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trying to improve motor speed
« on: December 16, 2011, 06:18:55 PM »
Greetings from the swamps of south Georgia.  My name is John, aka the sheepdog, and I've been trying to run my homemade CNC machine with Mach3 but to no avail.  It is a small 15x15 unit with unipolar motors and is controlled by a Hughes Automation AIO-500 motor controller, originally running at 12 v but now has been upped to 15v.  The original manual that came with the board gave all of the hookups for Kcam which ran ok but seemed awfully slow, 8ipm.  I've purchased new motors, (bipolar) drivers and breakout board in hopes of improving performance.  When I put together the new motors, etc. I tried them on both Kcam and Mach3.  They both ran with no problems and Mach3 was the best.  Now I want to try Mach3 on the existing unit before taking it down to see if the problem is the software or do I need the bigger motors, etc. From all I've seen on the forum Mach3 will run unipolar motors but I can't figure out how to set the pins properly.  I'm thinking the 5v supply is not getting to the motors because it is built into the board and does not have a way to pick it up separately but that's just a guess.  I'm doing this as a hobby so I really do not know what I'm doing. Have tried e-mailing the Hughes Corp. but never got an answer.  I'm open for suggestions and hopefully we'll get this thing checked out.  Thanks in advance  John

Offline stirling

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Re: trying to improve motor speed
« Reply #1 on: December 17, 2011, 07:43:58 AM »
Hi John - welcome to the forum.

You're very unlikely to get any sort of speed/performance from motors using 15V. Also it may be a typo but your 5V should be going to the drivers NOT the motors. If you post ALL the specs of your motors, drivers, power supply and the gearing method of your rig then I'm sure you'll get the help you need.

Ian
Re: trying to improve motor speed
« Reply #2 on: December 17, 2011, 09:18:29 AM »
OK. Let's see if i can get you all of the info you need.  Motors, brand unknown, only has a CS on them.  Voltage rating is 5.3v @ 1 amp.  The drivers and I'm assuming breakout board are all built together and are manufactured by Hughes Automation, model AIO-500, stepper motor controller.  The manual says that it is designed for unipolar motors and is designed to be used with a power supply rated between 8 and 18 volts.  I origionally used a 12v computer power supply but was able to find a 15v so that was the reason I stepped it up.  The board has its own 5v regulated supply built into it.  Everything is controlled thru this one board.  It was a part of a package deal that I had purchased that had the motors and board all together.  Have learned , after the fact, that a combonation board of this type is not a good idea and that you're better off with individual components.  The motors supply movement to the components by way of 1/4-20 rods.  The unit is a fixed gantry with a 16.5x16.5 bed.  The board only allows for either full steps or half steps and I have it set up for half steps.  I have added the Kcam Maxstepper to the unit, which helps give it a smoother input but to the board but did little or nothing for speed.  I realize that this will never be a set the world on fire, whiz bang unit but I feel that the software is the biggest part of what is holding this unit back and I'm just trying to confirm it before I tear everything down and build another.  Unfortunately I have a tendency to build something, get it working and then move on to a new challenge.  Hope this will help to get me going in the right direction.  Thanks  John

Offline ger21

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Re: trying to improve motor speed
« Reply #3 on: December 17, 2011, 10:04:12 AM »
You'll never get much speed out of that, due to the low voltage and 1/4-20 screws. To get the maximum usable rpm from a stepper usually requires 15-20x the rated voltage of the motor. Speed is proportional to voltage, so you're only spinning the motor about 1/5 of what it's capable of.
The 1/4-20 screws make it even worse. As steppers spin faster, the torque drops off, usually quite rapidly. To get any speed with 1/4-20, you need to spin very fast, which requires very high voltages.

Imo, the software has nothing to do with the slow speeds you're seeing.

On a low powered setup like that, even the slightest amount of friction or binding in the system will seriously reduce speeds.

Using half stepping makes the motors very susceptible to resonance, which can reduce speed. Microstepping drives reduce resonance and provide much smoother motion and higher speeds.
My guess is that even with better drives and 24V, the best you could expect would be maybe 30ipm?
Gerry

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Offline stirling

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Re: trying to improve motor speed
« Reply #4 on: December 17, 2011, 10:52:31 AM »
Voltage rating is 5.3v @ 1 amp.

This tells us straight away that these motors are not going to be good. 5.3V-rated is high and 1Amp-rated is low. As Gerry says - typically you need 15..20 * rated Voltage so you'd be looking at approx 80V..106V power supply to get the "best" out of them. Unlikely you'll get a driver for that voltage. Certainly your driver rated at 8..18V is not even close to the town the ballpark's in.

Even if you reverse the maths - to get anything close to speed/torque from your system the motors would have to have an inductance of 0.2mH for a 15V supply - and they'd be the first I'd have seen if they had anything close to that.

Couple this with the screws your using that demand a VERY high speed from your motors to get good linear speed and I'm afraid you're system is just all wrong. I'm betting your motors have a round can too rather than a square one?

I'm with Gerry - no way your speed problems have anything to do with software.

Ian
Re: trying to improve motor speed
« Reply #5 on: December 19, 2011, 03:27:35 PM »
OK Finally able to get back to you guys.  After reading what you guys felt, it's probably best to just go ahead and build the new one like I had planned.  However I do have to disagree about the siftware not affecting the output speeds.  I still have the electronics set up and I went back and tried both siftwares again.  The Mach3 was decidedly faster than the Kcam with identical settings.  You also have to realize that these motors are just turning and not driving anything, so there is no friction to drag the speed down.  Oh yeah, I forgot to say in my breakdown of the machine that it does have linear bearings, not just bushings.  So onward and upward to bigger and better machines.  Thanks for the input from everyone and I'm sure I'll have more questions in the future.

By the way Stirling, you lost the bet.  They're not little round things, they are Nema 23 construction. 

Offline stirling

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Re: trying to improve motor speed
« Reply #6 on: December 20, 2011, 04:01:02 AM »
Hi Sheepdog

By the way Stirling, you lost the bet.  They're not little round things, they are Nema 23 construction.  

Just for the fun of it... I'm not paying up yet  ;D

First I never mentioned little. Also, all Nema 23 means is the dimensions of the mounting flange and holes. You can get (old style) round can and (modern style) square can BOTH in Nema23 and all other nema sizes too. So are they round or sqaure section "cans"? - double or quits. 8)

Ian

PS

You also have to realize that these motors are just turning and not driving anything, so there is no friction to drag the speed down
You can't "drag the speed down" of a stepper motor. It either moves at commanded speed or it stalls. There's no in between.
« Last Edit: December 20, 2011, 04:45:01 AM by stirling »
Re: trying to improve motor speed
« Reply #7 on: December 21, 2011, 05:20:27 PM »
I think I'll just bow out this time.  Most people know more about cnc machines than me so I fiqure it would be a losing cause.  By the way, the top picture looks like the motors I have.
John
Re: trying to improve motor speed
« Reply #8 on: December 21, 2011, 07:12:12 PM »
Don't just leave without your winnings! Ian bet you the motors were round, but you indicated that yours look like the top picture - square canister. Call the bet!

lol

In any case, good luck with the rebuild, and don't forget to have fun with it. Do some poking around online at machines that others have built and posted info/specs if you need ideas. Learning about and building the machines can easily be more enjoyable than running them!

Enjoy!