[cheenky]

the control is a yasnac 2000gII.

i attached a jpeg to depict my problem

so i tried using G41 on a program i made for a part and a few things ended up being off. one being a decreasing diameter taper, and the other a g22 radius to front side increasing diameter taper. the decreasing diameter taper ended up being overcut on the z-axis, and the radius ended up starting too far in on the z-axis. i used the compensation on roughing the back taper and front separately as the stock was close enough to the OD of the plateau to not need roughing. when i rapid back to home i make sure all the contours will allow for 2x's radius to fit.

i'm not very sure what i'm doing wrong in the program, but can somebody give me some pointers on do's and don'ts while using G41 on this machine?

[BlueChip]

My guess ... and it is a "fanuc based" guess .. is this :

In the offset page you have a T value ... that describes the position of the tool tip to the machine. Did you enter a value in the area of the offset?
I have attached an image from our training software that might shed a little light.

In the drawing you show ... maybe the tool tip is different in the (2) areas? If this would be the problem my idea would be to finish the front contour one area ... pull away and cancel the comp ... then come back and do the back taper area with a different offset and different T value in the offset.

But this is my opinion ... and you can check with my wife about how much that's worth

Real World Machine Shop Software at Kentech Inc. - Real World Machine Shop and CNC Software

[dcoupar]

the control is a yasnac 2000gII.

i attached a jpeg to depict my problem

so i tried using G41 on a program i made for a part and a few things ended up being off. one being a decreasing diameter taper, and the other a g22 radius to front side increasing diameter taper. the decreasing diameter taper ended up being overcut on the z-axis, and the radius ended up starting too far in on the z-axis. i used the compensation on roughing the back taper and front separately as the stock was close enough to the OD of the plateau to not need roughing. when i rapid back to home i make sure all the contours will allow for 2x's radius to fit.

i'm not very sure what i'm doing wrong in the program, but can somebody give me some pointers on do's and don'ts while using G41 on this machine?

Why not post your program here so maybe we can help you figure it out?

[Waynno]

I do things the old way, forget the auto radius comp built into that control and lay out the comps in AutoCad LT, Sometimes its just quicker to do it this way instead of fiddling with it for hours on the control end

[dcoupar]

I do things the old way, forget the auto radius comp built into that control and lay out the comps in AutoCad LT, Sometimes its just quicker to do it this way instead of fiddling with it for hours on the control end

So, lets say for example he doesn't have a CAD system. He shoud shell out $300-$400 for a seat of ACAD LT just so he doesn't have to use tip-nose radius comp? I don't get it. TNRC isn't rocket science... I've been using it for years, because I don't like fiddling around drawing intersections in a CAD system when the control has the ability to do it for me.

[Waynno]

So, lets say for example he doesn't have a CAD system. He shoud shell out $300-$400 for a seat of ACAD LT just so he doesn't have to use tip-nose radius comp? I don't get it. TNRC isn't rocket science... I've been using it for years, because I don't like fiddling around drawing intersections in a CAD system when the control has the ability to do it for me.

Im just stubborn that way,almost 30 years I been doing it this way, Im quite sure if ya was to go this route you can pick up a generic Cad program to do geometry for free some where. I had fiddled with built in radius comps with mixed results, maybe im doing it wrong, But at least I know for sure if im making a aerospace fitting or something to that nature, it will pass inspection, because it takes the path I generate. If I make a mistake, its shows up by not creating a smooth path or leaves a step where something is supposed to be tangent

Lathe stuff is generally not too complicated, most only have 2 axis and the programs are generally short, so by time I wonder if radius comp is even giving me the correct path, I can have the part layed out on the PC, in the machine and running

Waynno

[dcoupar]

Well, I guess it's a moot point anyway. Cheenky seems to have moved on.

[cheenky]

sorry, been trying to deal with the lathe randomly shutting down on me again (thought i got rid of those gremlins).
dcoupar- i don't have the original program as i got so frustrated i just started from scratch and didn't realize i had saved over it. i ended up doing a little bit of what waynno described with the areas i couldn't trig and also to double check some of my math.

one question i have about the tool nose compensation is should i be cancelling it when i rapid back to my g50 and then re-starting it when i approach the part again? the examples the manual gives are unclear to me, since it only shows single passes over the part.

[dcoupar]

sorry, been trying to deal with the lathe randomly shutting down on me again (thought i got rid of those gremlins).
dcoupar- i don't have the original program as i got so frustrated i just started from scratch and didn't realize i had saved over it. i ended up doing a little bit of what waynno described with the areas i couldn't trig and also to double check some of my math.

one question i have about the tool nose compensation is should i be cancelling it when i rapid back to my g50 and then re-starting it when i approach the part again? the examples the manual gives are unclear to me, since it only shows single passes over the part.

Yes, you should cancel it (G40) on the return to G50 block.

[cheenky]

thanks, i'll give that a try.

[fordav11]

If you manually calculate TNR Comp it limits the complexity of the parts you can machine.

It's a lot easier to include the TNR comp. in the coordinates like all CAM software does when auto-generating programs. With TNR Comp if you are machining pockets using G71 and Type II Canned Cycles and using G41/G42 it can cause the tool to dig into the part.

It's a whole lot easier to invest in some cheaper CAM software and then you can program anything including complex parts and you won't have to check anything.

There's some simplistic calcs here to work out TNR comp manually....
http://www.webmachinist.net/toolradiuscomp.html

Not sure exactly why you are doing it the hard way?

[Waynno]

On the GII upon finishing a tool operation task,
The last line of code (Say if you are using T2)

G51 T0200

That sends the machine to home position and cancels out the current work piece offset
for that respective tool.

Its something to do on every tool change

[Waynno]

If you manually calculate TNR Comp it limits the complexity of the parts you can machine.

Really? I have cut accurate parabolas on the lathe by using creative cad work, Positive
and negative shapes that fit together, It just takes some inexpensive cad and cam
software, and still dont use the built in TNR

[fordav11]

If you created any program manually then it is not very complex, parabola or whatever.
If you are using CAM software then your whole point is moot because the software does the TNR calcs. I create programs for many complex parts each day. In minutes. Sure you could calculate each roughing pass manually with Autocad but why would you want to waste time (hours/days) when you could be doing the next job. and the next job and the next job.
Using a computer and proper CAM software to create the entire program is the present and future. Doing it the manual way is good to know but it's history. In the last 25 years I've written over 40000 programs. It is impossible to do that your manual Autocad way. I can do it both ways but I'd choose conversational software with manual time-saving tweaks to maximize productivity that only a skilled CNC programmer/CNC machinist could implement every time. Thanks.
Obviously I can't change your opinion (nor do I want to or care either way), but a newcomer should not be taught to think that doing it the old way is better and more productive because it's simply not.

This is getting a little off topic. My point and the answer to the original post is using G41/G42 on a lathe is only good if the part is simple. If it is complex with many tangents/arcs and requires hundreds of roughing cuts and multiple different tools then TNR comp won't cut it and you must use CAM software to create the program. There are dozens of posts about TNR comp on this forum and every one of the experienced guys who do programming daily has basically said use CAM software because TNR comp creates more problems than it solves. Do a search if you don't believe me......

[Waynno]

Not attempting to argue the fact, G71 is a very user friendly feature on that particular control, G40 codes do not always produce the results ya want, That is the only point I was trying to make

[cheenky]

unfortunately the control didn't come with any of the g70-76 codes enabled :violin:

i do agree some CAM software would be the easiest/most productive solution, but as of right now lack the funds to invest. any suggestions on low cost CAM software fordav? also thanks for the link, i had found that site and was contemplating purchasing the software due to its price. also i am currently trial-ing dolphin CAM, any input on that particular software?

[fordav11]

wow! no roughing cycles makes it tough. you really must use CAM software for everything except simple parts.
which CAM software you buy depends on your budget.
or you can try searching for older versions like OneCNC which I used about 6-8 years ago.
TurboCAD with the CAM plugin is pretty cheap and cheerful. The CAM plugin does not run on Win7 though.
Also I hear Mach3 has CAM built in?
Lazy CAM is discontinued but may be good enough and free(?)
Check here.....
ArtSoft USA - Software Downloads
Get demos first and try. Price is very cheap compared to the big guys. Of course there are lack of features and limitations :-)
http://www.machsupport.com/purchase.php

you should probably look/ask in the CAM forums. with so many different CAM programs available choosing the right one is not so easy.

[Waynno]

unfortunately the control didn't come with any of the g70-76 codes enabled :violin:

Are you sure you have a G2? Its pretty rare not to have that option

TV screen or single line read out?

[cheenky]

yep, it's got the crt monitor. but i've been having numerous issues with this control so maybe those options got wiped out or are no longer working. i think there's a problem with the memory, as well as either a bad relay or bad power supply. now when the control shuts off, it likes to stay off for a while. i can hear the big relays click but nothing turns on. been contemplating a retrofit from this company: MS-Tech Corporation - CNC System for a couple of weeks, but haven't gotten around to getting a quote. just so frustrated with how this machine is turning out...

ps. it errors when i tried g76 for threading and g74? for peck drill, not 100% sure on the others but i figured if one doesn't work, none of the others will likely work.

[Waynno]

The manuals to that machine were not too clear, my guess is have someone who knows that control check that for you. Once ya learn those G70s they are simple to use, the peck cycle G73 will only peck, it will not pull completely out to clear chips, so I dont use that one, the G71 rough cycles are really easy to use once you learn them, I suspect they are there, ya just need someone to show you how to use them, G76 can be a bit fussy, and if it goes into that cycle you cant just stop it in mid thread, it will retract and you have to re start the control to make it work again or it will give an alarm