On Friday, February 4, 2022 10:31:23 AM EST Kenneth Lerman wrote: > Chris -- At my house, computers are all over the place. I think I have > a spare atom floating around. Also a couple of other machines. > Gene -- The grinder is here. > <https://drive.google.com/file/d/1L8JiX0rtDZO99rVnQKNjUH7m-ZgFz2Un/view > ?usp=sharing> The > ways look pretty clean. The only accessory I have is a magnetic chuck. > Cute little thing Ken. And with a mag chuck, you stole it.
> I don't really need a surface grinder, but no shop is complete without > one. Once I started to use it, I realized that my right arm and > shoulder really aren't suited to this type of manual work. As the senior member here, I get to complain first :) But you're excused ;o) As to you gear ratio problems, I agree, which is why I designed a small variation of a harmonic drive for use on the A axis of my 6040 mill. But its too small I think for what you want to do. But the 3d slicer "cura" can scale, and if you've a 3d printer that can handle PETG, one of the higher temp plastics, on an everyday basis, this thing scaled up 200% should do the job for you ok. Gear ratio, about as high as it can go at the native size is 50/1 but could be as low as 30/1. I'm driving it with a 1NM version of the new 3 phase stepper/servo's, but that family of servo's can be had at 3NM or about 425 oz/in, as all have an 8mm diameter d-flated shaft, which I put on my milling machine, power up to lock it and make the flat bigger, so the measurement from flat to back of the round is 6.5mm. With a printed armature hub that grips the whole shaft its strong enough in PETG that no hard to machine metal hub insert is needed. In my size, I can make 2 of them out of a $20 kilo of PETG, and a small bottle of crosman bb's, or about 15$ a drive. At a scaleup for what you need, about 200%, will x4 the amount of filament, and probably x4 the print time too but I don't see why it won't work if you wanted to try it. My whole idea is cheap, if it breaks, print another. > The longitudinal travel is just over a foot, and it takes about 3-1/2 > turns of the crank to go that distance. I'm thinking around a second > per turn would be about the maximum. So, that's 60 RPM. I'm thinking > of a 1:6 ratio on the timing belt pulleys, so that's 360 RPM at the > stepper which is pretty slow. A full stepping rate would be 200 * > 360/60 => 200 * 6 which is only 1200 steps per second. > > An alternative would be to provide more gearing, but I don't think it's > practical to get more than about a six to one ratio in a single belt > reduction and I'd like to avoid mechanical complexity if I can. OpenSCAD, which I used to design this, is quite capable of doing any part that fits on the bed of your 3d printer. And if at 87 I can learn it, I'm convinced you could too. Two OpenSCAD master files, are text files, and this drive and the driver sprocket to replace the alu crap that came on this A drive originally, total about 1400 LOC, several hundred of which is comments so I can figure out a month from now, what the heck I was doing. Lots of it is from thingiverse, and modified by me. But the final version hasn't made it to my web site, yet... Something about the only time a program is finished is when someone shoots the programmer. I am also driving my converted 11x54 Sheldon lathe with the 3NM and 2NM versions of this motor/driver stepper/servo. And driven by LinuxCNC running on a rpi4, its doing dance steps that it could not do 80 years ago when it was shipped to the navy. Including correcting for the 13 thou of bed wear right in front of the chuck. This lathe has been rode hard, thrown across the truck bed going around a corner too fast and put away wet long before it followed me home in a cargo van. If interested, give me you PM address and I'll email the .scad to you. > Thoughts? Take care and stay well. > Ken > > Kenneth Lerman > 55 Main Street > Newtown, CT 06470 > 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, 1940) 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> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
