Plasma and Ethercat?
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30 Nov 2024 15:28 - 30 Nov 2024 15:29 #315657
by PCW
Replied by PCW on topic Plasma and Ethercat?
When an arc stops or starts, the connection is broken or established in a fraction of a nanosecond.
This generates a large current transient what starting and because the plasma source has substantial output
inductance, it causes a large voltage transient when the connection is broken.
This is the reason relay contacts typically have arc suppression devices, not just to preserve the contacts
but to suppress the massive EMI generated by the near instantaneous current interruption.
This generates a large current transient what starting and because the plasma source has substantial output
inductance, it causes a large voltage transient when the connection is broken.
This is the reason relay contacts typically have arc suppression devices, not just to preserve the contacts
but to suppress the massive EMI generated by the near instantaneous current interruption.
Last edit: 30 Nov 2024 15:29 by PCW.
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30 Nov 2024 23:39 #315696
by RDA
Replied by RDA on topic Plasma and Ethercat?
Sorry not sure what you mean, but when the arc is turned on or off its done in a controlled way. The ”whole” idea is to stabileze the molten hafnium, tungsten or whatever the electrode material is.
I think we are tallking about different things, sorry about that.
I think we are tallking about different things, sorry about that.
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30 Nov 2024 23:56 #315697
by tommylight
Would not be much use molten, and to get it to melt, the surrounding copper electrode would have melted loooooong before hafnium.
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PCW is trying to explain the induction phenomena that happens when applying voltage to a coil and then cutting it, the coil will induce current on it's own.
Find an electromagnet, apply some voltage to it and cut the voltage while watching the scope, it is amazing what voltages can be produced by it, way beyond what has been applied.
Replied by tommylight on topic Plasma and Ethercat?
Hafnium does not melt, it erodes.The ”whole” idea is to stabileze the molten hafnium, tungsten or whatever the electrode material is.
Would not be much use molten, and to get it to melt, the surrounding copper electrode would have melted loooooong before hafnium.
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PCW is trying to explain the induction phenomena that happens when applying voltage to a coil and then cutting it, the coil will induce current on it's own.
Find an electromagnet, apply some voltage to it and cut the voltage while watching the scope, it is amazing what voltages can be produced by it, way beyond what has been applied.
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01 Dec 2024 00:54 #315698
by PCW
Replied by PCW on topic Plasma and Ethercat?
While the current and arc voltage can be controlled accurately during cutting,
you have large transients at arc start and stop (which happens in a fraction
of a nanosecond) V=L di/dt is not your friend here...
you have large transients at arc start and stop (which happens in a fraction
of a nanosecond) V=L di/dt is not your friend here...
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01 Dec 2024 18:02 #315746
by RDA
Replied by RDA on topic Plasma and Ethercat?
Thanks! I will check this out.
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01 Dec 2024 18:10 #315749
by RDA
Replied by RDA on topic Plasma and Ethercat?
During cutting the hafnium is in molten state. Thats why you do controlled current ramps, to try and keep the hafnium steady.
HT link
”Most of this wear occurs at the start and stop of a cut when the molten hafnium material quickly heats up and cools down, melting then re-solidifying.”
HT link
”Most of this wear occurs at the start and stop of a cut when the molten hafnium material quickly heats up and cools down, melting then re-solidifying.”
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01 Dec 2024 20:48 #315754
by tommylight
Replied by tommylight on topic Plasma and Ethercat?
Still seems to far fetched, if it melts if will blow out the nozzle, very quickly, but might be just at the surface ...
Hypertherm, so lends to a lot of trust, although i am leaning to marketing.
I have read everything on Hypertherm, Kjellberg Finsterwalde, Thermal Dynamics, Cebora, Victor (now owner of most of these), etc, and never ever bumped into melting Hafnium, all say eroding, although technically that is melting small parts.
As for "controlled current ramps", it does help longevity, but older stuff never had that, just a relay switching on and off a huge transformer.
Some have another transformer to cut the cutting current for a short period while the pilot arc is on till it detects current flowing, then turns on the relay, Thermal Dynamic Pak90 has such a system, and uses high voltage pilot at 50Hz or 60Hz, not HF.
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We should move this discussion somewhere else, any ideas welcome.
Hypertherm, so lends to a lot of trust, although i am leaning to marketing.
I have read everything on Hypertherm, Kjellberg Finsterwalde, Thermal Dynamics, Cebora, Victor (now owner of most of these), etc, and never ever bumped into melting Hafnium, all say eroding, although technically that is melting small parts.
As for "controlled current ramps", it does help longevity, but older stuff never had that, just a relay switching on and off a huge transformer.
Some have another transformer to cut the cutting current for a short period while the pilot arc is on till it detects current flowing, then turns on the relay, Thermal Dynamic Pak90 has such a system, and uses high voltage pilot at 50Hz or 60Hz, not HF.
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We should move this discussion somewhere else, any ideas welcome.
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02 Dec 2024 12:41 - 02 Dec 2024 12:43 #315785
by RDA
Replied by RDA on topic Plasma and Ethercat?
Yeah quite out of the original topic. Maybe there could be a generic consumable thread?
Might sound far fetched but it is true. You will have a molten puddle, bead or what ever you want to call it, in the “root” of the arc. You try to constrain and keep it as steady as you can. The copper ( or silver) around the hafnium/tungsten gives means to conduct heat and electricity.
Of course in the old stuff you didn’t have anything “fancy”. You had plasma with electrodes made of tig rods. When the electrode wore, you could pull more from the torch.
I think it was in the -90’s where hypertherm came out with venting. So you don’t only ramp down the current but you match it to the flow rate of the plasma gas at the end of the cut. So you have a separate valve (close to the torch) that lets out the plasma gas. You then see how fast it gets rid of the plasma gas and you ramp down at the same time and rate. This improves the consumable life significantly.
There is quite a lot of cool stuff behind the “scenes” the more complex the systems get.
Might sound far fetched but it is true. You will have a molten puddle, bead or what ever you want to call it, in the “root” of the arc. You try to constrain and keep it as steady as you can. The copper ( or silver) around the hafnium/tungsten gives means to conduct heat and electricity.
Of course in the old stuff you didn’t have anything “fancy”. You had plasma with electrodes made of tig rods. When the electrode wore, you could pull more from the torch.
I think it was in the -90’s where hypertherm came out with venting. So you don’t only ramp down the current but you match it to the flow rate of the plasma gas at the end of the cut. So you have a separate valve (close to the torch) that lets out the plasma gas. You then see how fast it gets rid of the plasma gas and you ramp down at the same time and rate. This improves the consumable life significantly.
There is quite a lot of cool stuff behind the “scenes” the more complex the systems get.
Last edit: 02 Dec 2024 12:43 by RDA. Reason: Typos
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