Large ring bearings are not crazy-expensive. I was thinking about using some in a robot leg design. This one could work for your size reduction drive. Use them in pairs spaced as far apart as possible. They are deep groove so they can take some axial load. With wide enough spacing you don't get much play. This company, "uxcell", makes cheap but good enough bearings and sells on Amazon, eBay and other places like that. amazon.com/uxcell-6816-2RS-Bearing-80x100x10mm- <https://www.amazon.com/uxcell-6816-2RS-Bearing-80x100x10mm-Bearings/dp/B07RQ4RXDR/ref=sr_1_3?crid=21LZ75QCVNKGM&keywords=uxcell+ball+bearing+100mm&qid=1641234560&s=industrial&sprefix=uxcell+bal+earing+100mm%2Cindustrial%2C111&sr=1-3>
I generally press-fit bearing onto the plastic and have to always "post process" the plastic until the bearing slips on with slight hand pressure. I have a lathe but I'm lazy and mostly just sandpaper the plastic until the bearing fits. but if you turn the plastic you get better concentric fit. For cheap hardware I now just search for "uxcell" and find screws, nuts and bearings, precision ground rods and what not, all "decent Chinese quality". Also when you use big ring bearing, threat them as structural member in the design. A plastic part is very weak but a plastic part with a big stainless steel ring attached with CA glue is almost as strong as a big stainless steel ring. I discovered "hardware as structure" a few weeks ago as a fix for broken plastic parts. So I re-printed the part but with long internally thread M3 or M4 holes all the way through then I fill the hole with CA glue and put in a long screw. I call it "steel reinforced plastic". Like rebar in concrete. On Mon, Jan 3, 2022 at 12:57 AM John Dammeyer <[email protected]> wrote: > For fun I created Todd's version with 0.5module gears. The OD of the > assembly is now 60mm compared to 150mm. It would now be possible to > choose a far east harmonic drive tapered roller assembly to hold the driven > gear in place. Although they are expensive. > > Not sure what type of bearings, if any would be used for the planetary > gear clusters. I suppose one could press in bronze sleeves. I guess it > all depends on the duty cycle and target application. If it's a 6 axis > robot arm used for tool changing and placement/removal of milled parts then > it's not running continuously. Might well for the home or small shop be > more than adequate. > > This example still has 67.3333333:1 reduction but if the fit is well set > then the backlash is essentially zero which is different from normal > planetary reduction drives. Not sure how important that is for a 6 axis > robot arm. > > In either case, using a 4th axis to create all three spur gears at the > same time (one set of 40T and one set of 41 T) and then some sort of > broaching/indexing to create the two ring gears the real issue is the outer > bearing of the 101T output ring gear. But overall not that difficult to > create once you have the 0.5 module shaper style cutter. > > John > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
