Not that patient it turns out. Four hours later I tested the two gears and the only discouraging observation is how easily the excess epoxy scratched off the nylon gear surface. No worries about surplus epoxy clogging up the teeth. Not sure how well it will hold.
Put it all back together. Took a few tries until I learned the process. Everything worked except for the gripper on the end effector. Pull the arm off the base and turn the gear by hand. Sure enough, the next shaft lower down was also spinning inside the pinion. So. Close examination of the two companion shafts showed a hairline crack in both nylon pinions. There are 10 teeth on the pinion and measured across two teeth on each side with a caliper showed about 5.8mm. If I were to venture a guess I'd say pitch diameter is 5mm? With 10 teeth that's 0.5mm module. Those I can easily cut. These two pinions will be harder to lock onto the shaft. Might be easier to 3D print them to verify the module and then cut them from aluminium. At least epoxy will bond to that. A simple G-Code program to move the 5C collet indexer to cut the gear. Stop, rotate 36 degrees, rinse repeat... John > -----Original Message----- > From: dave engvall [mailto:dengv...@charter.net] > Sent: December-23-21 9:50 PM > To: emc-users@lists.sourceforge.net > Subject: Re: [Emc-users] Complex 6 axis robot arm. > > I must say John that you are much more patient than I. As long as the > parts will take the heat warming helps drive the epoxy cure. Roughly 10 > degrees C doubles the reaction rate. 175 F or 80 C is a good place to > start. Assuming RT is 20 then 80-20 = 60 or 2^6 X. Naturally one may > have to back off the temp for wimpy thermoplastics. ;-) > > Dave > > On 12/23/21 9:12 PM, John Dammeyer wrote: > > I bought one of these well over 30 years ago. > > http://www.autoartisans.com/armatron/SuperArmatron.jpg > > > > My sons played with it until either they were bored or it stopped working. > > It went back in the box and they never told me the > motor no longer ran. > > > > I ended up taking it apart and disassembling the small 3V DC motor. Bend > > clips back, pull off plastic brush assembly. Black greasy > gunk all over the armature and brushes. Once cleaned up and put back > together the motor ran but two of the joints were > problematic. I really didn't want to take apart the arm but I could see a > shaft turning but the gear not. > > > > When I did it burst apart and gears and gears mounted on shafts were > > everywhere. Took a while to figure it out what went > where. Now I've used the Dremel to carve some grooves into the shafts and > small vise on mill to drill 1.15mm holes into the body of > the nylon gears which, I'm guessing due to age, had cracked. Almost looks > like the gears were molded onto the shafts but no splines. > > > > http://www.autoartisans.com/armatron/ArmDisassembled.jpg > > > > Anyway, a bit of 60 minute epoxy and now I'll have to wait 12 hours for it > > to set good and hard and then the adventure of trying to > put it all back together. I know where it all goes now. > > > > All mechanical, one motor turns continuously, the joysticks engage six > > different gears to create the joint motion. The complexity > reminds me of IBM Selectric typewriters I repaired as an IBM OPCE so many > decades ago. > > > > Now it's all done with computers. I'm not sure there are even people > > around who could design something like this that is fully > mechanical. > > > > John Dammeyer > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
