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Stepper Motor Configuration
Based on the leadscrew and gearing of the stepper motor, the relevant files will need to be updated.
Now the SCALE values are set using the ℛ Settings tab within LinuxCNC. (See also, ℛ Settings in the User Manual.)
Previously, the files to be updated were in this folder:
| /home/reuben/linuxcnc/configs/RoseEngineButlerLocal/REB_Axes |
Data Needed for the Calculation
- Within the relevant axis file, note the UNITS in the [JOINT_#] section. This is the basis for many calculations. The typical settings are:
- linear axes (X, Y, Z, U, V, & W) - inch
- rotary axis (B) - degree
- Stepper motors used are typically 1.8 deg / step. If different on your configuration, this needs to be identified.
- The drivers (StepperOnline DM542T) are set to
- Microsteps = 32
- Steps / rev = 6,400
Based on that:
| 32 microsteps | = | 17.778 | microsteps | (1) | |
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| 1.8 deg | deg |
- Conversion of metric to imperial:
| 1 inch | = | 25.4 mm | (2) |
- The leadscrew's relevant information:
- Pitch = 2 mm
- Starts = 4
| 1 revolution | = | 2 mm X 4 | (3) | |
| = | 8 mm |
- The relevant information regarding gearing:
- Motor gear = 12 teeth
- Driven gear = 108 teeth
Based on that:
| 108 teeth | = | 9 motor gear rev | (4) | |
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| 12 teeth | 1 driven gear rev |
Calculations for Axis File
| STEP_SCALE | = | 6,400 microsteps | X | 1 rev | X | 25.4 mm | X | 9 motor gear rev | (5) | |
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| rev | 8 mm | inch | 1 driven gear rev | |||||||
| = | 182,880 | microsteps | ||||||||
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| inch | ||||||||||
| ENCODER_SCALE | = | STEP_SCALE | (6) | |||
Note: Do not include the comma (",") when setting the value in the file.
Linear Axis Resolution
For the item noted above with an 8mm/rev leadscrew and a 9:1 gearing ratio (182,880 microsteps/in):
| Axis Indexing Resolution | = | 0.000 005 47 inch | (7) | |
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| microstep |
A more typical ratio for a NEMA 17 stepper motor is a 2mm/rev leadscrew and a 1:1 gearing ratio (81,280 microsteps/in):
| Axis Indexing Resolution | = | 0.000 012 31 inch | (8) | |
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| microstep |
Spindle Indexing Resolution
For a spindle with a 9:1 gearing ratio,
| STEP_SCALE | = | 6,400 microsteps | X | 9 motor gear rev | (9) | |||||
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| rev | 1 driven gear rev | |||||||||
| = | 57,600 | microsteps | ||||||||
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| spindle rev | ||||||||||
| Spindle Indexing Resolution | = | 360 deg | (10) | |||||||
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| 57,600 microsteps | ||||||||||
| = | 0.00625 deg | |||||||||
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