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-----Original Message----- From: [email protected] Date: Thu, 25 Mar 2010 16:33:19 To: <[email protected]> Subject: Emc-users Digest, Vol 47, Issue 94 Send Emc-users mailing list submissions to [email protected] To subscribe or unsubscribe via the World Wide Web, visit https://lists.sourceforge.net/lists/listinfo/emc-users or, via email, send a message with subject or body 'help' to [email protected] You can reach the person managing the list at [email protected] When replying, please edit your Subject line so it is more specific than "Re: Contents of Emc-users digest..." Today's Topics: 1. Re: DAQ of the day. (D.C.Clark) 2. Re: Jogging inaccuracies (Gene Heskett) 3. Re: Jogging inaccuracies (Andy Pugh) 4. Re: Jogging inaccuracies (Mark Wendt (Contractor)) 5. Re: DAQ of the day. (Mark Wendt (Contractor)) 6. Re: Jogging inaccuracies (Mark Wendt (Contractor)) 7. Re: Jogging inaccuracies (Andy Pugh) 8. Re: Jogging inaccuracies (Mark Wendt (Contractor)) ---------------------------------------------------------------------- Message: 1 Date: Thu, 25 Mar 2010 11:58:44 -0400 From: "D.C.Clark" <[email protected]> Subject: Re: [Emc-users] DAQ of the day. To: "Enhanced Machine Controller (EMC)" <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1; format=flowed > I'll definitely join the list. When did you retire from > Goddard? Know a coupla fellas by the name of Kurt Wolko or Vic > Ezerski? Both real good friends of mine. > > Retired January '06. Those names don't ring a bell, but, it's a big place. I worked in Building 5, code 547, Advanced Manufacturing Branch. DC ------------------------------ Message: 2 Date: Thu, 25 Mar 2010 12:08:52 -0400 From: Gene Heskett <[email protected]> Subject: Re: [Emc-users] Jogging inaccuracies To: "Enhanced Machine Controller \(EMC\)" <[email protected]> Message-ID: <[email protected]> Content-Type: Text/Plain; charset=iso-8859-1 On Thursday 25 March 2010, Mark Wendt (Contractor) wrote: >At 08:43 AM 3/25/2010, you wrote: >>Mark Wendt (Contractor) pravi: >> > At >> > .001, sometimes I'd get no movement (I'd here stepper motor noise but >> > no movement on the dial indicator), other times I'd get a half-thou, >> >>This can be only mechanical then... Check backlash and endplay of nut... >>check coupler too.. If motor make step and gantry not then don't blew >>software :D >> >>Slavko. > >This is on a rack and pinion system, pulley mounted directly on >stepper, pinion has pulley mounted directly to it, with cogged timing >belt driving the pinion. All these numbers were with the gantry >moving in one direction, jog and hold, jog and hold, while watching >the dial indicator for movement between jogs, which there was >none. Does backlash come into play when all moves are in the same > direction? > >Mark Ahh so. I found when I was tuning up my new z axis drive which uses a gilmer belt with a 17 to 42 ratio, that it had to be _very_ taut, any visible amount of slack on the slack side of the movement and the detected backlash was very inconsistent. That belt has got to be tightly stretched. Even a year+ later, I'd imagine the tension is at least 25 pounds. That left me with about .0036" to put into the backlash setting, the lowest amount on that cheap HF mill. I could get better but the sled also tips on the post a few arcseconds if the gibs are loose enough to move it. Tight gibs, by raising the drag, actually make the tipping moment worse. Someday I have got to get a decent mill... > >--------------------------------------------------------------------------- >--- Download Intel® Parallel Studio Eval >Try the new software tools for yourself. Speed compiling, find bugs >proactively, and fine-tune applications for parallel performance. >See why Intel Parallel Studio got high marks during beta. >http://p.sf.net/sfu/intel-sw-dev >_______________________________________________ >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) VMS version 2.0 ==> ------------------------------ Message: 3 Date: Thu, 25 Mar 2010 16:18:26 +0000 From: Andy Pugh <[email protected]> Subject: Re: [Emc-users] Jogging inaccuracies To: "Enhanced Machine Controller (EMC)" <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1 On 25 March 2010 14:49, Mark Wendt (Contractor) <[email protected]> wrote: > ? ? ? ? I'm not sure at this point. ?I'm not sure if the errors > showing up are cumulative or not. Not if they are due to backlash or microstepping nonlinearity. > ?Actually, I am looking for + or - > .001" accuracy on the strips I'm going to be cutting. ?That accuracy > will be the height of the triangular cross section of the strip. But that accuracy is needed in the Z axis, which you have already stated is spot-on. (I am guessing it is a ballscrew?) > ?On > the tips of some of the rods I make, I routinely hand plane down to a > .025" flat to apex height, and can usually hit that measurement > within a thou. ?If the machine can't do that in production, it ain't > gonna work for me. ?So, I need to make it accurate. I don't think any rack-and-pinion system will be accurate to sub-thou positional accuracy. However, as you are cutting a slow taper you need far less X accuracy than Z accuracy. -- atp ------------------------------ Message: 4 Date: Thu, 25 Mar 2010 12:20:01 -0400 From: "Mark Wendt (Contractor)" <[email protected]> Subject: Re: [Emc-users] Jogging inaccuracies To: "Enhanced Machine Controller \(EMC\)" <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset="us-ascii"; format=flowed At 11:56 AM 3/25/2010, you wrote: >At 165 pounds, it may be that the gantry is actually taking up some backlash >as its stopping from the longer moves which would be faster. Can you, as its >hooked up & the motors enabled, induce a motion visible on the indicator by >manually pushing or pulling it? And, equally important, does this 'slack' >remain constant as you move it with the motors? If constant, then perhaps >adding some backlash comp might help (but that's only effective for motion >reversals of course), or if its position related, it might be possible to map >the screws error. Wear patterns can be elusive, and mapping a cyclic error >can be 'fun' for some definitions of fun. If you have many hours on the >machine doing the same cuts over and over it might even be advisable to >replace the screws. Or if the cutting dust can get to them, a really good >cleaning might help. I'll give it a try manually moving the machine while the motion control system is up and running. Haven't tried that as of yet. It's a brand, spankin' new machine that has not cut anything yet, so if there's wear patterns anywhere, it'll be on my forehead where I've been rubbing in consternation... ;-) > > I disconnected the pinion gears from the racks, moved the gantry > >back and forth the length of the X axis a few times by hand, and > >didn't really notice any binding. It seemed pretty smooth, and > >relatively easy to move a 165 lb gantry on the rails. > >Pinion gears, same thoughts about cleaning apply. I assume they are >preloaded? Pinions are preloaded. Here's the R&P setup: <http://www.cncrouterparts.com/product_info.php?cPath=21&products_id=50> >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) > >All that glitters has a high refractive index. Mark ------------------------------ Message: 5 Date: Thu, 25 Mar 2010 12:21:36 -0400 From: "Mark Wendt (Contractor)" <[email protected]> Subject: Re: [Emc-users] DAQ of the day. To: "Enhanced Machine Controller \(EMC\)" <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset="us-ascii"; format=flowed At 11:58 AM 3/25/2010, you wrote: > > I'll definitely join the list. When did you retire from > > Goddard? Know a coupla fellas by the name of Kurt Wolko or Vic > > Ezerski? Both real good friends of mine. > > > > > >Retired January '06. Those names don't ring a bell, but, it's a big >place. I worked in Building 5, code 547, Advanced Manufacturing Branch. > >DC Sounds kinda the same as it is here at the Naval Research Lab. Folks always ask me if I know one of their friend's that works here. Some I do, some I don't. Ya never know. I'll have to ask Kurt and Vic what building they work in and what Code they are. Mark ------------------------------ Message: 6 Date: Thu, 25 Mar 2010 12:24:34 -0400 From: "Mark Wendt (Contractor)" <[email protected]> Subject: Re: [Emc-users] Jogging inaccuracies To: "Enhanced Machine Controller \(EMC\)" <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset="us-ascii"; format=flowed At 12:08 PM 3/25/2010, you wrote: > >This is on a rack and pinion system, pulley mounted directly on > >stepper, pinion has pulley mounted directly to it, with cogged timing > >belt driving the pinion. All these numbers were with the gantry > >moving in one direction, jog and hold, jog and hold, while watching > >the dial indicator for movement between jogs, which there was > >none. Does backlash come into play when all moves are in the same > > direction? > > > >Mark > >Ahh so. I found when I was tuning up my new z axis drive which uses a gilmer >belt with a 17 to 42 ratio, that it had to be _very_ taut, any visible amount >of slack on the slack side of the movement and the detected backlash was very >inconsistent. That belt has got to be tightly stretched. Even a year+ later, >I'd imagine the tension is at least 25 pounds. That left me with about >.0036" to put into the backlash setting, the lowest amount on that cheap HF >mill. I could get better but the sled also tips on the post a few arcseconds >if the gibs are loose enough to move it. Tight gibs, by raising the drag, >actually make the tipping moment worse. Someday I have got to get a decent >mill... Belts are pretty darn snug, as is the turnbuckle tensioneer that holds the stepper/pinion assembly up against the rack. No gibs on this machine, just linear rails... ;-) >-- >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) > >VMS version 2.0 ==> Ah, VMS. DEC in all it's glory! Still my favorite OS! Mark ------------------------------ Message: 7 Date: Thu, 25 Mar 2010 16:28:53 +0000 From: Andy Pugh <[email protected]> Subject: Re: [Emc-users] Jogging inaccuracies To: "Enhanced Machine Controller (EMC)" <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1 On 25 March 2010 15:29, Mark Wendt (Contractor) <[email protected]> wrote: > ? ? ? ? Thanks. ?The pinion gear is held upward against the rack by > a hefty spring. This is a small effect, but if the rack and pinion are not working at their exact design centre distance then the relative motion will have a cyclical irregularity. The gear and rack will have been cut assuming the normal amount of backlash clearance. However, I think you are putting the cart before the horse. Don't invent problems, cut some strips and see if they meet your requirements before going through an intensive debugging process. If you really want that 52" DTI then you can rent a laser measurement system for the day. -- atp ------------------------------ Message: 8 Date: Thu, 25 Mar 2010 12:33:10 -0400 From: "Mark Wendt (Contractor)" <[email protected]> Subject: Re: [Emc-users] Jogging inaccuracies To: "Enhanced Machine Controller \(EMC\)" <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset="us-ascii"; format=flowed At 12:18 PM 3/25/2010, you wrote: >On 25 March 2010 14:49, Mark Wendt (Contractor) ><[email protected]> wrote: > > > I'm not sure at this point. I'm not sure if the errors > > showing up are cumulative or not. > >Not if they are due to backlash or microstepping nonlinearity. I'll have to make sure one way or the other. We have yet to determine that it's truly backlash that's causing the problem. > > Actually, I am looking for + or - > > .001" accuracy on the strips I'm going to be cutting. That accuracy > > will be the height of the triangular cross section of the strip. > >But that accuracy is needed in the Z axis, which you have already >stated is spot-on. (I am guessing it is a ballscrew?) Yes and no. In order for the taper itself to be accurate, those flat to apex (Z axis) dimensions have to be met at darn near the spot-on length (X axis). Remember, there's going to be 6 of these strips glued up to make a rod section, and that rod section would look kinda funky if the flat to apex dimensions didn't quite line up. > > On > > the tips of some of the rods I make, I routinely hand plane down to a > > .025" flat to apex height, and can usually hit that measurement > > within a thou. If the machine can't do that in production, it ain't > > gonna work for me. So, I need to make it accurate. > >I don't think any rack-and-pinion system will be accurate to sub-thou >positional accuracy. However, as you are cutting a slow taper you need >far less X accuracy than Z accuracy. Don't need to be sub thou. Just + or - .001". If the X axis is consistently off .001" or .002" per inch, and it's cumulative, it'll end up being close to .050" by the end of the strip. I'm thinking that's a bit much. >-- >atp Mark ------------------------------ ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users End of Emc-users Digest, Vol 47, Issue 94 ***************************************** ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
