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Author Topic: Setting Steps Per Unit in Mach3  (Read 19545 times)

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Setting Steps Per Unit in Mach3
« on: July 18, 2011, 03:37:07 PM »
Hi Guys,

After a few mods I have finally got my Denford Novamill up to the stage of configuring mach3. I have added new stepper motors, Nema 23 double stack motors on the X and Y axis and a Nema 34 single stack motor on the Z axis. The control I am using is from Rhonmac cnc with the controllers set to 8 microsteps.

The machine has a belt drive on each axis giving a reduction ratio of 1:2.5, the pitch on the ballscrew is 5mm. From this I worked out the steps per unit should be 800 (for a metric setup) I set this for each axis and when I commanded a movement of 1mm I got a very small movement on the machine. To get the machine moving the same amount as that commanded I had to set the steps per unit to 25889.97. I`m confused as to why my calculated number of 800 is so different to the actual one required?

Also, with such a high steps per unit the max speed is reduced to 57.94 which is about right from a crude measurement I did with stopwatch.

One thing to note is I`m only using the demo version of mach3 as I wanted to see if it was all going to work before I bought the license. Would this make a difference?

Any help would be much appreciated, thanks in advance!

Mike

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Re: Setting Steps Per Unit in Mach3
« Reply #1 on: July 18, 2011, 05:04:26 PM »
Sounds like you may have your native units set to Inch. You will see that from the Config menu, if its at Inch change to mm then reset your steps per unit etc to the 800.
Hood
Re: Setting Steps Per Unit in Mach3
« Reply #2 on: July 18, 2011, 05:24:08 PM »
Hi,

I have just checked the 'select native units' in the config drop down box and they are set to MM. Is this the only place I need to set the units?

Thanks

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Re: Setting Steps Per Unit in Mach3
« Reply #3 on: July 18, 2011, 05:28:05 PM »
Look on Settings page to the lower right and see if the mm LED is lit, if it is then I am not sure whats going on, if you attach your xml I will have a look and see if I can find the problem.
Hood
Re: Setting Steps Per Unit in Mach3
« Reply #4 on: July 18, 2011, 05:55:19 PM »
Just checked and MM is green.

I have attached the xml file from the backup folder, is this the right one? Thanks for your help on this..

Mike

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Re: Setting Steps Per Unit in Mach3
« Reply #5 on: July 18, 2011, 06:04:19 PM »
No its the one from the main Mach3 folder that is the current one, make sure you shut down Mach first before you copy it as Mach only writes to the xml on shut down.
Hood
Re: Setting Steps Per Unit in Mach3
« Reply #6 on: July 18, 2011, 06:10:35 PM »
Mike does it sound smooth when moving or really rough?
Re: Setting Steps Per Unit in Mach3
« Reply #7 on: July 18, 2011, 06:16:02 PM »
ok, I think this is the correct file.

It doesnt sound smooth to be honest. When my steppers move on the novamill is sounds more like a 'stepping' noise if that makes sense, same noise in both directions. I`m not sure what these are suppost to sound like so its hard to describe.

I have a step four cnc router and the motors on that have got a more high pitch constant noise when moving.

Thanks
Re: Setting Steps Per Unit in Mach3
« Reply #8 on: July 18, 2011, 06:16:41 PM »
best if I attach the file...ha

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Re: Setting Steps Per Unit in Mach3
« Reply #9 on: July 18, 2011, 06:21:47 PM »
I would say your acceleration may be on the high side, lower that and see if it helps, also worth lower the Velocity as well whilst testing things.
What kind of drives are you using? You may need a wider pulse or even need Sherline mode.
Hood