That's a good suggestion John F. Thanks. I did do some more playing around and it's clear the part flexing and the backlash both were at fault especially with the plunge to the next depth.
And that brings up another issue. One of my pet peeves with electronics project magazines is they are great at a schematic and either point to point wired or PC board but very little energy is spent on describing various ways of mounting or installing in a cabinet. Especially with the concept of Human Factor Engineering which is the practice of making something easy to use or even intuitive. Like an ESTOP button is always a red mushroom Not a toggle switch. Same goes with work holding. Youtube has tons of videos that show a tiring sequence of a milling cutter sprayed with coolant making chips for 3 minutes with 3 commercials interjected, one every minute. But very little on work holding. The next part I am making is shown in the attached screen shot rendering. My raw material is in the second photo. So the question is about work holding and how or what features of LinuxCNC can be used to make this easier. I can use my band saw to create the initial width and split it into two L shapes. But after that I start to have problems, due to lack of experience I think, on how to firmly hold it and mill the stuff with a 5mm and 6.35mm (1/4") cutter. Suggestions? Thanks John > -----Original Message----- > From: John Figie [mailto:[email protected]] > Sent: August-03-21 11:59 AM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] Something went wrong. > > Speaking of backlash. My tiered old Bridgeport has about 0.002" of backlash > in the ballscrews. So if circular interpolation is used there is a small > bump at each 90 degrees of the circle. But if I make the finish pass first > clockwise and then repeat counter clockwise the imperfections are much > smaller. I know from experience with my first CNC machine that's built that > actually used leadscrews with lots of backlash the clockwise followed by > counter clockwise method was remarkable compared to a single direction > final pass. > > John > > On Tue, Aug 3, 2021, 10:10 AM jrmitchellj <[email protected]> wrote: > > > You might try the run again without the backlash compensation in LCNC to > > get a feel of what it is actually doing. > > > > > > --J. Ray Mitchell Jr. > > > > > > �I predict future happiness for Americans, if they can prevent the > > government from wasting the labors of the people under the pretense of > > taking care of them.� > > > > THOMAS JEFFERSON > > > > > > On Tue, Aug 3, 2021 at 6:24 AM Gene Heskett <[email protected]> wrote: > > > > > On Tuesday 03 August 2021 05:31:56 andy pugh wrote: > > > > > > > On Tue, 3 Aug 2021 at 07:58, <[email protected]> > > > wrote: > > > > > I draw all this from my own ballscrew conversion of my own mill, > > > > > some 20 years ago. If I was doing it again, I would use two nuts, > > > > > with spring tension between the pair > > > > > > > > Springs might not be the best way. The common way to tension double > > > > nuts is to (basically) screw them into each other and lock the angular > > > > relationship. > > > > > > > > You _can_ get preloaded single nuts, using oversized balls. That only > > > > works if the ball track is the right shape, though, it needs to be a > > > > 4-point contact shape. > > > > > > Which I'd suspect as being subject to rapid initial wear until it was > > > just a normal screw with about a thou of backlash. > > > > > > For me, I bought C7 grade which may have 2 thou but in several years has > > > not gotten significantly worse. Protecting the screw from contaminants > > > is the most important thing for long life. On my Sheldon, the Z screw, a > > > 1450mm long 25mm C7, got sealed bearings on both ends, a collar to clamp > > > a bellows to on both ends of both sections, and 2 of the 6 mounting > > > holes in the nut were drilled all the way thru so air could get from one > > > side of the nut to the other as the nut moved. The nut gets one pump of > > > grease a year. Backlash, some of which is in the end bearing, was about > > > 1.9 thou 5 years ago and still is. It has not been uncovered in that > > > time. I don't have a bellows on the x screw but its channel in the > > > carriage is sealed top and bottom unless the carriage is clear in. > > > exposing the screw behind the QCTP boss. No compound since LCNC is > > > better than mechanical you set by eyeball. Plus it was busted from a > > > fallover when I bought it. I keep a rag over the slot in that event. > > > > > > That faint thumping? Me, knocking on wood, no swarf has gotting into it > > > yet... > > > > > > 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> > > > > > > > > > _______________________________________________ > > > Emc-users mailing list > > > [email protected] > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users
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