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Author Topic: I can´t get the table coord´s and "steps per unit" to work...not even close!  (Read 1410 times)

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Hi all!

First of all..thanks for all the help I already got from this forum!!
I´m new at this CNC stuff so excuse me in advance for any stupied questions and for not understanding all technical terms...
All my problems are probably some newbie mistakes...

I have just completed building my router and everything seems to work fine. I use the blue TB6550 driver board and 4 pcs Nema 23 motors (see technical spec. below)
My homing and limit switches works as they should I think. I have chosed to have my homing in the lower right corner.
Now I´m ready to start milling!!

So...here are my problems:

I can´t get the Nach3 table coord´s and "steps per unit" to work...not even close!

My cutting area is 800mm x 1200mm. When I load the roadrunner g-code the roadrunner is much larger than my whole cutting area!?
Why is that?

And when I moved my router from Y0 to Ymax the DRO showed 9.76someting...(My Ymax should be around 1200 mm)
Then I checked the "steps per unit" and when I typed in 1 mm the router took off to 120 mm and the calculator set the "step per unit" to 8.333 with DIP 1/2
With DIP 1/8 "steps per unit" ended up at 33.333 and 1/16 to 66.666

It feels very strange and I don´t where to go next!

I have read heavy amounts of text here and in different forums but I can´t find any answere...what am I missing!?!?
So I´m asking you guys instead and hope that you can help me out!


Here are the technical spec. for the stepper motors:

Part No.:                         57BYGH633  
Frame Size:                    NEMA23
Step Angle:                    1.8 degree
Voltage:                          3.0V
Current:                          3.0 A/phase
Resistance:                    1.0Ohm/phase
Inductance:                    1.6mH/phase
Holding torque:             13.5Kg-cm     270oz-in   (For Bipolar connecting, the holding torque is 270oz-in)
Rotor inertia:                  480 g-cm2
Detent torque:                0.68 kg-cm
Number of wire leads:    6
Weight:                           1.20lb (1.0 kg)
Length:                           78mm

When I wrote table coord's I ment machine coord's of course!
The whole thing feels stupid...what dumb newbie misstake am I doing?
Hi Martin being as you are new to Mach it sounds as if you machine is set to read imperial and you are assuming its metric, so 25.4mm is being read as 25.4inch. have a look at the first line of the program for the G20 and G21 code for the program units and the default setting of the machine!
As far as setting the steps per unit, I used the setting page of Mach and the set steps button just above the reset toggle on the bottom left of the page and used a digital vernier clamped to the table to set the steps per unit and push the sliding anvil with a metal bar in the spindle collet. Be careful if you use a Vernier to set your units as I ruined one by going in the wrong direction first time, luckily it was a £10 cheapo of ebay.
Hope this helps.
« Last Edit: February 19, 2015, 02:11:22 AM by jimthefish »
Hi jimthefish!

Thanks for your reply!
I've read that it is a very common mistake to mix up MM and Inch for new users so I've been very careful trying not to do that mistake...but somewhere I probably messed it up as usual ("Mess things up" is my middle name!) =)
The first thing I did in Mach3 was to set the native unit to MM and I haven't touched it since than. I´m gonna look into the G20/G21 stuff and see if I could find my answer there.

Thanks and cheers for now!
OK...lets walk the walk of shame!

I took a look in the XLM-file that I´ve got from the guy I bought my router stuff from....
There I saw that the Profile name was Mach3Mill...I followed the installation instruction and created my own profile with another name...quite obvious that nothing worked at all!

So...case closed...just some motor tuning to do!
Embarrassed but happy...now the fun begins!!