debugging Clock 16
Nearly two months ago I had never seen a 3Dprinter. Fascinated, I borrowed an old printer and built the easy clock, #16, because it seemed like a good (easy) place to start. Once finished, it ran on the first try.
Then I took it for a car ride and I was unable to get the clock to run again when I returned home.. For the next three weeks I built and rebuilt it, printed some new parts, verified the spacers -- printed new spacers -- which are a big deal becasue they easy to switch around.
After dozens of experiments I decided the stack of gears on the top arbor was 2mm longer that the available space. (Yes, I had pushed and positioned and adjusted a dozen times.) I was unable to reduce the height of the stack of gears by the necessary 2mm.
Interim Fix: I added a spacer on the top and bottom of the frame to add 2mm distance. The clock immediately began to run.
What could cause this clock to stop running after a week of running smoothly? My guess is that the frame was heated while in the car. My reason for saying this is that the flat surface of the upper tower did not seem parallel to the surface of the lower tower. (A straight edge and eyeball measurement.) My guess is that tightening the screws caused a bow in the front frame. The bow seized the upper edge of the spacer built onto Gear 5 which worked against Gear 4b. In the middle arbor, a bowing of the front frame would press against Gear 6, the hour hand driver. More importantly, Gear 6 would want to slide against 4b.
4b is the center of all three of the clock's gear transmissions. Relieving the pressure along the axis and relieving the negative toque freed all three transmissions. We are back in business. Do I want to spend 18 hours printing a new back frame to verify the thesis? Or assemble it with washers and spacers?
What I really want is to print the face frame in three colors. I can live with the spacers. for a while.
I remain very pleased with the entire process.
The clever design and the interplay of the gears -- it's been a real joy.
Thank you, Steve, for creating this.
.
Today I decided to add 2mm spacers between the front and back frame.
The low printing temperature of PLA is both a blessing and a curse. It prints easily without needing an enclosure. Yet, it also can soften and deform at temperatures as low as 60C (140F). Higher temperature filaments like ASA are much more tolerant of car ride temperatures. They are also significantly more prone to warping unless printed inside a heated enclosure.
Adding spacers solved your issue by giving enough clearance to make up for the frame warping. It may be equally as effective to reduce the height of one or two gears by the same amount. Most gears split cleanly along the layer lines.