Thc velocity low
- snowgoer540
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23 Sep 2021 22:57 #221452
by snowgoer540
Replied by snowgoer540 on topic Thc velocity low
Glad to hear it!
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23 Sep 2021 23:22 #221458
by phillc54
Replied by phillc54 on topic Thc velocity low
That is an easy "fix" if we can come up with a reasonable worst case number. I only need <0.5 but I have no clue for different power sources.Yeah i forgot that PlasmaC had 1.5 seconds of delay on the THC, i wonder who's idea was that?
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Glad you figured it out.
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23 Sep 2021 23:33 #221459
by tommylight
Replied by tommylight on topic Thc velocity low
Phill, sorry but i am sure it was not you who insisted on adding that delay .....................
Never used anything over 0.2, ever, and that was for cutting 15mm thick plate at 85A just to avoid torch moving up when motion commences. Otherwise 0 or 0.1 works 99.999% of the time.
Never used anything over 0.2, ever, and that was for cutting 15mm thick plate at 85A just to avoid torch moving up when motion commences. Otherwise 0 or 0.1 works 99.999% of the time.
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23 Sep 2021 23:38 #221463
by phillc54
Replied by phillc54 on topic Thc velocity low
paulsao got out of trouble with 0.5 so how about that for a starting point then?
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23 Sep 2021 23:45 #221464
by snowgoer540
Replied by snowgoer540 on topic Thc velocity low
If it helps for another data point, I have mine set at 0.5s as well, but suspect it can be lower.
I did want to do some halscoping to see when the voltage stabilizes, but I never seem to remember/get to it.
I did want to do some halscoping to see when the voltage stabilizes, but I never seem to remember/get to it.
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23 Sep 2021 23:47 #221465
by paulsao
Replied by paulsao on topic Thc velocity low
If Phill with 0.5 solves the problem and it goes very well, I tried it with 0 and it is also fine, although with 0 there is a small movement until the PID tries to control the voltage signal that at the beginning is very strong, I suppose that the The goal of putting 1.5s was to try to get the signal to stabilize a bit before controlling it, but that time is what is lost when cutting starts on a slope and not on a flat surface.
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23 Sep 2021 23:48 - 23 Sep 2021 23:50 #221466
by phillc54
Replied by phillc54 on topic Thc velocity low
I just took a look at the code and the default is 0.5
Oops, QtPlasmaC is 0.5, PlasmaC is still 1.5
self.w.thc_delay.setValue(self.w.PREFS_.getpref('THC Delay', 0.5, float, 'PLASMA_PARAMETERS'))
Oops, QtPlasmaC is 0.5, PlasmaC is still 1.5
Last edit: 23 Sep 2021 23:50 by phillc54.
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23 Sep 2021 23:57 #221468
by snowgoer540
Replied by snowgoer540 on topic Thc velocity low
One thing probably worth noting is that I believe Tommy does not use Auto Volts, so I think that would mean he can easily use 0s delay. If you use auto volts, I think you need a bit for things to settle.
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24 Sep 2021 00:24 #221471
by tommylight
BTW, just posted on instagram @toma.cnc one of my machines cutting at 4700mm/m, the client uses it daily at that speed. With a delay of 1.5 sec it would have breezed over 115mm before THC becomes active.
Replied by tommylight on topic Thc velocity low
That is correct Snowwy, although i do use it occasionally just to test things out and in QtPlasmaC it does work nicely even with my old power sources. Have not used it on PlasmaC in quite a while as it was usually keeping the torch to low. On this note, i do like to keep the new consumables quite high and lower it gradually as they become worn as that prolongs the usability by nearly twice.One thing probably worth noting is that I believe Tommy does not use Auto Volts, so I think that would mean he can easily use 0s delay. If you use auto volts, I think you need a bit for things to settle.
BTW, just posted on instagram @toma.cnc one of my machines cutting at 4700mm/m, the client uses it daily at that speed. With a delay of 1.5 sec it would have breezed over 115mm before THC becomes active.
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24 Sep 2021 19:34 #221516
by rodw
Replied by rodw on topic Thc velocity low
I don't think it really matters what default delay is used. Some people will have problems regardless due to their specific machine and table parameters.
Some machines return an arcOK after voltage has settled following the pierce. Some return it much earlier when the voltage is truly unstable.
Some people use auto volts and some don't. If you use auto volts, you definitely can get into trouble if you sample the voltage too early when it could be well above the stable cut volts and you will cut way too high.
I think everybody who builds a table should learn how to use halscope and plot a pierce on their machine. This thread shows two different plasma machines. Its just so important and lets you get the best out of your machine.
forum.linuxcnc.org/plasma-laser/41420-arc-voltage-on-piercing
One needs at least a 1 second delay and the other could use a 0.1 sec delay.
One has very stable voltage on an ArcOK and voltage could almost be sampled on an arcOK.
One is still all over the place on an ArcOk and sampling too early would see your set point far too high.
I think faster acceleration also has an influence. The faster you get to cut speed, the faster you get a stable arc voltage.
So when I think about this again. I wonder if there is any need to use a THC delay.
Why doesn't QTPlasmac monitor the voltage and enable the thc as soon as voltage has stabilised after an arc OK? On some machines, this may take 1 second or more, on others it may only take a few milliseconds. Man, that is a really clever idea the more I think about it. THC delay is a paradigm of the past!
Some machines return an arcOK after voltage has settled following the pierce. Some return it much earlier when the voltage is truly unstable.
Some people use auto volts and some don't. If you use auto volts, you definitely can get into trouble if you sample the voltage too early when it could be well above the stable cut volts and you will cut way too high.
I think everybody who builds a table should learn how to use halscope and plot a pierce on their machine. This thread shows two different plasma machines. Its just so important and lets you get the best out of your machine.
forum.linuxcnc.org/plasma-laser/41420-arc-voltage-on-piercing
One needs at least a 1 second delay and the other could use a 0.1 sec delay.
One has very stable voltage on an ArcOK and voltage could almost be sampled on an arcOK.
One is still all over the place on an ArcOk and sampling too early would see your set point far too high.
I think faster acceleration also has an influence. The faster you get to cut speed, the faster you get a stable arc voltage.
So when I think about this again. I wonder if there is any need to use a THC delay.
Why doesn't QTPlasmac monitor the voltage and enable the thc as soon as voltage has stabilised after an arc OK? On some machines, this may take 1 second or more, on others it may only take a few milliseconds. Man, that is a really clever idea the more I think about it. THC delay is a paradigm of the past!
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