Not enough holding power for z axis?

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PomeroyB
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Re: Not enough holding power for z axis?

Postby PomeroyB » Mon Dec 01, 2014 6:11 pm

I've used from Pololu to drive Nema 23 motors on a Plasma Cutter CNC. They're really nice because they are pin compatible with , so you can plug them into a RAMPs 1.4 board.

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Re: Not enough holding power for z axis?

Postby kakapoopie » Tue Dec 02, 2014 3:57 pm


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PomeroyB
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Re: Not enough holding power for z axis?

Postby PomeroyB » Tue Dec 02, 2014 9:28 pm

If the drivers are cool to the touch, you can try increasing the current by turning the little pot on the driver. Do this while the power is off, or make sure you use a ceramic screwdriver to avoid shorting the board.

The motors can get nearly 30C above ambient temperature, and the drivers can get way too hot to touch before you're in danger of burning them out.

Your motor should be able to easily hold your axis... We've used them to lift a grown person using just a normal lead screw. Turn up the power! :D

EDIT: just reread your post and saw the thing about the static torque. It also sounds like your motors may be turning off after each move. What firmware are you using? Are you sending it any motor enable/disable command?

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Re: Not enough holding power for z axis?

Postby kakapoopie » Tue Dec 02, 2014 10:05 pm

Thanks Pomeroy. I've tried turning the pot, it gets stronger up to a certain point then seems to cycle back to 0 if you keep turning. (no mechanical endstop on the pot) I think it's at max voltage...at least as high as it could go before it cycles back. I was using a metal screwdriver though while it was on..hopefully didn't damage anything.

It does seem like it's turning off after each move. I'm using sprinter...is there a setting in there for this? I'm not sending any enable disable command that I know of...I don't even know how to do that.

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cncbasher
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Re: Not enough holding power for z axis?

Postby cncbasher » Wed Dec 03, 2014 10:41 am

i'm wondering if you have the stepper enable configured incorrectly and it's working in reverse
the pots are only single turn , so once you reach max , it will drop to zero and start again , theirs no stops on the pots as you found out

what software / interface are you using ?

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Re: Not enough holding power for z axis?

Postby kakapoopie » Wed Dec 03, 2014 3:16 pm

Thanks CNC,

You're totally right.
Found the setting in Sprinter last night which disables the motor after moves and got it to stay on. plenty of holding power now :) The Nema 17 probably would've worked too if it was set up like this. I took off the brake, motor was actually making some noise while static but i turned the pot down so now everything is pretty quiet and smooth. Also staying very cool.

I got as far as putting salt water and resin into my vat, though for some reason the resin is sinking. Maybe I should've used more salt :/. Do you think adding salt after the fact would help? (with resin still in with the water)

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PomeroyB
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Re: Not enough holding power for z axis?

Postby PomeroyB » Wed Dec 03, 2014 11:48 pm

Good to hear you got it working!

I've got no idea on the saltwater... I keep hearing great things about it, but the info is so fragmented that I'm not really in the mood to experiment with it. Definitely make a post if you get it working -- I'd love to hear what worked for you.

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cncbasher
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Re: Not enough holding power for z axis?

Postby cncbasher » Thu Dec 04, 2014 7:13 am

great glad you found it in the end !

regarding salt water , i'm skeptical it would work , are you using Tap water or distilled water, distilled will be far better , and last longer , as is at least free of any Contamination
if the resin is sinking , i would hazard a guess that it's either going off or contaminated ,especially if it's been pre used , along with your vat being clean etc
use IPA etc to clean after use .

without having it in front of me it's difficult to pin down , sometimes the way the resin drops may give a clue
even grease from your hands can do it , so always wear gloves , when handling vat and resin

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Re: Not enough holding power for z axis?

Postby Phife » Thu Dec 04, 2014 11:16 am

You need a lot of salt in the water for the resin to float.

You must use distilled water, and I am using pool salt as its a very fine salt, very easy to mix. You could try water softener salt as long as its pure. Table salt can have other things in it so if you use that make sure its pure salt.

30% salt to water by weight. So if you have 10lbs of water you would dissolve 3lbs of salt into it.

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Re: Not enough holding power for z axis?

Postby kakapoopie » Thu Dec 04, 2014 2:40 pm



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