Newbie- tool nose comp?

[wronggrade]

total newbie ? but anyone know the formulas for tool nose comp as applied
to a lathe. i have been using g41,g42 and mastercam forever.i got asked this ?and feel real stupid that i dont know. iam a self taught guy who use to cut and check make a move cut and check before i learned about g41,g42 then got mastercam and ohboy who needs the math. now that i have people asking who want to know i would really like these formulas. feel real bad not knowing any help would be great thanks

[JWK42]

I think of G42 as American and G41 as British and the outline of your part as the centerline of the road.

G42 lets me drive on the right side of the center line and G41 lets me drive on the left side of the center line.

Then you program the actual outline of your part and tool comp offsets your tool based on the radius you enter in your tool radius table.

Thats kind of a simple explanation but it works for me.

[wronggrade]

thanks for the reply i know how to use g41,g42 what iam asking is what are the formulas used ie how to do this on a calculator long hand not with the machine

[JWK42]

In my Machinery's Handbook there is a chapter called "Solutions to Triangles".
I think you would find this helpful.
I used a lot of these formulas when I started programming our first CNC. It was an AB 7365 with no tool comp and 32 FT of tape memory. I was never so glad as when AB came out with an upgrade that had tool comp and 64 feet of tape. I can remember pulling my hair out because if you needed to change from a .032 tool nose radius to a .016 tool nose radius you had to re-program every X-Z point. Chamfers were not to bad but a blended radius into a chamfer or another radius was a nightmare.

[wronggrade]

looking this up right now thanks for the help

[SBC Cycle]

There is a CAD solution to this if the math is intimidating. I'll use an O.D. profile as an example. Before I begin, it is important to understand that this is a very limited method in that it assumes your profile is simple with no dips, grooves, or anything like that nature. Draw you profile as it appears on your print. Next, offset the profile by the radius of your tool, say 0.0313, to the right of the profile (to simulate G42). Then translate this offset toolpath in both axis' by the tool nose radius, X-0.0313, Z-0.0313.

That's it. Do this with many examples until you get your mind wrapped around what's going on and you will learn to trust it. Start with a simple fillet on a sharp corner or a chamfer then move to blending a radius into a chamfer. If you try this method first, you will get a better understanding of how the math works and eventually be able to do this without the help of CAD. Hope this helps.

[SBC Cycle]

Picture is worth a thousand words.

[cogsman1]

I have this from a past class


TNR - [TNR x (TAN OF ANGLE)]= (radius comp) x2 = ("X" dia.comp)

YOUR ANGLE IS;
print angle = 60'
[60/2] = 30 (for "Z" calc)
45-[[60 / 2]= 30] = 15' (for "X" calc)

TNR =.0312
TAN of 30' =.5774
TAN of 15' =.2679

.0312-[.0312*.5774]=.01318 ("Z" comp)

.0312-[.0312*.2679]=.0228 *2 = .0456(dia)

[zicci]

I wrote excel spreadsheet that calculates toolnose radius error for angles.
it is in metric cause thats what we use in south africa.email me if you want
it.also wrote simple visual basic programme that does the same.
zicci@cnctraining.co.za