Configuration Adjustment Guide

You are here:

How to Tune Your Laser

The default configuration file is set up for stock K40 style machine types. Each machine and its various components are unique and may require some alterations to dial in the settings. If you are experiencing issues with the gantry movement or skipping steps, this guide is a starting point for which settings to update.

For machines with larger dimensions (greater than a 300 mm x 200 mm work area), please refer to our Larger Laser Machine Installation Guide.

The values provided are recommendations which should be tweaked to optimize your machine performance:

    1. Power off the C3D Board and remove the memory card. No lights should be on.
    2. Put the board’s memory card into your computer, using a MicroSD / SD reader if necessary.
    3. Open the config.txt on the memory card using an editor such as Sublime Text. Do not use Notepad++.
    4. Decrease the feed rate (Ex: 2000 down to 1000 to test):
      default_feed_rate 2000 # Default rate ( mm/minute ) for G1/G2/G3 moves
    5. Decrease the seek rate to slow travel movement (not cuts), testing lower values incrementally until fine tuned (Ex: 12000, 9000, 6000)
      default_seek_rate 12000 # Default rate ( mm/minute ) for G0 moves
    6. Check your steps per mm to ensure it is accurate for each axis:
      1. Create a test file to run a simple square that is 100mm x 100mm at a slow speed like 25 mm/s on a scrap piece of laser material.
      2. Using calipers, measure the X (horizontal) and Y (vertical) lengths of the square to ensure they are at exactly 100mm.
      3. If the measurement is off, calculate the difference. (Ex: 99.5/100 = 0.995)
      4. Divide the default steps/mm in the configuration file by the calculated value. (Ex: 157.575 steps/mm divided by 0.995 = 158.367 steps per mm)
      5. In other words, if the square is coming out larger, decrease the steps per mm and if it is coming out smaller, increase this value for the respective axis:
        alpha_steps_per_mm 157.575 # Steps per mm for alpha stepper
        beta_steps_per_mm  157.575 # Steps per mm for beta stepper
    7. Decrease global acceleration to slow moves between cuts (Ex: 2000 down to 1000 to test):
      acceleration 1000 # Acceleration in mm/second/second.
    8. Decrease max speeds, testing lower values incrementally until fine tuned (Ex: 12000, 9000, 6000):
      x_axis_max_speed 12000 # mm/min
      y_axis_max_speed 12000 # mm/min
    9. Check the specifications on your stepper motors and increase current levels to dial in internal stepper drivers (not required for external drivers). See: Changing Stepper Motor Currents
      alpha_current 0.6 # X stepper motor current
      beta_current 0.8 # Y stepper motor current
    10. Save the config.txt file on the memory card.
    11. “Safely Eject” or “Unmount” the memory card.
    12. Put the memory card back into the board and power up.

For stepper motors which are larger than Nema 17, review our Cohesion3D LaserBoard Buyers Guide for recommendations on external stepper drivers, the stepper driver cable pack and Cohesion3D 24V 4A DC Power Supply. Also see the relevant documentation for Connecting External Stepper Drivers to your LaserBoard.

If you are still experiencing issues after making these configuration changes, you may be dealing with corrupt files. Reflash the SD card with fresh Cohesion3D LaserBoard firmware, make the necessary config file changes again, and resume testing.

For information regarding dialing in the laser power settings, refer to our PWM Tuning article.