On Saturday, March 24, 2012 11:27:23 AM charles green did opine: > looks like there are some numbered params listed in the master doc also: > > #<_x> - Return absolute machine X coordinate. Same as #5420. > #<_y> - Return absolute machine Y coordinate. Same as #5421. > #<_z> - Return absolute machine Z coordinate. Same as #5422. > #<_a> - Return absolute machine A coordinate. Same as #5423. > #<_b> - Return absolute machine B coordinate. Same as #5424. > #<_c> - Return absolute machine C coordinate. Same as #5425. > #<_u> - Return absolute machine U coordinate. Same as #5426. > #<_v> - Return absolute machine V coordinate. Same as #5427. > #<_w> - Return absolute machine W coordinate. Same as #5428. > #<_current_tool> - Return number of the current tool in spindle. Same as > #5400. > > i wonder if these are also effected in the released versions? this is > more like what i was imagining might be the access to various states of > machine and loaded table values like tool offset values. > > on many milling machine controllers, G43 Hxxx requires a movement of the > z axis to'take up' the tool length offset, like G0 G43 Z-3.0 H5. at > the end of the move (which differs from the commanded -3.0 units by the > length offset value in offset table position number 5) the end of the > tool is aligned with the currnt coordinate system. if you know the > parameter locations of the current tool and its length offset, the code > for taking up the current tool offset becomes G0 G43 Z-#[<current tool > number> + <tool length table parameter offset>] H#[<current tool > number> + <tool length table parameter offset>]. so there is no axis > movement, and that coding step in a tool introduction is uniform for > all tools, regardless of length. (the tool change is often near the > travel limit of the z axis, so a large tool offset might result in an > overtravel if the axis movement is not large enough. so in the first > example, G0 G43 Z-3.0 H5, if H5=10.00 and there is only another +1.0 to > go in the z axis beyond the tool change position, the limit will be > reached 6.0 short of completing this step.) > > at the place i have been working, all the mill controllers have been set > up with a macro override of the T word that encapsulates all the > discreet coding steps required for MDI tool changing, as well as part > programming. the result is improved setup time on the machine, and > faster part operation coding which is portable between the various > different machines. > > another handy macro (call it G192 for example) finds the center of two > touch off locations along an axis. the procedure goes like, > > touch the -x edge of the part with edge finder > G92 X0 > touch the +x edge of part > G192 X0 (<- "X0" is just convenient, the X-word value is not used in the > calculation.) > > where the G192 macro uses the machine coorinate parameter values of the > selected axis name (X in this example) to set the origin at the center > of the part edges. > > it would be nice to adapt such tactics in linuxcnc, using the custom M > codes perhaps? will the custom codes work from MDI? they would at > least be valuable for modularization of part programming, like for the > tool change routine. command M106 Txx Sxx: > > (M106 TOOL CHANGE MACRO) > M9 > G91 G30 Z0 M5 > T#5400 M6 > S#???? M3 > G0 G43 Z-[H#5400] H#5400 > G17 G90 M8 > M99 > > ..or something like that. > G38.2 doesn't demand a Z probe, it can do any axis, so LinuxCNC is quite able to do that.
I did something similar in tholefinder.ngc where I probe the open end of a small piece of brass tubing let into the pcb pallet to find all 4 contact points and declare the center, with all co-ordinates offset from that for the rest of a pcb etch & drill run. That worked well but needed a very fine wire, in the spindle with the spindle running, and a smallish capacitor to capture the first contact. I actually used a sewing machine needle threader wire for that. Repeatability seems to be about a thou. Often less. I don't own an edge finder, so I haven't a reference I can compare my method to. It works for me & cost $2. :) > --- On Fri, 3/23/12, Sebastian Kuzminsky <s...@highlab.com> wrote: > > From: Sebastian Kuzminsky <s...@highlab.com> > > Subject: Re: [Emc-users] Tool change question > > To: emc-users@lists.sourceforge.net > > Date: Friday, March 23, 2012, 9:29 PM > > On 03/23/2012 11:42 AM, charles green > > > > wrote: > > > nicer, but still only a handful of documented > > > > params. i was looking at a document dated a little > > over a year ago (11jan2011). > > > > > do you know if the params #31 to #5000 contain useful > > > > info? like g90/g91 state, for example, or any > > registration of the other groups apart from group 12? > > > > > "you started this. show me everything." - ellen > > > > ripley > > > > Oh... I don't think you want to mess with > > that... - Hicks > > > > Parameters 31-5000 are deliberately unused by linuxcnc, and > > thus > > available for the g-code programmer to use. > > > > Ah yes, that's even what the docs say (somewhat cryptically, > > focus on > > > > the "user parameters" part): > > > * > > > > > > /1-5000/ - G-Code user > > > > parameters. These parameters are global > > > > > in the G Code file. > > > > The (slightly) improved docs in the master branch > > (http://linuxcnc.org/docs/devel/html/gcode/overview.html#sec:parameter > > s) > > > > say this: > > > 31-5000 > > > > > > G-Code user parameters. These > > > > parameters are global in the G Code > > > > > file, and available for general > > > > use. Volatile. > > > > > > > > Oh hey look! In master (aka devel), there are some > > predefined named > > parameters that carry the g90/g91 state: > > > > http://linuxcnc.org/docs/devel/html/gcode/overview.html#_predefined_na > > med_parameters_a_id_sec_predefined_named_parameters_a > > > > I think those variables are new in the master branch, and > > not available > > in the 2.5 branch. > > ------------------------------------------------------------------------ > ------ This SF email is sponsosred by: > Try Windows Azure free for 90 days Click Here > http://p.sf.net/sfu/sfd2d-msazure > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > 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) My web page: <http://coyoteden.dyndns-free.com:85/gene> Hardware, n.: The parts of a computer system that can be kicked. ------------------------------------------------------------------------------ This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
