Posted by Joe Lorenzino on Thursday, November 14, 2002 at 11:12PM :
In Reply to: Millermatic 185 vs. 210 welder posted by Mark Toper on Thursday, November 14, 2002 at 6:24PM :
Sometimes, the machine itself does not change so much as the way it is rated. Up till a few years ago, almost All welders were rated at "NEMA class 1" (rated @ 60% duty cycle), but then, some companies started advertising theirs using the "NEMA class 2" (rated @ 40% duty cycle) numbers. Comparing a class 1 machine to a similarly rated class 2 machine is kind of like the old apples/oranges thing. (with the "same size" class 2 machine allways being less expensive... great if you are bidding contracts that don't specify ) Most all new machine model # are based on the lower class 2 rating ... except those few that use an even lower duty cycle, say 25 -35 %. If you can, check the data plate on the machine and see which rating system was used, then compare based on the same system. For what it's worth, the shop I work in has 9 or so welding machines, and the Millers seem to work the best : easier to set, hotter start, smoother welding etc.
Also for what it's worth, whenever we look at new welding machines, some of the Important things I want to know are
: The Shipping Weight -
you're buying copper (hopefully) wire on an iron core, so the heaviest machine (at the same rating) probably has more in it, no?
Duty Cycle-
same thing as the Nema rating...most times. Really means time-on / time-off. Nema Class 1 #s mean that it will weld @ that setting for 6 minutes, then needs 4 minutes cooldown time EVERY 10 minutes. Check to see what the 100% duty cycle rating is, as that is the highest continuous output you are going to get, and is a real good indication of how long and at what power the machine is REALLY good for. Also check to see if its rated output is a a specific Output VOLTAGE as well. With a wirefeed machine, as you turn the output voltage up, the duty cycle Also goes down from the rating. I have worked (sort of ) with a small tig welder that had a 25% duty cycle on AC. That means 2 1/2 minutes welding followed by 7 1/2 min smoke break for cool down, and it would shut itself right off till it was cool
Power Factor
A number or word that represents how Efficient the transformer is. A high PF machine probably has some capacitors in it to increase this and smooth out the load on your electrical service. Costs more to buy... but less to run. Power Factor Correction ( PFC ) used to be available as an option on some machines. Doesn't really change the output, but can have a significant effect on the input side. The PFC option on 1 machine a work let us put it on a 100Amp service rather than the 200Amp sevice that the nonPFC model needed.
Just a few thoughts Joe
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