Showing posts with label Aftek. Show all posts
Showing posts with label Aftek. Show all posts

New AFTEK-EHS Heavy Duty Air-Arc Gouging Power Supply Brochure

Air-Arc Gouging

Air arc gouging uses a generated electric arc to melt metal between the tip of a carbon electrode and the workpiece. High velocity air is shot down the electrode to blow the molten metal away, leaving a clean gouge. Gouging works on any conductive metal, including stainless steel, mild steel, copper, and aluminum. Typical applications include removal of surface and internal defects, removal of excess metal around welds, and edge preparation before welding.

Download the AFTEK-EHS Heavy Duty Air-Arc Gouging Power Supply Brochure here.

AFTEK-EHS Shows Quad Arc Welder at International Workboat Show 2017

AFTEK-EHS booth at Workboat Show with Quad Arc Welder
AFTEK-EHS booth at Workboat Show with Quad Arc Welder.
AFTEK-EHS (a division of Hotfoil-EHS) just finished a very successful exhibit at the International Workboat Show (the show ran from Nov. 29 - Dec. 1). The International Workboat Show is a trade-only conference and expo for commercial vessel owners, operators and builders as well as the vendors and suppliers that serve them. AFTEK-EHS featured of their most unique and popular products, the Quad Arc Welder. 

The Quad Arc Welder is designed for heavy arc welding and engineered for low maintenance in harsh environments. It is simple to operate and reduces space by combining 4 welders in one package. It is protected with thermostatically controlled alarms on both its rectifiers & transformers.  Dimensions are 51" wide x 40" deep x 57" tall. The Quad Arc is a perfect choice for many of the attending vessel builders, owners, and operators.

For more information, contact Hotfoil-EHS by calling 609.588.0900 or by visiting https://www.hotfoiehs.com.

Resistor Controlled Welding Machines

resistor controlled welding machines
Resistor controlled welding machines by AFTEK.
Resistor control has been used in multi-operating welding systems in shipyards and heavy construction for decades. In the heyday of nuclear power plant construction in the USA, nearly all were built using multiple-operator systems. From the thirties until about 1990, nearly all multiple-operator systems were the designed similarly. They used a large bulk power supply with “grids” connected by cables to form a system of distributed power. This system minimized the use of high voltage primary power, distributing 75-80 volts of secondary voltage instead.

As these systems grew in popularity, the concept of “packs” became popular. These packs provided 2, 4, 8, and 16 arcs in a steel rack, and all being connected to a separate power supply. A now defunct company named Big Four developed the concept of connecting multiple-operator systems in a loop arrangement, which resulted in greatly improved voltage stability. In 1990, this loop concept was further refined into integrated, modular welding packages. These newly designed systems provided an internal power supply sufficiently sized to provide power to all the arcs without any interference.

Loop systems are still being used today. They are viewed as a very economical welding alternative. For example, for a loop that needs twenty MIG arcs, it is possible to use (4) 500-amp power supplies connected to a single 500 MCM cable which circles the work space. Twenty control modules can be connected wherever needed on the closed loop of cable. A huge cost savings is realized in having to establish just four (4) primary connections instead of twenty (20).

Most conventional arc weld­ers use a transformer-like device called a reactor to control the "heat" of the welding arc. If you examine the Voltage/Amperage (V/A) curve for a con­ventional constant current (or constant voltage) welding power supply, you’ll see spikes. This is inherent in the design of conventional arc weld­ers. The V/A curve of a resistor controlled arc welder, on the other hand, is a straight line.

Resistor controlled arc systems provide more consistency of power - if you shorten the arc, thus lowering the arc voltage, the current will increase, and maintain virtually the same power (heat). If you lengthen the arc, you raise the voltage, but the power remains virtually constant. Why is this important? In any welding process, increasing the amperage increases penetration and increasing the voltage widens and flattens the head (and reduces penetration). With a resistor controlled arc, if you are welding along the seam and it closes, shortening the arc length will increase penetration. If the weld opens, lengthening the arc will lessen the penetration and widen the weld. This provides excellent control right in the electrode holder.

AFTek, a US manufacturer located in Chattanooga, TN and division of Hotfoil-EHS, is the sole remaining manufacturer of resistor controlled welding machines in the USA. Their resistance welders are an acknowledgement of the superior design Big Four developed years ago, while improving performance with edge-wound coils for better heat dissipation (thus better current control) and rotary switches for current selection, even under load.

Demand Pulse Welding: A Brief History

Demand Pulse Welder
Demand Pulse Welder
One of the oldest welding technologies still in use today is resistor controlled arc welding. The technology is old, but when combined with more modern controls, provides exceptionally high quality performance. Resistor controlled arc welding incorporates edge-wound resistors using a special current-controlling alloy.

From the 1930’s until 1990, nearly all Multiple Operator Systems were the same general layout – a big bulk power supply, with “grids” connected by means of cable to form a system of distributed power. Originally designed for use in shipyards, this system minimized the use of high voltage primary power, distributing 75-80 volts of secondary voltage instead.

Historically, the most common application of resistor controls has been in Multiple Operator Welding Systems, widely used in shipyards and heavy construction. Nearly all the Nuclear Electric Power Plants were built using Multiple Operator Systems.

Big Four Manufacturing Company of Saint Louis, Missouri, pioneered the concept of connecting Multiple Operator systems in a complete loop configuration. This LOOP concept greatly improved the voltage stability of  Multiple Operator systems, because with all the power connected to a single circuit, voltage drops were reduced or eliminated due to the nature of a DC circuit. In 1977, Big 4 Manufacturing introduced their innovative and very successful Series 77 Control.

After the Three Mile Island incident and the subsequent slowing of the Nuclear Power Industry, Big 4 decided it was in their best interest to expand into the general fabricating, refinery and petro-chemical markets. Their popular soft arc was great for most welding, but was inadequate on pipe root passes with 5P, then the most common method use for oil related pipe. To provide an arc better suited for pipeline, Big 4 devised a circuit to make their resistor grid “think” it was a Lincoln generator. They called this new system “Arc Ram”. Arc Ram worked beautifully with 5P and similar electrodes and led to the design of a MIG system which they called  Demand Pulse.

Not to be confused with ...

"Short-circuiting Metal Transfer" (Short Arc) welding was introduced by Linde in the late fifties for welding sheet metal. During the 1960s, short-arc became widely used, sometimes for the wrong applications. When using short-arc the wire can contact the molten weld pool resulting many times with the weld not fusing to the base metal. This is called a "cold lap". Cold lap associated with Short Arc became a reason why many welding shops won’t use “wire” welding processes on pressure welds. Unfortunately, mis-used Short Arc welding gave ALL GMAW welding on pressure welds a bad name.

Demand Pulse to the Rescue

Demand Pulse rarely extinguishes the arc. Metal transfers through the arc, and the arc’s are much shorter than those from Pulse Spray. The transfer occurs above the molten pool, so spatter doesn't explode from the puddle. It is a "constant current" process. The operator selects a base current, similar to some GMAW Pulse Spray applications, adjusts the wire feed speed to give the correct voltage, and begins to weld. Lower voltage will cause the puddle to freeze faster, higher voltage will cause the puddle to be more fluid.

In short arc, a current pulse is triggered by the short-circuit condition caused by the wire driving into the work piece. Demand Pulse forces the transfer to occur before short-circuit, at a voltage selected by the operator, above the weld pool. This has two important effects: the arc does not extinguish and the spatter level is greatly reduced because the molten tip of the wire does not contact the weld pool. Because the arc is not extinguished, cold laps are virtually eliminated.

Many reference books describe short arc as a "random pulse" method of welding. Random in the sense that the pulse is triggered as a function of wire feed speed. The faster the wire feed speed, the faster the short circuits (pulses). Demand Pulse is exactly the same, except it does not short!

This blog post was abstracted from a 2004 press release from Aftek Welders, the only remaining company providing resistor controlled welding machines, and parts supplier for all Multiple Operating Systems. You can read the full version of  "AFTEK – the Best Welders you never heard of…” here.

Air Carbon-arc Gouging: A Fast and Efficient Way to Get Rid of Metal

Air Carbon-arc GougingIn metal working maintenance and repair, it is sometimes required to repair or replace a weld, or remove excess metal from a worn or defective part. A process called air carbon-arc (also known as air arc) gouging, developed in the 1940’s, has become a widely accepted method for metal working. Compared to grinding, chipping, and cutting, air arc gouging provides a much faster, more efficient, and more cost-effective means to remove unwanted metal.

Air carbon-arc gouging differs significantly from oxy-fuel cutting (OFC) and plasma cutting. Air carbon-arc does not require oxidation to maintain the cut and is able to be used on many kinds of metal. Air carbon-arc gouging cuts and removes metal by an electric arc created a carbon or graphite electrode as it is drawn along the target metal. As the arc melts the target metal, a steady, high velocity air stream blows the molten material out of the way. The arc is supported by a constant current power source. A compressed 60 to 100 psi gas source supplies the air stream. A special air arc torch is required, as it not only holds the electrodes, but has unidirectional air ports built in to direct the air stream.

Air carbon-arc gouging will work on any material that will conduct electricity and which can be melted by the electric arc, such as carbon steel, stainless steel, cast irons, and many copper alloys. Metal removal rate is controlled by increasing the gouger’s amperage, slowing down the movement of the electrode, and by the efficiency of the air stream. Most common uses for air arc gouging are cutting, removal of defective welds, removal of bolts, removal of rivets, making holes, and casting finishing.

If you have any questions about air carbon-arc gougers, contact:

AFTEK-EHS Welders
6121 Airways Blvd.
Chattanooga, TN 37421
Phone # 423.424.0515
Fax # 423.424.0518

Multi-Operator Welding Systems

Aftek Quad Arc
Multi-operator welding system (Aftek Quad Arc 1200)
There are many different welding processes utilized in the welding industry today. Welding processes include stick arc welding, gas tungsten arc welding (GTAW), flux core arc welding (FCAW), shielded metal arc welding (SMAW), gas metal arc welding (GMAW), and air carbon arc gouging.

Most arc welding operations are performed using direct current from a DC power source an AC power source which has been rectified from AC to DC. Many industries use these welding processes in a wide variety of environments including factories, construction sites, power plant construction, boiler construction and repair, and shipyards.

Multiple operator welding equipment was developed to allow several welding modules to operate from a single common power supply. The power supply typically includes a transformer and rectifier to step down the supply voltage, and then convert the power from AC to DC.

Multi-station welding systems afford a number of advantages the principals of which are a lower initial capital cost, a much lower cost of installation, much lower maintenance cost and less power requirements as compared with single operator equipment. Multi-operator welding systems are practical and efficient as they provide a welding station where each welder has the ability to work. They provide for multiple simultaneous welding projects where workers can work efficiently and meet production deadlines.

The clear advantages of multi-operator welders:

  • Improved productivity
  • Lower total cost of ownership
  • Less equipment to transport
  • Reduced maintenance costs
  • Noise reduction

Aftek at CastExpo 2016

The single largest trade show and exposition for metalcasting in the Americas, CastExpo, is being held in the Minneapolis Convention Center April 16 through the 19th, 2016.

Held every three years, CastExpo offers metalcasters, suppliers, and casting buyers and designers the opportunity to connect and educate themselves on the latest metalcasting has to offer.

Aftek Quad Arc Welder
Aftek Quad Arc Welder
The Metalcasting Congress technical program and additional workshops cover a wide range of topics. Identify which specific technical presentations and workshops you would attend that is relevant to your company and its immediate and future challenges.

Aftek (Division of Hotfoil-EHS) will be attending displaying their Quad Arc heavy duty arc welder, Quad Arc are:
designed for low maintenance in harsh environments. Features of the
  • Submerged arc.
  • Air arc gouging to ½” electrodes.
  • FCAW (flux core MIG) all positions, self or gas shielded.
  • Performing outstanding results on stainless, or steel castings.
  • Power sources, rated for 100% duty cycle. Amperage range adjustable in 5 amp increments.
  • Designed with Harsh Environment in mind.
  • Designed with a single transformer on the MV1500G1.
  • Powder Coated for a long lasting durable paint job.
  • Protected with thermostatically controlled alarms on the rectifiers and the transformers.
  • Designed to shut down if any of the Alarms are Energized.
  • Easy-to-reset overload breaker for circuit protection.
  • Optional protection for incoming Primary Power.
  • Dimensions 51” Wide x 40” Deep x 57” Tall.
If you're planning to attend CastExpo this year, please plan on stopping by Booth 1346 and visit. 

Transformer Basics

Electric transformer
(courtesy of Aftek EHS)
Transformers are composed of an iron core ring wrapped in coils. One coil is connected to an AC input voltage and is called the primary coil. The other coil is connected to an output circuit with the load resistance, and is called the secondary coil.

The two coils are well insulated from each other and do not form a physical electrical connection. This gives a transformer its unique electricity altering properties. Transformers can either step up or step down a voltage.

In a step down transformer, the number turns in the primary coil is greater than the number of turns in the secondary coil step up transformer the number of turns in the secondary coil is greater than the number of turns in the primary coil. The constantly changing current driven by an alternating voltage source induces a changing magnetic field in the core of the transformer.

The magnetic field created by the alternating current in the primary coil generates the flux in the transformer core. The secondary coil converts the flux back into current flow and produces a voltage at the load, or resistance, in the secondary circuit.

If there are fewer coil turns on the secondary then on the primary, this is called a step down transformer. The resulting voltage in the secondary circuit will be less than the primary.

In this example we have 20 turns on the primary coil and 10 turns on the secondary coil. To determine the decrease in voltage occurring in this step down transformer, we can use a simple ratio formula. This formula simply states that the secondary voltage to primary voltage ratio, is the same as the secondary coil to primary coil turn ratio. Rearranging the formula and then dividing 10 turns by 20 turns, we get .5 multiplied by 120 V. This results in a calculated step down voltage of sixty volts.

Demand Pulse MIG Welding

Demand Pulse MIG Welder
Demand Pulse MIG Welder
(courtesy of Aftek-EHS)

Demand Pulse is possible because of the MOSFET, an extremely fast electronic switch. Using constant current DC power, a wire is fed into the arc zone. As the wire approaches the work, the voltage drops as a function of the arc length. At a pre-selected arc voltage (usually 15 volts), the MOSFET fire a pulse of current to expel the tip of the wire across the arc gap. This current is supplied by means of a parallel resistor in the main current control circuit and is generally 100 amps. Switching time is measured in nanoseconds, and the total cycle time is very short, perhaps 15 nanoseconds. An inductor is not required, nor desired, since fast switching is essential. Perfectly tuned, the pulse cycles 200 times per second or slightly less.

The arc looks and sounds like “short-arc”, but a close look will show that there is no short-circuit. The arc length is from .020” to .090”, very short compared to GMAW-P done with conventional machines. This short arc length, combined with the short duration of the pulse, and the low current required to effect transfer gives a total arc “heat” far below that of either short-circuit transfer, or conventional GMAW-P. Fusion is excellent, because the arc never goes “out”.

Below is a demo video using this technology on 18 gauge stainless steel, without any burn through.

For more information contact:

2960 East State Street Ext.
Hamilton, NJ 08619
Phone # 609.588.0900
Fax # 609.588.8333
Email: dap@hotfoilehs.com