Question re R0

[rdoty]

I've worked around this issue but I've never completely understood it so I'm hoping someone can provide a lucid, explanation.

For example, if I have the following G code:

M6 T6 (selects a tool)
G0 G90 X0.75 Y-2.75 E1 (positions my table/fixture precisely under the tool)
S3500 M3 (spindle speed @ 3500 RPM CW)
H6 Z0.3 M8 (selects tool length offset, sets I-plane [tool position] 0.3 above part, turns on coolant)

I'm working on a flat surface, no steps, no clamps to clear.

Now, I use G82 for my spot drill because I like the option of the dwell before retract. So if I program as follows:

G82 G98 R0+0 Z0.03 F12. P100 X0.75 Y-0.5 E1

Why can't I set R0 at zero? The Fadal manual states "The I-plane must always be equal to or above the R-plane" and "In the absolute mode the value for this location is relative to Z zero". The explanation and drawing in the Fadal manual clearly suggests that R zero (R0+0) would be at the surface of the part which is 0.3 below the I-plane.

Maybe I'm having a bad day but darn this R-plane concept baffles me.

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[denmar]

do not use Z on the R0+

[Dyad1]

Your R0 is okay. It would rapid the drill right to the surface of your part but you are then telling the machine to drill upwards. Needs to Z-.03

[rdoty]

I received a reply from txcncman which really clarified this issue for me and I thought I'd post it herealong with my reply in case some other "clueless" reader has the same question.

G82 G98 R0+0 Z0.03 F12. P100 X0.75 Y-0.5 E1

You are telling the machine to rapid to Z0. (R0+0) and then spot drill to Z0.03. How does that make any sense?

Needs to look something like this:

Z0.3 ---------- Initial Plane

R0+0.03 ------- Rapid Plane

Z-0.125 ------- Drill Point

H6 Z0.3 M8
G82 G98 R0+0.03 Z-0.125 F12. P100 X0.75 Y-0.5 E1

Thanks txcncman,

The confusion arises because of two things....nowhere in the Fadal manual does it indicate that R0 is actually relative to the "zero-plane" or what would be referred to as Z-zero (vise top?). Also, the only definition of "R" that I came across some time ago is that it referred to "retract"..which is obviously wrong (and in fact compounded by the horrible drawings in the Fadal manual). Unfortunately that definition stuck in my almost hairless head and created a great deal of confusion (and the loss of even more hair!). Your explanation is "lucid"...therefore bonus points!!! I realize that the R plane concept was created to minimize G code when having to clear a feature or clamps but I haven't had to deal with that yet and if I do I'll probably just add a couple of lines of more code.