Notebook / Entry 001
First knobs off the printer
Getting a press-fit bore right for 6 mm D-shaft encoders took five test prints.
The first thing I printed for the cockpit was the humble autopilot knob. It looks simple, and the outside is. The bore is where it gets interesting.
The problem with D-shafts
A 6 mm D-shaft drawn at 6.0 mm in CAD prints too tight on most machines, and a loose bore spins on the flat. After a few tries, this is what worked on my printer with PETG:
| Test | Bore | Flat | Result |
|---|---|---|---|
| 1 | 6.00 mm | 4.50 mm | Would not fit |
| 2 | 6.20 mm | 4.60 mm | Fit, but spun |
| 3 | 6.15 mm | 4.45 mm | Press fit, holds |
What I’d tell my past self
Print the bore as a small test coupon first. It takes ten minutes and saves an hour of reprinting full knobs.
The test coupon file is in the library.