- For the Last 20 Years…2018-04-03
By Mike Sammons, TIG Product Manager ― Miller Electric Mfg. Co.
Q: I’ve heard that inverters let me adjust the arc to stay in the electrode negative mode for up to 90% of the AC cycle. Can this really improve my travel speed?
A: Absolutely. You can increase travel speed, get better penetration or both because inverters let you direct about 25% more heat into the weldment in the same
amount of time. When welding at 100 amps, an inverter like the Dynasty? DX essentially gives you 125 amps of welding power.
Q: Why do inverters have an “adjustable output frequency” function?
A: Increasing the output frequency (which conventional machines cannot do) creates a tighter and more focused arc cone, directing the heat into a smaller area.
In fact, you can get better penetration and reduce the size of the weld profile. This may let you increase travel speed, use less filler metal and reduce or eliminate
pre-heating, pre-weld beveling and post-weld grinding.
Q: I don’t have much room in theSHOP, and my incoming power is at capacity. Would an inverter be a good solution?
A: Yes. For example, the Dynasty DX has a footprint of 17 in. x 12.5 in. x 24 in. and weighs only 90 lb. Even better, it draws just 26.3 amps of 230 V three-phase
primary power to create a 250 amp Squarewave output. A conventional Squarewave machine, which only accepts single-phase power, draws 92 amps on the primary side.
In 1974, Miller Electric invented and patented the Squarewave? AC output and balance control function found on their Syncrowave? series of TIG welders. Squarewave technology
made the transition through the zero amperage range faster than a regular sine wave, which improved arc starts and created a more stable arc. With balance control, the operator
could change the duration of the AC half cycle, adjusting the electrode negative (EN) from 45 to 68%.
Now Miller introduces the next generation of technology with their new AC TIG inverter, which features three advanced Squarewave capabilities. First, it produces incredibly smooth,
stable arcs because the Squarewave is driven through the zero point thousands of times faster than a rectifier-based welder. Miller’s Dynasty? DX is so fast that its built-in high-frequency
capabilities are used for arc starting only.
Second, inverter-based welders extend EN balance control. The Dynasty DX lets operators fine-tune duration times from 50 to 90%. Making the EN portion of the cycle last longer:Achieves greater penetration.Narrows the weld bead.May increase travel speeds up to 20%.May permit using a smaller diameter tungsten to more precisely direct the heat or make a narrower weld bead.Reduces the size of the etched zone for improved cosmetics.
Less EN time produces greater cleaning action to remove heavier oxidation, lessens penetration for work on thin materials and widens the bead profile.
Third, inverter-based welders let operators adjust the welding output frequency, from 20 to 250 Hz in the case of the Dynasty DX. Conventional welders have a fixed output of 60 Hz.
Lowering the frequency produces a broader arc cone, which widens the weld bead profile and better removes impurities from the surface of the metal. Increasing frequency above 60 Hz produces a tight,
focused arc cone. This drives more heat into the weldment for better penetration, and it narrows the weld bead, which helps when welding in corners, on root passes and fillet welds.
Note that when AC TIG welding with an inverter, the operator should treat the tungsten as if the weld were being made in the DC mode: select a 2%-type tungsten (thorium, cerium, etc.) and grind the electrode to a point.
Electricity likes to come off a point, which further improves controlling the weld puddle. For example, a skilled welder can make a 1/8 in. fillet weld
- Burnback Wire Stubbing Porosity2018-04-02
David Almy, Welding Engineer ― Miller Electric Mfg. Co.
Q: I have gas flow from the gun, but not a clean weld. How can I solve this?
A: Porosity and black welds indicate poor gas coverage or contamination.
To ensure good coverage, check for: proper gas flow (CFH), leaks in the system (loose fittings,
cuts in the gas hose, worn O-rings) and excessive spatter in the nozzle. Make sure the contact tip
is recessed about 1/8″ in the nozzle. To ensure 100% coverage and prevent contamination,
Miller designed a unique gas delivery system for its XR-Edge? gooseneck gun. It even sends gas through the contact tip with the wire.
This enhances the cleaning action and reduces porosity and post-weld clean-up.
Q: What causes aluminum wire to burn back to the contact tip?
A: 90% of “burnbacks” result from poor arc starts caused by incorrect run-in speed, not tuning the wire feeder to the power source
and poor electrical continuity between the wire and contact tip. (Note that the patent pending XR-Edge gun design helps eliminate poor electrical pick-up.)
Q: How can I prevent birdnesting?
A: Soft aluminum wire is prone to buckling, so using a larger diameter may help. Better yet, invest in a push-pull feeder. In such systems,
a torque motor at the wire spool steadily feeds the wire while a drive motor located in the gun precisely controls wire speed at the arc. This maintains
constant tension, so the wire feeds consistently, even when the cable is looped, and at distances up to 50 ft. The XR-Edge torque motor features a high and
a low torque setting, letting you adjust performance, respectively, for larger or smaller diameter wires.
The inherent properties of aluminum make it prone to poor MIG arc starts. For example, aluminum wire requires a lot of current to initiate the arc, yet the
wire melts very quickly once the arc starts. It requires a fast wire feed speed, but any oxide on the weldment delays arc initiation because it melts at a much higher
temperature. Thus, the solution to arc starting problems often involves fine-tuning the speed at which the wire approaches the weldment.
Assuming you have a “push-pull” style wire feeder, start by finding the run-in speed control. This sets the wire feed speed from the time you pull the gun trigger until arc
initiation (after sensing an arc, the machine switches to welding speed). Because run-in speed is generally slower than welding speed, the arc has more time to establish itself.
If you experience wire stubbing, use a slower run-in speed.
Always adjust run-in speed first. For additional fine-tuning, Miller incorporated a unique feature in its XR-Edge? push-pull feeder that adjusts how long the wire drive motors
take to ramp up to full speed. This “motor ramp control” can help tune the wire feeder to better match a welding power source’s arc starting characteristics. To prevent long,
flaring arc starts or wire burning back to the contact tip, increase ramp control. For example, ramp control is factory-set at maximum speed to match Miller’s fast-responding Invision? 354MP inverter.
Slower ramp speeds have benefited users who pair the XR-Edge with magnetic amplifier-type CV welders or CC machines for running larger wires.
Smooth Groove, Smoother Performance
The soft nature of aluminum wire leads to feeding problems. For example, when the wire slips through the drive rolls, burnbacks and arc stumbling often result. Don’t over-tension the drive rolls
or use knurled drive rolls as a “solution.” This inevitably deforms and defaces the wire, producing shavings. These wire particles then build up in the drive roll grooves, cable liner and contact tip.
Ironically, this also causes burnbacks and arc stubbing. Inst
- Applications Engineering Q & A2018-04-02
Q: I would like to do gas metal arc welding on steel and aluminum, using a small engine drive.
I am thinking about adding gas tungsten arc welding at a later date. However, I don’t want to spend the money for a Trailblazer 251 NT.
What is the least expensive way for me to go?
A: As you can see in the information below, the Trailblazer 251 NT is actually the more efficient buy in this case.
For only $34 more than a Bobcat 225 NT package, you can have a 3-phase vs. single phase arc, 20 HP engine vs. 16 or 18 HP, and 25 more amps of welding power.
And there are other advantages as well over the Bobcat 225 NT:Trailblazer can do short circuit transfer with small wires, and has adjustable stabilizer to fine-tune the arcTrailblazer has a built-in contactorTrailblazer has remote control for MIG or TIGTrailblazer uses the same interconnecting control cable for all processes, so there is no need for special cables for each process.
As you can see, there is a big advantage to looking at all the factors, before determining the bottom line on a purchase!
Information courtesy of Miller Electric
- Aluminations - Shedding light on aluminum welding issues2018-04-02
Frequency, or Hz, is the number of times the AC TIG arc switches between electrode negative and electrode positive in one second. Miller’s Dynasty? 300 DX inverter-based TIG power source permits adjusting output frequency from 20 to 250 Hz. Conventional TIG machines have a frequency fixed to that of the 60 Hz primary power.
Increasing the frequency narrows the shape of the arc cone and increases the arc force. This stabilizes the arc, reduces arc wandering and provides excellent directional control over the arc. On lap and T-joints, using a higher frequency lets you establish the weld puddle exactly at the root. This can ensure good penetration, control bead width and minimize the etched zone. With a 60 Hz output on fillet welds, the wider arc dances from plate to plate. The puddle starts at the toes of the weld and flows toward the center. On some joints, you’re almost compelled to over-weld to ensure penetration at the root.
Read aluminations TIG articles (download pdf files):
- When you control the shape of an AC TIG weld bead, you control profitability.
- How to TIG weld thin aluminum, adjust balance control and determine amperagerequirements.
- See if an inverter-based AC/DC TIG machine that incorporates advanced Squarewave technology can improve your operation.
Information courtesy of Miller Electric
- MIG Welding Q & A2018-04-02
Q: What are the advantages of MIG welding?
A: It’s easy to learn how to MIG weld with a little practice, even a first-time user can achieve a good-looking weldMIG welding is a much faster process than Stick weldingThe operating cost of MIG welding is lower than Stick welding because of the time savings, and because there’s virtually
no waste of filler metals (50 lbs. of MIG welding wire yields approximately 49 lbs. of deposition, as compared to Stick welding
where as much as 25% of each electrode is discarded as stubs.)In general, thinner materials can be welded more easily with MIG versus Stick welding MIG welding is a clean process and does not require chipping slag off the weld as in Stick welding.
Q: What are the disadvantages of MIG welding?
A:Initially, it costs more to set up a MIG system than a Stick welder, because of regulators and shielding gas
(some MIG welding is done with self-shielding flux core which does not require gas or a regulator)Strictly looking at dollar per amp, Stick welding is cheaper
Q: What types of material can be welded with MIG machines?
A: Virtually all types of material can be welded with a MIG machine. However, in the MIG process different materials
require different wire and gases. For instance mild steel can be welded with either self-shielded wire, (which does not require
separate shielding gas) or with CO2 or a CO2 mixed gas. Aluminum material requires the use of Argon gas.
Q: What material thicknesses can a MIG machine weld in a single pass?
A: Typically, less amperage is required to weld thinner material and more amperage is required to weld thicker material.
A general rule-of-thumb is, one ampere for every .001″ of metal thickness. For example, 10 gauge (or 1/8″) material equates to .125
decimals or 125 amps.
Q: Can MIG machines weld through dirty materials?
A: It’s always advisable to weld on the cleanest possible material, so for best results scrape off paint, rust or other debris where the weld is being made.
Self-shielding wires will help in poor conditions.
Q: What types of projects can I weld with a MIG machine?
A: MIG welding is great for a variety of applications, including:Trailer hitchesAuto body repair and restorationFarm/ranch equipmentHobby or household projectsRepair of wheel barrows, bicycles, etc. The key is to make sure you match the metal thickness of the item to be welded with recommended amperage output.
Information courtesy of Miller Electric