Contact Tip to Work Distance "CTWD"

Date 02-09-2015 21:21 Edited 02-09-2015 21:36

Gentlemen;

You are trying to read too much into the graph I included in my post.

The graph simply shows the welder the usable wire feed range, voltage range, and the corresponding welding current if the correct contact to work distance is maintained.

The welder selects the appropriate FCAW electrode diameter and usually begins with the machine dialed into the mid-range for the wire feed speed. Then the welder dials in the voltage by drawing a horizontal line from the wire feed speed to the appropriate electrode diameter. Adjacent to the voltage is the contact tip to work distance (as the WFS increases, the voltage increases, and the CTOD increases for the give electrode diameter). If the values selected are correct, and if the welder maintains the appropriate CTOD, the welding current will correlate to the value listed on the chart. Note that the diagram is for a specific electrode classification produced by a specific manufacturer and using the shielding gas recommended by the manufacturer.

The slope of the graph is simply a function of the scale used to construct the chart. It has nothing to do with inductance or any other aspect of the power supply.

AWS has similar diagrams for GMAW in their recommended practice for GMAW and the Welding Handbooks. The one thing to remember is to make sure the wire feed speed is not in the transition range where the power supply doesn't know whether to operate in the short circuiting or spray transfer mode. If one tries to operate in the transition range, the arc will be rather unstable.

Most GMAW power supplies only have two inductance settings because most welders didn't understand how inductance affected the arc and the machines response to varying the electrode extension.

I have encountered countless numbers of welders that insist on setting the FCAW and GMAW machines using amperage as their variable of choice. My point is that amperage is a variable, not a constant. Attempting to set the machine using a variable is a sucker's bet. When the machine changes "amperage" in response to the welder varying the electrode extension, the welders get frustrated and blame their woes on the "damn machine."

For that reason, I put black electrical tape over the ammeter to force the welder to set the three constants; voltage, wire feed speed, and electrode extension. Life is good once again.

Back to the chart I attached to my earlier post. Here's a couple of examples:

0.045 inch diameter electrode
350 ipm (mid-range as the starting point)
27 to 27.5 volts
3/4 CTOD
should shows about 215 amps on the ammeter

0.062 inch diameter electrode
250 ipm wire feed speed (mid-range as the starting point)
25 volts
3/4 to 7/8 CTOD
should show 300 amps on the ammeter

Using that particular electrode, the welder should be tickled pink. The machine can be readjusted to a higher setting for the WFS which means the parameters would have to be readjusted to keep everything running properly. Likewise if the welder wants to readjust the machine to a lower WFS setting. You can't adjust just one parameter nor can the welder change the CTOD without mucking up the works. That being said, I will increase the CTOD to reduce the amperage to reduce the amperage and joint penetration when I am fighting a root opening that is a little wider than I would like.

Best regards - Al

By electrode (***)

Date 02-10-2015 17:55

Good.
An adequate explanation as was needed, at least in my opinion.
Thank you and kind regards.

PS:
Just a quick note. I myself did never correlate the slope of the graphs depicted in your chart with the welding power supply's inductance or U/I-characteristics, respectively.

By 803056

Date 02-10-2015 18:01

If you receive the quarterly Inspection Trends from AWS, there is a brief article on the same graph included in this post. It might provide a better or at least a different explanation of the graphical presentation of the welding parameters.

Inspection Trends can also be accessed at the AWS Home Page.

Best regards - Al

By electrode (***)

Date 02-10-2015 19:04

You may consider that done, Sir.
I gratefully appreciate.
Any further advice maybe on the IT Volume and Issue?
I need to access namely via AWS' Home Page.
Thank you.

By welderbrent (*****)

Date 02-10-2015 19:05

If memory serves me correctly, you will also need to be a current CWI in order to access the IT (Inspections Trends) articles.

If you can't get it to let you see the magazine let us know. I know Henry linked someone a copy once so they could access one of my articles. Must be able to do it somehow.

Brent

By 803056

Date 02-10-2015 19:12 Edited 02-10-2015 19:16

I don't think that is the case if you access it through the AWS Homepage. I wouldn't bet a hot chocolate, but I'm sure we will find out shortly.

How's everything in AZ Brent?

I'm in Charlotte for an extra few days. My Monday flight was canceled due to the storm that hit the Northeast Coast. I should get home tomorrow evening, just in time for the next storm.

The good thing is we are located toward the West side of the storm, so we were not hit as hard as those poor devils 20 miles to the East! My wife reports that we only got about 12 inches with this storm added to the 6 inches we received from the storm before.

At least I got to spend several days with my relatives. See, not everything turns out bad.

It isn't just a job, it's an adventure!

I just checked the AWS Homepage. It is still listing the Fall issue of Inspection Trends. The Winter edition might be delayed a month.

Best regards - Al

By welderbrent (*****)

Date 02-10-2015 19:39

They changed the print date from Jan to Feb but I would have thought it should be out by now. And, we usually see the digital copy before the hard copy gets to us in the mail. Not always and not by much, but, usually.

Things are well here. Too busy. Can't be home as often as I need to be. May have sold the house. Looking for something with lower mileage to Phoenix and/or Flagstaff as that is where most of my work is. Have to try to get the house payment smaller, the mileage and driving time more reasonable, with a larger, newer house that has everything the wife wants. :lol:

Spent two weeks on a job in IL and got to spend the weekend with son and family in IN (less than 3 hrs from where my job was). I think Darrell is in WI right now and headed to parts south in the next couple of days. We have both been very busy. And can't find any help that I can trust to fill in on some of it.

I know, I live in a dream world, more like a nightmare. I also live in the state of ... confusion.

He Is In Control, Have a Great Day, Brent

By electrode (***)

Date 02-10-2015 19:31

Thank you, Brent + Al.

I just checked and can confirm.
Possible for me to read, but it still shows the Fall 2014 Edition.
I suspect it should be included then in the Winter 2014 Issue - most likely shortly to come.
Hence, I will be waiting in patience until having that available.

Thank you again, gentlemen.

By welderbrent (*****)

Date 02-14-2015 22:49

I just received my hard copy of the Feb 2015 (winter edition) of IT.

BUT, it is not yet on the digital availability from the AWS website.

Brent

By electrode (***)

Date 02-15-2015 08:47

Thank you again, Brent.
I will be having a look at the AWS Home Page occasionally.

Kind regards.

By welderbrent (*****)

Date 02-25-2015 22:38

Okay, it took a note to the editor to get the website techs off dead center. I was told they have been very busy trying to get some final aspects of the new website ready for implementation but they apparently took a few minutes and got the winter edition of IT up on the website for viewing.

You can now check out the great articles.

Brent

By electrode (***)

Date 02-28-2015 09:58

Brent,
thank you for the reminder.
I could read the Winter Inspection Trends's Q/A section involving the graph discussed.
Given the question's background, the answer makes sense.
Useful approach.

Kind regards.

By Lawrence (*****)

Date 02-13-2015 18:59 Edited 02-13-2015 19:02

Glad you mentioned that Al,

May I offer some images to help define terms for those of us who may not have given the topic the magnifying glass.

Electrode extension or (Stickout) and CTWD (contact tip to work distance), are not really the same thing.

This would prolly go better at the top of the thread, but hey... This conversation has been all over the place, literally.

CTWDStickoutElectrodeExtension1.jpg (21k)

CTWDStickoutElectrodeExtension-1.jpg (83k)

By electrode (***)

Date 02-14-2015 11:33

Yes. Not verbatim - internationally considered almost though.
ISO/TR 25901:2007 (Welding and related processes — Vocabulary) defines instead the 'Contact Tube Distance'; i.e. the "distance between the contact tube and the welding point". It does not mention, however, what "welding point" means. In addition 'Electrode Extension' is defined as the "distance between the end of the contact tube and the end of the wire electrode". That is, if 'arc length' (whatever that means) becomes zero; 'electrode extension' (say: E) equals 'contact tube distance' (say: C). As a consequence - all GMAW process variants involving 'short circuit droplet transfer', corresponding to droplet detachment frequency, should partially prove the condition: E = C.

I also suggest "electrode extension", if used for quantitative purposes, hardly definable; thus leading to observation abstractions as in the drawing posted by Lawrence.

By electrode (***)

Date 02-14-2015 17:04

Quote: "As per my typical position on welding terminology, I suggest we stick with standard AWS terminology to minimize confusion." Unquote.
This being the AWS Welding Forum - understandable.
Quote: "Maybe the term should be submitted to the AWS subcommittee on terms and definitions." Unquote.
Eventually one should suggest 'contact tube' rather than 'contact tip' but anyway, presumably it's just a question of time that this will find access to AWS Welding Terms and Definitions.

Maybe I'm wrong but in case of interpreting Lawrences's WPS excerpt correctly; Canadian Welding Authorities do at least already approach international welding terminology.
Certainly there are good reasons for that. One of which I suppose is the difficulty e.g. to relate an observation explicitly connected to the 'contact tube to work distance' which, however, cannot be similarly described using the term 'electrode extension'. Because, as so eloquently put by Lawrence: "Electrode extension or (Stickout) and CTWD (contact tip to work distance), are not really the same thing."

Kind regards.

By Lawrence (*****)

Date 02-14-2015 20:24 Edited 02-14-2015 20:33

Actually the term "contact tube to work distance" is used in AWS D1.1 Annex N, for the example of a properly produced WPS.

Maybe not in "Terms and Definitions". But an acceptable and appropriately used term nonetheless.

Edit: welding point?!?!

Not even Google can say what "welding point" is, or show a picture of it.

By 803056

Date 02-14-2015 21:49 Edited 02-14-2015 21:54

Is it defined in D1.1?

Many nonstandard terms can be found in AWS standards. The review process is far from proof.

"Contact tube" - nonstandard term for "contact tip." Yet "contact tube" can be found in several AWS publications. Just because a term can be found in an AWS standard doesn't make it correct terminology. It simply means the committee members didn't verify the terminology as found in AWS A3.0 or that the standard was published before the most recent edition of A3.0 was released.

Al

By 46.00

Date 02-16-2015 17:06

Many welding terms are not caught by AWS definitions, AWS D1.1 is not the definative welding review or dictionary for all things welding related. To limit people to AWS A3.0 terminolgy is a mistake,

By 803056

Date 02-16-2015 17:21

If miscommunication is the goal, I agree.

Al

By 46.00

Date 02-16-2015 18:04

LOL! To limit yourself to one standard restricts your overall view? Surely communication can overcome any issues with terminolgy? CTWD is not in A3.0

By jarsanb (***)

Date 02-16-2015 18:01

When dealing with codes and standards I would agree that AWS A3.0 is the document to be used, at least in the U.S. - ASME IX (QW-490) and API 1104 (section 2 and 3.1) both identify AWS A3.0 with regards to terms and definitions, not to mention the AWS D's.

By 46.00

Date 02-16-2015 18:05

Welding terminolgy is not just restricted to the US!

By jarsanb (***)

Date 02-16-2015 18:15

I agree. And if everyone in the different industries within the U.S. used different terminology, how could we expect to communicate outside our borders (or within them). If U.S. industry at least used a common welding vernacular it would be easier.

By 46.00

Date 02-16-2015 18:26

You know, as a Brit, working in the US, I had to talk to many welding type people. I was astonished at the difference in terminology, but I have always managed to convay my thoughts through communication!

By electrode (***)

Date 02-17-2015 09:20

46.00,

reading "You know, as a Brit, working in the US, I had to talk to many welding type people." made me smile.
Simply because to the best of my knowledge there's another "Brit", working in the US and as such certainly being faced daily with "talking to many welding type people".

If I'm informed correctly this gentleman is Mr Andrew Davis, professionally serving AWS and in charge of representing AWS - as excellently put by Mr Brent Boling (quote): "ONE of the foremost organizations for compiling and distributing information enhancing the science and technology of welding around the world."

I'll have to admit to not be a welding "codes and standards" person. It is, I confess, a little too administrative for me and, life's too short to get lost in - with all due respect - 'shifting commas back and forth'. As with many others here - I'm literally hooked to welding, and kindly be asked to believe me - on an academic stage I use to take that most serious. But, and that may sound ambivalent now (though it is not); welding means also passion to me and using my invaluable life time for endlessly arguing over the question whether "tip" or "tube" or maybe yet "nozzle" may be used when simply and straightforward asking for advice does not really make sense to me.

I presume it's just as with Quantum Mechanics. Some things remain hardly explainable using 'words' and as long as a high number of welding people is around (such as in an open welding forum) a certain lowest common denominator may properly serve to at least roughly understand each other.

However, I would judge myself silly of course to deny the truth; i.e. the need - and utilisation - of valid and (note relative term) reasonable welding terminology. I like what Al used to say: "...using slang or nonstandard terminology displays a lack of professionalism." Well said; I personally however, not a person knowing all different standardised terms by heart, will not condemn somebody out of hand just for maybe having mixed ISO, AWS or ... TWI terminology. On the contrary; I'm afraid that consistently facing fellow forum members (many welders I suppose) with the "evidence" of being "non-professional" may lead to reactions, such as recently noticeable in the 'Shop Talk' section.

Anyway, I agree that it should be our responsibility to question those questions being asked on this forum and as such we should also prove consistency in applying correct standard terminology. Finally for both improving the general comprehension level and particularly appreciate the work of those delegates active in numerous committees around the world, aiming at improving welding terminology.

That being said.
AWS is one - if not even the biggest organisation in the world of welding and joining and as such it has an immense impact on international standardisation activities. Coming back to Mr Andrew Davis again - outstanding in this respect and I suppose only some very few individuals on this planet, having similar expertise and competence. To me the reason for representing the whole AWS while interacting with ISO/TC 44.

Long story short. I consider the United States of America to have strong pace-making position and impact in many respects, last but very not the least also welding standardisation. And since we're living on one earth, I am sure that sooner or later this "book" of terminology will appear. If I myself will be happy enough to experience that someday I cannot say, however, this discussion shows that we're at least on a respectable way.

You've raised some valuable points here 46.00 and I agree - great conversation.

By welderbrent (*****)

Date 02-16-2015 18:50

Good day Glyn,

A major consideration with terminology is how easy it is to confuse issues when using totally differing definitions and/or terms to describe something.

This does take on a strange twist when you have API calling out a discontinuity with one term and AWS using another term and yet API claims to incorporate AWS A3.0 Standard Welding Terms and Definitions into their specification 1104.

And while most of us here do gratefully acknowledge the presence and participation of our forum members who are part of the brotherhood of welding but have been trained and currently practice the trade in a good many locations around the globe thus broadening all of our horizons it is still incumbent upon us to try to utilize terminology that will help all of us understand the question and answer/counsel given. So, while not trying to put down any institution in other countries it is also acknowledged that this is The American Welding Society based in the United States of America and that said organization is ONE of the foremost organizations for compiling and distributing information enhancing the science and technology of welding around the world and that it has been yielded to by many as the ground level foundational basis for connecting the dots for all other institutions. It is also incumbent upon us to realize that the majority of participants to this forum are from the US and seeking assistance from a common knowledge base that can be understood without compromise.

Again, this is no slam on anyone else, in fact I weighed it very carefully as I do not want to offend anyone and discourage them from participating. I think I have made that clear in previous posts in trying to encourage electrode, Joey, Shane, you/Glyn, nanjing (I do know the current status here but included it anyway), and others in their participation in this forum. Your input of knowledge and experience has been very respected and appreciated here.

Noting next the efforts being made in all the various AWS committees to also bring all technical, specification, standards, and codes into a uniform and complete conformance with A3.0 to eliminate confusion in the very organization establishing a common base it is important for us to do the same. This is likened unto calling the work lead the ground. Calling GTAW Heli-Arc (especially when not using anything close to the original Heli-Arc process). And so many other examples.

I agree, AWS is not the all inclusive or exclusive final authority in ALL things welding. We also have BSMC, PMA, SME, IIW, and others. Most of whom are working with AWS to standardize many items and especially terminology.

We all understand the confusion that takes place when a firm in one country is reviewing plans from another country with differing codes as to the applicable weld/welding symbols.

I would have to side with Al that there needs to be a common basis and the consistent use of proper terminology to keep communications decent and in order. And, in this particular case, it needs to be AWS A3.0.

Having said that, there are a good many items that need inclusion and/or revisiting in A3.0. The technical inquiry process yields to that better in 3.0 than it does in D1.1 I am glad to say. On this forum we often come across items that could use some clarification. It would appear to be an item that as we come across one, one of the participants should offer to do so. It is not a difficult process but should not be assigned to just one person. Share the load. If it is your issue, take care of it.

I don't believe Al's overall intent was to limit all people to nothing but A3.0 regardless of all other circumstances. But, just as the contract documents include a listing of applicable standards and codes for a building contractor to adhere to, I believe we need a standard here and as most of the content revolves around the US and AWS standards and especially the D1 codes then it makes sense that the terminology standard be A3.0.

That makes even more sense when say Joey may come and ask a question about an item of interest in D1.1. We need to use A3.0 to describe what is being explained in D1.1 so that we are all on common ground. Now, if you asked us about some EN code, then we need to set A3.0 aside and go to the responsible party's terminology to make sure we are all discussing the same thing. For us to use our terms and defs to describe an EN code situation would be silly. BUT, it would behoove the two organizations to have as much in common as possible so that engineers, designers, fabricators, welders from around the world don't get confused on projects in various locations. Doesn't matter whose, just pick one and get it taken care of.

He Is In Control, Have a Great Day, Brent

By 803056

Date 02-16-2015 19:04 Edited 02-16-2015 19:08

The point I am trying to make is that there must be a common denominator or a "book" of terminology that defines the terms we use to make communication more effective. Effective, efficient communication is near impossible if there is no standard available to look up the meaning of a term. Failing to use standard terminology in our communications can result in meaningless babble. I believe there is a reference in the "Good Book" to something called the Tower of Babble. Without effective communication, all we say turns into meaningless babble.

The cause of insisting on proper terminology is all the more important in the international arena. Many countries use American standards to construct all sorts of welded structures and machines. As such and in consideration that this is a Forum hosted by the American Welding Society, it is all the more reasonable to use terminology that is understood by the majority of the participants. At the very least, using standard terminology allows a reader to look up a terms that in not understood.

I am amazed at how well many of our friends from other lands (where English is their second or third language) are able to communicate with us. However, without slighting our friends, I believe most of us can agree that it is confusing when nonstandard grammar and nonstandard terminology is used. How many times do we find ourselves asking the originator to repost with a better explanation of the question? That being said, participation of individuals from other lands makes the Forum all the more interesting for all of us. Notice I do not participate in a Spanish speaking forum or a Russian forum. I recognize my language limitations and I appreciate the efforts of our friends struggling with American English. My tip my hat to all of them. After all, I remember all too well my Spanish teacher told me that I would never learn to speak Spanish. She recognized my limitations.

Slang terminology is fine on the production floor where the workers may not know the proper terminology, but using slang or nonstandard terminology displays a lack of professionalism. In this Forum, where technical matters are discussed, it is all the more important to use standard terminology when possible. Most of us are professionals and as such, we should use proper terminology in our communiques.

Best regards - Al