On Saturday 12 September 2020 13:31:18 John Dammeyer wrote: > Let me correct myself yet again. Where I said > > > But now add the A axis. G01 X2 Z1 A360 F4. > > I just ran that on the mill and and it took 34 seconds > Run G01 X2 A360 F4 and it takes 30 seconds > Run G01 A360 F4 and now the rate changes to degrees per minute and > it's still busy turning. > > So when there are combined XYZ along with A how can the distance along > the circumference be factored in so the ipm is correct? > > John > > > -----Original Message----- > > From: John Dammeyer [mailto:jo...@autoartisans.com] > > Sent: September-12-20 9:52 AM > > To: 'Enhanced Machine Controller (EMC)' > > Subject: Re: [Emc-users] G93 minimum value/behaviour > > > > Oops. I meant radius for the first Z dimensions. > > I've fixed that below. > > > > > From: andy pugh [mailto:bodge...@gmail.com] > > > > > > On Sat, 12 Sep 2020 at 05:19, David Berndt <ber...@uberwin.com> wrote: > > > > 2) Is there a minimum value for G93 feed rates. > > > > > > Not as far as I know. I just tried a test move of G93 G0 X100 > > > F0.01 and it moved 1mm in 1 minute. > > > > > > > rotating A axis with something like G93 A45000 Z-1 F.2. > > > > > > I tried this G-code in the axis-9axis sim. It complained that > > > there was no movement mode active. Putting in a G1 I got > > > approximately the expected result, in that Z moved 0.5mm in 4.5 > > > minutes. So I assume that the A axis was maxed out in the > > > simulator. > > > Bumping up the A axis max speed from 90 to 360 gave me a system > > > that did 25 revolutions in 1 minute. > > > > > > Had you done a G0 move? > > > > > > G0 X0 Y0 > > > G93 A45000 Z-1 F.2 > > > > > > Moves very fast. As G0 is modal. This ought to be an error, I > > > think. (G0 X0 Y0 F10 is accepted. It is valid G-code but probably > > > isn't what anyone intends. It says "set the feed rate to 10 and > > > then perform a rapid move") > > > > > > G93 with G0 active, however, clearly makes no sense and appears to > > > cause confusion. > > > > I've had some discussions with Mecsoft and their CAM generation for > > the 4th axis. I'm not sure the G93 solves this problem although > > perhaps indirectly it does. > > > > Assume the rotation of the 4th axis is in line with the X axis and > > assume you have a an object held in the 4th axis that has a taper. > > So at X=0 it's radius is say 2" and at X=2" the radius is 1". Now > > you want to cut a spiral slot on this taper from X=0 to X=2" in one > > revolution of the part. In effect a very coarse tapered thread. > > > > The feed rate for the cutter size and mill rpm is 4 ipm. > > > > If this were a standard 3D move Y would remain the same, G01 X2 Z1 > > F4 assuming the current position of X is 0" and Z is 2. > > > > The tool now moves down the hypotenuse of this triangle where the X > > and Z are calculated to move at a rate to create an F4 speed on this > > ramp. It should move the 2" X distance in 30 seconds. > > > > But now add the A axis. G01 X2 Z1 A360 F4. > > > > The X move completes in 30 seconds. The Z has moved 1" in 30 > > seconds. The A axis has moved 4 degrees per minute so in 30 seconds > > has moved 2 degrees. > > > > But wait, there's more. If the feed rate through the material has > > to be F4 the A axis speed has to change in proportion to the Z > > position. That's because the circumference at Z=2" is 12.56" and at > > Z=1" is 6.28". > > > > If the diameter was fixed at 4" (Z=2") then F4 results in 3.14 > > minutes for one revolution while at a diameter of 2" (Z=1") is 1.57 > > minutes for one revolution. > > > > Is it even possible to cut this sort of spiral in one G-Code line or > > does it require a long list of separate A and XZ moves? > > > > Or does somehow the G93 handle this situation. > > > > Thanks > > John
The point being missed is that a successful G93 completes all commanded moves at the same time, provided they are the equ of a g1, g2, or g3 move, moving the A axis however many degrees is specced on that line, at a speed that will complete that move at the same time as all the others. but if specing 45000 degrees and F0.2, you had better have a pretty high speed A axis. The cause of the error was the G0 move in front of that line. Those are different modes. > > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
