Advice/Help Printing Planetary Gears


#1

I recently purchased a Form 2 and I’ve been having a blast 3D printing with it. Last night I tried printing Planetary Gears with Herrington Teeth and although the print came out great the gears did not move and appeared to be fused. In the print file it looks like there was spacing but maybe I messed something on my end. I did the print in it’s original size and did not modify any settings. I realize there’s no mention of SLA compatibility or if that’s a limitation of the Form 2. But any help or tips would be appreciated. Thanks in advance.


#2

See this recent thread. Generally, the gap required to prevent fusing is different for an SLA printer than it is for an FDM printer.


#3

the magic gap works out to be 0.02 inches; so ALL contact clearances must be at least 2 thousands of an inch.

The teeth to teeth; the teeth above and below and the shafts and shaft holes.


#4

One more thing; each piece must be supported so that none move during the print.

Once in PreForm move the slices up and down to show that no moving piece is printed without enough support.


#5

I tried something similar before and found that the gap between the pieces is a lot bigger than 0.02" (.5mm). It wasn’t gears, it was a ball joint. I eventually gave up on that, but you can read my experience here:

https://forum.formlabs.com/t/print-a-ball-socket-joint-as-one-piece/11176/4


#6

Form 2 has a smaller laser beam diameter so you would expect the gap can be smaller(as laser settings, galvo speed, bleeding are probably very different).


#7

More than just the laser spot size, consider the layer thickness and double that and you should be ok. IE 100 micron use a 200 micron gap etc. Test it on a small part. If your pdms is starting to fog you may have to increase the gap since the exposure will start to scatter.


#8

Because they have a higher contact surface area, herringbone teeth really need to be made from a low friction material. So even if these gears were built separately and assembled they still would not work as well as cut gears made from for instance, POM/Delrin or Nylon12.


#9

The durable is apparently very low friction! :grin: