I like the information contained in all the responses, but I thought I would toss in my two cents worth.

Pulse spray transfer is a marriage between short circuiting transfer and spray transfer. Short circuiting transfer is a low heat input process that provides the ability to weld in all positions, but is prone to fusion type defects. Spray transfer is a high heat input welding process that provides excellent fusion, but the fluid weld puddle limits the process to flat grooves and flat and horizontal fillets.

Pulse spray transfer uses "background" welding parameters that are in the range that produces short circuiting transfer whereas the "peak" welding parameters produce a spray transfer. The short circuiting portion of the welding cycle, i.e., the back ground parameters, maintain the arc, but there is little or no transfer of filler metal to the weld puddle and it provides minimal heat input. The spray transfer portion of the welding cycle, i.e., peak welding parameters, is that portion of the welding cycle where the amperage and possibly voltage increases to produce a spray transfer where the weld puddle is larger, more fluid, and electrode material is transferred across the arc and deposited in the puddle. The short circuiting portion of the cycle allows the puddle to cool, whereas the spray portion of the cycle increases penetration and puddle fluidity.

The frequency is the term used to describe how often the machine is in the "peak" mode, i.e., spray transfer is produced, per second. When the machine isn't in the peak mode, it is in the background mode during which short circuiting conditions are maintained. Duration is the term used to describe how long the machine is in the spray mode, or the width (time) of the peak conditions. This produces "pulses" of high heat input. The greater the frequency and duration, the higher the heat input.

Controlling the frequency and duration allows the welder to control the heat input. High heat input for thicker materials, low heat input for thin materials. This provides the welder greater control when welding both thick or thin materials in all welding positions while obtaining good fusion and penetration.

The attached sketch shows simplified examples of how the heat input can be varied by changing the pulsing parameter - amperage and slope. Other welding parameters are ignored for the sake of simplicity. The possibilities are endless and therein lies the problem, the welder has to understand the interrelationship of amperage, voltage, inductance, slope, etc. in order to fully appreciate the machine's capabilities. A change in any one parameter has a dynamic affect on the others, i.e., you change one parameter and all the others change as well. 

To add to the confusion, not all manufacturer's use the same terminology. After all, marketing's job it to differentiate their product from the competition's. Marketeers do little to clarify the situation, they simple cloud the situation by using nonstandard terminology and making up their own terms to suit their needs.

In an effort to simplify the set up of the "pulsers", manufacturers have developed "canned" programs that set most of the welding parameters for the welder. Those parameters the welder does control have limited ranges to ensure the machine produces a stable welding arc. The welder simply dials in the base metal type, the thickness, electrode diameter, and possibly the shielding gas. The machine's canned computer program sets the parameters for the welder. The welder simply adjusts a single knob to produce an arc that suits their taste.

Best regards - Al

It's a good point Cliff.

All makers of GMAWP power supplies on the market today get where they are going with pulsation differently. As a matter of fact different powersupplies within the same company go about it differently...  This is one reason I linked both Miller and Lincoln data.. Assuming that he was operating one or the other.

On top of that... GMAWP Technology has changed from year to year... Nobody in the U.S. made a simple, reliable GMAWP power supply just 6 years ago. (this is of course debatable)......  Lincoln Electric has an edge here.. Their equipment is more easily upgradable as far as placing new programming.

Our Lincoln rep just gave us a demo of a new inverter GMAWP machine that has a "rapid arc" function that smokes our 355M's rapid arc function.. Faster inverter on the new one.  Vert up fillets with pulsed spray on plain carbon steel that looked simply amazing... The pulsed current somehow allowed alot of metal to be carried uphill, the toes were a thing of beauty

Miller Rep was there the same night... He rolled out a new aluminum GMAWP unit that hasn't hit the streets yet, with a synchronized current/wirefeed pulse that is something like the Feronis rig that joins Ferrari chassies...  Lincoln has "pulse on pulse" wrapped up with patents so Miller went in another direction... the new Miller worked nicely making dime-row aluminum fillets with a constant operator travel speed.

Lots of choice... Lots of research needed to pick the optimum unit for your purposes.

Cliff, what that machine did is frequently called "stitch" welding. The idea is to limit heat input while short circut welding thin sheet metal, auto body pannels in particular. Most of these will do a timed duration spot too. These same proceses could of course be done manually.