Help calibrate axis: 1" = 1"

[CNC Lurker]

I was running some test code on my router and realized that I didn't set something right because Mach3 isn't reading 1" as 1".

(By the way, I'm using 1/2-10 5-start ACME screws)

I went to the Config menu in Mach3 and selected "Select native units" and chose inches and restarted Mach3.

I moved the X, Y, and Z to a random location and zeroed them out so that I was at 0,0,0 on the user coordinates. I then moved the X axis 1" (measured using a tape measure) and the X read as .1981" (see first screenshot). In hindsight, that was probably supposed to have been .2" except I eyeballed 1" on my tape measure.

I'm not sure where exactly I'm supposed to tell Mach3 how many times to rotate to make it move 1". I went to the "Config" menu chose "Motor Tuning". Is that where I'm supposed to change things to make it rotate correctly? (see 2nd screenshot).

Am I supposed to change the "Steps per", "Step pulse", or am I trying to change it in the wrong location altogether?

[CNC Lurker]

I don't know the math behind it, I just bumped it around till it worked, but changing all steps to 4000 worked.

[jjacstcy]

I had bookmarked this video as I to was wondering how to calibrate my machine once I get through building it.
Hopefully it will help you out.
YouTube - anajonesr's Channel

[gjhammer]

You definitely adjusted it in the correct place, the "Steps per". The "Steps per" is the amount of steps required by the motor for your nut to travel 1 inch (or 1 mm).

I have 1/2"-10 5 start screws from McMaster-Carr, and I know they are documented that the nut will travel 1/2" per full revolution. So from the start I need to multiply my "Steps per" by 2.

Then the next part, I'm still not clear if it's a function of the stepper motor, or a function of the stepper driver. I have Nema 23 380oz-in motors from Keling and I'm using a Gecko G540. But either way, it seems it takes 2000 steps to turn the motor one full revolution. Taking this into account with the ACME precision rods needing 2 full revolutions to propel the nut a full 1", the calculation in my case:

2 x 2000 = 4000 Steps Per

I'm guessing your calculation is similar to mine.

[Fastest1]

Paul, in Mach 3 there is a settings page. Go to this page and generally in the lower left hand corner, there will be a box marked "axis calibration" & set steps per unit. Upon clicking this box, it will let you select the axis you want to move. Once the axis is selected, it will ask you how far you would like to move. Enter the amount you want and then it will move (some amount dependent on your previous set ups). You will need a way to measure exactly how far you moved because it will ask you, how far did you move? The more accurate you can measure here the better your machines calibration will be. If you enter in the exact amount the machine moved, it will figure out the steps. It will be good to repeat the step a few times for each axis. You really want to do this regardless of the mathematical equation, this will factor in all errors in leadscrews and such. Backlash can be measured once this is figured out. Good Luck

[Fastest1]

Actually you will need to double check everything here. Steppers are referred to as 1.8 degree which equates to 200 steps per rotation/revolution or .0005 per step with your claimed screws. Your screws are 1/2"-10? Shouldnt there be 10threads per inch? Each rotation should be a .1 distance traveled but I dont know about multi start threads. So 10 turns of the screw will make the nut travel 1". Therefore 2000 steps will be needed to make the nut/your table move the 1" commanded. Make sense? Anyway this is a setting in your Mach 3. Your Gecko G540 is a 10x microstepping controller. If I understand this correctly, it means you could break each step into 10ths, giving you a possiblity of 20000 steps for that same inch traveled or a theoretical accuracy of .00005". not likely but theoretical. Hope this helps

Originally Posted by gjhammer You definitely adjusted it in the correct place, the "Steps per". The "Steps per" is the amount of steps required by the motor for your nut to travel 1 inch (or 1 mm). I have 1/2"-10 5 start screws from McMaster-Carr, and I know they are documented that the nut will travel 1/2" per full revolution. So from the start I need to multiply my "Steps per" by 2. Then the next part, I'm still not clear if it's a function of the stepper motor, or a function of the stepper driver. I have Nema 23 380oz-in motors from Keling and I'm using a Gecko G540. But either way, it seems it takes 2000 steps to turn the motor one full revolution. Taking this into account with the ACME precision rods needing 2 full revolutions to propel the nut a full 1", the calculation in my case: 2 x 2000 = 4000 Steps Per I'm guessing your calculation is similar to mine.

[jjacstcy]

I believe he said 1/2-10 5 start. 2 turns for 1" I think.

[CNC Lurker]

Originally Posted by gjhammer You definitely adjusted it in the correct place, the "Steps per". The "Steps per" is the amount of steps required by the motor for your nut to travel 1 inch (or 1 mm). I have 1/2"-10 5 start screws from McMaster-Carr, and I know they are documented that the nut will travel 1/2" per full revolution. So from the start I need to multiply my "Steps per" by 2. Then the next part, I'm still not clear if it's a function of the stepper motor, or a function of the stepper driver. I have Nema 23 380oz-in motors from Keling and I'm using a Gecko G540. But either way, it seems it takes 2000 steps to turn the motor one full revolution. Taking this into account with the ACME precision rods needing 2 full revolutions to propel the nut a full 1", the calculation in my case: 2 x 2000 = 4000 Steps Per I'm guessing your calculation is similar to mine.

I'm using the 1/2-10 5-start from McMasterCarr also and running them on the Gecko G540 also. I wasn't sure about the math, but fiddling around till I got it, your math matches the screenshot in the 2nd post.

[CNC Lurker]

Originally Posted by Fastest1 Paul, in Mach 3 there is a settings page. Go to this page and generally in the lower left hand corner, there will be a box marked "axis calibration" & set steps per unit. Upon clicking this box, it will let you select the axis you want to move. Once the axis is selected, it will ask you how far you would like to move. Enter the amount you want and then it will move (some amount dependent on your previous set ups). You will need a way to measure exactly how far you moved because it will ask you, how far did you move? The more accurate you can measure here the better your machines calibration will be. If you enter in the exact amount the machine moved, it will figure out the steps. It will be good to repeat the step a few times for each axis. You really want to do this regardless of the mathematical equation, this will factor in all errors in leadscrews and such. Backlash can be measured once this is figured out. Good Luck

Thanks, this vid shows how to calibrate it like you said: YouTube - Improved Mach 3 Axis Calibration
I couldn't find it at first, but eventually I found that settings page. (see attached screenshot).

[Fastest1]

He did. I dont know about multi start threads but I would have thought 1/2-10 would mean 10 threads per inch with a .5" diameter. That is why I explained the calculation. Though regarding your concern about the G540 and the 10x stepping, it wont have an effect on your step per unit calculation. Btw my theoretical travel calculations would be wrong if you are both correct in your distance per revolution.

Originally Posted by jjacstcy I believe he said 1/2-10 5 start. 2 turns for 1" I think.

[CNC Lurker]

Originally Posted by Fastest1 He did. I dont know about multi start threads but I would have thought 1/2-10 would mean 10 threads per inch with a .5" diameter. That is why I explained the calculation. Though regarding your concern about the G540 and the 10x stepping, it wont have an effect on your step per unit calculation. Btw my theoretical travel calculations would be wrong if you are both correct in your distance per revolution.

Well if your math is wrong, your result is correct.

mcmaster part# 98940A627 LINK

Travel Distance Per Turn: 1/2"

It's working correctly, and that's all that matters

[ger21]

Originally Posted by Fastest1 He did. I dont know about multi start threads but I would have thought 1/2-10 would mean 10 threads per inch with a .5" diameter.

It is 10 threads per inch, but it's only 2 turns per inch.