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Potentiometer Planetary Reduction Drive Knob

by tmackay Apr 14, 2019
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As soon as I get done printing the 30m coil forms I designed, I'm going to attempt to print this for my ANC-4. It's either I print something like this, or replace the pots with 10-turn pots of the same values (which is much more expensive).
Are there any caveats or gotchas I need to look out for?
Tnx de AI8W

I'd be interested to hear how it performs. Clearance of the gears will probably be the limiting factor - too little and the gears will stick together initially causing "lumps" which will get smoother over time, too much and there will be a lot of backlash. Make sure the slicer leaves a layer gap between the centre gears or they will print solid.
This was intended as a cheap alternative for multi-turn pots, but it won't have the same level of precision. More useful for cases where you want to slow down how fast a dial can be turned or require to measure more than one revolution but precision is less important.

That's basically what I'm using it for... Unsure if you're a fellow HAM radio operator or not, but the ANC-4 is an antenna noise canceller. It uses phasing to cancel out local noise before it gets to the radio. There are two potentiometers, one for level and one for phase adjustment. The phase adjustment could be a little slower, and I'd thought about replacing it with a 10-turn pot, but, if this works as advertised, I won't need to.
I haven't looked hard at the options in the scad yet, but when I go to print it, I'll dig around and make sure it'll work for me.

I printed the "stock" version, ended up being a little too large for the equipment. The gears were also a little too "tight".
I'm unclear on the terminology you used. Which variable(s) do I need to tweak in order to make the planets and the sun gear looser inside the ring? Is it Gear Tolerance?
I also need to reduce the outer ring size to 40mm (I found that variable).
Overall, this is a really neat design; I might learn a thing or two from your code, too.

Yes, Gear Tolerance (Tol) is the one. There are also a number of parameters you can adjust on the slicer to dial in your printer. Over extrusion is probably the easiest to fix by dialling down the Extrusion % modifier and will have a big impact on clearances in the final result. Things like negative Horizontal Expansion can help too - if we didn't have the luxury of customizing.
Just be careful when adjusting things like number of gears and teeth on this model - there are a number of constraints in this arrangement that allow for a fused, single ring gear. There is a google sheet linked in the summary with valid solutions.
To get this smaller still, you could choose a solution with fewer planet gear teeth and drop the Shaft D (the hole through the planet gears).

I've managed to get it down to 25mm diameter: GearedPotDial25mm4x5x6S.stl. Printed successfully on an Ender3, but the details are starting to get quite fine.