Wednesday, July 31, 2019

Using model offset to fix partial 3d prints.

I've been doing some 3d printing for cosplay in the past couple of years. And as every 3d printer owner knows, stuff happens and prints sometimes get screwed for unforeseen reasons. I mean, so many factors can cause a problem it's not even funny or annoying to me anymore, I just sigh and try again after re-checking everything.
One of the common issues, especially with long prints (I'm talking dozen of hours and more) is when the filament runs out and you don't manage to swap it in time, or there is a power failure, and print outright stops midway. I'm sure it has happened to most 3d printing hobbyists at least once. Normally you would just swear a lot and write the spent filament off, but there is actually a way to salvage the print. Provided that it's the sort of print that you have planned to sand/paint anyway. The idea is to print only the remaining bit and then stick two parts together.

- Take micrometer calipers and measure the height of the printed part. Try to be as precise as possible.
- Go back to your model slicer and lower your model below the print base by the height of the printed part. I use S3D, but I assume it will work in other slicers as well - it should only slice the model above printing surface. So when you print it, you will end up only with a part that wasn't printed.
- Print the remaining part, and the glue the unfinished and new parts together. Since, in my experience, most plastic prints will deform slightly, you will likely need to fill the gap and sand it to get smooth surface. I prefer acrylic wood filler since it dries fast into a relatively hard and somewhat elastic substance, but still easy to sand. Then paint the model to get uniform color.

The same method can be used to print complex shapes without using supports. Most of my prints are going to be sanded and painted anyway, so I don't see this as extra work, and it saves filament. You can decide on the vertical offset, slice one part, then flip the model over and slice the other half.

I read about this trick on some facebook troubleshooting group, but fb is terrible for looking up information, so I'm putting this in a more static form. Hopefully it's going to be useful for someone.

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