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Old 10-21-2009, 01:09 PM
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Default plastic welding

Has anyone used one of those plastic welders that are sold at harbor freight? I am tempted to by one but I'm not sure how to use something like that. It seems like you would need a filler rod or something. Unless you just blow the molten plastic around until it mixes. I dunno
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Old 10-21-2009, 02:01 PM
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There are a lot of article links here:

http://www.plasticsmag.com/welding.a...ec-00&aid=3052
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Old 10-21-2009, 02:16 PM
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I recently bought a plastic welder from HF, and so far it appears to be performing very well. I am the problem. I can see where it will take a fair amount of practice on the different types of plastic. Last week I finally figured out how to weld PVC. Each type of plastic will have it's own heat range which is the hardest thing to adjust even though they give you a guide, this guide does not account for thickness of the plastic to be joined.........you just have to experiment. Clean, clean, clean.........I use a 91% rubbing alcohol which seems to work pretty good. Some sites state to use MEK which is a sort of solvent you can get at the big boxes in the paint departments. As an example, PVC has a shiny coating on it which must be sanded off, then cleaned. This shiny film will prevent the PVC rod from sticking to the parent material. Other than that, practice, practice, practice........I have found that getting the correct temperature, proper preparation, and patience is what matters most.

I guess you can use thin clean strips of material cut from what you want to weld for the filler, but I would suggest getting the rods. They are generally fairly cheap, and 1 rod can go a long way depending on what you are trying to accomplish. I am presently waiting for some rods to weld UHMW with that I had to order. Like metal, some plastics require more skill and different approaches. By the way, I got the $79.00 plastic welder after talking with the manager of the store. He is also into plastic welding and told me he tried the other ones that require a separate source of air, and that he did not like them as much as the on board air model like I have. He pointed out that if you go somewhere to weld some plastic for someone, most likely they will have an electrical outlet, but not a compressor. That means you would have to haul a compressor along with you.....mines a 60 gallon......no thanks.
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Old 10-22-2009, 05:48 AM
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These units are similiar in construction to a hot hair dryer gun but on steriods.

The filler never welds ( fuses) in the real sense of the word but becomes semi plastic as does the parent material.

Edge preparations are somewhat similiar to that of weld set ups with slots and vees for butts and square edges for fillets.

It takes a while to develop the correct technique of speed and heat as too hot and too slow tends to barbeque the work.

The technique is to roll the filler into the semi plastic parent material.
In my country, the brand Liester is a well known proffessional tool for this work.

Oz
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Last edited by OZWELDER; 10-22-2009 at 05:54 AM.
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Old 11-17-2009, 09:15 AM
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I brought a damaged piece of UHMW home from work to practice on. This piece is beyond repair, so they wanted me to experiment with it. I have not had very good luck so far. UHMW appears to be a completely different animal than PVC and some of the others. Part of my problem with it may be that I have not received the UHMW welding rod I ordered (ordered about 3 weeks ago), and have only tried using some skinny strips that I shaved off the damaged piece. I have cleaned the strips as well as the larger damaged piece, but I just can not get it to bond. Now I am wondering how far oil will penetrate this type of plastic, and if a person can get it clean enough to weld. This particular piece when installed was constantly being coated with drive chain oil because it is located right after the automatic oiler.

I may need to find something that removes lubricants better than MEK. On the other hand it may be possible that solvents do not penetrate UHMW as deep as oil does.
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Old 11-17-2009, 09:22 AM
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I understand that UHMW, because of its high melt viscosity, requires pressure to form a proper bond.
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Old 11-17-2009, 09:34 AM
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Have you got any pictures of welds you have made??
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Old 11-17-2009, 11:01 AM
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UCMCPOP,

Would it be possible for you to explain "High Viscosity Melt" for us uninformed? I guess to me it would mean that at it's melting point it would be fairly thick..........not sure. And as far as "Pressure", is this something that can be managed manually, or is there some special equipment I would need to get............thanks.

tnmike,

I do not have any means to take pictures at the moment. Are you looking for pictures of the failed UHMW welds, or just some plastic welds in general? The welds that I would call successful on PVC basically look like plastic sitting on top of plastic where I did butt joints on the 2" white PVC. I put a slight bevel on the pipe ends, then filled it in to the point where the weld was approx 1/16" above the surface of the parent material. It took me several attempts to get to the point where I think it is a good weld. Once it was done and cooled, I pressurized it to 80 psi and sprayed soapy water on it looking for leaks. I was told that the characteristics of a good weld on PVC will be having a weld that looks like it vulcanized to the parent material at the bead edges, and no brown heat discolored area in the weld zone. Like I have stated before, it takes some practice getting the right heat range. When I feel that the parent material has reached the right melting temp, I stick the rod into the joint, let it get to the melting point, then push the rod while turning it so it mixes with the parent material. Odd, but I have found that the gray colored PVC rod seems to work better when welding the white PVC pipe. I do not have any of the gray PVC to practice on. I do not even know if there is a difference between the white and gray other than color........something for me to google and find out.
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Old 11-17-2009, 11:03 AM
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I wanted to see some welds made with the HF unit. Im interested in the one with the onboard air supply
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Old 11-17-2009, 12:14 PM
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The way I understand it, UHMW is thicker and not as sticky as other plastics at the proper melting temperature, so it needs to be pressed together to form a good bond.
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