Centre Spotting
18 Oct 2019 23:33 #148238
by phillc54
Centre Spotting was created by phillc54
Is anyone actually using the Centre Spotting in PlasmaC.
From what I can gather it doesn't really do anything that cannot be achieved from GCode.
Also it seems that the variations in the way different plasmac cutters work make this feature very inconsistent which makes it hit and miss.
I am thinking that this feature should probably be removed.
From what I can gather it doesn't really do anything that cannot be achieved from GCode.
Also it seems that the variations in the way different plasmac cutters work make this feature very inconsistent which makes it hit and miss.
I am thinking that this feature should probably be removed.
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- tommylight
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18 Oct 2019 23:43 #148245
by tommylight
Replied by tommylight on topic Centre Spotting
I have dealt with a lot of plasma cutters so i know for sure it will not work as "one for all".
As an example, had an Oerlikon 100A that would pass through 6mm the instant it transferred from pilot arc, so it would successfully makes holes on anything, not spots. The Thermal Dynamics 90A i owned for several years was much more manageable as it would lower the pressure when striking an arc.
It would be a nice feature for sure, and if it does not cause issues, i would leave it there so whoever makes it work for his/her setup, lucky him/her!
As an example, had an Oerlikon 100A that would pass through 6mm the instant it transferred from pilot arc, so it would successfully makes holes on anything, not spots. The Thermal Dynamics 90A i owned for several years was much more manageable as it would lower the pressure when striking an arc.
It would be a nice feature for sure, and if it does not cause issues, i would leave it there so whoever makes it work for his/her setup, lucky him/her!
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18 Oct 2019 23:46 #148246
by bevins
Replied by bevins on topic Centre Spotting
What is it suppose to do?
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18 Oct 2019 23:50 #148247
by phillc54
Replied by phillc54 on topic Centre Spotting
This is the theory, but the practice is variable....
This was in the docs but I removed it earlier...
This was in the docs but I removed it earlier...
Warning: Spoiler!
== Center Spotting
For ease of centre spotting prior to drilling, PlasmaC can pulse the torch for a short duration to mark the drill centre spot.
This is done by first adjusting the on time for the torch in the <<config-panel,Config Panel>>. Times are adjustable from 1 to 999 milli-seconds.
The torch is then turned on in GCode with the 'M3 $2 S1' command which selects the plasma torch as a centre spot tool.
To enable centre spotting, see <<multi-tool, multiple tools>>.
LinuxCNC requires some motion bewtween an 'M3' command and a 'M5' command so a minimal movement at a high speed is needed.
An example GCode is:
G21 (metric)
F99999 (high feed rate)
g0 x10 y10
m3 $2 s1 (centre Spot on)
g91 (relative distance mode)
g1 x0.000001
g90 (absolute distance mode)
m5 (centre punch off)
g0 x0 y0
g90
m30
NOTE: The 'high feed rate' is to ensure that the motion is at the machines highest feed rate.
For ease of centre spotting prior to drilling, PlasmaC can pulse the torch for a short duration to mark the drill centre spot.
This is done by first adjusting the on time for the torch in the <<config-panel,Config Panel>>. Times are adjustable from 1 to 999 milli-seconds.
The torch is then turned on in GCode with the 'M3 $2 S1' command which selects the plasma torch as a centre spot tool.
To enable centre spotting, see <<multi-tool, multiple tools>>.
LinuxCNC requires some motion bewtween an 'M3' command and a 'M5' command so a minimal movement at a high speed is needed.
An example GCode is:
G21 (metric)
F99999 (high feed rate)
g0 x10 y10
m3 $2 s1 (centre Spot on)
g91 (relative distance mode)
g1 x0.000001
g90 (absolute distance mode)
m5 (centre punch off)
g0 x0 y0
g90
m30
NOTE: The 'high feed rate' is to ensure that the motion is at the machines highest feed rate.
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19 Oct 2019 02:46 #148268
by islander261
Replied by islander261 on topic Centre Spotting
Phill
I have not tried to use your spotting (center punch) tool yet. I did do some tests with torch timing and found my TD machine to be quite different from your HT one. One thing I do frequently is punch single pierce holes. I don't need any fancy setup to make it work with PlasmaC. I will have the this typical sequence of blocks perhaps many hundred times in a cut file:
...
G0 X1 Y1 (hole location)
M3S69
G1 X1 Y1 (hole location)
M5
...
The result is a hole with a diameter about the same as my usual pierce divot.
I will look into this further as I regain use of my right hand. For right how I can't even keep up with orders.
John
I have not tried to use your spotting (center punch) tool yet. I did do some tests with torch timing and found my TD machine to be quite different from your HT one. One thing I do frequently is punch single pierce holes. I don't need any fancy setup to make it work with PlasmaC. I will have the this typical sequence of blocks perhaps many hundred times in a cut file:
...
G0 X1 Y1 (hole location)
M3S69
G1 X1 Y1 (hole location)
M5
...
The result is a hole with a diameter about the same as my usual pierce divot.
I will look into this further as I regain use of my right hand. For right how I can't even keep up with orders.
John
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19 Oct 2019 02:51 #148270
by phillc54
Replied by phillc54 on topic Centre Spotting
Thanks John,
I think with some machines if a start attempt doesn't result in an Arc OK then they can't retry until the post flow finishes which totally negates what the PlasmaC spotting feature does.
I think with some machines if a start attempt doesn't result in an Arc OK then they can't retry until the post flow finishes which totally negates what the PlasmaC spotting feature does.
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19 Oct 2019 02:57 - 19 Oct 2019 02:58 #148271
by islander261
Replied by islander261 on topic Centre Spotting
Phill
My TD machine will try at every command regardless of post flow state. I was able to manually spot (center punch) marks in 2mm sheet using a very short pulse. The resolution of the pulse command was to low for repeatable testing. An .2 second difference in pulse length made the difference between no mark, a small crater and punching all the way through 2mm steel.
John
My TD machine will try at every command regardless of post flow state. I was able to manually spot (center punch) marks in 2mm sheet using a very short pulse. The resolution of the pulse command was to low for repeatable testing. An .2 second difference in pulse length made the difference between no mark, a small crater and punching all the way through 2mm steel.
John
Last edit: 19 Oct 2019 02:58 by islander261.
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19 Oct 2019 07:41 #148295
by tommylight
Replied by tommylight on topic Centre Spotting
Plasma cutters use R/C timers, meaning a small current passes through a resistor to charge a capacitor until it reaches the gate/base thresh-hold and that in turn activates the transistor and relay and the rest.
The issue with that is that it is not precise for what we need here, the time it takes from getting the torch on signal till actually firing varies by quite a bit. In normal use it is hard to notice, but it is noticeable.
The issue with that is that it is not precise for what we need here, the time it takes from getting the torch on signal till actually firing varies by quite a bit. In normal use it is hard to notice, but it is noticeable.
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19 Oct 2019 08:14 - 19 Oct 2019 08:15 #148302
by rodw
Replied by rodw on topic Centre Spotting
Phill, I'm sorry you did send me some code to try and so far I have not yet tried it out. I've done enough to know it will work on my TD machine, its just how well it works is the question. 
The new algorithm eliminates the variable delay from torch on to arc establishment by waiting for the arc to start but I don't know if that will work for non-TD machines.
The new algorithm eliminates the variable delay from torch on to arc establishment by waiting for the arc to start but I don't know if that will work for non-TD machines.
Last edit: 19 Oct 2019 08:15 by rodw.
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