Cut Parameters

More
29 Dec 2019 04:46 #153403 by rodw
Replied by rodw on topic Cut Parameters
Looking at the sheetcm manual it says
"Some plasma machines have a small delay between the torch being turned off and the arc
going out. If the machine starts moving before the arc has gone out you can get an ugly gouge
in the work. To prevent this set the 'Pause at end of cut' to a suitable value."

CandCNC is a bit more crypti. So this implies there is a delay after the M5 before the torch is moved so different to my thinking. But its not showing in the generated g code

Please Log in or Create an account to join the conversation.

More
29 Dec 2019 04:50 #153405 by rodw
Replied by rodw on topic Cut Parameters
And Jim Colt from Hypertherm says:
"Most plasma cutting software have a function that allows for a delayed off signal for the plasma....this keeps the arc on for a time period at the end of machine motion, which (on stainless especially) allows the bottom of the arc (which lags back at a 15 to 30 degree angle) to "catch up" with the top.

Some of the machines also can look ahead to the end of the cut and do an automatic slowdown.

When cutting materials like stainless or aluminum that do not oxidize easily the plasma arc is cutting with strictly thermal energy (melting). When cutting steel...the 20% oxygen content in air adds an exothermic reaction with the steel, which actually burns a bit ahead of the plasma arc....so less lag in the bottom of the arc."

Please Log in or Create an account to join the conversation.

More
29 Dec 2019 04:59 #153406 by phillc54
Replied by phillc54 on topic Cut Parameters
So it is another example of plasma cutting, everyone has their own idea.

Like this as well, some research turns up "overcut" as continuing the cut past the start point with the torch on others say it is turn the torch off at the start point and continue past the start point.

Like Alice said "curiouser and curiouser"

Please Log in or Create an account to join the conversation.

More
29 Dec 2019 06:11 #153411 by phillc54
Replied by phillc54 on topic Cut Parameters

rodw wrote: I'm not even sure "Pause at end of Cut" is supported in the sheetcam post processors we are using. I would have expected to see a G4 Pnn before an M5 but I'm not seeing that in the generated code. I suspect the value needs to be written in the onPenUp method in the sheetcam post but I could not see the variable name in the help file on a quick look.

It is endDelay, so PlasmaC would need something like:
function OnPenUp()
   if endDelay > 0 then
      post.Text (' M64 P3 (disable torch)\n')
      post.Text (' G4 P' ,endDelay, '(pause for ', endDelay, ' seconds)\n')
   end
   post.Text (' M5 (plasmac stop)\n')

That means PlasmaC does not need to consider "Pause at end of cut". That makes it a bit easier.

I guess the question now is should PlasmaC even have a "Torch Off Delay" as it is currently configured???

Please Log in or Create an account to join the conversation.

More
29 Dec 2019 06:27 - 29 Dec 2019 06:28 #153413 by rodw
Replied by rodw on topic Cut Parameters
Yes I just found endDelay after spilling a full cup of tea all over my desk which was piled in paper... Looks like it took out my keyboard too. I'll add that to my post as endDelay is not being used at present. Let me know your gcode syntax for rs485 commands...
Last edit: 29 Dec 2019 06:28 by rodw.

Please Log in or Create an account to join the conversation.

More
29 Dec 2019 06:35 - 29 Dec 2019 06:44 #153414 by phillc54
Replied by phillc54 on topic Cut Parameters

rodw wrote: Yes I just found endDelay after spilling a full cup of tea all over my desk which was piled in paper... Looks like it took out my keyboard too.

You need to swap to a iMac ;), I have done that and just run the keyboard under a hot tap then quick dry with a compressor. Works for beer as well...


I'll add that to my post as endDelay is not being used at present.

Yeah, I added it to mine and it seems to work OK according to halscope.


Let me know your gcode syntax for rs485 commands...

At this stage there are none, it just reads any required values from the "Cut Parameters"
Last edit: 29 Dec 2019 06:44 by phillc54.

Please Log in or Create an account to join the conversation.

More
29 Dec 2019 08:12 #153418 by rodw
Replied by rodw on topic Cut Parameters
Nah, I'll never own another Laptop, Windows Box or even a Mac. Chromebooks rule!
I gave it a good blow out with the compressor and am letting it dry out but its just a wireless keyboard with a couple of keys with letters worn of so it won't be a biggie if it dies.

I suspect users will want to control pressure and amps while cutting so think about how to do that...

Please Log in or Create an account to join the conversation.

More
29 Dec 2019 08:22 #153420 by phillc54
Replied by phillc54 on topic Cut Parameters

I suspect users will want to control pressure and amps while cutting so think about how to do that...

Change the current or pressure spinboxes while cutting???
We can't get realtime action so it would probably be good enough.
Stefan hasn't mentioned on the fly changes so I hadn't given it any thought to be honest.

Please Log in or Create an account to join the conversation.

More
29 Dec 2019 09:53 #153422 by rodw
Replied by rodw on topic Cut Parameters
This is an interesting read www.plasmaspider.com/viewtopic.php?t=16534
I wonder if rather than gcode, you also allowed setting of amperage and pressure reduction (eg 80%) when the corner lock was enabled.

Does it really matter if there is a lag to changing the current?
If nothing else it adds one more feature that other controllers don't have.
It would be interesting to see how users use the feature and see if it adds value.
And we can lean on PCW to implement an RS485 state machine in his mythical smart serial plasma interface becasue at least then the latency would be just on the comms link becasue the HAL commands would be real time...

Please Log in or Create an account to join the conversation.

More
29 Dec 2019 11:01 #153424 by phillc54
Replied by phillc54 on topic Cut Parameters

rodw wrote: This is an interesting read www.plasmaspider.com/viewtopic.php?t=16534
I wonder if rather than gcode, you also allowed setting of amperage and pressure reduction (eg 80%) when the corner lock was enabled.

That could be done relatively easily I think. It would take a bit of experimentation to determine the reduction values required for current /pressure compared to velocity.

Does it really matter if there is a lag to changing the current?

Probably not when ramping down but it would when ramping back up so that THC is enabled when everything is back to "normal".
I could probably add a pin to my 485 component to achieve this with not too much trouble. (with the caveat below)


And we can lean on PCW to implement an RS485 state machine in his mythical smart serial plasma interface becasue at least then the latency would be just on the comms link becasue the HAL commands would be real time...

There is also the lag in the machine itself. I have no clue how long it takes the machine to physically change the current/pressure
Also I don't know if when reading the current/pressure that the result is the actual current/pressure or what the last current/pressure force command was.

A lot of unknowns and difficult to test without a machine...

Please Log in or Create an account to join the conversation.

Moderators: phillc54
Time to create page: 0.101 seconds
Powered by Kunena Forum