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Author Topic: Twin Steppers on slave axis  (Read 9910 times)

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Offline Katoh

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Re: Twin Steppers on slave axis
« Reply #10 on: September 18, 2008, 11:07:14 PM »
Thanks again Greg
I'm really starting to lean towards loosing one motor on the Y What I am probably going to do now is cut the X shaft in two using each motor to run one side independent to the other. If I find the machine Racks and binds I can always put a coupling back in the shaft and connect up as one again. Just to back track a bit The main reason I designed the machine to use twin motors is all my linears are Igus W200 slides not bearings, and in my thought I always believed that ill need double the power to make the machine move at any decent speed, From what Ive seen now on the Y axis with one motor 6000mm/min is not a problem but with the 2 I could only achieve 2000mm/min. The X axis with the linked motors runs at 2500mm/min but the belts are slightly longer an must just have a little more give in them.
Any More comments , suggestions or Recommendations are GREATLY APPRECIATED.
Cheers
Katoh
Re: Twin Steppers on slave axis
« Reply #11 on: September 18, 2008, 11:12:52 PM »
What I meant was to at least have each slave on the same board and port as its master.

Offline Katoh

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Re: Twin Steppers on slave axis
« Reply #12 on: September 18, 2008, 11:36:06 PM »
Hi Overloaded
Have Tried that used BOB 1 to run X master and Slave and used BOB 2 to run Y master and Slave, Made no difference to performance. When I tried Greg's suggestion of just using one Step and Direction Signals to run both motors there was a slight improvement Not Much. with the motors hard mechanically connected I can not get to run nowere near what I can with only one motor. What really gets me is I have seen Two steppers coupled together with a steel coupling  joining the shafts that was used in a commercially made CNC embroidery machine. Just tells me it can be done somehow.
Cheers
Katoh

Offline bowber

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Re: Twin Steppers on slave axis
« Reply #13 on: September 19, 2008, 04:46:39 AM »
I can't see 2 steppers fixed together working unless they are syncronised.
I've been told that steppers can be slightly out on micro steps but will always be correct on a step
If 1 is only 1/2 degree out of step from the other then they will fight each other all the time, they would have to be completly in step.
I think someone already said to try unlocking one pulley and power both steppers up and then lock the pulley back up.

Steve

Offline Katoh

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Re: Twin Steppers on slave axis
« Reply #14 on: September 19, 2008, 05:15:59 AM »
Hi Steve
I tried that as well, The problem I came across is it works fine till one looses a step then it seems to escalate, I can get it going with the two motors at a decent speed until the first lock up, Then after that you find for some reason you cant get motors back into sync, at a low speed they work fine, but for a timber router a bit of speed is not a bad thing. Ive being giving it some thought and I agree with the Philosophy that you really cant run twin motors in the way I have been. The X axis should work fine if split one motor controlling either side, the y axis the only way to run twin motors is to have a second ballscrew both driven individually from their own motor. I may have the opportunity in the morning to cut my X axis shaft in half, I will keep everyone posted on what happens after that. Thanks again to all your suggestions it has taken me a long way to resolution of my troubles.
Cheers
Katoh

Offline Katoh

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Re: Twin Steppers on slave axis
« Reply #15 on: September 19, 2008, 09:05:37 AM »
One last Thought before the X drive shaft meets its fate with angle grinder.
Because the steppers work OK at low speed could Power be the problem here,
My 48v 4amp per motor needs to be a lot more to have the top end speed.
Or will the extra power just mask for a while the main problem?
Cheers
Katoh

Offline ger21

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Re: Twin Steppers on slave axis
« Reply #16 on: September 19, 2008, 11:14:30 AM »
What's the current and voltage ratings of the motors?
Gerry

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Offline Katoh

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Re: Twin Steppers on slave axis
« Reply #17 on: September 19, 2008, 08:55:04 PM »
HI Gerry
The motors are rated in Series 4 amps 3.0 volts cant run the motors in Parallel as they require 8 amps and geckos only go up to 7.
Cheers
Katoh

Offline ger21

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Re: Twin Steppers on slave axis
« Reply #18 on: September 19, 2008, 11:36:33 PM »
If you run them bipolar parallel at 7 amps, you'll probably get more top speed out of them than running them in series.

And for best performance, power supply voltage should be 32 times the square root of the motors inductance in mH. The 48V might be a little high for parallel, but the 20 amps should still be plenty, even when parallel wired.
« Last Edit: September 19, 2008, 11:38:33 PM by ger21 »
Gerry

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http://www.thecncwoodworker.com/2010.html

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http://www.g-forcecnc.com/jointcam.html

Offline Katoh

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Re: Twin Steppers on slave axis
« Reply #19 on: September 20, 2008, 05:19:40 AM »
Gerry
I have thought about doing that, But wont I run out of power even by loosing one motor on the Y axis still leaves me with 4 motors each wanting 7 amps thats 32 amps in total.
Cheers
Katoh