For Those Last Minute Gotchas
Fit check before proceeding with your assembly.
Last updated February 2019
You have all the parts manufactured and off-the-shelf parts have been ordered and received. Heat-set inserts and bearings have been pressed in. You are ready to start putting the pieces together to create the assembly. One by one, pieces are fitting flawlessly. “This is looking sweet,” you say to yourself. One final piece and you can show this thing off. Uh oh, the holes don’t line up. Exactly what happened to a team I had been apart of to build a CubeSat. The camera mount hole dimensions were incorrect. The spacing was off by 2mm! A hard lesson learned for a team that had a fast-approaching deadline to meet.
Before assembling the final product, or even starting to epoxy pieces on or pressing bearings into place, I would recommend fit-checking everything you can. Line things up. It’s like a puzzle. You’re not screwing, pressing, or mounting anything just yet. You’re trying to verify that everything will go together as planned. You don’t want to do assembly twice, right?
Maybe you’re working on building a cabinet for a data acquisition system or controller. You have many pieces of equipment to mount and install. Don’t just start installing everything and then realize that the last piece of hardware won’t fit. Place things in the cabinet and make sure before even screwing in your first fastener. You could even make a drawing to scale!
A scenario like this could also happen for a PCB assembly. You just received your board from a board house. First IC you go to place and the footprint is wrong. How do you avoid this? Before putting the board order in, perform a fit-check. You can print out the board on a sheet of paper with a 1:1 scale. This allows you to make sure each IC, resistor, capacitor, etc. will fit on its footprint.
What did we learn?
- Before doing any type of assembly, take as many precautionary measures as you can to avoid costly rework.
The measurements in datasheets can be wrong. Ever heard of the saying “trust, but verify.”