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Gaining Steps with SmoothStepper
« on: September 19, 2009, 04:12:25 PM »
My SmoothStepper gains a step when changing direction ie when any axis is in motion (in a + direction on the DRO) and then changes direction towards the -direction the SmoothStepper will gain .0001" until the axis passes thru .0000 on the DRO and starts the -direction on the DRO and then it will loose the .0001" extra step until the axis changes direction towards the +direction which the axis  will gain a extra step of .0001" again until it passes thru .0000 on the DRO. A dial indicator on the machine table confirms the extra step. I can run Mach3 and the SmoothStepper without the stepper motors hooked up and get the same results on the DRO's also (jogging and running a test program).  If I run Mach3 without the SmoothStepper I do not get the extra step so I think I have narrowed it down to the SmoothStepper. I am using the latest driver and plugin from the Warp9 site with the latest version of Mach3.
If anyone has run into this before or knows of of a setting that I should be looking at I would greatly appreciate any help offered.

Offline Jeff_Birt

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Re: Gaining Steps with SmoothStepper
« Reply #1 on: September 20, 2009, 10:43:31 AM »
I'm not sure what you are seeing on the DROs as Mach tells the SS where to go, the SS does NOT set the DROs. You probably have your step polarity set incorrectly. Many drives expect to see a falling (high to low) signal indicate a step, if you have your step pulses set active high then it won't work right.
Happy machining , Jeff Birt
 

Offline RICH

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Re: Gaining Steps with SmoothStepper
« Reply #2 on: September 20, 2009, 11:47:18 AM »
I get simular DRO numbers once in a while, and just ignore the silly 0.0001" because it's meaningless from a practical point of view. If i do a reset, then i don't get say 3.999 instead 4.000 post jogging numerous times.
How do you really know that your loosing or gaining a single step?
IE: for a step per unit of 20304 on my lathe, 1 step=0.000049251"
To truly measure that you would need to be at some 400x with a calibrated microscope and no i would not trust the  simple reverse movement of an indicator as i can prove that it's not indicating 0.0001" on reverse.
Not all steppers are created equal. Some are made better than others relative to how their poles line up and lock in at a postion ( which can be a silly 0.0001" of movement).
Just some thoughts on the matter,
RICH

Offline Jeff_Birt

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Re: Gaining Steps with SmoothStepper
« Reply #3 on: September 20, 2009, 12:05:58 PM »
Hey Rich your correct about the DROs, good thinking. Depending on your steps/unit you may not get an even number in the DRO due to rounding to the number of units displayed.
Happy machining , Jeff Birt
 
Re: Gaining Steps with SmoothStepper
« Reply #4 on: September 20, 2009, 12:07:25 PM »
Hi Jeff
Thanks for your tip, I have played with changing polarity on both step and direction but still have same result, I know the SS has no say in what the DRO's indicate, if I do not select the SS on start up of Mach3 and run a test program or jog I do not get the extra step so this is why I think there is some setting with the SS that is causing the extra step. If I change the steps setting in motor tuning to the 30000 area the extra step problem dissappears but that is way too many steps for my setup, I require 8000 steps to obtain the proper travel for my machine.

I guess Rich is right it is small and meaingless from a practical point of view but it was not there until I switched to the SS and this old dog is not used to seeing the extra .0001"

Jim

Offline RICH

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Re: Gaining Steps with SmoothStepper
« Reply #5 on: September 20, 2009, 12:18:27 PM »
I guess you can change the DRO to display additional digits. Looking for such a small unit, like a step or small
movement requires some realy good equipment that most folks just won't have.
We are somewhat spoiled as time goes on and want all to come out perfect on what we see and sometimes it's
just not so.

Jeff, will a single skipped step have the same same affect as if you were to skip 10 steps such that the stepper
motion is lost?
RICH

Offline RICH

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Re: Gaining Steps with SmoothStepper
« Reply #6 on: September 20, 2009, 12:31:01 PM »
At 8000 your resolution is 1/8000 = 0.000125 which is the smallest step you can make. Mechanicaly you may be plus or minus whatever. So even if electronicaly all was perfect, a mechanical measurement may show differently.
RICH
Re: Gaining Steps with SmoothStepper
« Reply #7 on: September 20, 2009, 02:39:44 PM »
Thanks for your input Rich it is all making sense now that I am past the tunnel vision state and I now see it is really a small issue of resolution and there is nothing that can be done about it, again many Thanks for your help.

Jim