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Almost exactly a month ago, I picked up a new hobby: 3D printing. I’ve been reading about it for a long time – years – and have only recently realized that they are now both affordable and reasonably precise for hobby work (they can make gears!)
After some research, decided to go with open source and build my own; for that, I bought a Prusa Mendel i2 kit from MakerFarm - I highly recommend them should you get into this: they were helpful, and their kit price was generously fair by all considerations.
Since this is a kit for an open source, open hardware printer, I’m on the hook to align it and configure it properly.
Which brings me to this: my 20mm calibration cube ended up looking spongy. While this is a small measure of success (I produced an almost solid object instead of numerous strings of molten plastic), it was really a failure: cube shouldn’t look like this — it should be solid.
Freenode IRC #reprap people were very helpful. At first glance, they guessed that the filament was slipping while being fed by the extruder. After removing the device, I tried manually feeding filament by moving the large gear, and realized it was slipping. That made me realize something was wrong, so I went for a full teardown and reassembly.
Check thickness of your washers. They can be inconsistent.
The culprit was traced down to just that – one of the washers was noticably thicker than the rest, and that caused a misalignment that in turn caused grip force to be distributed unevenly. Below are illustrations of the problem.
| Bad: though it’s difficult to eyeball it, hobbed bolt does not line up with feed hole exactly. Washer between the bolt head and the bearing was too thick (right side). |
Good: hobbed bolt lines up with feed hole more accurately, with a replacement washer. |
| Image may be NSFW. Clik here to view.  |
Image may be NSFW. Clik here to view.  |
| Culprit: washer from a box ended up being significantly thicker than the rest: 1.86 mm |
Much better with a replaced washer: 1.57 mm |
| Image may be NSFW. Clik here to view.  |
Image may be NSFW. Clik here to view.  |
Lesson learned: get a digital caliper, measure everything, and doubt every piece of hardware.
Better lesson: there’s always a rational reason why something isn’t going your way. So long as you can identify that problem, you can solve it.
The post Did your RepRap calibration cube come out spongy? Check your extruder for slippage appeared first on Dino's Anabasis.
