Not as much of a newbie, but still one *sigh*... TNC Question

[Jorge-D-Fuentes]

Hi, it's me again.
A long while ago (in this thread I was a newbie looking for information on how to run a few programs on an OL-1 CNC Lathe.

Fast-forward a few months, and I've followed the advice of the good people here, and now we're doing production rather well.

My question has to do with an incident that happened at work:

I've been programming the toolpaths for the rings we're cutting here. I decided not to use Tool Nose Compensation, since I found out what the specs of the Sandvik Coromant tool were (about 0.016" Tool Nose Radius), set up as a Front Face tool. I also found out what the geometry of the other two tools (Inside Round and Part-Off) were, and incorporated all the specs into my programming code (generated easily by using a combination of Microsoft Excel and SolidEdge V18, as well as what I learned here and in a number of other manuals).

Rings are coming out perfect specs-wise, down to the mil.

Then the company decided to change Tools on me. They purchased a different Insert with different Tool Nose Radius.

After much arguing, I managed to get the company to purchase the correct Insert for that tool (tool #1, the front-face looks like THIS , courtesy of the other thread's attachment from someone who helped me here).

However, had they decided not to comply, I would've had to recode everything based on the new tool insert's specifications.

I'd like to avoid such an incident from happening in the future, so I'm thinking of using TNC for all the tools, so that if they ever change tool inserts on me, I can just input what the Tool Nose Radius is, into the Tool Geometry page of the Lathe.

I'm not too familiar with TNC, however. I know that with Insert 1 (the top-trimming tool that's front-faced), I'd have to set up a G42 somewhere so that the tool is offset to the correct direction as it makes the profile cut. However, when it comes around, when do I switch it to G41? DO I switch it to G41?

The Haas manual has barely one third of the page dedicated to TNC, and while I get the 'gist' of how to use it in a program, I'm uncertain about many things, such as the Tool's influence on the X axis (the G code suggest a shift to the left or right, but says nothing about top).

If you kind people could point me to a source of exactly how to use the TNC correctly, I'd very much appreciate it.

And yeah, knowing the company I work for, it's likely that they'll purchase different tools. Right now it's not too many programs, but later on it'll get worse, as new styles get made, etc.

Please help.

Thanks,
Jorge

[Geof]

Originally Posted by Jorge-D-Fuentes .....If you kind people could point me to a source of exactly how to use the TNC correctly, I'd very much appreciate it......

If you insist on keeping the "exactly" in your request you are doomed to disappointment .

I think you may have missed a few pages in your Haas manual. If you look for G41, G42 which are the TNC commands located in the G codes portion of the manual you will find about one third of a page. Check the Index for Tool Nose Compensation and you will find some more pages. I have a manual dated January 2005 which I got with a GT20 and it has a longer explanation running from page 46 to page 64.

[Jorge-D-Fuentes]

Hmm... perhaps I did miss it (I'm not home right now).
Please forgive me for my English...

From what I recall, the G41 and G42, when looking in "G Codes & M Codes" section of the manual, was only one third of one page. I did not think the manual had more, but apparently it does.

Forgive me.

[Geof]

Originally Posted by Jorge-D-Fuentes ....From what I recall, the G41 and G42, when looking in "G Codes & M Codes" section of the manual, was only one third of one page......

In that section yes it is about one third of a page and nowhere on this one third does it tell you there is more elsewhere. The Haas manual is not very well written.

[ajl6549]

Basicaly it's the same as a machining ctr. using CDC (cutter diameter compensation)

[Geof]

Originally Posted by ajl6549 Basicaly it's the same as a machining ctr. using CDC (cutter diameter compensation)

It is not really the same. On a machining center the cutter can approach the work from any side but on a lathe the tool is directional; left hand, right hand, inside, outside and this adds a bit of complexity to tool compensation. This is what is described on the pages I referred Jorge too.

[ajl6549]

So let me see if I got this right... as a guess, if I was turning an OD from the right end of the work, (tail stk end) twords the chuck, (left) I would use...G42? And if I was boring, ID the same way would it then be G41? or do I have it backwards?

A.J.L.


P.S. my lathe skills are a little... rusty.

[Geof]

Originally Posted by ajl6549 So let me see if I got this right... as a guess, if I was turning an OD from the right end of the work, (tail stk end) twords the chuck, (left) I would use...G42? And if I was boring, ID the same way would it then be G41? or do I have it backwards? A.J.L. P.S. my lathe skills are a little... rusty.

Here is a link to the pdf file that contains the Haas lathe manual;
http://www.haascnc.com/customer_serv...he/96-8700.pdf

The TNC explanation starts on page 53 and runs to page 63 and is followed by an explanation for using manual compensation incorporated into your program

[Jorge-D-Fuentes]

Originally Posted by Geof In that section yes it is about one third of a page and nowhere on this one third does it tell you there is more elsewhere. The Haas manual is not very well written.

AMEN to that!
It really isn't. Often I have to lurk in this forum to see answers to questions that would be so simple to just look up.

Anyway, I'm still not at work (I meant to say 'not at work' at my earlier post), but thanks for all your responses. I will take a look at the pages mentioned (and I saved the PDF too) when I return to Work.

My inserts always cut towards the chuck, never away from it, as they're not double-sided tools (well, the inside grooving one appears to be, but still 'moves' into the chuck, never away from it).

I'm always afraid of doing some mistake in the code and breaking a tool insert; though I'm happy to notify that that's YET to happen (they do break, but it's never due to the code being incorrect, it's always something like the stock material is held wrong, etc.).

Although the company I work for is thinking of adding Live Tooling to the list of things. HEADACHE!

I really need to push for a CAM system if they do that, 'cuz I don't think I can do it with my brain alone.

[broby]

Jorge,
I find the easiest way to get teh "correct" G41 or G42 direction for cutter radius compensation is to visualise standing behind the tool and looking down the direction of cut. If the tool is on the Right Hand side of the job, use G42 compensation, if it is on the Left Hand side, use G41!
From a Lathe point of view this translates into G42 for OD turning (Tailstock to Headstock direction) and G41 for ID work, As for Facing use G41 as the tool is on the Left of the cut going across the face of the part!
This may seem confusing unless you visualise programming from the "top" of the drawing. i.e. draw a picture of a shaft with the centreline of the shaft across the page, if you think of the tailstock as being on the Right Hand side of the drawing and the Chuck on the LH side of the drawing, with the tool coming in from the top rh corner. You will then see that the OD turning tool is on the Right when turning the shaft=G42 and on the LEFT when facing the tailstock end of the shaft = G41.
Hope this helps.
Regards
Brian.