I have MachIII running on Vista with a SS (did not install the Mach LPT driver at all). Today I noticed that if I tried to run a bit of GCode when first firing up the Mach/SS all three axis (X, Y, A) move about 1/100th the correct speed, although Mach still shows correct feed rate. If I jog all three axis (X and Y with the KB jog buttons and A with the MDI), and then run GCode the correct feed rate is used. It continues using the correct feedrate until Mach/SS are restarted.

On this particular machine I have no limits configured, so no homing is tried before trying to run code.

I set things up in a subroutine to make it easier to keep track of the # of parts run. Below is the code. after each completion of the program I have to jog each axis or I get the really, really slow feedrate (still shows properly in Mach)

O0001
G91
F20
M98 P0002 L75
M30

O0002
Y-0.05
X0.7874
Y0.05
Y0.3803
A360
M99


Interestingly if I issue a G0 at the very beginning of the program then everything is fine. I even tried reinstalling Mach and creating a new profile to no avail. I think this is a Mach related issue as it happens even with no driver selected (and a new profile).

Jeff
 did you try installing the driver and just not using it?
Hood

Yep, tried that combination too. I don't understand why sticking a naked G0 at the start of the program solves it but it does.

Jeff, even though you have no home switches, try to ref all once and see if that helps. If no homes are enabled, should just zero the dros where it is and give you the green ref led around the axis buttons beside DROs. Interested in your findings.

Brett

Ref all works as it should. Still same problem though...

Jeff, the F line needs a g1 I think. Try G1 F20.

Brett

Nope, still does it.....

Jeff, I tried it here. You need to put G1 values in front of your F moves and G0 for the rapids. Right now you have none. If you go to MDI and do a G0 move, it is modal, the reason it goes fast after the MDI input, it is still in G0, Rapid. Never sees a G1 to change it. I got the exact same results as you here on the office PC with no SS or Vista. The A is going to 360 at 20 degrees per minute unless I give it a different value or a G0 initially. I can edit your code but I'm not sure how fast you want what to do when. 

Hope this helps and I'm not misunderstanding.

Brett

OK, I mislabeled my post. It should have read, "Mach III + Vista + SS + Jeff with his head up his butt = weirdness"

Thanks guys, that was it. I was just not thinking...

Thanks guys, that was it. I was just not thinking...

That is out of character for you Jeff. But, it happens to all of us. I know the pressure you've got on you to get the parts made for the solar project. Glad you are sorted. 

Brett