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Negative tool offsets

Ncauman

Plastic
Joined
Dec 28, 2021
I'm trying to switch 2 of our machines in the shop to negative tool offsets because it's what we use on the other 4 and I would like them to be uniform. The obsolete tool setters we use on those 2 just add extra steps that make setting them and the z offset more difficult because we have no probes in our machines. I'm trying to do this on an Akira Seiki. Any help is appreciated.
 
I'm trying to switch 2 of our machines in the shop to negative tool offsets because it's what we use on the other 4 and I would like them to be uniform. The obsolete tool setters we use on those 2 just add extra steps that make setting them and the z offset more difficult because we have no probes in our machines. I'm trying to do this on an Akira Seiki. Any help is appreciated.

Not sure what your question is?
 
There is probably a Z Neg. in your work offset page, get rid of that (set to zero) and reset your tool offsets. They should read neg.
 
For what it's worth, it would better to switch the other 4 to positive offsets. They are better in every possible way.
 
oh! now you did it!
thee infamous positive versus negative debate.
i'll check back in when this thread hits 5 pages:D
 
oh! now you did it!
thee infamous positive versus negative debate.
i'll check back in when this thread hits 5 pages:D

There is a debate? I've never seen anyone make a case for negative tool offsets that went beyond their own intransigence with what they were originally taught and carried on for far too long.

Every layer of abstraction in this ballgame is another opportunity for mistakes, inaccuracies, crashes, and frustration.
 
We do it the way we like.
It is for the machine to decide whether it is positive or negative value.
 
Either will work.

That said, only positive is logical to me.....

I’ll counter with, how is an offset that is the distance from tool tip to Z0 not logical. Very easy for someone to visualize using negative. Of course it’s also easy for someone to visualize positive as the length of the tool assembly. Two methods to achieve the same result.
 
Either will work.

That said, only positive is logical to me.....

Yes, they will both work.....
But!!!
Here is another counter: If the top of your part is 0, then why are all features below it negative?
'Cos if that makes sense to you, then so should negative tool offsets.
 
Every layer of abstraction in this ballgame is another opportunity for mistakes, inaccuracies, crashes, and frustration.

Hence the reason for negative tool offsets.
The math is the same for positive or negative numbers, might as well keep it consistent and stay negative. :stirthepot:
 
Yes, they will both work.....
But!!!
Here is another counter: If the top of your part is 0, then why are all features below it negative?
'Cos if that makes sense to you, then so should negative tool offsets.

Bottom of the part could be zero.

So all features could be positive.

Using positive tool length offsets.

Just sayin'

(Actually this was taught to me by the Makino tech way back when)
 
Bottom of the part could be zero.

So all features could be positive.

Using positive tool length offsets.

Just sayin'

False comparison.
Doesn't matter where the zero is. Anything and everything below it is still negative.
Just like everything below the spindle nose is negative.
Nobody thought this to me, though I first self educated myself on lathes, and from there negative offsets just made all kinds of sense with the mills as well.
I do understand positive offsets, I just have a very very negative opinion on it.
 
I'm trying to switch 2 of our machines in the shop to negative tool offsets because it's what we use on the other 4 and I would like them to be uniform.
Like or bad for positive or negative.
The op has a system in use and wants to keep it consistent.
All of our views on the plus/negative do not matter and are not helpful.
Bob
 
......All of our views on the plus/negative do not matter.
Bob

+1^

In the 40+ years now that I've been involved with CNC machines, I've developed an opinion that things like preference of tool setting is often related to how one visualizes spatial concepts.

Similar issues come up when training folks on 4 and 5 axis mills. Had a new HMC user where I spent 2 weeks doing training with lots of that trying get them to understand why they could not just change a tool length offset on a face mill to get an undersized casting to clean up without affecting bore locations on the 90 and 270 faces.
 
No matter which offset method we use and consider best, accidents are always possible if there is some mistake in the offset procedure or if a wrong offset is programmed. Therefore, before executing a new program, it is advisable to execute G43 Z_ at a safe position, and check if the tool has gone to the expected Z position.
 








 
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