Upgrading a k40 Laser Cutter Bed

At about $400, a k40 Laser Cutter is a wonderful low-cost entry into the world of laser cutting and engraving, and also a great platform for hacking and upgrading.

The biggest limitation of a k40, however, is the size of the engrave-able area, which is limited to just 8x12 inches.  This suffices for many projects, but often is a source of frustration when trying to create something larger, or even just for efficiently using materials that come in 12x12 sheets.

While enlarging the k40 bed is a common desire, the most popular upgrade along these lines is a full 12x24 rebuild of the laser gantry, gutting both the electronics and gantry parts of the case, building a custom gantry in its place, and relocating the electronics to an external case.

12 x 12 cutting / engraving area

For myself, I wanted to try something more restrained; a 12x12 cutting area retrofit to fit entirely into the existing cutting bay.  I found inspiration when I came across a budget laser engraver kit for just $99 on Amazon.

When assembled it would be tight, but seemed like it would fit in the existing k40 bay with a little encouragement.  My plan was to laser cut some adapter pieces to hold the y-axis mirror and laser head, then adapt the gantry, gut the k40, and swap in the new for the old.

Unfortunately, after gutting the k40 internals, I found out I had mis-measured.  The back of the k40 has reduced vertical clearance due to the laser tube compartment hanging down from above, and the x-axis from the diode laser could never fit underneath it to allow the full 12" of y-axis movement I wanted.

The only way I could get it to fit was to reuse the original k40 x-axis, mounting it in place of the one from the diode laser with some acrylic adapter plates.  

My laser cutter was now inoperable, so I hand fabricated various pieces from acrylic and plate metal to hold everything together well enough to make the laser cutter operational again.  This included a new mount for mirror 2, attaching it to the end of the x-axis...

and a holder for the laser head, adjusted to tuck underneath the laser tube compartment.  These would get rebuilt later once everything was up and running, but in this early version, it was finally fully functional after a fair amount of tweaking, and had a full 12x12 cutting and engraving area I wanted.

Movable cutting bed (z-axis)

After getting the laser operating again with the enlarged cutting area, my attention turned to the cutting bed.  Since I sometimes cut 1" foam sheets such as for camera case inserts, I wanted a bed that could move up and down to adjust for different material thicknesses, all without affecting levelness.

My idea was to create a frame for the bed that would be supported on all 4 corners by captured nuts and threaded machine screw legs that turned in sync by gears driven by a circular toothed belt.

A small gear-motor would drive the gears in either direction in response to a DPDT toggle switch to move the bed up or down.

A spring-loaded idle wheel maintained tension on the belt, and could be released it I needed to turn one of the screw legs manually to level the bed.

Here is the completed bed (upside-down), built from scrap aluminum fence post material and the above-mentioned gears, belt, and motor.

And here is the completed bed right-side-up during motion testing.