Z zero position after Facing

[shiv.kmr003]

I see a similar question asked before but it didn't answer my question and/or the vocabulary used was not familiar to me 😄. 

Questions:

1. What's the difference between a "Job" and an "Operation"? 
2. Do I need to set the Z zero position after a facing operation?

Let me explain what I'm doing

Step 1: I face the stock down to the "Model Top" (approximately 0.75 in)

Step 2: I now need to change the tool/end mill. In doing so, I've obviously lost Z zero. There is no place left (all stock removed) I can set Z zero using the previous (what would be considered "Stock Top" in Fusion) height. So I obviously need to the "Model Top" surface to get a Z zero from this. However, when I run my next tool path..... well those who know will know what happened 😲. Well, essentially, the router/tool dug through the remaining stock (the model essentially, a was already smoking before I could stop).

The remaining tools paths (which are Adaptive), have their top set to Model Top. When I run the simulation (stock Colorization set to Comparison), there is no "additional" stock to be seen and the operation starts exactly where I'd expect. But I'm guessing the Z zero is (obviously) assumed to be the original Z zero (with additional height of approx. 0.75 in.).

It seems to me, that I need the rest of the tool paths to be a part of a different setup where there is no additional stock and my WCS is set to the top of the "Model" essentially. Or, is there are way?

[seth.madore]

How are you establishing the length of the tool; touching it off on the finished workpiece, or using a tool setter of some sort to establish the length?
What is your machine and controller and how do you establish the WCS location of your model/part?

[shiv.kmr003]

I'm using a Onefinity and the Z probe.
For the facing operation, I'm setting Z zero on the "Stock".
My WCS location is set to the top surface (of the Model)  at the bottom left (X = 0, Y = 0) of the model.

Once the facing operation is done, the Z zero is set to the top of the "Model". Since I have to change tools through the rest of the operations, I only have the top of the "Model" available since all of the "Stock" has been removed. Hope that explains things better?

[seth.madore · Accepted solution]

Hmm. I don't think I'm too fond of that workflow, as it forces you to continually update/modify your Z work offset. It would be better to either:

A) Establish zero on top of stock and then adjust that value a small amount to account for cleanup. Is that not possible?
B) If it's not possible and you will find yourself for setting tool lengths on finished surfaces, it sounds to me that you're going to need to have two setups, one for Facing only (where Z is Stock Top) and another Setup for everything else (where Z is Model Top)

[shiv.kmr003]

Hell @seth.madore ,

Thanks you for your replies. 

As to you option A:
In this particular case, I don't have any "stock" left to Z zero off of, since the entire top surface has been surfaced
Your B option has actually answered by doubt. That's is I need to have two different set ups in those cases where I won't have stock left to use for Z zero setting. I'm fine with that, particularly, because the "stock" is not "finished" to start with. At least not as cleanly/smooth as the finished surface I get once the facing operation has completed.

It's what I ended up doing in order to proceed anyway and all was good when I did this.

[programming2C78B]

Always zero tools off something permanent, like the machine table or a fixture.