General question on tool diameter compensation

Hi all,

I am just starting to do some of my own research into milling machine features. My only CNC experience is with a 2-1/2 axis Prototrak AGE3 controller. I can change the diameter of the end mill on that machine fairly easy without affecting the program in order to fine tune a feature size. I was wondering if that is a common feature on most if not all of the bigger, regular, CNC machines. I'm thinking of something like the Akiri-Seiki, More-Seiki, Okuma, etc. Is it possible to fine tune the tool diameter without having to reload the software.

I understand that this is a very basic question but any help would be greatly appreciated.

Thanks,

Randy

Yes, it is called tool radius compensation or simply cutter compensation. They all have it. G41,G42,G43.

Hi. I appreciate your response. If I want to tweak the tool diameter does that have to be done in the cad/cam program causing me to have to reload the program or can that happen right at the mill without having to re-load the program. I've heard that some cnc mills have a "tool wear" entry that can be changed quickly.

Thanks again,

Randy

Hey Randy, you can change the amount you want to offset your cutter at the machine. When you make your program theres an option to turn cutter comp on or off. If you choose to turn it on for whatever youre programming, you will be able to do a tool offset at the machine then. Hope this helps. Any other questions dont be afraid to ask.

Yes, that helps a lot. Thank you very much for your time. I'm sure that I will be asking more questions as time goes by.

Thanks again,

Randy

In general - In milling operations on steel and aluminum parts - Do programmers program end mills full size for example: A 1/2" end mill (program it at .500 diameter) or do they take in consideration the tolerance of the end mill as stated by the manufacture? I am just wondering what the rule is for programmers to go by for this?

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Originally Posted by camminc

In general - In milling operations on steel and aluminum parts - Do programmers program end mills full size for example: A 1/2" end mill (program it at .500 diameter) or do they take in consideration the tolerance of the end mill as stated by the manufacture? I am just wondering what the rule is for programmers to go by for this?

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Hey camminc,
The tolerances as stated by tool manufacturers is barely noticeable on the finished part, (only if you are in the aerospace field should you worry). The tolerances only serve as a guide depending as to how critical YOUR part size requirements are. With newer CNC machines it is possible to measure both length and radius of the cutter automatically. If you require very tight tolerances on your workpiece, you can program using the measured radius from the machine (obviously if the machine has that measurement feature.) In my experience most cutting tools always measure to be slightly oversize, approx. 0.02mm over diameter) this is due to the manufacture (grinding or sharpening) of the actual cutter. After initial cuts, the cutting edges will have probably be worn to size.( Note, I'm referring to a brand new cutter.) I personally would not worry, because we have not had any oversize or undersized work pieces for our plastic injection moulds thus far, and our tolerances are fairly strict.
As for programmers rule, I have not come across any so far. Hope this helps.

Thx
sa1

Hi sa1:

I see your in SA. Here in the US the end mills are all plus nothing and minus .000-.002 basically, on the cutting edge, not the shanks.
We are an Aerospace manufacture with tolerances to hold to .001 a lot of the time, so if the end mill is undersize by .002 we are already out of tolerance on the part at the programming stage. I am wondering what is the norm for programmers out there, I have your input now so thanks SA1. What are others thoughts on this?

The norm would be to program it with the nominal size of the endmill. You would then run a test part (or just a test block if a complex part), then adjust your tool radius/diameter on the control until it cuts to size. As you said, endmills are generally a bit undersize so a program run with nominal tool radius will cut a part too big, allowing you to tweak the diameter down until it cuts true.