MakerBot Industries

colorbroken's Film Advance Crank

Colorbroken on Thingiverse just uploaded a 120 Film Advance Crank.  Replacement cranks and knobs are nothing new to Thingiverse.  Replacement cranks and knobs are probably the first repair people think of when looking at a MakerBot.  They’re easy to model, small enough to print without too many problems, and relatively easy to print.

What makes this particular knob special is how colorbroken designed it.  A typical knob design would include a thin cylinder sitting atop a flat… knobby bit.  Using Skeinforge, you would then set the desired fill ratio of plastic.  However, there are different benefits to different fill ratios. ¹  The problem with a heavy fill is that the part uses more plastic, takes longer to print, and is heavier – the upside being it will be a more sturdy part.  The problem with a low fill is the part is more sparse and potentially weaker² , but it prints much quicker and conserves plastic.

But what if you need one area of the part to print quickly and another area of the part to be extra sturdy?

Well, colorbroken thought of an interesting way around this problem.  By putting a hollow core inside the axle for the knob, the MakerBot printed a thick ring inside the axle.  The end result is the knob is whatever fill he specified, but the axle has a thick sturdy hard core running all the way through it providing additional strength and durability.  I love this design tip for its simplicity and effectiveness.

Thanks for the idea colorbroken!

1. Fill ratios aren’t rocket science.  I use 20% fill on all of parts unless I absolutely have to change that setting. [↩]
2. Although, I’ve printed amazingly sturdy parts using a fill as low as 10%.  It’s really a testament to the strength of ABS. [↩]