On Wednesday 22 January 2014 19:14:34 Jeshua Lacock did opine: > On Jan 22, 2014, at 10:25 AM, Jon Elson <[email protected]> wrote: > > On 01/21/2014 11:10 PM, Jeshua Lacock wrote: > >> Greetings, > >> > >> I am the proud new owner of an Bolton Tools AT750 combination lathe > >> and mill see here: > >> > >> <http://3DTOPO.com/Bolton-AT750.jpg> > >> > >> I am super impressed with the machine so far. > > > > Ugh, we have a somewhat similar machine at work, it is > > pretty awful. > > I wish you'd asked here before buying it. there are so many > > limitations in workspace, etc. it is a real pain to do > > anything bigger than > > a thimble in size. > > Hi Jon, > > Hmmm, what machine are you referring to? I just checked and I have full > 8x12x3 inches of travel for the mill. > > I have been using it to lathe hardened steel shafts and has been turning > like a dream so far. Haven't yet milled anything though. > > > Will you be using the original leadscrews? They have a lot of > > backlash. If you tighten a vise on the "table" it binds the > > Y travel. The Z mechanism is really laughable, backlash between > > the quill and pinion is probably several mm. I did a > > square-column > > mill some time ago and replaced the Z rack and pinion with an > > eBay ballscrew. The X and Y screws on that machine were quite > > tolerable. > > I figured backlash was common to just about all reasonably priced mills, > and I was wondering what folks did with them to compensate with CNC. I > just checked the backlash on my Z and with the micro-adjust knob I can > not feel any discernible backlash. I certainly can feel backlash on the > Z quick feed and on the X and Y leadscrews. > > Eventually I would like to replace them with anti-backlash ballscrews. I > would like to get the machine up and running first if I can expect > reasonable results from it. I think I read somewhere a while back > someone compensated for the backlash in software and virtually > eliminated the problem without having to replace the leadscrews. > > Speaking of anti-backlash ballscrews, have you guys seen this printable: > > http://www.thingiverse.com/thing:125529
That is a cute idea, but you likely have zero real repeatability. And that IS the name of this game. The only place that would be usable would be with real servos getting feedback from a linear scale encoder driven by the table you are moving. That of course adds 300 to 500 USD per axis. There is a link for how to make nuts that fit your screws, usually with less than a thou of backlash, using acetal/delrin for the nut material. <http://bbs.homeshopmachinist.net/threads/43645-Making-Acetal-leadscrew- nuts-the-easy-way> These have the advantage of less friction than a std nut under load, very low wear rate and virtually zero backlash when molded around your existing screws. I don't know as I would try and make a half nut assembly that way, but a full nut on the Z with my ball screw and nut on my lathe has not been a problem as I just use the keyboard to move it. I have the stuff on hand, and will fit at least the X/Y on my small mill come warm weather again. They are pushing 15 yo, and are very close to shot. > I have printed them out - and they work amazing! On a 3/4" shaft it > takes over 100 pounds of force before it slips - and you can pretty > much make it tight as you like within reason. NIce thing is it just > slips too - no damage when overloaded. It is also configureable for > travel per revolution. > > > The Pico USC will be fine, but depending on the drivers used, > > may not be necessary. If you use Gecko drives with the 10 X > > microstepping, the USC starts to look good due to the required > > step rate. The Gecko drivers are VERY good. > > Yeah I was planning on going with Gecko. Good to know, thanks Jon! > > I guess the biggest uncertainty right now is how much torque I might > need on a machine like this. I was guessing something like the first > stepper listed here: > > http://www.kelinginc.net/NEMA23Motor.html > > > Cheers, > > Jeshua Lacock > Founder/Engineer > 3DTOPO Incorporated > <http://3DTOPO.com> > Phone: 208.462.4171 > > > ------------------------------------------------------------------------ > ------ CenturyLink Cloud: The Leader in Enterprise Cloud Services. > Learn Why More Businesses Are Choosing CenturyLink Cloud For > Critical Workloads, Development Environments & Everything In Between. > Get a Quote or Start a Free Trial Today. > http://pubads.g.doubleclick.net/gampad/clk?id=119420431&iu=/4140/ostg.cl > ktrk _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> NOTICE: Will pay 100 USD for an HP-4815A defective but complete probe assembly. If you just try long enough and hard enough, you can always manage to boot yourself in the posterior. -- A. J. Liebling, "The Press" A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. ------------------------------------------------------------------------------ CenturyLink Cloud: The Leader in Enterprise Cloud Services. Learn Why More Businesses Are Choosing CenturyLink Cloud For Critical Workloads, Development Environments & Everything In Between. Get a Quote or Start a Free Trial Today. http://pubads.g.doubleclick.net/gampad/clk?id=119420431&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
