Author Topic: x and y axis move at different speeds  (Read 3007 times)

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Offline dareng

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x and y axis move at different speeds
« on: November 28, 2012, 12:09:16 AM »
Hello

I have a problem I hope you can help me with, I built my 4 x 8 plasma cutting table and I've actually been cutting with it for a few months but tonight I realized I I have a problem.

The inches per, for my X and Y axis are set up and accurate 1 inch = 1 inch but the Y axis moves much faster than the X axis and tonight I actually lost my cut on 18gauge stainless steel in the Y direction.

On my x-axis I'm running 3 to 1 planetary gear heads, the y-axis I'm running direct drive, rack and pinion on both, my original understanding was when I built this that that would not be an issue. 

I am hoping there is something simple I am missing here and that you can help me out with my problem

                                    Thanks Darren

Offline RICH

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Re: x and y axis move at different speeds
« Reply #1 on: November 28, 2012, 05:59:58 PM »
Mach will move the axis at whatever velocity setting you have for the axis and if a combination move then will move at the slower
velocity of the two axis's. So if you have a difference in the gearing ratio just adjust velocities appropriately based on gearing so they are equal. Provided the axis can achieve the velocity..............

RICH

Offline BR549

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Re: x and y axis move at different speeds
« Reply #2 on: November 28, 2012, 07:48:04 PM »
Running direct drive with a rack and pinion is ASKING a lot out of the drives. Normally with R&P you run a reduction of 3-5:1 to slow the axis down to a usable range of speed VS torque.

SOunds like you may be loosing steps in Y.

Mach3 will always use the lesser of the velocities for multi axis moves.

(;-) TP

Offline Ya-Nvr-No

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Re: x and y axis move at different speeds
« Reply #3 on: November 28, 2012, 08:52:37 PM »
Your X-axis drive velocity settings would have to be three times the velocity set for Y.

Does make me wonder what the acceleration ratings would need to be set to keep them in sync.

Offline BR549

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Re: x and y axis move at different speeds
« Reply #4 on: November 28, 2012, 11:03:32 PM »
IF the steps per are set correct for each axis and the velocities are set the same then the speeds will be the same. WHAT will be different is the MAX accelleration of each axis. The direct drive will be much slower as it will be geared much faster(less torque) than the geared axis less speed(moreTOrque)

Mach3 will use the slower of the 2 accelleration rates when driving BOTH axis at the same time.

(;-) TP

Offline dareng

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Re: x and y axis move at different speeds
« Reply #5 on: November 28, 2012, 11:51:41 PM »
hi there

thanks for your help guys, very much appreciated, what I found is my velocities were set way different my x axis was 145 and my y was 500.

Obviously I am still learning, now I know my speed problem but it opened another can of worms that I had dealt with from the start, my y-axis which is run direct drive runs quietly and smoothly with the velocity of 500, but if I set my x axis above 145 it runs terribly rough and extremely noisy. As I said before my X axis is geared down 3:1 and you would think it would run quieter and smoother than the y-axis which I'm running director drive.

I am running drives from home shop CNC, model RSD 110 –  does anybody know anything about these drives? Could they be my problem?

any input would be awesome   hope to hear from you
                                                                                                 thanks Darren

Offline BR549

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Re: x and y axis move at different speeds
« Reply #6 on: November 29, 2012, 01:19:08 AM »
NOPE When you gear it down TOO FAR it overuns the torque band of the stepper motor (too fast) and causes lost steps.  That is the trade off for speed vs torque with steppers.

(;-) TP