I finally, totally get 3D printing

I’ve been flopping back and forth about what equipment to get/build next, assuming I saved up a few thousand dollars: a CNC router? …a laser cutter? …a 3D printer?

This weekend I totally got what I would do with a 3D printer: print mechanical parts of machines.

In search of stepper motors in old, broken devices, I tore apart an ancient HP Deskjet inkjet printer – something like an 810C – I forget what model exactly. At any rate, disassembling that printer was an education in the mechanical design of moving parts.  It used normal DC motors (no steppers) to drive the printer head and paper, then used stripes on film sensed by photo-interrupters to determine where exactly the print head was and exactly how far the paper had advanced.  Very impressive!

In going over the design of this amazing machine, and in thinking about what parts I could salvage from it, it suddenly struck me: I could reuse many expensive parts if I could print my own mounting and connecting pieces – the application-specific parts that hold, for example, a linear rail or connect a print head to the bearings that ride on the rail, or even a piece that holds a tension spring and the sprocket that it tensions.

So many things in this printer are accomplished by little custom pieces of plastic – the sort of pieces you could print in a 3D printer.

This short video on open-top printing has some nice closeups of the sorts of mechanisms and parts that I’m talking about.