Need to control speed of Z Axis before and after a cut

[blain1976]

Hello,

I have been using and enjoying V-Carve pro for several years now, but there is one thing that I need to see if it's possible to control because without it, I run the risk of ruining my work.

My Z-Axis has trouble moving up at a fast rate of speed. It will lose its position if it tries to go too fast. Otherwise, it is ok. For example, before a cut, if it tries to go from 0.00 to .800 inches above the work piece, it goes up too fast and will lose its position. If I set the default to be .25 inches above the work piece, it is usually ok. Another alternative is that I can manually move the Z up before starting the toolpath and it will be fine as well.
However........If during the toolpath,it needs to go up fast, it will lose position and ruin my work. Also, a lot of times at the end of the cut, it will go up fast to clear the work and will sometimes ruin my work.
Is there any way at all to control the speed of the Z-Axis at the beginning and end of cuts as well as during a cut when it shoots back up to clear the piece? The default that it is at now, is just too fast for my machine, but if I could control this, then I would be perfectly happy.

I have adjusted the settings in the material setup and I have adjusted the plunge rate for each bit, but these are not the settings that I need to adjust. (Or these are not helping me with this problem).

I am using V Carve Pro 7.514
If this is solved in a later release that would help me also. I just need to know.

Any help would be greatly appreciated.

[Rcnewcomb]

This is better handled in your control software.
Are you running Mach3, or something else?

[TReischl]

You can do what you want in the post processor.

Rapid moves are handled by G0 so they are easy to find in the pp. So what you are looking for is lines that have "G0" and "Z" which create the rapid Z moves.

What you will need to do is change the G0 to a G1 and then add a feedrate to the Z motion line for that rapid with something like "F50" or whatever feed you would like the Z to retract at.

I do exactly that in my post processor. It does not affect XY rapids by doing it that way.

[blain1976]

Thanks for the replies.

I am using Mach 3. Is there a setting in Mach 3 to apply to all future?

Otherwise, I appreciate the tips on editing the code and will have to try and figure that out.

Best Regards,
Blain

[martin54]

Your control software should be handling this as has been said, it comes under motor tuning in mach3, try searching for that on google. Plenty of info out there on tuning motors with mach3, something you should really have done when you first got the machine

[Will Williamson]

I inserted a M48 into my post processor, this lets me control the rapids with the feed rate override

[ger21]

Reduce the Z axis Velocity in Mach3 motor tuning.

[blain1976]

Thank you all. I completely agree that I should have done this when I set up the machine.
I was and would say, still am new to the CNC world since I don't even use it once a month.
I built the machine and always figured it was something that i built wrong (and still could be). I managed to put up with it and it wasn't usually a big deal since I could hit "stop" in Mach3 at the end of a toolpath and just manually raise the Z. However last night, I was drilling several holes that had this fast Z after each and every hole. I managed to ruin the work piece on the second attempt of cutting the first hole.

As i learned more and more about the software, I started realizing the questions i should be asking, and here we are....

i really do appreciate all of the input. I will hopefully get to take a look at these motor tuning settings this week and hopefully fix my problem. It sounds promising, so I'm excited to give it a try.

Merry Christmas everyone!

[blain1976]

One more quick question regarding the Z-Axis motor tuning....

Does this sound like my problem, if my z axis is otherwise correct?

What I mean is that it is correctly going .50" when it is programmed to go .50" So those inputs should be correct.
The feed rate speed on Z axis is otherwise perfectly fine. It's just these quick moves that is causing it to not be able to handle the fast speed. And these moves usually happen when it has a lot of travel to cover.

Does that makes sense? Because I did set all of that up originally.

Maybe I should just get out there and see what these motor tuning settings are...

[blain1976]

Scratch my last question. It is in fact my problem. I just went and checked and the Z velocity was 187.5 and I changed it to 20 and am LOVING IT!
Man, I wish I would have known to do this years ago. This is like a whole new machine.

Thanks a lot everyone!

Have a Merry Christmas!

[martin54]

Why have you changed it to 20?? While that may well work ok it may not be the optimum setting for your machine & could well make carving times a lot longer than they need to be, not sure if it is still there but there was a tutorial on motor tuning on the mach website years ago, there are also probably some on YouTube but I can't personally recommend any. Really you need to take the time to learn a little about mach3 to get the best out of your cnc

[blain1976]

Martin, you're absolutely right.

I simply put it on 20 because I knew it needed to slow down. And 20 is a whole lot better than 187.5, so I'm better off here than where I was.
It could definitely speed up a bit and I do plan to try and figure out what that setting should be now that I know it's possible to change and where to change it.

Thank you,
Blain

[TReischl]

I misunderstood what he was wanting to do or what his issue was?

There are some things I do that I want the Z axis to retract at a feed rate rather than rapid.

The good news is that he has gotten a lot of help and is now happy as a clam!