Another plasma component...

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15 May 2019 06:37 - 15 May 2019 06:38 #133820 by phillc54
I wondered why I couldn't see kerfcross-is-locked.
What is your height-per-volt setting?
Could you try kerfcross override at 200%.
It would also be nice to trigger from kerfcross-is-locked and see what is happening when it switches.

Cheers, Phill.
Last edit: 15 May 2019 06:38 by phillc54.

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17 May 2019 09:18 - 18 May 2019 06:15 #134038 by phillc54
I have pushed an update, it is a configurator that will (or should) create a complete plasmac configuration.
It doesn't affect plasmac so if you have a working config then there is no need to update.
I have attached a copy if you would like to try it without updating.

Before running this application you need to have:
1. a working machine config.
2. a local clone of the plasmac repo.

Double click on configurator.py in the configs/sim/gmoccapy/plasmac directory and follow the prompts.
The configurator.py MUST remain in the configs/sim/gmoccapy/plasmac directory so it knows where to copy the plasmac files from.
It creates a sub directory in ~/linuxcnc/configs named {machine_name} and writes a {machine_name}.ini and {machine_name}.hal file in that directory.
I makes a backup copy of the original HAL and INI files in the above folder.
It creates a {machine_name}_connections.hal file for the connections between plasmac and the original config. This moves the connections/comments from plasmac.hal to allow it to be overwritten by an upgrade.It copies all the plasmac application files to the new directory.
It also leaves the original HAL and INI files untouched so they could be changed and the configurator could be run to rebuild the config.
It shows only the relevant HAL connections for the selected mode.

It can also be used to upgrade an existing config, although it probably shouldn't be used to update a config that wasn't built by the configurator.

Cheers, Phill.

Mode0
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Upgrade
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Last edit: 18 May 2019 06:15 by phillc54.
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18 May 2019 07:07 #134107 by phillc54
I pushed another update, just some enhancements and code cleaning for the configurator.
To aid the configurator I have changed the layout of plasmac.hal. There are no code changes, just layout and comment changes plus additional comments in the ini files.

Cheers, Phill.
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19 May 2019 10:36 - 19 May 2019 10:37 #134259 by rodw
Replied by rodw on topic Another plasma component...
Tommy laid down a challenge! Time for a bit of fun!

I know we discussed it on another thread but I managed to spreadsheet a mathematical model shared with me by Dewey Garret who wrote the external offsets branch we use that now calculates the maximum velocity and acceleration the Z axis needs to cut corrugated iron. So lets look at the specs first.

Aussie Corrugated iron measures 76mm peak to peak and is 17mm high from the lowest to the highest and its 0.48mm thick.

So lets look at the cut charts. The lowest they go is 1mm at 3266 mm/sec at 40 amps. At a guess, if I drop it to 30 amps, the cutting speed might be around 4000-4500 m/min

So what I'd like to understand is how much of the raw Z axis velocity and acceleration does plasmac allow us to use for torch height control? So looking at my ini file I settled on a max velocity of 60mm/sec and 700 mm/sec/sec max acceleration

So if I run it at 4300mm/min, Dewey's model says I need a max velocity of 50mm/sec (3000mm/min) and an acceleration of 430mm /sec/sec. The acceleration seems well within spec and hat gives us about 17% headroom on the velocity.

So Phill, can Plasmac achieve those speeds on my machine and how should we set the machine to manage it? If not, what is the maximum cut velocity should I use? This test is what really will put plasmac on the map.
Last edit: 19 May 2019 10:37 by rodw.
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20 May 2019 03:11 - 20 May 2019 03:12 #134321 by phillc54
I did a bit of searching and it seems that angles for corrugated are around 33o to 37o which gives a worst case gradient of 1.327.
For each 1000mm/min of X velocity it would require 754mm/min of Z velocity so for your 4500mm/min X velocity you would require 3392mm/min of Z velocity.
Say if you decide 40o to give a margin the gradient would be 1.192.
So you would then require 3775mm/min of Z velocity.

The theory is that plasmac calculates the maximum offset counts that the Z axis is able to handle in each period, then while in THC active mode if it senses that a correction is required it sends that calculated maximum count (tempered by the THC Speed (P) parameter in the run tab) to the axis.z.eoffset-counts pin every period until the number of correction counts required is exhausted. For fastest response, wind that parameter up to the maximum (I think it is 1000).

Acceleration is determined by your ini file settings and should not be affected by plasmac.

You also need to ensure that the side of your nozzle/torch has enough clearance for that angle and cut height.

Cheers, Phill.
Last edit: 20 May 2019 03:12 by phillc54.

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20 May 2019 07:04 #134337 by phillc54
I have pushed an update that allows the configurator to upgrade and old manually setup version.

Cheers, Phill.

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20 May 2019 07:30 #134339 by rodw
Replied by rodw on topic Another plasma component...
Phill, thanks for your notes on corrugated iron. Your rule of thumb is not that far away from what Dewey calculated at 4300 mm/sec. The slope of course varies (tangential to the curve) and Dewey worked out the maximum velocity required. I think I'll drop back to 4000 mm/min. That will be 2810 mm/sec and 400 mm/sec/sec. Looks like the Plasmac speed setting is able to go to the maximum but is set to 80% of that right now.

It would be nice to use an unshielded tip becasue it has a lot less mechanical interference than the shielded one as it has an open pencil shaped tip. But then I won't be able to use ohmic sensing to find the surface. Anyway, I'll give it a go one day soon. It would be nice to just work up to the machine and prove it works first go so I wanted to do some homework on these settings first.

If this doesn't work sounds like I'll have to lean on Tommy to send me or lend me a Lam Technologies stepper motor..
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20 May 2019 08:26 #134341 by phillc54

rodw wrote: Looks like the Plasmac speed setting is able to go to the maximum but is set to 80% of that right now.

No, THC is ALWAYS allowed 100% of available velocity.
The setup speed spinbox is for the height changes for moving to cut-height, probe-height, pierce-height etc.

If you hover over the spinbox, the tooltip will show you that.

Cheers, Phill
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20 May 2019 22:24 #134407 by Grotius
Replied by Grotius on topic Another plasma component...
@Phill,

I have a little idea for you to investegate, only when you have time or are interested in the suggestion.

It would be nice to replace the gremlin cone (tool) or tube (when tool select) for a plasma torch head. :laugh:
In fact it's the expansion of some gremlin source code. The cone object itself is problably a few lines of code for shaping the cone.
If we replace this shape code for a plasma torch, this would be realistic or not?
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20 May 2019 22:36 #134408 by JTknives
A quick question. Where and how are you guys calling out your axis limit switches. I have my float switch working but my XYZ Reed switches and not. When I look in the machine.hal I see reference to limit switches but no place to spec a pin as thy are labeled as joint. Also how do I use a single limit switch as a homing switch and limit switch. Thanks guys - JTK

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