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Author Topic: Math check on motor tune please  (Read 3328 times)

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Math check on motor tune please
« on: April 07, 2010, 09:44:07 AM »
New to the board and just have a few questions. I just got my motors set up and the are moving at a lightning speed of about 1 inch per min but at least they are moving. I am retrofitting a Practical cnc plasma 4x4 table.
I bought a kit from Tom at CandCNC I have 740 oz steppers on the x and y and 850 oz servo on the z axis with gecko drives. I have asked Tom a million questions already with the set up and thought it would be best to move on to the forum.

X and Y axis---The belt reduction from the motor to the pinion drive is 1-2.5 and the distance of travel on the rack is 2.625 inches per rotation of the pinion gear assuming 200 steps per revolution and 10x micro stepping on the gecko my steps per inch should be 1905 Right????????
Z axis it takes 5 rotations of the z axis to move 1 inch 5:1 assuming 500 encoder steps per revolution my step set up would be 2500 right?????
I would like my table to move at at least 200 inches per min so this figure would go in the velocity box? what would be a reasonable number for the acceleration box? and the step pulse and Dir Pulse numbers have me completely bamboozled
Please help me ???
Greg

Offline Tweakie.CNC

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Re: Math check on motor tune please
« Reply #1 on: April 07, 2010, 10:25:15 AM »
Hi Greg,

Steps per revolution calculations are OK but enter the complete figure (1904.7618) not just 1905.

The steps per revolution go into the 'steps per' box the velocity and acceleration are done by trial and error. Try velocity at 2000 and acceleration at 200 to start with and work from there. Select one axis, enter the figures and try the result with the up/down arrow keys, when correct click 'save axis' and then move on to the next axis etc. You may need to go back and fine tune them again when testing the whole machine.

Tip; Don't go for the highest possible speed as best overall reliability is probably some 10% to 20% less than the motors will reliably run at.

Hope this helps,

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Math check on motor tune please
« Reply #2 on: April 07, 2010, 11:31:08 AM »

I would like my table to move at at least 200 inches per min


We all do  ;D

But i don't think your gonna get that as Tweakie.CNC says better have consistency than speed = less scrap

Phil
The Good Thing About Mach3, Is It's very Configurable

The Bad Thing About Mach3, Is It's Too Configurable
Re: Math check on motor tune please
« Reply #3 on: April 07, 2010, 12:31:16 PM »

why won't I be able to get the faster speeds? on the system I replaced I was getting 6oo ipm without proplems

Offline RICH

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Re: Math check on motor tune please
« Reply #4 on: April 07, 2010, 06:18:05 PM »
Quote
kit from Tom at CandCNC

Ask Tom if he has any motor curves at different voltages and wiring for those steppers. If you have that you can get a relative idea of performance.
If not then you will need to test on your owne. Go to the Gecko site and you will find some good reading on motor basics.
Steppers can be like apples and oranges.....
RICH
Re: Math check on motor tune please
« Reply #5 on: April 07, 2010, 06:29:18 PM »
thanks for the help guys

Offline Sam

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Re: Math check on motor tune please
« Reply #6 on: April 08, 2010, 04:56:45 AM »
One thing that you have going in your favor is that your driving a plasma cutter, and not a heavier setup that a spindle would require, and there are no cutting forces. I don't see 200 ipm being unrealistic, even higher, if the rest of the components of the machine are up to it.
"CONFIDENCE: it's the feeling you experience before you fully understand the situation."