Steppers boost heat to compensate for tip wear and contamination.

This boost is added to the "base heat", or the heat schedule that starts out with new tips. The common way of expressing this boost is to program how much boost is to be added at a certain weld count. This boost is fine-tuned to match the actual wear that welding causes on the tips.

Note that any change in the schedule, weld force, or heat time will affect the wear on the tips, therefore will require an adjustment to the stepper boost.

It is therefore very important to start with a known good schedule, or we will be adjusting the stepper for all the wrong reasons.

It is equally important that we do not adjust the schedule when the tips are worn and require a stepper boost. If the schedule heat were raised during production instead of increasing the stepper boost, then we must take the heat back out when new tips are installed. This is a common cause of expulsion and tip sticking after a tip change.

This "Known good schedule" must be capable of making good welds with worn tips. Then the starting schedule is just a "lower heat version" of that schedule. You must remember the "target". We are trying to set-up the welder to give good welds throughout the life of the tips. If the schedule we choose cannot make good welds with old tips because of the force or time parameter, then we are set-up for failure before we start. No amount of boost will make up for this situation.

A common mistake is to set-up the weld schedule with new tips. It is very hard to set it up with old tips, because you don't get old tips until you have run the welder in production. And who wants to go into production without setting a proper schedule?

There are two ways to get past this "Catch 22" situation:
1. Have a lot of experience with similar applications, and use one of the proven schedules, or
2. Make small adjustments every 500 welds until you get to the end of the tip life, commonly 4000 to 8000 welds. Now you have old tips to experiment with.
This is a difficult feat of timing, because if production is in progress, you must change tips and let them continue production. You can't save the old tips and put them back, as you will never get them aligned as they were, and any experiment based on this will be flawed right from the start.

This is the great value of standards, set-up by the welding group. The set-up parameters they picked must have been able to weld in production, or they would have adjusted them until they did. If you don't have this done for you by the welding group, then you must continue to try to end up with a set of old tips at the end of production that you can experiment with. Sometimes it is easier to go set-up a manual weld gun and just make 4000 or so welds, and now you have your old tips to play with. Try not to be too mad at the "do-gooder" that changed those old nasty tips for you while you were away from work. He won't understand why you didn't like it...
I will make up example numbers in Red, just for reference
Lets say you got to 6000 welds and stopped there.

Now, we can optimize the Pressure Time and Heat ("PTH") for these old tips. Experiment with values that are centered between expulsion and cold welds (undersize welds) and chart them out. This process is known as charting the "weld lobe", a method of documenting all combinations of "PTH" on grid paper, showing which samples were acceptable, and which were not. Perhaps this will be another page on this website someday...
Lets say you found: 600 pounds force, 14 cycles at 15,000 amps was about proper.

Once you think you have arrived at the best combination of PTH, test it.
Make a weld with pressure 10% higher, current and time 10% lower.
Make another with pressure 10% lower, time and current 10% higher.
What this does is test all three parameters at a large amount of variance, when they are all in the direction of "cold" (1st test) or "hot" (2nd test).
OK we tested at 660#, 12 Cycles, 13,500 amps, and it was a little cold, we had to raise the heat to 14,000 amps to pass the test.
This means that the 2nd test should be done at 17,000 amps, not 16,500 as we would have calculated. Too bad, but we do want a robust setting.
So the 2nd test was done at 540#, 16 cycles, and 17,000 amps. It was hot, but acceptable.
So our "center" point that allows 10% (or more) variance in all parameters is 600#, 14 cycles and 15,500 amps.

If your schedule passes this test, then you have TWO things:
1. The final schedule, or the "target" we will hit with old tips,600#, 14Cyc., 15.5Ka. and
2. The starting schedule, it justs needs some current removed so that it will be civilized when using new tips.
So change tips, and find the highest heat you can use without sticking or expulsion. Be sure to leave the pressure and time alone...
We had to turn the heat down to 9500 amps.
so this schedule is: 600#, 14Cyc., 9.5Ka.

As a pleasant surprise, we now have all the stepper parameters. You have:
Starting schedule (the schedule you just made by removing boost heat).
Stepper boost required (however much you had to take out to get the "old tip" schedule to work with new tips). 6000 amps
Stepper count (the amount of welds you had to put on these tips to make them "old"). 6000 welds

OK, let's program the stepper:
1. Put the boost in the window on your stepper screen called "boost".
2. Put the count in the associated "weld count" window.
You now have a "one-step" stepper. It looks kinda silly, because your stepper probably has 5 or more steps to fill in. Let's fill them in...

Most steppers give a warning of a tip change coming up. I like about two hours' warning, so I can get ready for it. You might find that other welders will also want new tips soon, and you might as well do them all at the same time.
This warning is issued when the stepper enters the last step. To calculate this point, figure how many welds it does in 2 hours, and subtract that from your total.
Lets say this is 600 welds

Another thing I just learned from Rob Slazinski, one of the best Project Engineers you will ever meet, was that they DO display a stepper graph that shows where you are on the stepper at any given time. I was even given permission to show you, but remember that you should refer to Square D for any changes or improvements, I won't necessarily have the newest info.

This is a stepper chart from the Square D EQ5300. It shows everything graphically, very informative for stepper development.

You can zoom in and see details...

This is a screen showing a change being made (in red).
Isn't this way better than numbers, for seeing what you are adjusting?