Just wondering if there any other plastic welders out there. I work for a company the manufactures custom serface finishing equipment. There is a lot of hot air thermoplastic welding involved. I have about 4 years experiance in the field. I was wondering if AWS has a certifacation for this field yet? I know they have one in Germany. If there is any other plastic welders out there, I would love to exchange tips on the practise. Thanks in advance.
Dax
Hi Dax,
Well you found one, at least I used to be one. My former company had a plastic/FRP fabrication shop that was part of their pipe fabrication shop. It was only natural that a company in the plastic manufacturing (including lined pipe) business would also use their products in many of the chemical processes.
In the mid-60's Saran, Penton, and PVC were prevalent. By the early 70's, Poly-Pro pushed the Saran and Penton out. As time marched on and chemical processes changed or were tweaked Teflon (non-welded), Kynar, and HDPE picked up the lion's share of materials being welded or bonded.
I'd be more then happy to exchange info and practices with you over a subject that recieves so little acknowledgement. I doubt that many on this particular forum would be interested in any future exchanges, so if you'd like, feel free to e-mail me.
Interesting, I've encountered more welding engineers who turn up their noses ( no disrespect intended) at plastic, whereas very few material engineers will! I've gathered enough experience to suggest that welding or bonding of plastics is as highly a skilled profession as many metal joining processes (eye/hand coordination) because of the temperature/pressure/travel speed techniques required by the welder or bonder in order to achieve a quality, pressure containing weld or bond.
Look forward to talking with you,
I have a PVC/CPVC Bonding procedure that I had to develop for the gluing and welding of pipe for the ASME Code. If you would be interested in seeing it, send me an e-maill adress.
Tim
Seldom is right. For some misterious reason, most welding engineers turn up their noses at plastic welding as if it was a less noble specialty. However, this is true only in the U.S. Even AWS is rather poor in standards and publications regarding plastic welding.
Access TWI (The Welding Institution of Great Britain) site and you'll find plenty of information there regarding plastic welding: www.twi.co.uk
Giovanni S. Crisi
Sao Paulo - Brazil
Dax,
I am not presently a plastic welder but might be able to make good use of the talent... developing it had long been on my long list of things to do, but unfortunately tools, training, and technical advice are not easy to find. Candidly, much of my work involves repair of various descriptions and often when I run accross a situation that may be served by attempting to perform a welded repair it is on a resin tht has been degraded, and I doubt the material could properly be considered as weldable. I have no idea.
I'm interested more in various repair rather than fabrication techniques as well as how to identify a good tool... how do I determine if it has the power for the job, etc.? In the meantime I marked the link provided by Dr. Crisi and plan to peruse it presently.
I just wish I had some kind of tips to offer you.
Regards,
D
Hi Dee,
Your post reminds me of cracked or broken nozzles on farm fertilizer/spray tanks. There’s a fertile field (pardon the pun) out there for people who can weld thermoplastic. The tanks are roughly handled and are usually contaminated to some degree but I’ve known a few individuals that have got into this field and command extremely high wages. I’ve often thought I’d get back into it myself now that I’m retired but I enjoy my part-time QA/consulting too much to do so.
In general terms about all you need is a good hot-gas gun, proper filler material, compressor, 110V supply, spark tester and/or vacuum tester, and a variety of modified woodworking tools.
Thermoplastics do have an absorption rate, which is specific to each type of resin, but usually not to a degree that makes it unweldable with proper scraping and solvent washing. Also, identifying and locating the filler resin material required is usually the most daunting task for people in this type of work.
Good luck
Seldom,
Great to hear from someone with experience.
My concern about degredation is more toward a phenomenon I do not completely understand. It seems some resins are attacked by components in some oils and solvents which I imagine is hydrocarbon related and seems to attack the plasticiser or whatever it is that gives it flexibility and resilience... in any event it becomes more susceptable to (stress) cracking and in extreme cases turns to crumbling rubble within seconds before one's eyes. Prehaps hydrogen related cracking of plastics? In any event I have not gone so far as to measure anything (durometer, tensile, etc) before and after exposures (WD40 brand oil and trichlorethelene are common culprits) but merely evaluated what is obvious. Lexan and Makrolon seem to be the only two I can identify with this sensitivity (Makrolon being the more sensitive of the two; I would characterize it as being slightly to moderately sensitive), but I can provide sample of an unidentified resin which is extreme in it's sensitivity. There are many.
So what do I look for in a hot gas gun? My experience is that that price is rarely a good gauge. I know Ford prescribes a typical hot-air heat gun for repair of auto bumper and other flexible parts, so I can merely guess as to why it's hot gas and not air.
I was unable to access much on the likk provided by Dr Crisi but there remains a lot to see.
Thanks &c
D
Well it looks like you’re finding out why there are so many different resins out there. They all have their use depending on the service conditions.
As for welding equipment, I’d suggest taking a look at Leister’s hot-gas/air hand welder, which you can find at www.Leister.com. There are other manufactures of thermoplastic welding equipment out there, some are kids toys and others, such as Leister’s are quality equipment. Wegner (German) manufactures an extrusion welder that is a quality tool for larger work but I don’t know if they still have their outlet in Chicago.
Concerning the use of hot gas verse hot air. We used hot nitrogen (off the plant system) for welding PVC, SARAN, and PENTON years ago but it was determined by our materials group that it was acceptable to use air instead for POLYPRO and HDPE. The nitrogen acted similar to argon by helping keep the semi-melted surfaces from oxidization and burning of the surfaces, which would adversely affect fusion between the filler and base materials. The PVC’s and SARAN were very heat sensitive and burned quickly.
By -
Date 04-10-2002 21:49
Hi again thanks for the replies. As for plastic welding guns. We use Kamweld guns. You can view there products on www.kamweld.com. I perfure these guns to wegner because the handles are a lot thinner and the barrel is longer (for getting in hard to reach places). Also, Harbor Freight sells a plastic welding gun for $30 at www.harborfreight.com. Ive used it and its not bad. The only thing is that the there is no temp control, it stays on the highest temp. It would be best to use it with a compresser versus a blower with a air regulator so you can get your desired temp.
Thanks and Ill let you know how I make out
D
