z-axis scary plunge...

[Wooden Payload]

Hey all,

I've been lurking on the site for a while and can't tell you all how much great info I've found on here. That said, I have a question that I did some searching on, and couldn't find an answer for.

I operate a pcnc 1100 at work, and had an interesting thing happen to me the other day. My normal boot up procedure is to flip the computer switch on, wait for the computer to boot up, then hit the machine start button, and proceed to reference, etc... The other day, though, I decided to hit the machine start button while the computer was booting up, which turned out to be a bad idea. After about 30 seconds, the spindle started a rapid movement towards the table, which I stopped fairly quickly with the e-stop before anything bad happened. My coworker also did the same startup procedure a couple days after (no idea why we both did it) and luckily I was there to tell him right before the machine did it again.

So, my question is, is there something wrong? Or is the answer to simply not startup the machine that way?

Thanks in advance.

[holbieone]

there is something posted about that on here last week

they want the machine turned on and off in a certain order to prevent the "z" axis from falling

[Wooden Payload]

I think I just found the post that you are talking about. Sounds like the answer is definitely to follow the start up/shut down procedure, at least until Tormach comes up with a solution. Thanks for pointing me in the right direction.

[jeffrey001]

There is a boot up procedure in the parallel port also so you should never turn on the machine before the computer loaded Mach3.

This is not a problem with the machine(I think).

Jeff

[Kevin45]

I run a Proto Trak at work and on occasions it will do the same thing. Not every time, but once in a while it gets a mind of it's own

[LeeWay]

I still don't have one hooked up in my systems yet, but wouldn't a charge pump stop this from occurring?
I have been reworking my controls and putting them in commercial control boxes and will include a charge pump. My lathe is the closest to complete in the new box, but still lacks the charge pump. We have certain start up procedures with each machine as well. If we don't follow those, unexpected things can happen. Not always, so took a while to get the procedures down.
I think a charge pump should stop all movement until Mach is ready and you are too.

[TXFred]

Check your Z axis gib. Some Tormach users with the new steppers have head drop issues. Others don't. It seems to be dependent on gib tightness.

Frederic

[VaderSpade]

I have had no problems on startup BUT I have had Z axis plunges after a programed tool change. No rhyme or reason, sometimes everything goes fine other times the head plunges with the same G-code.

This has ruined a few expensive parts, and end mills and has shaken my confidence in Tormach. I’m still trying to figure it out; standing with one hand on the stop button is not what I had in mind when I bought this thing.

[Wooden Payload]

Thanks for the replies, I'll definitely be checking the z-axis gib next time I'm in.

I have had no problems on startup BUT I have had Z axis plunges after a programed tool change. No rhyme or reason, sometimes everything goes fine other times the head plunges with the same G-code.

This has ruined a few expensive parts, and end mills and has shaken my confidence in Tormach. I’m still trying to figure it out; standing with one hand on the stop button is not what I had in mind when I bought this thing.

I had one instance where my tool change code progression was a little off, and the tool height offset wasn't applied until after the tool returned to z0. Luckily I saw it in the code before I ran it. If it's code that works sometimes and then fails when you run it again, I have no idea.

One more question for you guys. If the machine loses power, will the z-axis fall? I don't exactly know how the e-stop works, so I'm not sure if it will stop without power...

[philbur]

There's always a rhyme or reason, you just haven't found it yet. Have you contacted Tormach.

Phil

I have had no problems on startup BUT I have had Z axis plunges after a programed tool change. No rhyme or reason, sometimes everything goes fine other times the head plunges with the same G-code.

This has ruined a few expensive parts, and end mills and has shaken my confidence in Tormach. I’m still trying to figure it out; standing with one hand on the stop button is not what I had in mind when I bought this thing.