Drive strength on Z axis

Machine: K40 w/lightobject z axis
Board: LaserBoard
Firmware: Smoothie
Problem/ Question:

I have a LaserBoard which seems to be doing fine, except that the drive for the lightobject Z axis table doesn’t seem to be strong enough, in that it’s stalling at spots and missing steps. It’s just barely not strong enough since I can help it a bit with my fingers on the belt and it doesn’t miss any.

I’m wondering if I missed a setting in the LaserBoard/Smoothie which controls the stepper motor current. Or if there’s another setting which would result in a higher effective drive strength.

I’d like to avoid moving to an external driver.

The Z axis is referred to as gamma in the Smoothie config.txt file on the board’s memory card.

Use Sublime Text as your Text Editor.

You will need to set the correct steps per mm for your Z Table on line 17 for your table.

gamma_steps_per_mm 157.575 # Steps per mm for gamma stepper

You will also need to increase your stepper driver current on line 58.

gamma_current 0.6 # Z stepper motor current

The board supports up to 1.2 (amps) for this value. There are 2 ways to go about this: bump up in increments of 0.2 until the issue stops. Or, set to max and monitor the motor to make sure it does not get too hot. I have been known to do both ways at different times :slight_smile:

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I just bumped it up to 1.2A since I didn’t want to risk missed steps, and the motor seems to be happy at that point (not getting warm at all).

In case someone else is looking for it, I found the following value for the lightobject z axis table, which seems to be correct based on measurements.

gamma_steps_per_mm 316.9 # Steps per mm for gamma stepper

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