b) Pulse Rate
Changes in wire feed speed are accompanied by changes in pulse frequency. As wire speed
increases, the pulse frequency and therefore average current must also increase so that wire feed
speed and burn-off rate are continuously matched. The increase in average current causes an
increase in heat input. Pulse frequency can readily be used to control arc length.
c) Pulse Width
Pulse width is the time at peak amperage. Average amperage and heat input are directly effected by
pulse width- both increase with increasing pulse width. Increasing pulse width also has some effect
on increasing droplet size and widens the arc cone (bead width increases).
d) Peak Amperage
Peak current must be high enough to be above the spray transfer transition. Peak current detaches
droplets and propels them across the arc. Peak current directly affects arc length - arc length
increases with increasing peak current. Some power sources produce a spike to promote droplet
detachment from the electrode tip.
e) Background Amperage
Control of current rise and fall during the pulse cycle is used to control droplet shape and to shape the
electrode end in anticipation of the next droplet detachment.