Miller MDX 100/Tweco 150 for Pulse

robert-r · Sat Jul 10, 2021 3:09 pm

I have a Millermatic 255 and want to use a smaller gun. Am wondering if a Tweco 150 can be used with pulse welding because I have one. Or if it won't work, would a Miller MDX 100 be adequate?

Oscar · Sat Jul 10, 2021 4:37 pm

At what proposed amperage levels do you plan to pulse weld?

robert-r · Sat Jul 10, 2021 6:02 pm

Would use mainly for the roll cage, etc on my Jeep: .18 and .12 DOM. Miller does not list amperage for the pulse setting. They give a wfs of 270 and 330 using .035 wire for metal thickness of 1/8" and 3/16".

I have used the Tweco to weld similar thickness of tube and plate without problems. Had a 212 at the time. It was not used for continuous production. Was careful not to burn it up. For some reason (could be wrong), I'm under the impression that the MDX gun that Miller supplies with the 255 was developed to work with pulse.

Oscar · Sat Jul 10, 2021 8:33 pm

robert-r wrote: ↑Sat Jul 10, 2021 6:02 pm I'm under the impression that the MDX gun that Miller supplies with the 255 was developed to work with pulse.

Yes, basically any MIG gun will work with pulse, it's all about how much heat it can handle and if there are high-heat tips for that MIG gun. The MDX will be better than any mig gun that is rated at a lower amperage rating over-all. In general, whatever a MIG gun is rated at for short-circuit, de-rate it by about ~30% to account for the high peak-pulses during pulsed spray-arc. So what you were able to accomplish in the past with the 212 does not carry over here. Once you run pulse and see just how hot it gets the gun, then you'll understand. Look up the predicted amperage at the WFS's you indicated to see what is really what. For 120A on pulse, I'd recommend the gun you are planning to use be able to withstand 200A @ minimum 30% duty cycle on short circuit, and at least 150A @ 30% duty cycle on pulse operation. Use high-heat tips if they are available, nozzles with the thickest wall-thickness, and do not use a combined set-up that recesses the tip; that will have the nozzle closer to the arc and it will heat up dramatically faster. Use a set-up that keeps the tip flush with the nozzle and keep 3/4" stickout from the contact tip to the weld pool.

robert-r · Sun Jul 11, 2021 11:00 am

Oscar, thanks for the information! Very much appreciated.

Think I'll stay with the Tweco gun and use it non-pulsed. It works just fine on the 255.

And fwiw - the contact tips for the MDX-250 are heavy duty compared to the ones for the Tweco and my old 212.