Setting Up the Correct Bed Size

Setting Up the Correct Bed Size

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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.

The work area is based on the Cartesian coordinate system with (x,y) coordinates.

Axes of machine and peripherals:

X = Alpha (left to right)
Y = Beta (front to back)
Z = Gamma (top to bottom – Z table)
A = Delta (depends on what is connected, typically a rotary)


The standard setup has origin in the lower left (0,0). Most machines home to the top left where the endstops are triggered (0,200) at Home A. In some instances, the endstops will trigger in the upper right corner at Home B. Additional configuration changes are needed in order to home to the second location, so ask before updating. The max values may be higher, depending on your bed size.

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). The system homes against the limit switch in the rear, and then uses the max setting to determine where the origin is (relative to the rear endstop). Increasing it will move the origin point towards you in the work area and decreasing it will move it towards the back on the Y axis.

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, see our Larger Laser Machine Installation Guide.