Plastic Welders

I just bought one today and I fixed my gauge cluster. Seems the white plastic back on the 5th gen gauges becomes very fragile over time. I tried twisting the bolts and the plastic just broke with no real pressure.

This is the unit I bought:
http://www.harborfreight.com/cpi/ctaf/disp...temnumber=41592

Anyway does anybody here know the right way to use a plastic welder. I did manage to fix the gauges but it was tough going. I was using high heat low air flow. Is there a better way?? Any input would be great as I really need to get working on the plastics for 1986 vf750r I am trying to restore. Thanks George

Why not use a chemical to weld? I think using the tool you have shown would melt too much plastic, whereas PVC cement will only melt a very thin layer on each side of the repair. I have used this method on fairing mounting tabs with incredibly thin plastic and thousands of miles later it is as good as new. It is also good for cracked fairing as it only leaves a hairline where the crack was and doesn't disturb paint.

well, ive done a bit of time plastic welding. The trick with those guns is either get the speed tip (not available for the cheapo guns) or use 3 hands. yes 3.

The leister guns are waaaaaaaay better at 10x the cost, and come with many many wonderful tips. the speed tip is kind of like a Y where the rod goes in one side, the air in teh other, and it has a shoe on the end that is smooth and rounded to apply pressure and hold the two pieces together as you move it.

Kind of like a mig welded but without fully melting the rod.

if you have 3 hands, then get someone with a small wooden roller to roll right behind where you are heating and pressing the rod into the crack to set the bead. by the time you get the rod hot enough to stick, it is too soft to apply any pressure with.

you can also get things too hot if you go too slow and then it wont stick for sure. also, beware those heat guns have a limited number of heat up/cool down cycles before they quit. they used to last me a week, while the expensive ones went years and still didnt fail. make sure everything is cleaned with alcahol first and scraped second. you dont want the skin of the plastic left when welding, it has oxidesed and absorbed contaminents like oil and will not give a good weld. scrape the crack, around the crack, in the crack, etc with a flat sharp chisel at 90 degrees.


also, you NEED to have a clean air supply as a typical shop compressor (except the oiless ones) lets enough oil through simply from being a piston/oiled design that it will fark your weld.

for extra clenliness in the weld, use nitrogen instead...

that answer your question?

captainchris13, Mar 12 2007, 01:35 PMwell, ive done a bit of time plastic welding. The trick with those guns is either get the speed tip (not available for the cheapo guns) or use 3 hands. yes 3.

The leister guns are waaaaaaaay better at 10x the cost, and come with many many wonderful tips. the speed tip is kind of like a Y where the rod goes in one side, the air in teh other, and it has a shoe on the end that is smooth and rounded to apply pressure and hold the two pieces together as you move it.

Kind of like a mig welded but without fully melting the rod.

if you have 3 hands, then get someone with a small wooden roller to roll right behind where you are heating and pressing the rod into the crack to set the bead. by the time you get the rod hot enough to stick, it is too soft to apply any pressure with.

you can also get things too hot if you go too slow and then it wont stick for sure. also, beware those heat guns have a limited number of heat up/cool down cycles before they quit. they used to last me a week, while the expensive ones went years and still didnt fail. make sure everything is cleaned with alcahol first and scraped second. you dont want the skin of the plastic left when welding, it has oxidesed and absorbed contaminents like oil and will not give a good weld. scrape the crack, around the crack, in the crack, etc with a flat sharp chisel at 90 degrees.


also, you NEED to have a clean air supply as a typical shop compressor (except the oiless ones) lets enough oil through simply from being a piston/oiled design that it will fark your weld.

for extra clenliness in the weld, use nitrogen instead...

that answer your question?

YES!! Thank you. here are some pics of my abortion of a weld job. It seems to hold well.

[image: gallery_6880_2758_145286.jpg]

[image: med_gallery_6880_2758_95572.jpg]

[image: med_gallery_6880_2758_7022.jpg]

wow, that pretty rough... if it hold though who cares as its all hidden anyway. Also, make sure you are using the correct matching filler rod for the plastic you are welding, ABS FOR ABS, Polypro for polypro, pvc for pvc, etc. some plastics cannot be welded either.

Crosslinked polypro is sometimes used in molded items (maybe resoivior?) and while it is stronger than reg poly, it CANNOT be welded.

also, if it begins to smoke or burn you are too hot or too slow, and the burnt stuff will contaminate the weld. PVC is most touchy about overtemping easily. usually better to glue it and use a patch of flat pvc and more glue.

captainchris13, Mar 12 2007, 02:03 PMwow, that pretty rough... if it hold though who cares as its all hidden anyway. Also, make sure you are using the correct matching filler rod for the plastic you are welding, ABS FOR ABS, Polypro for polypro, pvc for pvc, etc. some plastics cannot be welded either.

Crosslinked polypro is sometimes used in molded items (maybe resoivior?) and while it is stronger than reg poly, it CANNOT be welded.

also, if it begins to smoke or burn you are too hot or too slow, and the burnt stuff will contaminate the weld. PVC is most touchy about overtemping easily. usually better to glue it and use a patch of flat pvc and more glue.

Its holding strong now. As you can see there was a piece miss. I tested all three type of plastic rod and the green seemed to work the best for the gauge plastic. Like I was saying it is very brittel. I am happy with the hold but not the way it turned out looking. I am glad it will be hidden.