HF continuous on DC?

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Zap, you never said why you use continuouse HF when DC welding.http://www.weldingweb.com/vbb/showthread.php?t=13298Does anybody have any pros or cons for this.Also, I understand that new "square wave" AC inverters do not require continuous HF for AC.
Reply:The only need for HF on DC is for starting the arc.No need for continuous.I'm curious as to why you say you need it zap.- Paulhttp://all-a-cart.comWelding Cart Kits and accessories
Reply:Originally Posted by ZTFabThe only need for HF on DC is for starting the arc.No need for continuous.I'm curious as to why you say you need it zap.- Paul
Reply:Ok, thanks expanding on why.
Reply:Originally Posted by zapsterTry it yourself..Nothing to loose.....zap!
Reply:Well there you have it.. Arcing noise??From inside the machine?...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:I want to assure everyone that I am not negating anything or anyone here, just using my electronics background to try and understand what is going on here. HF DC doesnt make sense, DC is a flat line and AC alternates at a frequency. Does the HF DC setting cause the voltage to go from 0v to your set target voltage back and forth at a high frequency? It is a fact that AC alternates from negative to positive, but if DC is alternating from 0volts to a target voltage at a frequency, it would be a DC pulse, not flat DC.Miller Syncrowave 200Hobart Handler 140Thermal Dynamics Cutmaster 38E-Z Tube BenderPlasma Cam DHC2
Reply:I'm glad someone straightend that out..In a nutshell..Where I learned had a revolving door installed..Thats how fast people were in and out of this place..I counted 45 in the time I was there..I lasted 5 years..How?I have no idea..But you did not ask questions there..They told you..They showed you...And that was IT..End of sentence... Maybe some of the practices (like this) were just the way they did things..But I have really nothing to complain about..Thats where I learned to TIG...And I think by now I know what I'm doing.They really knew there sh!+But it was a he!! hole to work in..Learned everything I know about machine work where I am now..Oh well.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by QuciferI want to assure everyone that I am not negating anything or anyone here, just using my electronics background to try and understand what is going on here. HF DC doesnt make sense, DC is a flat line and AC alternates at a frequency. Does the HF DC setting cause the voltage to go from 0v to your set target voltage back and forth at a high frequency? It is a fact that AC alternates from negative to positive, but if DC is alternating from 0volts to a target voltage at a frequency, it would be a DC pulse, not flat DC.
Reply:My Zena welder runs HF DC.  I am not in anyway endorsing this product, I don't even work for them.  Just thought this might add relevant information to the post.http://www.zena.net/htdocs/FAQ/whati...ml#HFDCdefined
Reply:SO what you are saying is that a carrier wave is riding on the DC voltage. That is possible, when I used to repair High frequency test equipment, a lot of the calibrations required setting the proper carrier wave on a dc signal.Miller Syncrowave 200Hobart Handler 140Thermal Dynamics Cutmaster 38E-Z Tube BenderPlasma Cam DHC2
Reply:Originally Posted by QuciferSO what you are saying is that a carrier wave is riding on the DC voltage. That is possible, when I used to repair High frequency test equipment, a lot of the calibrations required setting the proper carrier wave on a dc signal.
Reply:High frequency is only needed to start an arc. This is why when guys are TIG welding on DC- they put the machine in the START position. Once the arc is established the high frequency is automatically turned off. Now the aluminum guys are going to ask why they need it on all the time to weld. Answer, for the same reason. When TIG welding aluminum an AC current is used. An AC current travels in the shape of a Sine wave. As the current peaks at DC+ it will start to come down to peak at DC-. At some point the current will hit the middle point of the sine wave and current will drop to ZERO. It will then peak on the bottom half of the sine wave at DC-. It will then rise back towards DC+ and once again current will go to ZERO at the midpoint. If there is no continuous high frequency the arc will not be able to reestablish itself at the ZERO points. The new inverters use square wave instead of sine wave AC. This allows the arc to pass through the ZERO point fast enough that the arc never goes out, which is why you can get away without high frequ. on some inverters.
Reply:Originally Posted by reddoggooseHigh frequency is only needed to start an arc. This is why when guys are TIG welding on DC- they put the machine in the START position. Once the arc is established the high frequency is automatically turned off. Now the aluminum guys are going to ask why they need it on all the time to weld. Answer, for the same reason. When TIG welding aluminum an AC current is used. An AC current travels in the shape of a Sine wave. As the current peaks at DC+ it will start to come down to peak at DC-. At some point the current will hit the middle point of the sine wave and current will drop to ZERO. It will then peak on the bottom half of the sine wave at DC-. It will then rise back towards DC+ and once again current will go to ZERO at the midpoint. If there is no continuous high frequency the arc will not be able to reestablish itself at the ZERO points. The new inverters use square wave instead of sine wave AC. This allows the arc to pass through the ZERO point fast enough that the arc never goes out, which is why you can get away without high frequ. on some inverters.
Reply:Originally Posted by gnm109I don't know what the frequency might be (400 Hz?) I just know it works.
Reply:Well here's My report on the subject for today..Had a couple of journals to weld up today..4" dia..14" long..Did the start only all day..Like ZTFab had stated earlier..Its just quieter... Used alot of 3/32 70S-2The other half of the pile is scattered about the shop..I throw them at targets...Place is full of them..But in the end I see no diffrence..But why does the machine do nothing at all when the freq. switch is in the off position?No arcNo gasNo water But the machine stays running.. Beats me.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Zap,sounds like your machine is wired to not allow any TIG welding without the HF on start or continuous, since you say you get no gas or water flow.  Of course if you had gas and water, but no HF, you could scratch start the arc, that's what I have do on my system at home.
Reply:Originally Posted by pulserZap,sounds like your machine is wired to not allow any TIG welding without the HF on start or continuous, since you say you get no gas or water flow.  Of course if you had gas and water, but no HF, you could scratch start the arc, that's what I have do on my system at home.
Reply:I was just thinking about this..I suppose you can't stick weld with the switch on off either..Strange.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by zapsterBut why does the machine do nothing at all when the freq. switch is in the off position?No arcNo gasNo water But the machine stays running.. Beats me.....zap!
Reply:Originally Posted by enlpckI will guess that you can scratch start in that position. Once the machine detects the start of current flow, it should enable gas and water solenoids. Press the pedal, scratch the arc, off pedal to stop. Or, turn off the remote completely, scratch in, and break the arc to stop.
Reply:You guys know how SOME stick electrodes are hard to strike an arc? If you're using a stick/tig machine for stick welding , try w/the selector in the "start" position. on my miller dial-arc 250 H F , it starts almost before you are ready .[SIZE="5"Yardbird"
Reply:Hey, I like that, continuous HF with Stick, may help the stick not get stuck!
Reply:Originally Posted by pulserHey, I like that, continuous HF with Stick, may help the stick not get stuck!