Can I set Safe-Z differently on different toolpaths?

[EEDesigner]

Is there any way to set the Safe-Z height on a per-toolpath basis? I am cutting thick material with complex hold-down hardware and long-reach tooling. I need my tools to rise above the hold-down fixtures when cutting near the edge of the material with short bits. I also need to rise just above the material with long-reach tools that stay within the boundaries of the hold-down hardware.

The problem is that the Safe-Z distance can only be set on a global basis and my machine does not have enough Z-axis travel to needlessly raise a long-reach tool over the hold-down hardware, never mind the inefficiency of doing so. Setting the global Safe-Z to clear said hardware will cause my Z-axis to stall, which will catch the motor driver on fire, which will spread to my workshop and burn the building down, thus igniting the Earth’s atmosphere and causing the planet to explode. Are there any clever tricks people use to avoid destroying all Earthly creation when the only Safe-Z setting gets applied to ALL toolpaths?

[Adrian]

Save each toolpath separately and you can set whatever Z settings you want.

Moves from Z1 to Z2 should be rapid moves (depending on your post processor) so it shouldn't be that much of an inefficiency to run with a higher Z than really needed if you want to run all the toolpaths as one instead.

[EEDesigner]

Thanks for your reply. I did end up saving the outer toolpaths as separate files as you suggest and yes, that works, but folks that are a little bit touched in the head as I am are going to forget to continuously reset the Safe-Z and save only those toolpaths that require the change, set it back, and on and on. Aggravating the situation is the fact that ALL toolpaths are forcefully re-computed every time the Safe-Z is changed so I cannot simply exclude paths where I don’t want the change to take place. I will not remember which paths are new or old, and this whole mess ends up being a configuration nightmare if I walk away from it for more than 15-minutes and forget the nuances.

I tried setting the start depth to a negative number and modifying the top depth steps for tools that must clear the hold-down hardware. I cannot get that to work because it looks like the software does not handle negative depths. Maybe someone else knows how to do that? It might work to set the zero-depth plane artificially high and modify the first cut depth to blow past the extra height, but that does not solve the problem on my machine with the limited Z-axis travel. The Earth still blows apart.

The only solution I see that avoids the messy configuration and solves my machine problems is to use two separate Cut2D projects. I use one project for tools with higher Safe-Z requirements and another for long-reach tools. The only issue is that the 3D View simulations are not consolidated. That works, and I can deal with it.

[wb9tpg]

Thanks for your reply. I did end up saving the outer toolpaths as separate files as you suggest and yes, that works, but folks that are a little bit touched in the head as I am are going to forget to continuously reset the Safe-Z and save only those toolpaths that require the change, set it back, and on and on. Aggravating the situation is the fact that ALL toolpaths are forcefully re-computed every time the Safe-Z is changed so I cannot simply exclude paths where I don’t want the change to take place. I will not remember which paths are new or old, and this whole mess ends up being a configuration nightmare if I walk away from it for more than 15-minutes and forget the nuances.

I'm dealing with the same issue now carving 1911 grips. Once the grip is roughed out I don't really need all the extra Z and the long retracts on the V carve onto the 3D shape are bugging me. I already have split the file into a "Machine Bed" and "Material Surface" Zero so I'd need to do another file to do that.

Not to steal your thread but why when I tell Vcarve to recalculate a single toolpath (by right clicking it) does it give me warnings on other tool paths being too deep. I mean it didn't recalculate them (or did it).

[TReischl]

Not being snarky here so don't take this the wrong way. . .

The issue is actually that you do not have enough Z travel. I have a little experience with this myself. I built my own machine (it is essentially an Avid CNC). Originally I figured that 6 inches of Z travel would be plenty. Like you I tried to finagle thicker jobs via software. The solution was to add 4 inches to the Z travel on the machine.

Most people forget, if you want to cut something 4 inches deep you are going to need a tool at least 4 inches long when it is sticking out of the collet. So right away 8 inches of travel minimum is required. Start adding for clamp clearance and pretty soon even 10 inches is not all that much.

When I decided to bite the bullet I not only added 4 inches to Z but I also dropped the work surface another 6 inches. Of course the tool cannot even reach that depth. But what I did was put a sub table on the machine base to raise it back up. Weird eh? It is until I need to work on something that is 8 inches or more thick. Off comes the sub table and I got lots of room. Sooo, if I want to carve on a log that is over a foot in diameter, no problem.

One other tip: when cutting thick stuff mill a few slots on the edge of the blank for clamps. That way they are not sticking up above the surface of the work.

[Wayne Locke]

You could make tool path groups named by the "safe z" to help keep it straight.

It might be more of a nightmare than a solution but you could, after you have finished the design, do a "Save As" and create a duplicate file or files with different tool path parameters.

[EEDesigner]

Sorry for the late reply -
@wb9tpg: I am a new user to this software so I cannot answer your question - sorry. In fact, this is my very first thread started in this group!
@TReischl: Your machine sounds like a lot of fun, but it all depends on what you're requirements are. I have a mill, not a gantry style router, because I need the rigidity and accuracy that a router cannot offer.
@Wayne Locke: Hmm, interesting. As a new user I am still trying to understand the toolpath groups. That might be a good solution, but I'll need to play with it. Doesn't the Safe-Z setting apply globally? Does it not affect Groups?

Thanks for all your comments!

[Wayne Locke]

Yes the groups would recalculate but you could save the appropriate tool paths after every change and the groups would just help to keep it straight even you have to later recalculate.

[IslaWW]

If your machine is up to the task, I would look at the "RAPID PLUNGE TO START Z" feature. It will allow you to reduce plunge times on high safe Z files and use the machine Z zero as a safe height

[EEDesigner]

I am not so much worried about Z travel time as much as the fact that my machine does not have enough Z-axis travel to handle the needless additional Safe-Z distance.

I have a DIY mill named Frank, after Frankenstein, because all of its parts came from this and that from all over the place. Maybe what I should do is look into what TReischl said about extending the Z-axis travel since Frank's design was, and still is, completely up to me. I might make a second replaceable Z-axis stage so I have one for my precision work, and one for extended travel when I don't care so much about machine bending and other related performance compromises. That will be another subject for another day.

Once again, thanks for all your comments -

[TReischl]

I had the same concern with the Z axis hanging way out there and flexing around. That is why I built the riser sub table. When it is on the machine the Z only has normal extension. When I do thicker work and remove it I slow down the feedrates to compensate on the deep cuts. I do not do a lot of the thicker stuff so most of the time the machine can run at full tilt.

If I had to do mostly deep cutting type work then I would start changing the machine design completely. Of course making a machine rigid enough to do deep cuts adds weight so that means bigger motors, etc.