[Malish]

So I'm still getting the wrong diameter when I do lathe programs. I usually end up being around 0.010" to small when I run the part. Below is the code I did for a 2" diameter part I programmed. As you can see it goes right to 2" on line 9 (My lathe uses diameter mode). But since the tool is an 80deg bit shouldn't it move out slightly to accommodate the tool nose radius? I'm not sure what I am doing wrong that is casing me to be undersized on all my parts. Any ideas?

I tried changing the cutting angle of the insert on the tool page, but that made no difference in the post.


O0100
(Machine Setup - 1 Turn Rough )
(TOOL #1 )
N1 G40 G99 G18 G20 G90
N2 T0101 M06
N3 M41
N4 G50 S1000
N5 G96 S500 M03
N6 M08
N7 G00 X2.5 Z0.
N8 G71 P9 Q10 U0. W0. D.06 F.015
N9 G00 X2.
N10 G01 Z-3.3996
N11 G40
N12 M01
N13 M09
N14 G00 X10. Z0.
N15 G00 Z5.
N16 M05
N17 M30

[RAF.]

I don't run a lathe but I have a question.

On a 2 inch dia. you say you're approx. .01 under to small.

How much to small on a 1 inch dia. and maybe a 3 inch dia.?

[Malish]

It seems to be always around 0.01" small no matter what diameter I turn. That's why I am wondering if it's a comp error or something I am doing that it's not offsetting off the part slightly to account for the tool radius.

[RAF.]

How is the Z axis reading?

[The Engine Guy]

Do you run with either/both the System Comp and/or the Machine comp on, I never have them enabled, too many issues with them



If you do have either of them on then give it a try with both switched off

Also do you set your TNR at the machine control or in BobCAD ?
If you are able to it in your tool library at your machine control then set you tools in BobCAD to 0.00 for the TNR, , if you don`t use the control for TNR settings make sure they are all at 0.00 in the machine.

Regards
Rob
:rainfro: :rainfro: :rainfro:

[Malish]

The code above was with the System comp on without collision detection, below it with system comp off

N8 G71 P9 Q10 U0. W0. D.06 F.015
N9 G00 X2.
N10 G01 Z-3.3996

Bobcad gives me the same code either way, this is why I believe I am having a comp issue where it is not offsetting properly. Would this be a post issue maybe? I assume if turn off comp I should get a different X value then if I had the system comp on correct?

I do not believe we put the tool radius into the control when we load tools. We do have a tool setter on the lathe, so I am reasonably sure that the tool offset on the machine is set correctly.

[Malish]

I did have the wrong post selected....

Here is the code with system compensation set "On without Collision Detection"

G71 U0.06 R.1
G71 P1 Q2 U0. W0. F.015
N1 G0 X2.
N2 G1 Z-3.3996

Here is the code with system compensation set "Off"

G71 U0.06 R.1
G71 P1 Q2 U0. W0. F.015
N1 G0 X2.
N2 G1 Z-3.3996

Exactly the same either way.

[The Engine Guy]

If the code has been generated telling the machine to go to X2 then it can only be something at the machine that is moving the tool to make it cut deeper and that would be likely to be a tool setting somewhere, I think you need to check all your tool offsets and TNR and machine offsets if any are being used.

It`s not likely to be BobCAD, a G code of X2 means go to X2 so if BobCAD is outputting X2 then it is correct as far as I can see

[LeWhite]

Tool nose rad ser to virtual sharp has no effect in straight turning or facing it will only have an effect on diagonals.
Tool nose radius set to center effects all. The key is a consistant use of either