Setting Up the Correct Bed Size


(Starla Fox) #1

Setting the correct size for the Y axis

When the head homes to the rear left of the machine, it thinks it is at 0, 200 (where 200 is the default C3D config file value for a stock K40’s Y axis size). So when you move to the front, you are moving closer to 0,0. As a result of this, you have to properly tell the C3D the dimensions of your bed so that 0, 0 is actually where you want it to be (and not too far up). Maybe you’ve got a larger machine or are just able to squeeze a few more centimeters out of your K40.

Home, then try jogging to see how much travel you actually have. It is not uncommon for a K40 to actually have 210 - 230mm of total travel in the Y axis, and every machine is different.

  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. Find the ## endstops section
  5. Find beta_max around line 265 and change that value to match your bed’s Y dimension
    Change beta_max 200
    to beta_max 210
  6. Save the config.txt file on the memory card.
  7. “Safely Eject” or “Unmount” the memory card
  8. Put the memory card back into the board and power up.

Finally, make sure your bed size values match - they must be the same in the C3D Board Config File and in LightBurn's device setup.


Now if you home and then go to X 0 Y 0 coordinates, the head should move to the proper position you desire in the front left of the machine.

For larger bed sizes, some other config file parameters may need to be modified, such as the stepper driver currents, speed/acceleration, and possibly seek rate values, to fine tune it.

  • Increasing the motor currents in the config file by 0.2 amps at a time will help dial it in. The board’s per driver max is 1.2 amps. Do not exceed the stepper motor max. Ensure the motors are not overheating after increasing.
  • Decreasing the acceleration will help slow down the cornering speed.
  • Decreasing the seek rate will help slow the moves between cuts.

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