Sheetfuls of Ear Savers

The laser cut version of the surgical mask straps (or ear savers) was made in a very timely fasion. A few days later I saw this viral post from Charlie Swift, who was collating 3D printed straps for the Leicester General Hospital. He had an ambitious goal of 1000 straps so I offered to chop up a sheet and made him 150 straps in just over an hour to get him close to his goal.

Turns out all the straps went down well and the other local hospital, Leicester Royal Infirmary now would like a batch. Given that the laser is so much faster and I just took receipt of more polyproylene sheets I offered to cut all 1000 this time. I made a few tweaks to the design to make it faster for cutting (svg here) and I also optimised them onto a half sheet of material (svg here)

The first step towards optimising a sheet is figuring out the best way to stack the design and then working out roughly how many will fit into a sensible sheet size. I'm using half sheets because I can magnet the edges and not worry about it overlapping the edges of bed. There aren't a lot of common edges on a curvy design like this but joining up the flat edges will still shave a little time off. I got 24 in a row by making them a half a mm thinner and 3 high by making them 4mm narrower. It's a miniscule change to each unit but you can easily fit an extra row and column (30 units) onto the sheet by doing it.

The most important thing I did was colour them in; the laser cutter selects it's order by colour. This way I can cut out all the holes in the middles which cut fine, I can then put magnets on some of the holes to hold the sheet down (knowing that the magnet places won't be cut again). I coloured every third head band because when you cut two immediately next to each other the material heats up and starts to bend, this way I can spread the cutting out across the sheet (fractionally slower but worth it). 

Even something subtle like making the central hole rounded instead of straight shaved 50 seconds off this morning making it just under 16 mins for the sheet instead of just under 17 mins, this is because the laser head doesn't have to slow down to go into the corner, it can take the larger radius at a sensible speed. Hopefully this information will help someone make the next iteration even faster.

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