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Press spot welders

Press style welders are going to be your most versatile type of resistance welder. It’s the workhorse of the industry. The main thing to understand about Press style welders (and how they differ from Rocker Arm style welders) is that the upper ram comes down in a linear fashion. This is unlike a Rocker Arm style welder, whose welding electrodes effectively rotate into place.

Some instances where a Press style welder really come into play are when:

• Welding studs or weld nuts
• High electrode force applications
• Projection welding
• Using special tooling to fixture a part
• Frequent tooling change-overs are necessary

Projection style spot welders

The main difference with the Press welders vs the Projection style welders is the lower knee. A spot welder traditionally has a round lower arm, whereas a projection welder has a box-construction lower knee for mounting tooling and fixturing. It is common to mount t-slot platens to a projection welder to enable quick change-over of tools. Ever seen t-slot platens on a vertical mill or a drill press? This suits the same purpose.

If weld arms are used on platens, they need to be square so that they can mount onto a flat surface. Projection welders without platens typically have square arms as well.

A “Projection Welder” is so named because many metal stampings will use weld “projections” on the part to enable multiple welds at once, or to ensure a quality weld. To weld multiple welds at a time typically takes more weld force than a traditional spot weld, so a more robust frame is required to prevent flex with the higher forces.

Combination Press/Projection spot welders

A Combination Press/Projection typically has a lower box-construction knee that holds a round lower arm. Some Combination Press/Projection welders have both platens and round weld arms, for greatest adaptability.

Rocker Arm spot welders

Rocker arm welders, due to their construction, tend to be the most economical style of spot welder. For this reason, they are also extremely common. Aptly named, the upper arm of a rocker-arm style welder will pivot into place, with the electrode following an arc, essentially “rocking” the upper arm until the electrodes touch.

One advantage of a rocker arm machine is the ability to rapidly change over the throat depth of the machine by simply changing arm lengths. This can be beneficial for a job-shop who one day may need to weld thin-gage pipe at 36″, but the next day needs to weld heavy-gage material and can use a shorter throat depth.

Another thing to note about rocker arm spot welders is that, as you change the throat depth, you also change the amount of electrode force the machine is capable of producing.

Of course, as is the case with any spot welder, as you increase the throat of the machine or the welding gap, you are decreasing the maximum current capability of the machine.

Seam welders

Broadly speaking, a seam welder will use two copper wheels that are motor driven. The copper wheels roll against one another. When steel (or other sheet metal) is placed between the two wheels while they’re rolling and current is applied to the copper wheels (at a prespecified force), a “continuous” weld will occur. (Welding current is usually pulsed, but the end result is ideally a hermetic seal).

Knurlers are often used for welding coated materials such as galvanized, aluminized, and galvanneal. A knurled wheel will ride along the outside edge of the wheel(s), tangentially, and effectively “clean” the welding surface while the wheels are turning. Sometimes the knurled wheels actually drive the seam wheels.

A Circumferential Resistance Seam Welder welds from left-to-right (or vice-versa, depending on the direction of the motor).

A Longitudinal Resistance Seam Welder welds “in and out” of the machine, from the operator’s perspective, standing in front of the machine. Again, depending on the configuration of the machine, you can either weld with the material coming out of the machine or with the material going in.

Rapid-Fire seam welding is using a modified spot welder to perform multiple spot welds in a row, overlapping each other slightly, to make a seam. This can be done rapidly, but is not as fast or easy to use as a traditional seam welder.

“Butt” welders

Butt welders are used to join two ends of a profile together. Solid wire, square/round/rectangular/hex/other shaped rod, tubing sections, and more can be butt welded together. Drill rod extensions, saw blades, and wire fed forming machines all use butt welders in their process.

Some other welder styles

• Bench top welder
• “Dot” welder
• Flash-butt welder
• Heavy duty welder
• Dual head welder
• Manual weld gun
• Servo weld gun
• Micro welder
• Economy welder
• Capacitive Discharge welder
• Multi-gun “pass-through” welder
• Mid-Frequency Direct Current (MFDC) Inverter welder
• Frequency Converter (Sciaky)