Saturday, June 25, 2022

Y Size Limit of the MK3S

In an earlier post, I wrote about splitting large gears into parts to print them on a Prusa MK3S. My current project includes a gear which is strictly larger than the official size of the print bed, but by using a trick you can still make it work.

The gear is 281.33mm in the Y direction from tooth tip to tooth tip. The Prusa MK3S print bed is 250x210mm. However, you can go beyond these limits. First, in the PrusaSlicer printer setting, change the bed size to 250x230mm with an origin offset of 10mm in Y, 10mm being half the difference 230 and 210. Now load the model, move it until it is within the printable area and slice it, with skirt turned off. If you just go ahead and print it, the printer may come up against its Y limits. Nothing terrible happens at this point. You can hear a slight "clunk" as it reaches the limit, and the print it truncated, like this:

The trick is now to adjust the Y position of the model so that we minimize the truncation at both top and bottom. I found that for this model, 103.5mm was the best compromise, leading to a very small amount of truncation:

This is probably OK as the very tips of the gear teeth are not doing much.

Note that you have to peel off the pressure release strip as soon as it has printed, otherwise the print overlaps it.

This looks to be about the limit of what is achievable. With a slightly smaller model you could avoid any truncation at all while still exceeding the official limits. I guess 217mm would be OK.

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