 2013, 06:57:24 PM »
Do you have an option to choose velocity, velocity step, single step, or multi step using the plugin?  Might be worth mentioning the multi step and velocity only are really the only 2 modes that work well in Mach.

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: MPG motion and following error help needed!
« Reply #6 on: May 11, 2013, 10:37:15 AM »
Do you have an option to choose velocity, velocity step, single step, or multi step using the plugin?  Might be worth mentioning the multi step and velocity only are really the only 2 modes that work well in Mach.

Brett

I have played with Mach3`s MPG settings with much frustration.  From my experience, the DSPMC ignores everything MPG related in mach 3.... It does not matter what the settings are set to.  The only thing that has any relation, is the the mpg counts per click in the ports and pins setup page and the step values in the general settings screen.  I believe the DSPMC takes these values, and when MPG mode is enabled, The MPG is directly and electronically geared to the axis at this ratio.  No other motion processing is occurring.   This is of course my own thoughts on what is going on inside the box....  example.... my MPG is 100 ppr, and ends up at 4 pulses per click (100 clicks per revolution, x 4 for quadrature signal).  Set at .010 per click, or 1" per rotation, the axis attempts to instantly, with no motion limitations applied, move in direct ratio to the MPG.   If the operator is very careful they can eliminate the following errors by being smooth, but making an abrupt change in direction, or trying to move an axis as fast as possible to zero a part or whatever, causes a Max following error and it simply shouldn't.   The operator can, and will spin that wheel beyond what the electronically geared axis can handle for acceleration and velocities.   This is of course not a problem set to .001 or .0001 per click, as the axis can handle it at these gearing ratios.  Of course the 10 thou is the most used!


« Last Edit: May 11, 2013, 10:41:26 AM by dkyuss »

Offline Chaoticone

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Re: MPG motion and following error help needed!
« Reply #7 on: May 11, 2013, 10:44:48 AM »
This may well be problems in the plugin but I better let those that are more familiar with the DSPMC reply before I pull you off on a tangent.

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: MPG motion and following error help needed!
« Reply #8 on: May 11, 2013, 10:47:38 AM »
My experience has been that I don't use an MPG just yet. Itis on thelistof things to do however.

Mike

Thanks Chaoticone, I did, and finally got a response this afternoon.... (I know I am a little impatient  :P)  

Hopefully this will be implemented soon.   I still am surprised that no one else has encountered a similar issue?  To all the other DSPMC users, what has been your MPG experience?  

Thanks again.

How do you Zero a tool?  Or zero in on a part?  Or must be a plasma table or something where these do not apply?

Offline Chaoticone

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Re: MPG motion and following error help needed!
« Reply #9 on: May 11, 2013, 11:20:34 AM »
I use an out dated auto touch routine for the Z and a MPG with a piece of paper for x and y.  I have used a game controller for a pendant in the past.  You can also hit the tab key and adjust the MPG fly out and use key strokes but no idea what will apply with the DSPMC.

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!