Pin Bed

Last Updated: 12th February 2012

My laser cutter came with a honeycombed panel which can be used to support sheet materials for cutting. However, the mesh area is only 170x190mm and the nature of the honeycomb means that the beam frequently hits the edges of the mesh (which can lead to scorch marks on the underside of the material being cut). The honeycomb cells also tended to trap vapours and small bits of material that fall out of the work piece.

The cutting bed of the HX40A

Removing the top and bottom edges of the frame improved things as a) it allowed longer sheets to be placed on it and b) the slight gap this created under the top edge allowed (prior to my replacing the installed fan with head mounted fume extraction), vapours to be sucked out from below.

I have now replaced this with a pin bed:

laser cutter with pin bed

I'd had my laser cutter for some time prior to making this modification and had only ever wanted to cut sheet materials betweem 0.25mm (thin card) and 3mm (acrylic) thick. So provided my pin bed could be adjusted to accommodate these materials, I knew it would work just fine for me.

My starting point was to acquire suitable "pins" and I found these in the form of pop rivets. I then acquired a sheet of 5mm thick aluminium, which I cut to fit into the recess where the cutting takes place. I also obtained some lengths of aluminium angle extrusion from which to make supports. A handful of M4 machine screws completed my parts list for the project.

Pin Bed MeasurementsThe drawing to the right is a cross section through the assembly. DO NOT rely on my measurements if you want to do something similar; as your laser cutter may be different.

The material being cut (red) needs to be 57mm below the plate on top of the cutting head (blue) plate. My pop rivets (grey) are 34mm long to the shoulder and fit into 2.5mm dia holes drilled into the aluminium plate (green). The plate then rests on some aluminium angle (yellow) via some screws (light blue) which are then used to adjust the height of the whole assembly in order to focus the laser onto the top of the material being cut.

My laser cutter had some rather conveniently positioned holes, tapped for M4 screws, some 88mm below the top of the cutting head plate. The drawing and the image below left show how I took advantage of them to fit the aluminium angle for the pin bed to rest upon.

Aluminium angles mounted using the M4 holes that conveniently were tapped on my laser cutter The finished aluminium sheet for my laser cutter pin bed

The image above right shows the aluminium sheet, cut to size and drilled. Note that:

  1. Various notches had to be cut in the edges to clear the screws holding the aluminium angle brackets into place.

  2. I marked out a 1cm grid but haven't drilled holes in all of them. I figured that would be overkill but they're marked so I can drill out any more that might prove useful.

  3. There are 4 holes near the edges, tapped for M4 machined screws, which allow the height of the bed to be adjusted. These are shown more clearly in the images below:

Height Adjustment Screws Height Adjustment Screws

A further thing to note about the height adjustment screws is that I painted the tops white with one quarter painted red. This makes it easy to see how many times I've turned them. 1.5 turns = 1mm with the screws I've used.

The finished pin bedWith everything assembled I adjusted the screws (by moving the laser's cutting head close to each and measuring, such that the aluminium plate was a consistent distance below it. A further adjustment was then required such that the 3mm acrylic shown in the image was at the perfect height for cutting...

...and that's the pin bed complete. Yay!

My next job is to install home limit switches (the original switches were removed when I converted my laser cutter to use Mach 3).

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