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MM255 tip question

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  • MM255 tip question

    After welding for a good bit the tip seems to constrict on the wire and the feed becomes erratic. Has anyone else had this issue?
    .035 er70, 90/10, on pulse, mostly 3/16" setting, gas 25 cfm. I've been content using the autoset function.

    Welding 5/8" a while back and I had to deep changing tips and letting them cool down. It's really aggravating.


  • #2
    What series tips are you using....MDX or S-series? The S series should be more durable and handle more heat.


    • #3
      I had to check but we are using the S-series.


      • #4
        Would it hurt anything if i changed to the .039 tip?


        • #5
          The likely cause is a ball of spatter has welded itself to the contact tip. My MM255's (yes two of them) have explosive arc starts that blow sparks all over our shop. Hit the tip with a flap wheel and see if you get sparks. This is evidence that there is a ball of steel welded to the tip. Grind it off and see if your problem goes away for a while. I have been in conversation with Miller since January on this and other issues and have no resolution as yet.


          • #6
            Buy some of that Mig welding spray......and pull the cone off and spray your tip and then your cone inside and out and nothing sticks.....needs to be done on a regular basis ( every hour or so) and can be a very slight mess.....but the gain vs the balls sticking everywhere far exceeds that...and the MX ( newer) Vs S ( older) series don't interchange unless you have a conversion tip in your old torch...