Over the course of half a decade (!), the 3D printed arm on the XYZ positioner I use with the stereo zoom microscope sagged:
It’s about what you’d expect from a plastic beam carrying a big lump of brass and steel:
The near side of that arm (the -Y end) drooped about 5 mm below than the side nearest the Z axis slide, so it was time for an update.
Having some MakerBeam ready to hand, this didn’t take long:
Protip: before dismantling a fitted slide, mark one end so you know how to put it back together. Bonus points for taking a picture:
Double bonus points for writing a blog post.
Rather than fight with the existing fine-pitch USA-ian screws, I drilled out their threaded holes:
And epoxied 3 mm brass inserts in their place:
Those holes match up with a pair of corner cubes normally appearing on the end of the beams:
It turns out M3 button head cap screws will slide into the beams if you file the slightest angle on opposite sides of the button, although a small bag of tiny tee nuts should arrive in a while.
Then a variety of brackets spliced everything together:
Although it looks strictly from industrial, it actually wasn’t much better than the plastic edition and, in fact, the beam supporting the XY slides sagged about the same 5 mm. The plastic upright post also contributed a bit of wobble.
It turns out that the extruded aluminum beams have plenty of longitudinal and torsional stiffness, but all those flat steel fittings don’t.
There’s a way to work with the beam strengths, rather than against them, but that’s a story for another day …