I have tried to watch as many videos as possible, it's such a new machine, there's not a lot.
I think one of the biggest upsides and but I'm not sure how much I'll fully appreciate and can make use of is the MIG Pulse and Double Pulse on aluminum. I mainly run 4043 .047 wire on 1/8" to 1/4" thick stock with my Fronius.
On aluminum, Pulse-MIG is extremely valuable because it allows for much easier out-of-position welds compared to standard axial spray transfer. Double-Pulse can help control heat input because there is a period of low heat input at the base, can create "dimes" for aesthetics, but also produces some desirable effects:
- (1) A periodical welding current generates an oscillation of arc force and droplet pressure, which produces a weld pool stir effect.
- (2) Periodical heat input generates expansion and shrinkage of the weld pool, which causes an unusual remelting and resolidification of the previously solidified metal. DP-GMAW has an increased solidification growth rate and cooling rate compared with conventional pulsed welding at the same heat input.
- (3) Microstructural refinement of fusion metal by DP-GMAW is reported by several researchers. The mechanism of microstructural refinement is revealed as combined effect of the weld pool stir effect and an increased cooling rate. The numerical and experimental results indicate that a refined microstructure can be achieved by adjusting the pulsing parameters instead of changing the heat input. DP-GMAW features diverse grain orientation due to the expansion and shrinkage of the weld pool.
- (4) The weld pool stir effect improves the fluidity of liquid metal in the molten pool. Therefore, a larger number of hydrogen bubbles have a chance to float out and release from the molten pool, and fewer hydrogen bubbles are trapped in the solidification wall and form pores.
- (5) Improved solidification cracking susceptibility is achieved due to refined solidification structures by DP-GMAW.
Source:
Perspective on Double Pulsed Gas Metal Arc Welding, Applied Sciences Sept 2017.
Talking to Kemppi about their mig guns and aluminum liners and the HTP 2500, it should be able to handle pulse and double pulse for 4043 and .047 wire just fine..... I just don't have a good sense for how complicated to setup it up and use on that machine for the less experienced welder. I'm under the assumption that I'm left with setting the amps, wire speed, voltage, peak amp, background amp, frequency pulses per second and for double pulse the off time portion of the extra pulse.... that seems like a lot to dial in and get it right...a bit fear of the unknown.
I'm glad you mentioned this so I can hopefully clear it up. Pulse-MIG, while it shares some similarity with Pulse-TIG, is a completely different animal. In Pulse-
TIG, you
can simply turn it On, or turn it off; the ease of which is due to the fact that the tungsten rod is the electrode and is a non-consumable. Nothing else needs to happen other than the tungsten conducting the set currents at the set intervals/ratios.
In Pulse-MIG and Double-Pulse-MIG, you can't simply "add" pulse/DP to just
any wire alloy/diameter. Pulse-MIG operation (in general) is not simply the machine/welding current going "low to high to low, etc, etc" the way it is in TIG.
Pulse-MIG is a highly specific process due to the fact that the electrode is the filler metal and has to undergo momentary spray transfer (one-droplet-per-pulse (ODPP)), not just simply conduct high/low voltage/currents at user-set arbitrary intervals the way it is in TIG. ← So there is the hidden catch that many don't know about pulse-MIG. The machine's software has to be preprogrammed (non adjustable internally) with the correct amp-volt curves to assure that proper droplet detachment (ODPP) occurs during pulse-MIG operation, and this operation is wire alloy
and diameter specific. So going back to 0.047" ER4043: the reason the 2500 (and the other HTP Pro Pulse 200A MIGs) don't have neither pulse nor double-Pulse for 0.047" ER4043 is because the momentary peak pulse requirement for proper droplet detachment is more than much, much more than 400A! This is irrespective of the user's desired average amperage output; IOW to run 0.047" ER4043 at low overall levels in pulse, you still need to hit the momentary 400A+ peaks to get the
proper droplet detachment (← this is the key!), as it is an independent mechanism from the user's set wire-feed speed. Higher average welding amperages/WFS's simply causes the momentary peak pulses to occur more and more often (more droplets delivered). In the 2500 (and other HTP 200A MIGs), The power supply is only capable of ~300A for the momentary peaks, so given the fact that to have double-Pulse means you have to have single-pulse-MIG operation in the first place, it tells us that it's just not happening with this class of machine. On the other hand, the Pro Pulse 300 is a monster with a power supply capable of supplying momentary peaks of ~600A, and that is why it is capable of both single- and double-Pulse for a lot of common aluminum 0.047" wires.
Now for 0.035" ER4043 wire, since the 2500 is capable of proper single-pulse, you do get the added option of fully adjustable double-pulse. This (DP) operation is more akin to Pulse-TIG. Now that the wire is
already undergoing proper single-pulse operation, the user can vary the rate of this output by adjusting the pulse parameters that we are familiar with from TIG: welding amps/WFS, base amps/WFS, duty cycle, and PPS (frequency). So here is where the machine is taking care of the single-pulse ODPP mechanism behind the scenes, and then the user sets up the overlay-ed pulse parameters
Hopefully this makes sense.