Tool Nose Comp lathe problem

[singist48]

Hi all,

After many years of programming Fanuc lathes at the machine, I took the plunge today to actually use the TNR comp. As I feared I have hit a problem. WIth a 0.8 mm tool rad, in T3 after facing off to Z 0.0 , I approach the work, G0 X32.0 Z2.0, THEN G1 G42 Z0.0. At this point the tool goes into the face, almost as it the compensation is too much. Hope that explains it enough. Any ideas why?

Pete , UK

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[dcoupar]

What is the next block?

[singist48]

What is the next block?

Hiya

Ok, at work now so these are the actual figures

G0 G42 X47.0 Z2.0
G0 X26.5
G1 Z0.0 F0.1
G1 X30.0 C1.75
G1 Z-39.5
G1 X46.0
G0 G40 X200.0 Z200.0 T1000

[ProToZyKo]

I think you need to start lower, now the tip is at X26.5, so if you have 1.2 in nose radius start at x24.(0.1 clearance) But if you change to R1.6 it will plunge, but if you change to smaller it's ok.
A little tricky to start compensation on a chamfer you need to think of the nose radius of the tool, 30-(1.75*2)-(1.2*2)=24.1

G0 G42 X47.0 Z2.0
G0 X24.
G1 Z0.0 F0.1
G1 X30.0 C1.75
G1 Z-39.5
G1 X46.0
G0 G40 X200.0 Z200.0 T1000

[sinha_nsit]

Make sure that you have the correct nose number in the offset.

[singist48]

Hi

Yes its a 0.8mm tool nose rad, and quadrant 3

[singist48]

Hiya,

It's a 0.8 rad insert, not 1.2.
But from what you say it seems I have to allow for the tip rad in my x calculation? I.E 0.8 x 2 = 1.6 so 30mm - 1.75 -1.75 - 1.6 = X 24.9. If so, surely thats the point of the G42 isnt it? So I dont have to work this out?

Pete

[MysticMonkey]

I think you need to start lower, now the tip is at X26.5, so if you have 1.2 in nose radius start at x24.(0.1 clearance) But if you change to R1.6 it will plunge, but if you change to smaller it's ok.
A little tricky to start compensation on a chamfer you need to think of the nose radius of the tool, 30-(1.75*2)-(1.2*2)=24.1

G0 G42 X47.0 Z2.0
G0 X24.
G1 Z0.0 F0.1
G1 X30.0 C1.75
G1 Z-39.5
G1 X46.0
G0 G40 X200.0 Z200.0 T1000

ಠ_ಠ

T1010

[singist48]

ಠ_ಠ

T1010

Yes the line before has T1010

[ProToZyKo]

Hiya,

It's a 0.8 rad insert, not 1.2.
But from what you say it seems I have to allow for the tip rad in my x calculation? I.E 0.8 x 2 = 1.6 so 30mm - 1.75 -1.75 - 1.6 = X 24.9. If so, surely thats the point of the G42 isnt it? So I dont have to work this out?

Pete

It's only where when you start you need to consider this, if you tell the machine to go to x26.5 it will undercut to make the chamfer.
Maybe you can do it like this instead, it will go under with the tool radius.

G0 X47.0 Z2.0
G0 G42 X26.5
G1 Z0.0 F0.1
G1 X30.0 C1.75
G1 Z-39.5
G1 X46.0
G0 G40 X200.0 Z200.0 T1000

[singist48]

It's only where when you start you need to consider this, if you tell the machine to go to x26.5 it will undercut to make the chamfer.
Maybe you can do it like this instead, it will go under with the tool radius.

G0 X47.0 Z2.0
G0 G42 X26.5
G1 Z0.0 F0.1
G1 X30.0 C1.75
G1 Z-39.5
G1 X46.0
G0 G40 X200.0 Z200.0 T1000

You are the man! Thank you so much. It seems such a simple
Answer but I could not get my head round it. Works
Perfectly now.

Thanks again

Pete

[ProToZyKo]

Glad it worked, i don't use compensation much because issues like this, but i never thought about starting compensation X start of chamfer, i always started compensation on Z so i always had to give it enough space in X direction before chamfer.