I’ve spent a fair amount of time designing and printing a couple of parts. What both have in common is that they interface with existing objects (a pepper pot and a lawnmower) and so they have to fit into their intended homes. That makes things a more complex than standalone designs – measure, make, test and iterate as many times as required.

One thing that goes some way to reducing the costs of material and time is that you don’t have to print the whole part each time. You can isolate a section or thin slice and visually check that the dimensions are at least close. It is still time consuming and costs a bit of plastic but much less than if I had to do the full piece each time. Even with that, it is rare to nail everything down on the first complete print but it gives me a bit of a start.

For example, the lawnmower needed a replacement pinion, the small gear that interfaces with the inside of the wheel and drives the rotors. Will plastic be up to the job considering one of the metal teeth has broken? Possibly not long-term but I can’t find anywhere to buy a replacement for a machine that was probably out of production a decade or more before I was born! If it holds up for a few years, I can always run another one off down the line. Even if it only manages a few trims of the garden before breaking under the strain, at least then I’ll have a tired and tested model that can be sent off somewhere that can produce items in stronger materials than I can print.

Postscript: I did a bit of searching and found one example of someone having done this before. He did find them online but at a stupidly high price. Even his originals were plastic of some kind and he didn’t feel they lasted much longer than his printed replacements. My mower is much older but from the same lineage and exactly the same mechanical design. Here is his video for reference: