I have mentioned in the past my home made vacuum plate for holding printed circuit board material flat while milling the copper trackwork. As a technique this works really well and the results are very consistent using 5 and 10 thou miniature milling cutters from Think and Tinker.
When the artwork design needs holes drilling through the PCB material, care has to be taken not to drill through into the aluminium surface of the vacuum table. To protect the carbide drills and the surface of the vacuum table I use a sheet of 3mm MDF underneath the PCB material to act as a sacrificial board . While the MDF is ‘transparent’ to the vacuum suction it does degrade the downward vacuum grip and this has always been a frustration. If the board does not need through holes then the MDF is not required.
My wife uses an anti-slip perforated rubber sheet on the kitchen sink draining surface. This is very flexible and looks like a weird cobweb of holes. It struck me that this could be used as a sacrificial sheet between the PCB material and the vacuum table surface. The rubbery material is not perfectly flat but is very easily compressed to become consistently flat over a large area.
I begged a sheet of the material from the kitchen ‘sub stores’ and mounted it on the vacuum table with the PCB on top. I measured the overall depth of the PCB and the mat under vacuum compression to be circa 80 thou and I usually set the depth of cut for drilling to 68 thou. This looked like it should leave a safety margin to avoid damage to the drilling tool and the vacuum table surface.
The idea worked a treat. The PCB was very rigidly clamped in place and no damage was done to the drill bits or the vacuum plate. Here is an image of the first board being run using this backing material technique.
This looks like a step forward in my PCB milling process and has the added advantage that the rubber sheet can be hand washed afterwards and re-used.
Anyone needing some 3mm MDF ?
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