CAD: Tweak Spool Fitment Values #122
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Trying not to be *too* aggressive... a little goes a long way.
The flaps *must* move freely without binding, otherwise the display does not work. Given the variability of online laser-cutting services, tolerance stacking, and the imprecision of hand assembling the 7 separate components that make up the spool, it seems imprudent to reduce this value without being able to test the results firsthand. Some narrowing here would be beneficial, but it's difficult to say exactly how far to go before binding will occur on outlier assemblies. Put another way: a display that may sometimes stall due to misalignment is preferrable to a display that does not 'flip' at all. This partially reverts commit f4e7714.
On my last acrylic build (circa f4e7714) the magnets were a very tight press fit and cracked one of the spools. After some light sanding the other magnets went in more easily and still held fast. Reducing this ever-so-slightly to try and prevent cracking.
I received my spools using commit c4ff415 and the magnet is still too tight - one spool cracked and the rest were sanded before pressing. Reducing this further.
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Good catch; agreed on reverting the flap slop. |
scottbez1
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Feb 28, 2021
Increases the clearance between the motor chassis and the right outside wall of the previous module. Also refactors this variable from 'slop' to 'clearance' for a better description of what it represents. This is still playing a bit of catch-up from the thickness change (#93). In the previous release where the thickness parameter was set to 3.2 mm but the manufactured panels were actually 3.0 mm thick, there was extra space between the motor chassis and the previous module. This change adds that additional 0.4 mm of clearance back as part of the motor clearance variable. The additional clearance also makes the widths between the two designs approximately equal - `enclosure_width` is 82.2 mm on v0.6, and 82.25 mm here. (The discrepancy is the additional 0.05 of flap width slop that was added in #114.) Note that #122 bumps this further to 82.35.
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On my latest order from Ponoko (3 mm acrylic) the spool struts are still loose and will need to be glued. This increases the interference a bit more (+ 0.04 mm) to hopefully reach a point where the struts will fit into the spool and hold there by friction alone.
Also increased is the flap width slop, in a reversion to the change from #114. On my order based around f4e7714 the flaps do fit and swing but it's tight - a little bit of misalignment with the spool end pieces or burrs on the parts will cause them to bind. And after gluing the end pieces in place not perfectly parallel (+/- 0.15 mm across ~48 mm diameter) that's exactly what has happened: some flaps on the spool do not 'flip' freely which breaks the whole display.
Originally I thought a slight increase to the flap slop would do the trick, but after giving it some more thought I think the slop decrease should be reverted in its entirety. It's one of the only critical dimensions in the design that can break the entire display if it's too tight, and there are too many factors that can influence the total clearance. Better to play things safe and keep this loose. If there is continued binding due to misalignment of flaps within the spool, the
spool_width_slopvalue can be increased further.I also parameterized and slightly reduced the magnet hole interference. On my displays the magnet press-fit is tight and I ended up cracking one of the spools. The magnets seemed much happier and still held tight after some light sanding of the hole, so this value is being reduced ever-so-slightly.