The modela MDX-20 is very widely spread in many fablabs as many and compact CNC for different uses..

This machine is used to make PCBs for digital fabrication. The problem is that most people are using the double sided tape to fix the board in place, and it is so obvious why I don't want to use this approach.

I made this design for Fablab Dhahran in Saudi Arabia in King Fahd University of Petroleum and Minerals. You can visit the website here: http://fablabdhahran.org/

This bed made it very easy to mill PCB, especially the double layer once.

Step 1: What You Need and What Are the Tools

This design is made for the Roland Modela MDX-20, but it can be modified to fit in any CNC machine.

I used a laser cutting machine "Epilog mini" to cut the acrylic parts.

only two kinds of acrylic I needed (6mm & 3mm).

also I needed:

- 4 x m4 screws

- 6 x m4 bolts

Step 2: Take Measurements

In the beginning start by taking the dimensions of your bed. Make sure that the boundaries don't collide with any of the parts of the machine!

ALWAYS test the design alignment and size on cheap disposable material (i.e. cardboard) before applying on some expensive material.

Step 3: Start the Design

The approach I am using is to make the some T shape clamps that are attached using screws and bolts to clamp the board in place.. Since the PCB milling doesn't apply much of a horizontal force, only two clamps are enough.

I made the drawings using Inkscape software to do my cutting in laser machine.. (you can use any vector editing software)

The bed I made is composed of two layers and the clamps. The bottom layer is fixed and doesn't wear out. The top layer is my sacrifice peace and you have to change it every once in a while.

I made two holes at each side for the screws to give me more area in case I needed to move the PCB or use larger PCB>

Step 4: The Top Layer

The top layer is the sacrifice layer. It is only 3 mm deep and contains the holes for the screws to penetrate from the T clamps through it to the bolts in the bottom layer.

ModelaBed-top3mm.pdf
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Step 5: Bottom Layer

The bottom layer is 6 mm thickness to give me space for the screws to tighten the clamps more in the board.

Modela Bed-bottom6mm.pdf
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Step 6: T Clamps

These are just T shape clamps with a slot in it to allow the screw to move within them.

I made a pocket in it to make the PCB more secure on the bed.

ModelaBed-holders.pdf
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Step 7: Place the Bolts in the Bottom Layer and Do Some Cleaning

I used super glue (crazy glue) to attache the bolts in their holes.. Make sure to glue them flush with the surface or a little bit lower than the surface. I used a screw to lift the bolt to the height I want then I glued them.

Because the laser cutting is hot it will make the pocket in the clamps a little bit not too straight, so do some cleaning using some file.