# Welding HDPE



## Chuck Daehler (Mar 17, 2015)

My dog gone HDPE slingshot chewed by my lovin' pooch Alfie made me sick. I mulled over it a few weeks and decided to cut off the chewed forks since I still had enough fork to work, albeit shorter. I used the cut offs and fragments Alfie left me to weld to the handle and other sites where chewing had made nice craters and missing parts.

I had welded HDPE before to a minor degree with a pencil electronics type soldering iron to much success so I got to work.

It turned out well.

So just to prove that welding with a soldering iron works, here's the pic of before and after.

I don't think I'd weld broken forks however, just something telling me it may not hold...I welded only on non stressed areas for a "body/fender job" cosmetic mend only.

It turned out like a cross between a Rambone and a shallow chalice. It shoots nicely with no issues of a shallow forked frame...no fork hits, flies true.

To weld I melt both sides and squeeze the two parts together so plastic oozes out...that indicates it's a true weld. A weld involves melting both parts to be joined, as in metal welding.

To fill pits I grab a small 3x3mm chip on the soldering iron tip, while it's melting I bore the tip into the pit to melt it, by that time the chip has melted enough to smear it over the new melted crater and it's done...a perfect fill. file, sand, finish as usual. You might try that on fork hits for HDPE frames to fill in cosmetic irregularities. If you have a light color frame the soldering iron will scorch the plastic making it a darker color or brownish and the patch is clearly visible. I tried putting a fashioned HDPE stick into a hot glue gun with some success but again, you use the tip of the glue gun to first melt whatever you want to weld then play the melted HDPE over the area to smear it and fuze it in. I tried hot glue itself, too pliable and won't stick well to HDPE even though the HDPE was melted first.

For large parts such as the index finger appendage on this slingshot and the extended pinky tang, I melted both sides with a blow torch carefully to not set it on fire or scorch the parts then pressed the two melted sides together until plastic oozed out of the joint. That works.

Chuck


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## DestroyerOfEVIL (May 11, 2015)

That turned out very nice!

-Destroyer


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## flipgun (Nov 14, 2012)

Nice save. Why DO th' lil' buggers like to chew on our shooters? You hear about this quite a bit.


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## stej (Jan 16, 2013)

The slingshot looks very comfortable. I also wanted to fuse two parts together - add a palm swell to a slingshot, so I'm quite curious how it will work.


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## Chuck Daehler (Mar 17, 2015)

The secret to welding such things as appendages and palm swells is to heat to melting point each surface to be contacted and joined. Don't burn it.

You'llshootyoureyeout (Matt) has done this as well, before I did in fact and cautioned me to melt both surfaces well before I joined them. I followed his advice and it turned out perfect on several frames.

I use a small blow torch held a distance away form the plastic so it doesn't catch on fire/burn/scorch but I think Matt used a heat gun which is less risky. Cigar lighters (much more potent than a Bic) are little miniature butane blow torches good for welding HDPE, but I don't have one (am not a tobacco user). For small pieces and filling small pits as I said I use a soldering iron, melting first the pit then applying melted HDPE into the pit and smoothing it over allowing it to cool thoroughly (can use a wet rag to speed it up) then file, sand, finish.

Thanks for the complements fellas! I was shooting it this evening and by gum my dog Alfie's mod is more comfortable yet since the forks are shorter and therefore less torque. I think in the future thanks to Alfie's engineering skills I'll make my forks a bit more short. I frankly must have been too paranoid of "band bunch up" or congestion as the pouch passes through the fork so I made deep forks. I could trim off 3/4 inch from all my forks actually but they're already made so I'll let it be...just will make future frames with forks less high.

Thanks again Alfie for your mod!! I guess it's not deep enough to be called a true chalice, so can we dub it a "champagne glass"? LOL Alfie's Champagne Shooter no less.


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## flipgun (Nov 14, 2012)

" Alfie's mod is more comfortable yet since the forks are shorter and therefore less torque. I think in the future thanks to Alfie's engineering skills"

Blessed by an act of dog?


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## Chuck Daehler (Mar 17, 2015)

Yep Flipgun, Susi and I have the good fortune of being blessed by not only Alfie but the acts of six dogs no less, all are such loves. We don't have kids so these "babies" are our family. We live on a farm in the Andes where they can run and play endlessly and they do. They much contribute to our happy care free life here, contribute to lots of fun and are of course all full of love and affection. Both Susi and I have been raised with dogs all our lives so naturally when we find one needing adoption we either adopt them or find a good home for them. Six is our limit however so we actively find good homes for orphan doggies. They range from Alfie's year and a half age to almost 14, all healthy and happy "kids". Susi's two white miniature poodles, age 13, Mini and Molly are the smallest, Nicole, age 2 and a half is next in size, Katyusha (Kathy) who is Alfie's mom and Nicole's sister, is next, and Osa which means "bear" in Spanish the half collie female is the largest. So Alfie and I live in a house full of females one way or the other (guys have to stick together in these outnumbered situations).

I see that many SSF participants are dog or cat owners, I guess love for pets goes with the territory. Dog gone it's a nice forum, ain't it?

Flipgun, I think they like to chew up our shooters because they smell like us since we use them so much and our doggies love us so much they are like magnets to our stuff that smells like us. My sox are a prime target (they sure smell alright!). Work gloves are another. Humans are supposed to be smarter than doggies so it's my fault the caty was chewed up...I left it in front of the catch box when Susi had a "honey do" for me to do (a honey do is "Honey, will you DO this for me?" I once had a friend in CA who had a business called "The Honey Do Express", he did all sorts of odd jobs from minor construction to simple fix its and did well in business...all those wives "honey dos" made him a living.


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## Bob E (Mar 23, 2015)

Chuck Daehler said:


> ... So just to prove that welding with a soldering iron works, here's the pic of before and after...
> 
> ...To weld I melt both sides and squeeze the two parts together so plastic oozes out...that indicates it's a true weld. A weld involves melting both parts to be joined, as in metal welding...


I use a soldering iron to weld plastic too. It's a cheap-0 harbor freight special. It came with a flat tip for plastic welding that works pretty good, but It gets too hot for HDPE and scorches it a little. I bet one of those fancy soldering irons with a dial thermostat would work pretty good for welding different types of plastic.

My HDPE never seems to get as fluid as the stuff I see pictures of on here. It doesn't really flow together. I almost have to knead it like bread dough to get good fusion. Melting both surfaces to be welded and pressing them together doesn't work very well for me. The melted plastic just squeezes out of the joint. I like to hold the two pieces I'm going to weld together and tack them on at least a couple sides first. It doesn't have to be strong just enough to keep them from falling apart. Then I use the flat plastic welding tip to push a trench all the way to the center of the joint from one side. I hold the tip against both pieces inside of the trench to melt them making the welded area a good 1/8"-1/4" wide. Then I push all the squeeze out back into the trench mixing the melted plastic together real good and adding filler plastic as necessary to leave a good 1/16"-1/8" bead on the surface. I Let it cool a little to solidify then move onto the next side.

One thing I noticed while welding clear/white HDPE from milk jugs, sometimes while cooling down a fracture might appear under the surface in the area of the weld that was only warmed, half molten and untouched by my soldering iron. I figure it's caused by internal stress :iono: I go right back in and re weld it and it seems fine, but It won't be visible in the colored stuff. I find this concerning because one of the ways I break down the thicker bottoms of some jugs is by scoring it with a box cutter, then it snaps right in half...


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