Do you prefer to program in G90 or G91?

lowCountryCamo

Stainless

Joined

Jan 1, 2012

Location

Savannah, Georgia, USA

• Dec 18, 2014

• #1

I just ran my first few simple programs in incremental and was unsure what the pros and cons were for each system. Sorry for the basic question but I am learning from a Fanuc manual.

 

J

Jashley73

Titanium

Joined

Jan 24, 2013

Location

Louisville, KY

• Dec 18, 2014

• #2

Absolute. Incremtal only when dealing with repetitive cycles, subprograms, and macros...

 

scadvice

Titanium

Joined

Jan 16, 2009

Location

"Stuck in Lodi", Ca

• Dec 18, 2014

• #3

Absolute... 99.999% of the time.

 

toolsteel

Titanium

Joined

Nov 9, 2012

Location

NW Wisconsin (BFE)

• Dec 18, 2014

• #4

Incremental only when a specific reason arises.......

 

J

jimk1960

Aluminum

Joined

Nov 27, 2011

Location

Idaho USA

• Dec 18, 2014

• #5

I agree
Absolute. Incremtal only when dealing with repetitive cycles

 

J

jgrasty

Aluminum

Joined

Sep 19, 2013

Location

Texas

• Dec 18, 2014

• #6

I use whichever method is easier to program for the particular part, about 75% absolute and 25% incremental. Single point threadmilling is much easier to program incrementally, for example.

 

RC Mech

Stainless

Joined

Jul 21, 2014

Location

Ontario, Canada

• Dec 18, 2014

• #7

^ which would be a sub.

G91 for subs and in the G28 Z home line but otherwise G90. G91 in arbitrary moves (Z particularly) is tempting fate.

 

H

HuFlungDung

Diamond

Joined

Jan 19, 2005

Location

Canada

• Dec 19, 2014

• #8

Yup, one screw up in an incremental program and you won't know where you're at. Plus, when working around a standard Z0 plane at the top of your job, it gets a bit confusing because the incremental moves look a lot like absolute......you won't see it coming....

G52 is the nifty way to run a program written in absolute as though it were portable like an incremental program.

I don't know how many CAM systems out there will allow you to mix incremental and absolute without any issues, I know mine won't.

 

Mike1974

Diamond

Joined

Nov 5, 2014

Location

Tampa area

• Dec 19, 2014

• #9

As stated, absolute for everything but the special occasion. I've had the incremental bite me in the ass more than once (shame on me), and every time its like "oh CRAP!" didn't even see it until the part was screwed up...

 

7

706jim

Titanium

Joined

Jun 14, 2006

Location

Thunder Bay Canada

• Dec 19, 2014

• #10

There's no question that incremental is easier to follow when doing a milling profile.

And a combination of absolute and incremental works great for subroutines.

But when a CAM system is generating the code, absolute makes the most sense, if only for mid program startup.

A person should be familiar with both systems to be proficient at hand writing simple programs or subs and also to debug CAM output.

 

M

mjk

Titanium

Joined

Oct 20, 2005

Location

Wilmington DE USA

• Dec 19, 2014

• #11

"A person should be familiar with both systems to be proficient at hand writing simple programs or subs and also to debug CAM output"

I think that says it all

And don't forget their bastard cousin G92, which if used and cancelled properly is great for repair work

 

Mike1974

Diamond

Joined

Nov 5, 2014

Location

Tampa area

• Dec 19, 2014

• #12

I remember a part we used to run at another shop that was all incremental, just want to add this to what I said earlier. This program was brilliant!! No BS, absolute would have been a nightmare in this case. Think a spiral flute insert cutter, but a much larger diameter (3"-8") and sometimes up to a hundred, or more, insert pockets. All of them with a tapped hole, chamfer, cutting relief, etc. Oh I mentioned spiral right, so you had a chip gullet on a spiral path down the length of the body as well. When I first looked at the part I assumed it wsa probably a 2 day or so job to program.. LMAO, the supervisor 'finger-cammed' it at the control in about 20 minutes! BUT the subs were not labeled very well, I never could follow along with it. This is the crux IMHO of incremental and subs (maybe macros as well) - They need to be clearly labeled!!

 

M

mjk

Titanium

Joined

Oct 20, 2005

Location

Wilmington DE USA

• Dec 19, 2014

• #13

"This is the crux IMHO of incremental and subs (maybe macros as well) - They need to be clearly labeled!!"

because just because you are the author of the program, you may not understand why you did what you did 3 months down the road and have to walk the path again before pushing the button..

 

Mtndew

Diamond

Joined

Jun 7, 2012

Location

Michigan

• Dec 19, 2014

• #14

mjk said:

because just because you are the author of the program, you may not understand why you did what you did 3 months down the road and have to walk the path again before pushing the button..

Click to expand...

Exactly. I have my post to output a program that is labeled everywhere.
So if someone else runs my program 10 years from now, there will be zero questions.