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Author Topic: Feedrate override with MPG  (Read 15056 times)

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Feedrate override with MPG
« on: July 02, 2009, 04:56:12 PM »
I have an MPG pendant for manual jogging of my mill, and it works great.  I'd like to extend its capabilities by using the MPG encoder for increasing/decreasing the feedrate override % (FRO) and the spindle speed override % (SRO).  The pendant has a 6-axis selector switch for jogging, and since I don't need axes 5 and 6 for my mill, I'd like to use these selections to control FRO and SRO.

I have some experience programming PLCs, but I'm having trouble getting my Brain to behave as I wish.  Here's the behavior I'd like for the feedrate override function:

1)  Turn the axis selector switch to FRO.
2)  Rotate the encoder CW or CCW to increase/decrease the FRO % from its current value.
3)  Upon turning the selector switch from FRO to another mode, I'd like the FRO value to remain at its setting from step 2, even if I spin the MPG.

Has anyone attempted this?  If so, can you send me your brain?  I've used the better part of a vacation day on it, and I don't have anything to show for it.  BTW, I'm not using ModIO since I have enough inputs on my parallel port to do the job.


Re: Feedrate override with MPG
« Reply #1 on: September 26, 2009, 01:44:12 PM »
I have been watching this post for an answer, also. I have issues getting MPGs to do the functions (similar to yours) I need. I have tried a couple of posted brains and have written 2 of my own and keep hitting a brick wall at some point. Maybe someone will have pity on us!

Offline poppabear

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Re: Feedrate override with MPG
« Reply #2 on: October 16, 2009, 09:34:22 AM »
you guys dont want to do that in a brian unless you just like pain.

Do it in VB where you can compare an old value, and set your range limiters.

Commercial Mach3 & Mach 4, Design/Build/Retrofit CNC and Industrial machines.
Re: Feedrate override with MPG
« Reply #3 on: July 14, 2011, 12:21:59 AM »
I did it.  It took me awile, but I wanted it so that I could reset my override and not have the potentiometer in an "off-zero" position and I didn't want the delay of macropump.  Not sure if I worded that well.  Anyhow, the trick is to reference the MPG velocity and not the counts. 

--input = MPG Velocity--  --Lobe = A/10--  --Terminate=V1--

--Input= V1--  --Lobe=Pass through--
                                                            ---Lobe=A+B---  --Terminate=FRO DRO--
--Input= FRO DRO--

You may need to adjust the A/10 Formula to A/100 or A/500 etc. depending on your MPG.  Just tweak it till it works good for you.


Offline BR549

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Re: Feedrate override with MPG
« Reply #4 on: September 28, 2011, 09:59:10 PM »
What type of pendants are we talking usb modio LPT ??????

(;-) TP

Offline BR549

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Re: Feedrate override with MPG
« Reply #5 on: September 28, 2011, 11:25:12 PM »
IF I remember correctly we did this years ago. Bring the MPG in also as an encoder(use the same pins/ports and set teh steps per to the resolution you want to control the FRO. THen when you need to do the FRO FUNCTION send the encodered dro value to the FRO % of override value DRO.

When you call the function into play at the same time reset the encoder dro to the same value as the current FRO value so it is in sync at startup of the function.

Just a thought, (;-) TP

Re: Feedrate override with MPG
« Reply #6 on: July 24, 2012, 09:50:28 PM »
Did it with the help of Bob's brain. Tweaked it a little to work only when MPG jog LED is off and give out exactly one % FRO change on each click of DRO. Here's the brain I am using with Nemicon MPG connected to PP. Nice little add-on to my machining center.

Re: Feedrate override with MPG
« Reply #7 on: July 25, 2012, 05:30:54 AM »
 :( MPG doesn't work during program execution. So this brain is useless for FRO during a program. I have to try a few more ideas. Let's see ....
Re: Feedrate override with MPG
« Reply #8 on: September 04, 2013, 09:58:30 AM »
OK. It's done. I can use my Parallel Port MPG to control the FRO, even during program execution too. Here is a screen shot of the brain and macro I've used for this. I am using 2 userdro's and one userled for this application. The macro can be assigned to a button on the screen and the userled acts as an indication of enabling of this function. If anyone needs more clarification I will put up a simple tutorial on how to do it.


Offline Chaoticone

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Re: Feedrate override with MPG
« Reply #9 on: September 04, 2013, 11:40:15 AM »
Very slick Zafar!  :) Thanks for sharing.

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

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