How can I cut an arc in the Z axis?

[Fluxion]

Ok, I am new to all this but I'm trying to learn. I am wanting to cut a concave sanding block with a 20" radius. I am not sure how to go about it. I was thinking I could cut an arc along the Y axis in the vertical plane the step over something like 25% of the diameter of the cutter then cut the arc again then repeat over and over until I make a concave surface in a block of wood. Is there a G code for cutting an arc in the z axis along the y axis something like the G2 or G3 command for cutting in the x and y axis? Is this where the G19 command comes into play? Is it as simple as using the G19 command to switch to the Y-Z plane then cut the arc using the G3 command?

I am sure this is simple but Like I said, I'm new to all this.

Thanks in advance for any help, Bryan

[hawkburger]

Yes, it is that simple, try laying down on your side and program it the same as g17 g02 etc. Ha Ha just kidding, but it really works, I and J and all that good stuff. Try using a ball or rounded tip end mill for best finish.

[Geof]

Originally Posted by Fluxion ...Is this where the G19 command comes into play? Is it as simple as using the G19 command to switch to the Y-Z plane then cut the arc using the G3 command?..

That is it.

Your 25% step over is probably too much; you need to use a ball nose cutter which is as large as possible and step over something like 10% of the cutter diameter, or less.

[One of Many]

On some controls when switching to G19, you may need to also use I and K rather than I and J.

DC

[Fluxion]

Thanks Guys! I'll give it a try here in a little while, I have a couple of things to do first. I was planning on using a 1" core box bit and I was thinking about the 25% and I agree 10% or less would definitely be better.

Thanks again, Bryan

[Fluxion]

Ok, this worked beautifully! I do have another question though. I was wondering if there was a way to just enter some code like this:

G3 x0 y3 r20 z0 f50
G2 x0.030 y0 r20 z0f50

then have it move the x axis 0.030" then cut the same radius again. I was thinking there must be a way to do this as opposed to having to input all the lines to get it to cut something like 12" long.

[Geof]

Yes, use incremental and subroutines; can your machine handle subroutines?

You put the arcs in a subroutine which is called after an incremental move of .03 on the X axis.

If you cannot figure it out from this meager description you will have to wait until tomorrow, I have had too much wine to come up with the code at this time of night. Were are you located? You should probably be in bed by now.

[Fluxion]

Thanks Geof, I think it will run subroutines, I am running Mach 3. I might be able to figure it out tomorrow because I have had too much beer and It is past my bedtime.

[Geof]

I just checked your location...Topeka!!! There is (or was) a fantastic Italian restaurant in Topeka down in a basement on a street that runs ninety degrees to the main drag. There is (or was) also a nice Brewhouse and Restaurant down the opposite end of the main drag.

Or at least that is what I remember froma busines trip there back in 1997 or so.

I also remember the drive from Topeka back to the airport at Kansas City, MO was nerve wracking with thunderstorms every direction as far as the eye could see.

EDIT: corrected my geography, I hope.

[Superman]

I agree with using a sub-routine

As a suggestion , program to the centre of the ball and you will get a true rad
ie required rad = 20. tool rad =0.5 --- tool centreline rad = 20.5 ---
(Using 1" Ball-nose)( tool length set to ball centre )

O0001 (sub start)
G0 G90 Y-21. ( absolute, Y clearance )
Z-20. ( ball centre on quadrant line of semicircle )
G1 G41 D1 Y-20.5 ( take-up comp onto arc )
G19 G2 Y20.5 R20.5 ( do arc on YZ plane)
G40 G1 Y21. ( cancel comp )
G0 Z22. ( retract to clearance plane )
G91 X.1 ( incremental step )
G90 ( absolute for safety )
RTS (sub end)

(in program)
T1 M6
G0 X-.5 Y-21. ( initial start of sub)
S2000 M3
G43 Z22. H1 ( take-up tool length)
M8
CALL O0001 Q105( Okuma is Q for repeat count )( 105 will cover 10" @ 0.1 pitch )
G0 Z22.
M9
M5
M30

[Fluxion]

Geof,

I know the restaurant you are talking about, I can't remember the name but i do know the Brewhouse well. Its called the Blind Tiger Brewery I live about 4 blocks to the west and I will probably meet my wife there for dinner after work! As far as those thunderstorms go, that's Kansas weather. Its normal.

Superman,
Thanks for the code. I'll give it a try later today. BTW Since Geof has been to my little town I guess I should mention I was in Melbourne a few months ago. My wife is from Sydney, actually she was born in Broken Hill, and we try to go back to Australia as much as possible. If you have read my other posts in this thread I mentioned I had been drinking beer last night, I was actually drinking the last of my VB stash.

[Superman]

So you scored an Aussie girl, myself, born and raised at Hay NSW, not far from fron Broken Hill ( bloody and flat out that way )
Got a couple of VB in the fridge, I'll be thinking of you as I drink 'em