On Thursday 12 August 2021 12:09:28 Ned Young via Discuss wrote: > Gene, I think the problem you're dealing with is intrinsically part of > FDM, and possibly other 3D printing methods as well. At root, the > technology is using an icing bag and attempting to achieve precision. > There are so many production-time variables that can affect the result > that it is impossible to solve the problem at design time. > > I created test blocks in OpenSCAD for different fasteners. Through > holes, self-tapping holes, tapped holes, in several orientations. > _Before_ beginning the design of an object, I run the test blocks > using _exactly_ the same production parameters (temps, feeds, > materials, and yes, even color) to discover what values I need to > specify at design time to get the dimensions I need. Well, I have since done an autopsy on the failed drive, and that has given me the seeds of a better idea that wold be hard to assemble. I had not used ball bearings on an arm, but an eccentric armature with 2 printed bearings wrapped around it to transfer the eccentricity needed to the floating ring. The inner bearing races were too thin at the bottom of the bearing groove, so it split at the bottom of the bearing groove and chewed up the inner races. Everything else is dirty but 100% OK and could theoretically be re-used. Now I need to nap on the changes as they would make for a more difficult assembly.. :o( Or make the armature smaller and give that room to the bearing race. I like that idea better. But first, find and fix the plastic leak. On a prusa, thats a major teardown. I had about a dozen bb sized plastic balls loose on the build plate from the last print. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene>

On Thursday 12 August 2021 13:09:41 Gene Heskett wrote: > On Thursday 12 August 2021 12:09:28 Ned Young via Discuss wrote: > > Gene, I think the problem you're dealing with is intrinsically part > > of FDM, and possibly other 3D printing methods as well. At root, > > the technology is using an icing bag and attempting to achieve > > precision. There are so many production-time variables that can > > affect the result that it is impossible to solve the problem at > > design time. > > > > I created test blocks in OpenSCAD for different fasteners. Through > > holes, self-tapping holes, tapped holes, in several orientations. > > _Before_ beginning the design of an object, I run the test blocks > > using _exactly_ the same production parameters (temps, feeds, > > materials, and yes, even color) to discover what values I need to > > specify at design time to get the dimensions I need. > > Well, I have since done an autopsy on the failed drive, and that has > given me the seeds of a better idea that wold be hard to assemble. I > had not used ball bearings on an arm, but an eccentric armature with 2 > printed bearings wrapped around it to transfer the eccentricity needed > to the floating ring. The inner bearing races were too thin at the > bottom of the bearing groove, so it split at the bottom of the bearing > groove and chewed up the inner races. Everything else is dirty but > 100% OK and could theoretically be re-used. > > Now I need to nap on the changes as they would make for a more > difficult assembly.. :o( Or make the armature smaller and give that > room to the bearing race. I like that idea better. But first, find and > fix the plastic leak. On a prusa, thats a major teardown. I had about > a dozen bb sized plastic balls loose on the build plate from the last > print. > Is anyone interested in what I found with the prusa and how I /think/ I've fixed it? > Cheers, Gene Heskett Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene>