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Re: Motor tuning question
« Reply #10 on: May 24, 2006, 02:48:02 PM »
Okay 24  ;D
Fixing problems one post at a time ;)

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Offline MarkR

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Re: Motor tuning question
« Reply #11 on: May 24, 2006, 06:45:57 PM »
For the record, the HobbyCNC board will take a max of 48 VDC  ;D

I am curious, I have 2 12 VDC supplies, one with a 10 amp rating, and one with a 60 amp rating. If I were to put these in series to get 24 VDC, would that work (at least to run tests until I get the whopper transformer I am ordering)?

Thanks for the feedback!

Mark
Re: Motor tuning question
« Reply #12 on: May 24, 2006, 07:29:30 PM »
It will work but try not to go over the 10Amp... That would be Very bad for the power supply...
Fixing problems one post at a time ;)

www.newfangledsolutions.com
www.machsupport.com

Offline MarkR

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Re: Motor tuning question
« Reply #13 on: May 24, 2006, 09:17:09 PM »
I am just checking motor movement and have yet to get a cut made with the table. I will see what I am missing at 12 volts by trying it together. I don't think basic movement will over stress the motors to pull more than the 3 amps each that they are rated for.... Will it?

Re: Motor tuning question
« Reply #14 on: May 25, 2006, 12:08:22 AM »
Maybe.. Lower Voltage = Higher amps (Ohms LAw).  I'd get a DC Current Meter and test it.

HTH

Sid

Offline MarkR

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Re: Motor tuning question
« Reply #15 on: May 27, 2006, 02:14:53 PM »
***EDIT***
Just discovered my X axis lead screw motor coupler was loose... BIG problem if you want to get a motor to turn the lead screw....Friction fitting will only move the screww so much :(  Maybe this is the source of my problems !!   :-\


Hi Again:

I don't have enough hair left to be pulling it out. So, I again turn to the gurus of Mach to see if I am missing something.

I am getting almost zero torque today when testing at any setting. Do I need to shut the program down and re-start it when I make changes in the motor tuning section? I hit the sliders (per video instructions) and then reselect the axis and push the arrow keys.

What I am getting is jumpy motors. I believe I have set the speeds up properly (500 rpm to start = 100 inches @ 5 tpi) and the acceleration is around mid way on the sliders.

I am running at 12 volts, so I am not really sure the speed I should see at max velocity. So, I am going to spend forever trying to get this set up to work, but atleast I see movement!

I ran my first cut last night and the dropped steps left my X axis about 1/2" short of the place it should have stopped. Y seemed fine.

Sorry if this just seems like repetitive questions on the same problem, but I am stumped, and I used to think I was pretty good with thinking this stuff through.

Perhaps it is my laptop? I tried to get it set per the optimized recommendations, and STILL had the same graph profile as before I did anything! BIG spikes and lots of them. Using a Dell Laptop with 1.5 GHz processor and 1 gig of RAM. My desktop has a great graph profile when testing and I am thinking of trying this one to see if that matters....

Thanks for helping me think this one out!

Mark
« Last Edit: May 27, 2006, 02:35:45 PM by MarkR »
Re: Motor tuning question
« Reply #16 on: May 27, 2006, 02:35:40 PM »
Hey Mark,

Not sure if this is any help to you but perhaps it might stimulate your hair folicles to grow back...

Like you, I am runing a 12V Stepper system.  When I first installed it, I tried to get get max resolution min 2000 steps per unit which would equal a cutting accuracy of .001"-kinda the industry standard.  I got things to work that way but, like you it was either exscruciatingly slow moving with buttloads of torque or zippy speedy with almost no torque and would mis steps if you blew air in the general vicinity of the machine.

I spoke with the dude who made the driver board and he said "more voltage" will solve the problem.  Well, after having purchased the 12v supply, installed it in an enclosure that was already on the verge of being too small, combined with the additional cost of getting a larger pwr supply, I thought... Do I REALLY need .001 resolution?

In my case, I decided that I did not.  So, I changed out a couple of pulleys to give me more speed and settled on a resolution of .01 for the time being.
 
I suppose that for most people this low of a resolution is insuffiecient but for me cutting wood and foam, it works great.  I have better than 1/64" accuracy which, when cutting wood is a splinter so small I doubt most people would even notice the diff.

The machine immediately started runing faster (around 200 ipm) with torque to spare.

Food for thought- Good Luck!

Regards,
Sid
Re: Motor tuning question
« Reply #17 on: May 27, 2006, 02:42:48 PM »
I think running your steppers at 500rpm, with 12 or 24 volts, might be pushing it a little, I could be wrong.
Most laptop paralel ports output 3 volts, instead of the usually needed 5 volts, try your desktop, unless you have a breakout board that takes care of that voltage difference.
You dont have to restart Mach everytime you tune the motors, but you do need to save the axis settings with each modification for it to work.
You could try out Sids suggestion, steppers have the most torque at low speeds, so if you add a 1:2 pulley system (1 turn of the motor=2 of the leadscrew, not the other way around) it just might have enough torque to run your cuts without loosing steps, and increase the speed in the process. You could check the torque speed curve of your steppers to see what would happen to the available torque and speed with the 3 scenarios (1:1, 2:1, 1:2 ratios).

Dont give up, have patience.
Regards
Fernando

Offline MarkR

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Re: Motor tuning question
« Reply #18 on: May 27, 2006, 06:15:12 PM »
Hey Guys!

Thanks for the encouragement! I will look at modifying the machine with the pully system. Great idea.

After posting, I hit my x carrage and it moves on it's own, making me look underneath and seeing the motor connector was loose and not even connected to the motor. This was causing the 'slipping' to the extent it was. I re-attached the lead screw, and now at least I have movement. What I was initially thinking was a stalled motor, was an un-attached motor (Good grief!).

BUT, I am having some erratic motor speeds (the lead screw does not turn very smoothly, but in rapid jumps of turns). It is rapid enough to get a decent linear motion, but not the silky smooth operation I had thought I would see.

Most of my requirements will not require .001 accuracy, so your suggestion to make a ration reduction unit is well taken. I too and just cutting wood and foam, so it is not like I am doing the kind of machining the big boys here are doing.

Thanks again for the encouragement! :)

Mark

Offline MarkR

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Re: Motor tuning question
« Reply #19 on: May 27, 2006, 06:18:16 PM »
BTW, I DID find that using 500 RPM was way too fast. I dropped the velocity to 40 ipm and saw a decent torque to speed, so I left it there.

I actually cut my first part and now am trying to learn how to compensate for the tool diameter.

THAT is a subject for a new thread in the Lazy CAM area :)