For at least 5 years now our centre console lid in our car has been missing a latch. We’ve learned to live without it and just lifted and closed the lid. I found over time the lid would slide side to side eventually loosening the lid screws and I’d have to tighten them regularly. Luckily when I was studying overseas it was mandatory that students either take the home economics or technical drawing class. I chose the latter and did quite well at it.

With that in mind I kept the original broken latch hoping one day would redesign and print it. That day came and after a few goes I drafted up a prototype replica using 123D Design and a pair of digital calipers.

It took a few revisions to get it right since when I first printed it I mistakenly printed it in ABS without considering the direction of force that would be applied when installed and in action. It snapped on the first try. The 3 images below show the first print laid in the wrong orientation.

I then realised I needed to print it upright with supports so the layers were laid perpendicular to the direction of force. This kinda worked for a day but then snapped again, this time near the screw wholes. I found that even though this design was identical to the original part it was a lot stiffer and harder to flex. It appeared that while ABS was strong it’s layers didn’t bond as strongly as PLA layers do.

While trying to figure this puzzle out and refusing to admit to myself that my design was flawed I printed some other parts and used a brim 1cm wide on them. After removing the brim I noticed that the thin brim itself was very flexible. I took this lesson and revised my design so the part which would flex was thinner than the original.

I printed it at 0.2mm layer height and installed it again. The part has been in use for 2 weeks now with no sign of cracking or separation. I don’t think the wife has noticed it’s installed yet and my friends are still in disbelief I did this with only a digital caliper.

I’ll upload the final 3d model files to thingiverse very soon.