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...
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.
