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Friday, 10 May 2019

The Failures of 3D Printing

Not 3D printing in general, but the 3D printed parts that were no good, for whatever reason, when I was building my prototype can transformer. The finished article is here:

and makes things like this:

When I was building the prototype I printed many parts, a lot of which didn't work. This is normal for my builds, but this time I kept the failures. It was surprising how many there were:

The histogram of failure

I laid them out grouping the same part, so you can see which bits I had trouble with. The X carriage, for instance, is there as four failed parts, and the Z carriage is there in a form that isn't in the final machine. There are some gears in the picture (a lot of gears, in fact) which are also not in the final machine. I started off driving the Y axis using gears as they 3D print well. They have a lot of backlash, however, and just didn't work well enough. The final machine uses MXL belts.

The biggest failure is the part that engages with the top of the can and has to grab the can well enough to stop it moving as the Y axis rotates. They are the two rows of circular objects just down from the top. I had a lot of trouble with that poart and still don't have it perfect. In the end I made a common base for the part and screw inserts of different shapes in to it. This means I don't waste (any more) plastic and time printing the main body.

Most parts are failures for mechanical design reasons, the printer itself is very reliable now and I only had one or two print failures and they tend to be operator error in some form anyway.

The reason for black and white is that I have two printers, one set up for black and one for white. I found they print slightly different sized objects, so having different colours was useful as I knew which printer had printed what.