Dampening Material Calculator
Enter internal case dimensions and layer choices to get cut sizes, sheet area needed and a thickness recommendation for each foam layer.
Tool Operation Area
Cut sheet
- Case foam (PCB to case floor)312 × 107 mm @ 4.0 mm
- Plate foam (plate to PCB)312 × 107 mm @ 1.5 mm
Trace standoffs, the daughterboard cable route and the reset switch onto the case foam before cutting. Start with case foam only and add layers one at a time so you can hear each change.
Working Principle
Foam changes a keyboard's sound by removing air volume and by absorbing the higher-frequency components of each impact. Three layers are used, and they act differently. Case foam sits between the PCB and the case floor and fills the largest air cavity, which is what removes the hollow, reverberant tail from each keystroke. Its thickness is limited by the gap between the PCB underside and the case floor, usually 3 mm to 6 mm; poron and EVA are the common materials, with poron being softer and slightly more absorbent. Plate foam sits between the plate and the PCB and is thin, typically 1 mm to 1.5 mm, because that is the physical clearance in most gasket-mount stacks. It damps the plate's own ringing and reduces switch-to-plate resonance, at the cost of some typing flex. PCB foam, sometimes called the sandwich layer, is the thinnest and mainly stops the PCB slapping against the plate. Cut sizes follow directly from the internal case dimensions minus a clearance allowance so the foam does not bunch against the walls, which would push the PCB out of plane; 1 mm to 2 mm of clearance per side is standard. Sheet consumption is then the cut area plus a waste factor for the switch and stabilizer cutouts you remove from the plate layer, which the tool reports so you can order the right sheet size.
How to Use
- 01Measure internal case length and width, or take them from your kit's spec drawing.
- 02Select which layers you want to add: case foam, plate foam, PCB foam, or all three.
- 03Set the clearance per side; 1.5 mm is a safe default.
- 04Read cut dimensions, total area and recommended thickness per layer, then compare against the sheet size you plan to buy.
- 05Common mistake: cutting foam to exactly the internal size. It will compress against the walls and lift the PCB.
FAQ
Does more foam always sound better?
No. Excess foam produces a dead, muted sound and removes the flex many builders want. Start with case foam only and add layers one at a time.
Poron or EVA?
Poron is softer, more expensive and slightly more absorbent. EVA is firmer and cheaper. Both are acceptable; the thickness matters more than the material.
Can I use plate foam with a flex-cut PCB?
You can, but it partly defeats the flex cuts. Many builders skip plate foam on flex-cut boards.
Do I need cutouts in the case foam?
Only for standoffs, daughterboard cables and the reset switch. Trace them by laying the foam over the case before cutting.
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