I really like the idea of making this machine and I’m almost done printing all of the parts to start assembling. While the items have been printing I’ve been researching the rest of the build, especially the electronics part (since this is very new to me). I’m trying to put two and two together as far as how the machine knows how far to travel and how it correlates to the pullet gears. I believe the firmware is set for 22T pullet, and unfortunately I’m having trouble finding this part. The 20T is readily available, and I was wondering if there is a formula or way to accommodate using the 20T rather than the 22T?
Hi,
You are correct, changing the number of teeth of the pulley will change how far the machine will travel. All controllers define this parameter by the number of
steps per mm
This is very common and is used to tune to movement of the machine.
This website is extremely handy at finding out what value you should use.
Please note this needs to take into account the microstepping of the stepper motor driver you’re using.
If you are planning on using Marlin as the motion controller. This parameter is defined in the file:
configuration.h
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Thank you for your help. I can not wait to get to this to point and give it a shot. I’m assuming those values would be defined under the #define DEFAULT_AXIS_STEPS_PER_UNIT ?? And then fine tune from there after taking measurements of actual results? I also plan on using the DRV8825, which looks like the resolutions can be adjusted down to 1/32 (just don’t know if there is any benefit of one resolution over the other besides precision). Thanks again!
-Joe
Hi Joe,
You are correct again. Tbh the values from that website are normally bang on. But always worth verifying the actual movement with a digital caliper or something similar to ensure its spot on. I would recommend double checking the z axis, as these could have different size pulleys and will need checking as the ratios are never perfect.
With regards the microstepping: 1/32 I’ve found to be too high. More often than not, I use 1/16 as a starting point. As the resolution that offers is more then adequate for this CNC machine.
Ie if its 200 steps per mm. Then the resolution is 1/200 or 0.005mm. More than fine enough.
Also more steps means more pulses need to sent from the processor in a given amount of time. At high microstepping the max travel speed of the machine might be limited by the processor.
Keep us posted on the build!
Kind regards pete
Does anyone already calculate the steps for a 20T pulley?
How many tooth do you use in your calculation if the pully on your motor is 16T and your pulley on the leadscrew 20T? Maybe 18T?
I would recommend looking at this link - https://blog.prusaprinters.org/calculator_3416/
its really helpful at getting the correct steps per mm.