[Greolt]

My question is more general but using the Proma SD and 150 for example. Just trying to get my head around the requirements of a simple THC


I understand that the Proma150 sends "ArcOK", "Z up" and "Z down" signals to the controller (Mach3 in my case). Mach3 reads"ArcOK" and then drives the Z axis up and down as needed.


The Proma SD passes the Z step and direction signals from Mach3 to the Z stepper driver when the arc is not active.

And overrides Mach3 step and direction signals and sends step and direction signals directly to the Z axis driver when arc is active.


Mach3 takes care of the probing cycle to establish piercing height.... Fires plasma....Waits for pierce delay..... Moves to cut height..... Starts X and Y motion as required. All his done by the correct Gcode and Mcode commands.


I am assuming the above is pretty much correct. Stomp on me if not.

Question 1,
So why does the Proma SD not have an "ArcOK" signal? Does the logical process not need it? What happens if the arc fails for any reason, does Mach3 carry on oblivious to the fact no cutting is happening?

Question 2
There is no communication from Mach3 to the THC. The THC just senses the voltage. Is that all it needs to know?
Does Mach3 not need to tell the Proma SD to stop responding or not to dive when rounding a tight corner or small hole ETC?

Thanks for any help.

Greolt

[Torchhead]

Question 3 If the THC moves the Z how does MACH know where it is when it's turn comes . Thats like loaning your neighbor your mower and they use it then don't bring it back.

[xjdubber]

Question 3 If the THC moves the Z how does MACH know where it is when it's turn comes . Thats like loaning your neighbor your mower and they use it then don't bring it back.

Hey I recently got an extra lawnmower, ill sell it to you cheap....

[Greolt]

Does question three matter? I might be wrong but I can't see as it does.

As soon as Mach3 gets control of Z back, it moves to clearance height....moves to next cut position....does a touch off to re establishes Z position. Hey presto...it knows exactly where Z is.

Won't be much of a concern if Z is a couple of MM high or low when Mach takes over again.

Anyone got any thoughts on question one or two?

[Beefy]

Does question three matter? I might be wrong but I can't see as it does.

As soon as Mach3 gets control of Z back, it moves to clearance height....moves to next cut position....does a touch off to re establishes Z position. Hey presto...it knows exactly where Z is.

Won't be much of a concern if Z is a couple of MM high or low when Mach takes over again.

Anyone got any thoughts on question one or two?

You mirror my thoughts. My system always knows the Z position but I've thought about systems that don't.

If a tables slats are flat relative to the linear rails, PLUS the plate does not suffer much warping, then yes I can't see how you could be more than just a few mm out. And like you say a touch off will re-establish zero height each time.

If you are cutting thin steel that warps and climbs to the heavens then you are going to have a bit more than a few mm from the original zero position, but that can be compensated for in the slow zone of your touch off. From what I've heard a lot of plasma cutting systems don't have continuous monitoring of Z, they just do the initial height sensing at the beginning of each cut, which my system does in any case even though I have continuous monitoring of Z.

[Greolt]

OK I did not do so good with my first two questions. I will try this one.

Again using the Proma product just as an example of what I call a simple THC combined with Mach3.

The best I can tell from reading is that Mach3 handles all of the "Anti Dive" type control. That is to say that it ignores the up/down signals (coming from Proma 150) at certain points of the cut. Sharp corners for example.

If that is correct, then with a THC that takes direct control of the pulses to Z axis while cutting (Proma SD) is all "Anti Dive" features lost? Or is there some more subtle control happening that I don't yet know about?

Maybe a smoothing or delay to the THC reaction to sudden arc voltage changes.

[Beefy]

I've always found the term "Anti-Dive" to be rather vague, I mean anti-dive based on WHAT ??

Mach3 anti-dive is actually a "Z lock" based on reduced feedrate. You set the % of feedrate and when the feedrate falls below that % level the torch does not move up or down in response to any up/down signals. The reduced feedrate typically happens with deceleration / acceleration at corners. It even gets called Corner Lock in Mach3.

The other type of "anti-dive" is based on torch volts and is used to stop the torch diving down when going off the edge of the plate or crossing over a void. Those situations cause a sudden rise in voltage and thus the torch wants to react and dive down in an attempt to reduce the too high voltage. How would Mach3 know about this ? Is Mach3 monitoring the arc volts ? As far as I'm aware this is normally a function of an external THC itself (if it has such a feature). I don't recall seeing any such thing in the Proma manual when I glanced through them a few weeks ago, but double check to be sure.

So there's two different anti-dives operating in completely different ways and serving completely different purposes. A good system will have both.

[Greolt]

Thanks for that Beefy

I see you are in Frankston. I am over in Cockatoo.

Mach3 anti-dive is actually a "Z lock" based on reduced feedrate. You set the % of feedrate and when the feedrate falls below that % level the torch does not move up or down in response to any up/down signals. The reduced feedrate typically happens with deceleration / acceleration at corners. It even gets called Corner Lock in Mach3.

I guess "Z lock" is at least part of "Anti-Dive". Can't dive while it is locked. That is Mach's part of the deal. Mach can see when travel slows down but the THC can't.

The other type of "anti-dive" is based on torch volts and is used to stop the torch diving down when going off the edge of the plate or crossing over a void. Those situations cause a sudden rise in voltage and thus the torch wants to react and dive down in an attempt to reduce the too high voltage. How would Mach3 know about this ? Is Mach3 monitoring the arc volts ? As far as I'm aware this is normally a function of an external THC itself (if it has such a feature). I don't recall seeing any such thing in the Proma manual when I glanced through them a few weeks ago, but double check to be sure.

Yeah this is where the Proma info is a bit hazy. It has a setting for "sensitivity". What does that mean?

It might be a filtering of very rapid voltage changes, such as you might get crossing a cut.

Or it might just be a dead band where reaction does not happen untill a few volts change in arc. Sort of damper. Maybe a clever combination of both.



EDIT: Actually reading it again Proma only have a "Hysteresis" setting. And that only on the 150, not the SD.

[mikie]

Thanks for that Beefy

I see you are in Frankston. I am over in Cockatoo.



I guess "Z lock" is at least part of "Anti-Dive". Can't dive while it is locked. That is Mach's part of the deal. Mach can see when travel slows down but the THC can't.



Yeah this is where the Proma info is a bit hazy. It has a setting for "sensitivity". What does that mean?

It might be a filtering of very rapid voltage changes, such as you might get crossing a cut.

Or it might just be a dead band where reaction does not happen untill a few volts change in arc. Sort of damper. Maybe a clever combination of both.



EDIT: Actually reading it again Proma only have a "Hysteresis" setting. And that only on the 150, not the SD.

Hey Greg,

Did the machine you bought have the Proma 150 unit on it. I've decided i need a table and was going to buy a Proma controller.

Does it work? Should i buy something else.
Would love tontalk with you over the phone if you dont mind in your table and what should be done differently.

Will drop you a PM with my mobile #