I am a relative newbie to EMC2. I have a rotary table, and have also wondered about a method to reset or home the rotary axis without backing up. By Always moving the table in the same direction I avoid backlash. Always keeping the position within 0 and 359.999 might work if it is treated as a modulo 360 operation. I certainly would like to be able to make greater than 360 degree moves as it is an easy way to specify a spiral with more than one revolution. If no way to reset the count, what is the limit on degrees you can accumulate before truncation errors etc start to creep in? I recently performed an operation similar to what Alan envisioned by introducing an artificial manual tool change that returned control to the operator where the operator hit home and then continued the program. If the operator failed to hit home the table unwound and started over.
Thinking about it further I would rather live with it this way than loose the ability to specify multiple rotations by rotating greater than 360 degrees. I like being able to mathematically describe a helix and cut it as one long extended cut. Hubert Stuart Stevenson wrote: > Gentlemen, > I have previously requested the rotary axis usage as follows: > > 1: the rotary position stays within 0 and 359.999 > you never see 360 (or more) in the program nor on the position screen > 2: the sign (+ and -) tell the machine which direction to move > the sign has nothing to do with the commanded position of the rotary > table > 3: the rotary table is positioned to the 0 thru 359.999 degrees regardless > of the sign > ie. the position +90 and -90 are the same position > the difference is the direction of the table to arrive at the > position > an MDI command of 720 is a move in the positive direction to the 0 > position > an MDI command of -360 is a move in the negative direction to the 0 > position > on my machine with the Fanuc 15mb control the rotary scale errors out > when the internal register reaches 9999.999 degrees regardless of G92 zero > resets. on the EMC2 control this would not be a limit and the effect would > be essentially unlimited rotations without the need to wind or unwind > > ################# > further explanation to differentiate between linear and rotary > > linear positioning is as follows > > 1: the position of the rotary table is allowed to move + and - just as the > linear axes with direction (+ and -) and magnitude determining final > position and the quantity of table rotations > 2: the position +90 and -270 are the same position > > ################# > my opinion as follows: > most people (initially myself included) think the linear positioning is > the only valid option > in practice the rotary is the easiest to use as the direction of rotation > is immediately recognizable by the sign of the command > it is easy to adjust to the positioning paradigm and seems intuitive > rather quickly > > > ################ > I seem to remember some discussion about this but I have not pursued it as > the machine I want to use it on is a few of projects away > > ################ > I don't know if this is what Alan was requesting > If not, I am sorry for hijacking his thread to inject my request > thanks > Stuart > > On Wed, Sep 30, 2009 at 9:38 PM, Frank Tkalcevic < > fr...@franksworkshop.com.au> wrote: > > >> I know you can get the current position, then do some math to move to a >> multiple of 3600... >> >> # save the current absolute position in 5161-5166 >> G28.1 >> # move to a multiple of 3600. #5164 should have the current A position >> G0 A[ROUND[[#5164]/3600]*3600] >> # set A to 0 >> G? >> >> >> I just don't know how you 0 the coordinate system from Gcode. In the Axis >> source code, it uses G10 L2 to touch off, but I don't think that is what is >> wanted. >> >> >>> -----Original Message----- >>> From: Alan Battersby [mailto:alan.batter...@ntlworld.com] >>> Sent: Thursday, 1 October 2009 5:54 AM >>> To: emc-users@lists.sourceforge.net >>> Subject: [Emc-users] Question about using a rotary table >>> >>> Hi everyone, >>> >>> If I make a full turn from 0 to 360 degrees say on the C >>> axis, I want then to reset the coordinate system back to >>> angle zero degrees in order to save an "unwinding" movement >>> that occurs if I make a rapid move back to zero. For a >>> couple of rotations I could use g54 etc but there is >>> obviously a limit to this method. Perhaps I could use g92 but >>> can it be cumulatively used over and over again? >>> >>> I envisage cutting paths which require several depth and >>> width passes and this is multiplicative so 3 width passes and >>> 4 depth passes gives 12 rotations to be unwound when the path >>> is complete in order to go onto the next path and that is >>> with the pattern cut in a single rotation. I can generate >>> patterns that take up to 20 rotations to complete. >>> >>> So I am wondering which is the best way of resetting back to >>> the original zero position and can I avoid multiple >>> unwindings? On should I think in terms of many smaller >>> programs run sequentially? >>> >>> My apologies If this is an obvious beginners question I admit >>> it I am, band I could not see anything obvious in the emc >>> documentation. >>> >>> Thanks >>> Alan >>> >>> -------------------------------------------------------------- >>> ---------------- >>> Come build with us! The BlackBerry® Developer Conference >>> in SF, CA is the only developer event you need to attend this >>> year. Jumpstart your developing skills, take BlackBerry >>> mobile applications to market and stay ahead of the curve. >>> Join us from November 9-12, 2009. Register now! >>> http://p.sf.net/sfu/devconf >>> _______________________________________________ >>> Emc-users mailing list >>> Emc-users@lists.sourceforge.net >>> https://lists.sourceforge.net/lists/listinfo/emc-users >>> >>> >> >> ------------------------------------------------------------------------------ >> Come build with us! The BlackBerry® Developer Conference in SF, CA >> is the only developer event you need to attend this year. Jumpstart your >> developing skills, take BlackBerry mobile applications to market and stay >> ahead of the curve. Join us from November 9-12, 2009. Register now! >> http://p.sf.net/sfu/devconf >> _______________________________________________ >> Emc-users mailing list >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users >> >> >> > > > ------------------------------------------------------------------------------ Come build with us! The BlackBerry® Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9-12, 2009. Register now! http://p.sf.net/sfu/devconf _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
