Calibration of Linear Motion Systems Driven by a Stepping Motors
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This is an instructional video describing the process and calculations needed to calibrate a linear drive system using a stepping motor for power. The mechanical means can vary widely including, but not limited to lead screw, roller chain and sprocket, rack and pinion, timing belt and pulley, etc. The video was intended to serve as a way to calibrate CNC machines; however, this method will work on many systems.
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perfect....clear and to the point......no fancy measuring gauges or artificial intelligence required.
Thank you
Thanks
@karandex I haven't really experimented with 400 step motors.
Oh, yea, in order to calculate the actual number of steps per inch, you can pick up a calculator and do (assumed_steps_per_inch * desired_distance) / actual_distance. In your example, that's (1422.22 * 94) / 94.5 = 1414.695, no need to repeat the process until it's perfect. Not that your answer was off enough to matter, but it is a little faster this way.
This is good. Only comment is on the end. As per previous comment (SCALE)=(desired distance)/(actual distance) is a scaling measurement. If math is right you can just do (adjusted steps per inch) = (current steps per inch) * (SCALE).
Unless there is some weird rounding going on with the steps that I am not understanding. If this works it is easier to follow.
@satishchaphekar That's unfortunate. This will ultimately be determined by the mechanism that you have on each axis and the weight and force against the thing that you are moving with the motor in question. One rule of thumb is that full step is not the best for maximum torque. I have found that 1/4 or 1/2 stepping is the best for full torque in my experience, so put that configuration on the worst case scenario in your setup.
Hi. Greate explanation, you save my life.
I am using a "Long Motors" stepper drive (DM860A) with a nema34 1600oz motor who give me many pulse per revolution choices as 400, 800, 1600, 3200... what i have to use 400, 800 or 1600 and how its reflect in you formula?
A) For sample if i choice 1600 its same as 1/8 since 1600/200=8 or if i choice 400 its same1/2 since 400/200=2? So i need to use 200x2 to determine the number of steps if i choice 400. I am confuse now.
B) What the best choice to give good torque?
Thanks and sorry my bad English.
Edit.: I am using a ballscrew with 5mm/rev.
My stepper motor driver.
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www.google.pt/search?q=dm860a&client=firefox-b-ab&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiJrayCmNbPAhWKJMAKHbsdCgMQ_AUICCgB&biw=1280&bih=855#imgrc=QZ2DpqrZj3rmmM%3A
On the chain drive with the nine-tooth sprocket, I found a way to calculate the revolutions per inch without knowing the pitch. I measured the links per inch on the chain (4) and then divided the number of teeth (9) by that number (9/4 = 2.25) to get the inches per revolution.
Hello, My CNC machine has a Nema17 stepper motor, T8 trapezoidal shaft and nut (nut advances 8mm in 1 turn, Start: 4, Pitch: 2mm) and DRV8825 driver using 1/16 micro stepper. In this case, how many mm does my CNC machine move in 1 revolution in the z-axis?
If you are using Mach3, I would recommend using the "set steps per unit" button on the settings tab to do the calibration through a wizard. It's far easier.
Thanks you are very good man
thank you.
It was very helpful.
Is there any description of the metric version?
Great job ever, I was waited for
I LOVE YOU PATRICK!!!
Cant you just take 94/94.5 and x 1422.22?
i am having intersting problem, i got 5 drivers and 2 of them are not working, out of other 3,2 work in full step only and 1 in half/full both. which should i use for which axis. I am thinking half step for z and other full step for xy, is it right ?
What do you recommend for measuring z axis? It's a little bit trickier being vertical.
Thanks a lot. It's really helpful to me.
Nice explanation
does the above method for chain will it work for rack and pinion also
Great Explanation!
Thanks
@karandex If your lead screw is single start (meaning there is only one thread wrapped around the rod), then yes, the 15 threads per inch is equal to 15 turns per inch.
Hello
Thanks for the grait vedio
I notice that you count the 0.5 inch as 711.11 steps , and in the real world it is nor
I see the real steps can get by this equal
real world steps per inch = (1422.22*94)/94.5
this give me 1414.695
I belive this number is more acurate
sorry for bad English
It is very funny and obvious how most of the commenters here have absolutely no engineering background.....get ur asses back to the books and stop spamming
Please stop being so America centric - the normal convention in the engineering world uses the metric system., so therefore as you take so much pride in your videos you should include both systems
I do try to do this now. When I started this occupation, I was working only in the imperial system, but I have learned to include both when I can. Thanks.
Hi Daniel. Great video. If I may ask could you go over a cnc that uses direct drive? The stepper motors drive the ball screw shaft directly.
Hi Danny,
If you know the linear travel for one revolution of the motor, then you can use the formula:
step/inch= (natural steps * microsteps) / (linear travel for one revolution)
For instance: if you have a lead screw that is 10 TPI and 5 starts, then the travel distance for one revolution is 5/10 = 1/2". If you don't know how many starts you have, look at the end of the screw and count the number of thread starts around the circumference of the end of the screw.
Hope this helps. Of course, this is only the beginning of the calibration process to get close to the real number. you should continue to calculate the real world steps/inch by calculating it, or using the control program like Mach3 to perform this calculation.
@MrHobbyrommet Thanks for the feedback. I also use this method, but the intent of this video is to provide an intuition on the process of calibrating an axis and this method of explaining it (the long way) can bring this concept home in a more visual way.
Oh, thank you. I've been running my machine for about a year off and on, and I have a major project I need to have my machine dead-on accurate for, and was starting to despair because I kept having problems. I'll run though this asap and hopefully that will help me get back to being on target.
@kurtnelle Nice!!
@aggrav8d ... good point. Do basically the same thing, only use something like a vernier caliper, just because the distance is so much shorter. .. If you try it and you aren't off 'much', it could be OK to assume correctness, but that is your choice! ... I got a plastic vernier caliper that has a thin metal rod attached to the movable jaw (it runs the length of the caliper), and it extends as the jaw is opened. It is great for making this kind of measurement. I hope you can find a similar one
@karandex yes... if you have a 'single start' threaded rod (like from the 'store' and not an industrial source)
that is a very good video which cleared my doubt..thanks..
so what the hell is cnbc?
hey pactrick,, what about backlash..
I believe that is something that should be address mechanically rather than in software. I have found that software doesn't do a very good job with backlash compensation.