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Up Topic Welding Industry / Technical Discussions / D1.1 Table 3.8 clarification: Change in wire feed speed...
- - By Bowler_Hat (**) Date 02-26-2016 13:00
Hey All,

When D1.1 states:

" Table 3.8 Prequalified WPS Variable Process Parameters 13) A change in wire feed speed (if not amperage controlled)"

Am I correct in reading that a Constant Voltage welder does not need to apply the rule of +/- 10% to the Wire Feed Speed because it controlls the wire feed speed?

I know a large number of machines allow an operator to choose between WFS and Amperage. So long as the operator is setting the Amperage in a CV machine they WFS is out of their control right?

Thanks!
Parent - - By Lawrence (*****) Date 02-26-2016 13:58
With CV (Constant voltage) GMAW or FCAW or SAW

When WFS increases Amperage increases.

When WFS decreases Amperage decreases

For example:  our WPS's list both current and WFS ranges we desire, with an asterisk on the current*  and an associated note saying: "*Current is not set by welder and is approximate".

Current will also vary with stick-out (CTWD) so with CV is always approximate.. Therefore always best to provide a range.
This one says *"WFS is not set by the operator and is approximate"

There are some CC (constant current) operations that actually vary the WFS to maintain amperage.  We do this on some AC SAW procedures... It is only possible because the SAW head is mechanized and the CTWD is relatively constant.
Parent - - By Bowler_Hat (**) Date 02-26-2016 15:03
My concern here is I'm building a Pre-Qualified WPS for a batch of Flux core, and the ranges for everything except for Wire Feed Speed match up with the manufacturers recommendations.

Which means I need a separate WPS for each 20% (Plus and minus here) for the wire speed. If I went by the voltage, amperage I can have the applicable ranges covered in two WPSs, with the need of WFS, that now takes... four.

But...now the question is as per 3.6 Limitation of WPS Variables "...The weldign parameters set forth in Table 3.8 shall be specified on the written WPS, and for variables with limits, within the range shown. Changes to the essential variables beyond those permitted by Table 3.8 shall require a new or revised prequalified WPS, or shall require that the WPS be qualified by test in accordance with Clause 4.

I believe 'revised' would include the detailing of multiple means of how to perform the weld. ALL (Root, fill cap)  can be welded using settings  X X and X. or ALL can be welded using settings Y Y Y, or ALL can be welded using settings Z Z Z, or ALL can be welded using settings Q Q Q." ?

Correct me if I'm wrong with that intention.

That is a good note to include, thank you for that suggestion! And thanks for your help on this topic!

Cheers!
Parent - - By Lawrence (*****) Date 02-26-2016 16:05 Edited 02-26-2016 16:08
The WFS ranges don't match with the manufacturers recommendations...???

That is curious.

I wonder if you could "make them match" by some tweaking of CTWD, meaning; adjust slightly the distance your contact tube is recessed into your nozzle (assuming gas shielded FCAW) or by slight modification of operator technique, and run a few trials...

Small changes in the distance from the contact tube to the work (even within limits) can make a huge difference in current output for any given wire feed speed.

For example:  a 1/4" difference in CTWD in a 280 amp. (typical) .052 solid wire GMAW weld made at 350 IPM can be as much as 50 amps.  Meaning: if you watch a live weld at a given WFS and are recording current, it will swing pretty widely depending on CTWD changes.

Matching Amps to what you "expect" to see for a given WFS might be a matter of operator technique (keeping the gun a little closer or further... Or a small change in consumable configuration at the gun.

Just a thought that might save some extra paperwork.... *IF* I'm understanding your questions.
Parent - By Bowler_Hat (**) Date 02-26-2016 17:33
Clarification here, I'm working with Ultracore 71A74 Dual (I enjoy it greatly...nice and smooth)

It one ches out the wire certificate/details you'll see that the wire feed speed is in stages (All position)

125
175
200
225
250

so..+/- 10% at a time...to cover that entire range would take....

125-152
125-185
189-226
205-250 (There's overlap with this last one)

Where as for suggest amps, detailed in stages:

195
215
235
265
285

Which  using the +/- 10% for amperage one can cover that bridge with

195-238
234-285 (Overlap here as well)

Same with Voltage, the stages are listed as
20-25
21-26
22-27
23-28
24-29

With the +/- 15% on voltage that allows one to cover the range with:
20-27
22-29

http://www.lincolnelectric.com/assets/global/Products/Consumable_Flux-CoredWires-Gas-Shielded-UltraCore-UltraCore71A75Dual/c3128.pdf

OR...am I bound to the limits set for each line (one value of wire feed speed, and one value of amperage)

Thanks for taking the time to challenge this one. As far as I know, CTWD is not required in table 3.8. Thoughts?
Up Topic Welding Industry / Technical Discussions / D1.1 Table 3.8 clarification: Change in wire feed speed...

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