Re: [Emc-users] Gantry Best Practices
On Feb 19, 2014, at 12:42 AM, Charles Steinkuehler char...@steinkuehler.net wrote: If I'm following things correctly, you're doing something very similar to the HAL gantry component I just created: applying the same commanded position to each gantry joint, providing for an offset between the individual joints to avoid racking. Yes, the offset is applied during the homing sequence and was calculated using a large square drawn on the table. Homing is substantially different, but then I don't have fancy Granite drives that will home themselves, so I had to work with LinuxCNC. :) Yes, the Granites cost their weight in gold ;-) but they are very nice drives!! We have large door stops fastened to the ends of the rails and the granites reduce torque, move until they hit these, press against them until a (very low) configured ferror is reached and declare this home. The gantry then moves out to the index pulse on each encoder and then the configured offset it applied to one side. It is very repeatable. Well, first Mesa has to make a BBB cape! Although there are beginning to be some FPGA add-ons for the BeagleBone that might be able to run the hm2 firmware. I'm waiting on my LogiBone kick-starter and there are a few other designs in the works I'm aware of. Will be nice to see these things. -Tom -- Managing the Performance of Cloud-Based Applications Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. Read the Whitepaper. http://pubads.g.doubleclick.net/gampad/clk?id=121054471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gantry Best Practices
On Mon, Feb 17, 2014 at 5:47 PM, Steve Blackmore st...@pilotltd.net wrote: Sorry, but I don't consider changing the machine to fit the tool to be an acceptable solution. Then your stuck with a known problematic design. I wish I had a pound for each complaint/query/moan I've seen and heard about twin steppers on a gantry machine. Other fixes include servos or closed loop steppers but keeping both sides in synch with software without any feedback is nigh on impossible. Steve Blackmore You won't get any whining, bitching or complaining from me on my twin stepper, gantry setup. Works like a charm, and the machine is designed rigidly enough I never worry about racking. Mark -- Managing the Performance of Cloud-Based Applications Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. Read the Whitepaper. http://pubads.g.doubleclick.net/gampad/clk?id=121054471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gantry Best Practices
If you design a machine to be affordable, lightweight, and easy(er) to manufacture, but requires some software assistance to do that, that's not necessarily problematic. I would call that innovative - making use of all of the tools and resources available to you to solve a problem. Len Then your stuck with a known problematic design. I wish I had a pound for each complaint/query/moan I've seen and heard about twin steppers on a gantry machine. Other fixes include servos or closed loop steppers but keeping both sides in synch with software without any feedback is nigh on impossible. Steve Blackmore -- -- Managing the Performance of Cloud-Based Applications Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. Read the Whitepaper. http://pubads.g.doubleclick.net/gampad/clk?id=121054471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gantry Best Practices
On Tue, 18 Feb 2014 10:37:12 -0500, you wrote: Hey, all! I normally just listen to the wisdom spouted by all you experts (the status of which I aspire to reach someday!). I built my own gantry-style router running LCNC. Each side of the gantry is driven by it's own stepper and Acme screw. HOWEVER, to avoid racking, I have both sides locked in alignment via a toothed drive belt connecting the two sides. Nice one :) I saw a laser cutter that had two coarse pitch ballscrews on the x axis linked by a timing belt at one end and driven from one servo. The op was telling me it was a bitch to set up initially. The ballnuts were threaded into the mounts under the gantry uprights and had a locking nuts to fix the position They had to be tweaked to get the whole gantry square but once done, never touched again. Took two installers three days to get it set up. I can't remember the machine manufacturer - some Swiss company, IIRC. Steve Blackmore -- -- Managing the Performance of Cloud-Based Applications Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. Read the Whitepaper. http://pubads.g.doubleclick.net/gampad/clk?id=121054471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gantry Best Practices
I will just (once again) point to http://wiki.linuxcnc.org/cgi-bin/wiki.pl?GantryPlasmaMachine Two servo motors/encoders on the Y axis, trivkins configuration (configs are in the links on the page). Gets an amazing amount of use at Maker Works in Ann Arbor and runs great. See catchy video here ;-) http://maker-works.com/wordpress/tools/cnc-plasma-cutter/ It isn't running a BBB w/ Mesa but that would be great at some point in the future!! -Tom -- Managing the Performance of Cloud-Based Applications Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. Read the Whitepaper. http://pubads.g.doubleclick.net/gampad/clk?id=121054471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gantry Best Practices
On 2/18/2014 6:13 PM, Tom Easterday wrote: I will just (once again) point to http://wiki.linuxcnc.org/cgi-bin/wiki.pl?GantryPlasmaMachine Thanks, I somehow missed that previously. Two servo motors/encoders on the Y axis, trivkins configuration (configs are in the links on the page). Gets an amazing amount of use at Maker Works in Ann Arbor and runs great. See catchy video here ;-) http://maker-works.com/wordpress/tools/cnc-plasma-cutter/ If I'm following things correctly, you're doing something very similar to the HAL gantry component I just created: applying the same commanded position to each gantry joint, providing for an offset between the individual joints to avoid racking. Homing is substantially different, but then I don't have fancy Granite drives that will home themselves, so I had to work with LinuxCNC. :) It isn't running a BBB w/ Mesa but that would be great at some point in the future!! Well, first Mesa has to make a BBB cape! Although there are beginning to be some FPGA add-ons for the BeagleBone that might be able to run the hm2 firmware. I'm waiting on my LogiBone kick-starter and there are a few other designs in the works I'm aware of. -- Charles Steinkuehler char...@steinkuehler.net signature.asc Description: OpenPGP digital signature -- Managing the Performance of Cloud-Based Applications Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. Read the Whitepaper. http://pubads.g.doubleclick.net/gampad/clk?id=121054471iu=/4140/ostg.clktrk___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gantry Best Practices
On Sun, 16 Feb 2014 16:51:06 -0600, you wrote: On 2/16/2014 4:03 PM, Steve Blackmore wrote: On Sun, 16 Feb 2014 14:11:13 -0600, you wrote: With the recent release and general popularity of the ShapeOko V2 desktop mini-mill, I have several folks who are trying to use LinuxCNC running on the BeagleBone as a control. If you are unfamiliar with this machine, here's a link: https://www.inventables.com/technologies/desktop-cnc-mill-kit-shapeoko-2 Cant help with the best way to run that with LinuxCNC, but I'd be tempted to remove one stepper and run a cross shaft driving both belts with possibly a bigger stepper motor. Sorry, but I don't consider changing the machine to fit the tool to be an acceptable solution. Then your stuck with a known problematic design. I wish I had a pound for each complaint/query/moan I've seen and heard about twin steppers on a gantry machine. Other fixes include servos or closed loop steppers but keeping both sides in synch with software without any feedback is nigh on impossible. Steve Blackmore -- -- Managing the Performance of Cloud-Based Applications Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. Read the Whitepaper. http://pubads.g.doubleclick.net/gampad/clk?id=121054471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gantry Best Practices
On 2/17/2014 4:47 PM, Steve Blackmore wrote: On Sun, 16 Feb 2014 16:51:06 -0600, you wrote: On 2/16/2014 4:03 PM, Steve Blackmore wrote: On Sun, 16 Feb 2014 14:11:13 -0600, you wrote: With the recent release and general popularity of the ShapeOko V2 desktop mini-mill, I have several folks who are trying to use LinuxCNC running on the BeagleBone as a control. If you are unfamiliar with this machine, here's a link: https://www.inventables.com/technologies/desktop-cnc-mill-kit-shapeoko-2 Cant help with the best way to run that with LinuxCNC, but I'd be tempted to remove one stepper and run a cross shaft driving both belts with possibly a bigger stepper motor. Sorry, but I don't consider changing the machine to fit the tool to be an acceptable solution. Then your stuck with a known problematic design. I wish I had a pound for each complaint/query/moan I've seen and heard about twin steppers on a gantry machine. Other fixes include servos or closed loop steppers but keeping both sides in synch with software without any feedback is nigh on impossible. Steppers are not the problem, the issues I mentioned apply equally to machines with servos and encoder feedback. I'm asking for the suggested best way to configure LinuxCNC for controlling a gantry system, that presents the user with the least opportunity to shoot themselves in the foot. For instance, how do you avoid racking the gantry when jogging in joint mode? Do you have a servo gantry config that avoids or minimizes this possibility you could point me to? I know folks are controlling gantry systems with LinuxCNC, I'm wanting to know how, and what are the pros and cons of each setup. -- Charles Steinkuehler char...@steinkuehler.net signature.asc Description: OpenPGP digital signature -- Managing the Performance of Cloud-Based Applications Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. Read the Whitepaper. http://pubads.g.doubleclick.net/gampad/clk?id=121054471iu=/4140/ostg.clktrk___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gantry Best Practices
Charles, I use LCNC on gantry routers and plasma machines with dual steppers on the X axis all the time. I simply slave the second motor in the HAL file with an inverted DIR signal. I have my motors driving on a Rack and Pinion setup always and I have a spring loaded motor plate to apply constant tension to the pinion. If need be one can just release the motors and place the gantry in a neutral position before homing. I found that if the machine is setup to be NOT close to it maximum performance, it will never give any problems. If the gantry has racked, I simply run it into the stops slowly and the slippage will correct the skew. I have never had the need to run a router in joint mode so I dont have the problems that come with that. For my sake please explain the use of joint mode with the router. On 2014-02-18 01:19, Charles Steinkuehler wrote: On 2/17/2014 4:47 PM, Steve Blackmore wrote: On Sun, 16 Feb 2014 16:51:06 -0600, you wrote: On 2/16/2014 4:03 PM, Steve Blackmore wrote: On Sun, 16 Feb 2014 14:11:13 -0600, you wrote: With the recent release and general popularity of the ShapeOko V2 desktop mini-mill, I have several folks who are trying to use LinuxCNC running on the BeagleBone as a control. If you are unfamiliar with this machine, here's a link: https://www.inventables.com/technologies/desktop-cnc-mill-kit-shapeoko-2 Cant help with the best way to run that with LinuxCNC, but I'd be tempted to remove one stepper and run a cross shaft driving both belts with possibly a bigger stepper motor. Sorry, but I don't consider changing the machine to fit the tool to be an acceptable solution. Then your stuck with a known problematic design. I wish I had a pound for each complaint/query/moan I've seen and heard about twin steppers on a gantry machine. Other fixes include servos or closed loop steppers but keeping both sides in synch with software without any feedback is nigh on impossible. Steppers are not the problem, the issues I mentioned apply equally to machines with servos and encoder feedback. I'm asking for the suggested best way to configure LinuxCNC for controlling a gantry system, that presents the user with the least opportunity to shoot themselves in the foot. For instance, how do you avoid racking the gantry when jogging in joint mode? Do you have a servo gantry config that avoids or minimizes this possibility you could point me to? I know folks are controlling gantry systems with LinuxCNC, I'm wanting to know how, and what are the pros and cons of each setup. -- Managing the Performance of Cloud-Based Applications Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. Read the Whitepaper. http://pubads.g.doubleclick.net/gampad/clk?id=121054471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Regards /Groete Marius D. Liebenberg +27 82 698 3251 +27 12 743 6064 -- Managing the Performance of Cloud-Based Applications Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. Read the Whitepaper. http://pubads.g.doubleclick.net/gampad/clk?id=121054471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gantry Best Practices
On 2/17/2014 3:47 PM, Steve Blackmore wrote: On Sun, 16 Feb 2014 16:51:06 -0600, you wrote: Sorry, but I don't consider changing the machine to fit the tool to be an acceptable solution. Then your stuck with a known problematic design. I wish I had a pound for each complaint/query/moan I've seen and heard about twin steppers on a gantry machine. Other fixes include servos or closed loop steppers but keeping both sides in synch with software without any feedback is nigh on impossible. It's such a simple design concept to run a shaft across the gantry to connect to a chain or belt or rack on both sides, or to use a screw down each side and connect them at one or both ends with a chain or belt. Never racks, ever, and doesn't use up two motor control outputs from the control electronics. A friend of mine has a big Torchmate table, uses a rod across the gantry with a rack on each side, rod is turned by a cogged belt. Don't ask me why they used an ACME threaded rod when nothing runs on the threads! Plain shaft would work just as well. A while back on this list, someone was attempting to replace the control on a Thermwood gantry router with a PC and LCNC. Thermwood used a motor on each end of the gantry, and to make it especially challenging the gantry stretched across the long dimension of the table. Never had any racking problems with the OEM control but the person doing the refit couldn't get it to work with LCNC. I would have just got out the tools etc and fixed the @#%$@% thing to use a cross shaft rather than screw around trying to use software to fix a hardware design problem. What might provide some insight into an anti-racking system is to study how pivot sprinkler lines are made to handle fields which are not perfectly flat. They have sensors at each wheel pylon that detect if that point is advancing or lagging then the speed is adjusted to get it back in line so the pipe doesn't end up kinking and wound up around the pivot like a dog that's too dumb to change directions when it gets its chain wound up. Design the gantry with the end bases long and stable then have the cross bar mounted so it can pivot just a little. Add sensors to detect the tiniest amount of racking then have a system to automatically adjust the speed of each side to straighten it out. That could be completely independent of the CNC control. But still far more complex than mechanically coupling the ends of the gantry. -- Managing the Performance of Cloud-Based Applications Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. Read the Whitepaper. http://pubads.g.doubleclick.net/gampad/clk?id=121054471iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
[Emc-users] Gantry Best Practices
With the recent release and general popularity of the ShapeOko V2 desktop mini-mill, I have several folks who are trying to use LinuxCNC running on the BeagleBone as a control. If you are unfamiliar with this machine, here's a link: https://www.inventables.com/technologies/desktop-cnc-mill-kit-shapeoko-2 Invariably, one of the first questions I get is how to setup a configuration to deal with the gantry setup of the ShapeOko. I know of at least three different ways to control a gantry system with LinuxCNC, each with it's own pros and cons: 1) Use gantrykins, and hope users are intelligent enough not to rack the gantry when moving around in joint mode. 2) Use trivkins and setup HAL to turn one axis into two by craftily combining the commanded motion with the homing switch states. This is easiest if HAL is doing software stepgen (just mask the step pulses in the base thread), but I'm pretty confident I can make this work pushing the logic in front of the PRU drive step/dir component (as a bonus, this setup would also work with Mesa hm2 cards and other hardware based controllers). 3) Ignore the gantry complexity, and just drive both servo motors from the same stepper driver. This works _OK_ for the Z axis on a 3D printer, but probably isn't a good idea for something that is actually making chips. Questions: Did I miss any significant options for controlling a gantry style machine? Which option would be recommended for novice users new to the LinuxCNC and CNC world? I'm thinking the Magic HAL Wye / Y Cable that splits one joint into two is probably the simplest for most folks to deal with, but am open to suggestions. -- Charles Steinkuehler char...@steinkuehler.net signature.asc Description: OpenPGP digital signature -- Android apps run on BlackBerry 10 Introducing the new BlackBerry 10.2.1 Runtime for Android apps. Now with support for Jelly Bean, Bluetooth, Mapview and more. Get your Android app in front of a whole new audience. Start now. http://pubads.g.doubleclick.net/gampad/clk?id=124407151iu=/4140/ostg.clktrk___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gantry Best Practices
On Sun, 16 Feb 2014 14:11:13 -0600, you wrote: With the recent release and general popularity of the ShapeOko V2 desktop mini-mill, I have several folks who are trying to use LinuxCNC running on the BeagleBone as a control. If you are unfamiliar with this machine, here's a link: https://www.inventables.com/technologies/desktop-cnc-mill-kit-shapeoko-2 Cant help with the best way to run that with LinuxCNC, but I'd be tempted to remove one stepper and run a cross shaft driving both belts with possibly a bigger stepper motor. Steve Blackmore -- -- Android apps run on BlackBerry 10 Introducing the new BlackBerry 10.2.1 Runtime for Android apps. Now with support for Jelly Bean, Bluetooth, Mapview and more. Get your Android app in front of a whole new audience. Start now. http://pubads.g.doubleclick.net/gampad/clk?id=124407151iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Gantry Best Practices
On 2/16/2014 4:03 PM, Steve Blackmore wrote: On Sun, 16 Feb 2014 14:11:13 -0600, you wrote: With the recent release and general popularity of the ShapeOko V2 desktop mini-mill, I have several folks who are trying to use LinuxCNC running on the BeagleBone as a control. If you are unfamiliar with this machine, here's a link: https://www.inventables.com/technologies/desktop-cnc-mill-kit-shapeoko-2 Cant help with the best way to run that with LinuxCNC, but I'd be tempted to remove one stepper and run a cross shaft driving both belts with possibly a bigger stepper motor. Sorry, but I don't consider changing the machine to fit the tool to be an acceptable solution. LinuxCNC is more than capable of handling this setup, my question is which option will be the easiest for a novice user to understand, or is there an even better option I missed? -- Charles Steinkuehler char...@steinkuehler.net signature.asc Description: OpenPGP digital signature -- Android apps run on BlackBerry 10 Introducing the new BlackBerry 10.2.1 Runtime for Android apps. Now with support for Jelly Bean, Bluetooth, Mapview and more. Get your Android app in front of a whole new audience. Start now. http://pubads.g.doubleclick.net/gampad/clk?id=124407151iu=/4140/ostg.clktrk___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
