Configuration with Timing Belt
- spaceghost
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I am using a GT2 timing belt with a 16 tooth pulley with 2mm pitch. Based on the LinuxCNC documentation with 1/8 microstepping I believe the SCALE number should be 50. Is that correct? Are there other values I need to change to get this to work? I haven't been able to find complete examples of people using timing belts related to the ini config file.
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The scale setting is simply the amount of motor steps required to move one unit ( probably 1 mm in your case )
how far will the axis move with one rotation of the stepper motor?
Chris M
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- Todd Zuercher
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I am using a GT2 timing belt with a 16 tooth pulley with 2mm pitch. Based on the LinuxCNC documentation with 1/8 microstepping I believe the SCALE number should be 50. Is that correct? Are there other values I need to change to get this to work? I haven't been able to find complete examples of people using timing belts related to the ini config file.[/quote]
Are you using two pulleys both with 16 teeth or two different sized pulleys?
I use a pulley system with a14 and a18 tooth and getting the positions wrong in step config produces what you describe.
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- spaceghost
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While I continued searching online I did find a post somewhere else that gave me some hints to what I was supposed to do. Here is what I tried:
Drive Microstepping: 4
Pully Teeth: 1
Leadscrew pitch: 32
which gives 25 steps/mm. After testing this it seemed to give reasonable results. My math to get these number make (some) sense to me but I am more interested now if I did this correct and would it be correct for other situation. The problem is compounded by the fact that the Stepconf UI makes no reference to a belt system so I am left to guess which values go in which field and what formula I need to get the numbers to put in. I looks like I might have this working but it would be nice if it was easier to find a more complete expert example (or at least easier to find if it already exists).
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A 16 tooth 2mm pitch sprocket will move the axis approximately 32mm every revolution.
200 step motor times 4 microstepping mode = 800 steps per revolution of the motor.
800/32 = 25 steps per 1 mm movement.
I would bet in practice you may need to adjust that a small factional amount due to pitch/diameter tolerance but test and see.
When stepconf was built that style of axis movement was not that popular.
glad you figured it out!
Chris M
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2.2.9.3 Stepper
SCALE
= 4000 (hal) Specifies the number of pulses that corresponds to a move of one machine unit as set in the [TRAJ] section. For stepper systems, this is the number of step pulses issued per machine unit. For a linear axis one machine unit will be equal to the setting of LINEAR_UNITS. For an angular axis one unit is equal to the setting in ANGULAR_UNITS. For servo systems, this is the number of feedback pulses per machine unit. A second number, if specified, is ignored.
For example, on a 1.8 degree stepper motor with half-stepping, and 10 revs/inch gearing, and desired machine units of inch, we have
Rick G
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