MIG Drive Roller Discussion

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MIG wire rollersIn another post, I shared that as a test, I would try running .025” wire in a set of .030” rollers.  A couple of the responses made me think that a discussion on MIG rollers might be of interest.  My limited search did not find anything...I would like to thank John T and Willie B for the subject idea.For my part of this little study, I am only looking at rollers from my Millermatic 200 and Millermatic 255 (Yes, the rollers fit in both, so my study is admittedly limited). I have roller sets in .035” V, .045” V, .035” U, and .047” U.I use “V” groove rollers for solid steel wire.  I use “U” groove rollers for aluminum wire.  This is just how I was taught 30+ years ago.   Okay, just like it sounds, a “V” roller has a “V” shape that the wire sits in.  The V shape gives each roller two points of contact with the wire, for a total of four points of contact driving the wire (two drive roller system). The first picture is a picture of the “V” in a Miller V groove roller.  The pictures were taken with a USB microscope – sorry these are not great pictures, but it shows the idea.

The second picture shows what it would look like with a round wire in the V groove.

Notice that I sketched the opposite roller, showing four points of contact between the wire and the two rollers.  Also notice the rollers do not touch.  There is a gap between the rollers.  I validated this condition on my welder.  The .035” V rollers with .035” solid wire had .010” of gap between the rollers – as measured with a feeler gauge.  I will admit that these are pretty new rollers, with maybe only two 33 pound spools of wire have run through them.  I did not think to do the same measurement with on my old machine that has had 50+ rolls of wire run through the rollers.My MIG welders have a spring tension system to push one roller toward the other roller, in effect squeezing the wire.  My Millermatic 200 has a simple wing nut to adjust the amount of preload on the spring.  The Millermatic 255 has a knob with a “scale” to show the preload.  On the 255 I almost always leave the preload at “2” and it works fine.  If the groove in the roller were a ½ circle and the two rollers together made a circle the diameter of the welding wire, there would be no reason for a spring and tension system.  You could fix the rollers in position.  Obviously this would not work if the wire diameter varied.  This makes it reasonable to accept that the rollers normally would not contact each other when the wire is present, otherwise, there would be no ability to compensate for manufacturing variation of the wire. For my example of .035” wire in .035” “V” rollers, the separation between the rollers was .010”.  I did not measure the “V” angle but it looks like about 90 degrees – 45 degrees per side.  The math is pretty easy.  The Sine of 45 is .707   This means that closing the .010” gap to zero would mean the effective diameter would close by close by .007”   This suggests my .035” rollers might work with a wire diameter of .028”.Using the rollers I have, I did a test on my Millermatic 255 and verified that .035” wire fed using the .045” “V” rollers.  It worked fine.  The gap between the rollers was less than .004” – the smallest feeler gauge I had with me.  The gap most likely was close to zero.The “U” groove roller pictures show the “U” shape of the wire groove.  Third picture.

I believe it is important to note that the “U” of the “U” groove roller is not a ½ circle, and it is not a tall thin “U”, it is a wide flattened “U”.  Hopefully you can see this in the picture.   My suspicion is that aluminum wire is softer, and may distort a little under the pressure of the rollers, so the contact is the top and bottom of the wire, with the “U” shape confining and grabbing the wire as it flattens and ovalizes (ever so slightly) under the pressure of the rollers.  This is just my personal theory, no data to back this up.  See the fourth picture.

My spool gun and my AlumaPro push pull gun both have rollers with “traction” ridges that leave marks on the wire.  I cannot see any indication that standard Miller “U” groove rollers have “traction lines”. I did put .035” solid steel wire in my Millermatic 255 and installed the .047” “U” rollers and tried it.  The wire fed the complete length of my 25 foot AlumaPro gun.    I should have, but did not check the gap between the rollers with .045” or .047” solid wire.   Because “U” groove does not follow the same math as “V” groove, the change in gap between rollers is closer to 1 to 1 rather than Sine Theta. (My theory)I have run .030” rolls of solid wire in my Millermatic 200 with .035” rollers.  It worked fine.  When I did this, I did not know .030” rollers were even available.  I have since found Miller rollers marked .030/.035.  I do not have a set of these.  Does anyone know if these rollers have one groove on one side for .030” and one groove on the other side for ,035”?  Or, does the groove work for both sizes of wire?  Are there different rollers for .023” and .025”? Are there differences for other brands of welders?Thank you for reading.  Looking forward to hearing what others think.Geoff
Reply:The rollers for .030 and .035 have different grooves. When installed the side you read would be the opposite side groove which feeds the wire.
Reply:I think certain diameters for wire feed products are actually the manufacturers making one product to serve both Metric and SAE sized markets.The diameter tolerance for solid metal weld wire is like +0.001"/-0.002" for the AWS. If you're buying drive rolls for 0.025" weld wire you can also make them work for a metric wire diameter of 0.6mm since that converts to 0.023" (really it should be 0.024" if you round up).  The metric wire diameters are also where things like 0.047" diameter wire come from I believe since that would be the conversion for 1.2mm wire. The metric sizes seem to go up by .2mm starting at .6mm (0.023") where as the Imperial/SAE wire diameters go up by 0.005" until 0.45" when they jump to 1/16th (0.062" or 0.063").
Reply:

Originally Posted by ToolFanGeoff

I have since found Miller rollers marked .030/.035.  I do not have a set of these.  Does anyone know if these rollers have one groove on one side for .030” and one groove on the other side for ,035”?  Or, does the groove work for both sizes of wire?  Are there different rollers for .023” and .025”? Are there differences for other brands of welders?Thank you for reading.  Looking forward to hearing what others think.Geoff
Reply:Now I need to check. I'm old & things I accepted as fact are not always fact. Miller 189285 is a V groove for .035 or .045" hard wire. U groove is for flux core wire & knurled U groove is for aluminum wire. I think conventional feed guns will be problematic with all but very large aluminum.An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.
Reply:

Originally Posted by Willie B

U groove is for flux core wire & knurled U groove is for aluminum wire.
Reply:Also interesting to note, that groove included angles can vary greatly.  Here are the roller specs from the drive rolls from HTP Pro Pulse MIGs



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Reply:

Originally Posted by Oscar

I think you have that backwards unless it is at the spool gun?  Pushing aluminum at the machine with a knurled drive roll will shred it and clog up a liner fast.A single groove for 035 and 045 sounds odd indeed.  Seems to me there is too much of a disparity between the wire sizes to still get proper fit in the groove.  Edit:  My bad, I assumed you meant that drive roll had a single groove for both wire sizes, but a google image search shows that it has two separate grooves.