plasmac cutting holes

AgentWD40
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19 May 2021 16:16 #209527 by AgentWD40

Replied by AgentWD40 on topic plasmac cutting holes

robertspark wrote:
It seems that there is a bug in the sheetcam post processor that Les posted in this thread in that it lists the feedrate (fr) as 100 and not 4800.
forum.linuxcnc.org/plasmac/42374-sheetca...code?start=40#207300

I do see where your fr=100 but I don't seem to be able to duplicate your problem where the post changes the feed rate from the value in the operation's settings. My first question is did you double check the feedrate setting for the operation (not the tool)? Otherwise you might raise the issue in the thread you linked.

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robertspark
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19 May 2021 17:09 #209529 by robertspark

Replied by robertspark on topic plasmac cutting holes

thats interesting (I've not had that before....) the operations feedrate is different to the tool?

in the past it has always followed the tool.....

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AgentWD40
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19 May 2021 20:44 #209546 by AgentWD40

Replied by AgentWD40 on topic plasmac cutting holes

robertspark wrote:
thats interesting (I've not had that before....) the operations feedrate is different to the tool?

in the past it has always followed the tool.....

The tool has default settings, you can tweak them if needed in the individual operations.
So are you saying that was your issue? Maybe you accidentally manually set the feedrate in the operation?

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rodw
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19 May 2021 21:34 #209548 by rodw

Replied by rodw on topic plasmac cutting holes

AgentWD40 wrote:
I'm just curious, per the hypertherm video are you adjusting the current on the fly or using O2?

Extending the state tags feature allows Linuxcnc to know the arc radius and the heading in real time.
If you know the arc radius, you can calculate the centripetal limit, the maximum velocity the arc can be negotiated at a given machine acceleration.

Armed with this info and working kerf crossing, you have all you need to replicate true hole technology as you can use Pythagoras to calc the external offset required to adjust for the wider kerf when the velocity is below the cut velocity. You can then lock height and let the THC to manage current to achieve constant voltage. It can be done without Gcode. One day somebody will be curious enough to listen to me..

The following user(s) said Thank You: grijalvap, thefabricator03

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robertspark
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19 May 2021 22:49 #209568 by robertspark

Replied by robertspark on topic plasmac cutting holes

rodw wrote:
One day somebody will be curious enough to listen to me..

its not the curiosity, its the implementation.... i understand gcode better than i understand linuxcnc

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robertspark
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19 May 2021 22:51 #209571 by robertspark

Replied by robertspark on topic plasmac cutting holes

AgentWD40 wrote:

robertspark wrote:
thats interesting (I've not had that before....) the operations feedrate is different to the tool?

in the past it has always followed the tool.....

The tool has default settings, you can tweak them if needed in the individual operations.
So are you saying that was your issue? Maybe you accidentally manually set the feedrate in the operation?

I use the tools to hold my material settings (kerf, feedrate, voltage, amperage etc.....

in the past I just "clicked" update operations and the tool settings transposed across to the operation.

At the moment the feedrate does not transfer across from the feedrate to the operations.

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phillc54
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19 May 2021 23:13 #209577 by phillc54

Replied by phillc54 on topic plasmac cutting holes

robertspark wrote:
No problem Phil, I understand, there is no way to satisfy everyones needs, I may just pass the parameters via m-code 100-199 P or Q parameters (exc. M190 obviously).

I have an algorithm to stop the torch as the leading kerf crosses the trailing kerf, and with PlasmaC that is obviously possible via M62 P3.

I also like an arc for a leadin given it allows for a smoother transition (IMO, YMMV, each to their own), between the leadin and the cut and the lead out and allows for smoother acceleration / less jolt and jerk, especially on thinner materials (2mm / 14g / 0.080")

Is all that not done by the postprocessor?
I think I am probably missing something and am not sure why you need an extra parameter in the cut parameters.
I have seen true hole before but i thought it was only for the high definition cutters, does some of it scale well to air plasma and give some benefits?

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phillc54
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20 May 2021 04:40 #209612 by phillc54

Replied by phillc54 on topic plasmac cutting holes

rodw wrote:
Extending the state tags feature allows Linuxcnc to know the arc radius and the heading in real time.
If you know the arc radius, you can calculate the centripetal limit, the maximum velocity the arc can be negotiated at a given machine acceleration.
Armed with this info and working kerf crossing, you have all you need to replicate true hole technology as you can use Pythagoras to calc the external offset required to adjust for the wider kerf when the velocity is below the cut velocity. You can then lock height and let the THC to manage current to achieve constant voltage. It can be done without Gcode. One day somebody will be curious enough to listen to me..

I hear you but I ain't goin' down that rabbit hole for air plasma.

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