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Old 04-10-09, 12:48 AM   #12
AC_Hacker
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Default Polyethylene Fusion Device (AKA: the 'Mini-Hack')...

I took my Polyethylene weld tests down to show Howard-the-Machinist this morning. When I showed him what I was able to do with a Teflon skillet on the kitchen stove, he was rightfully impressed. So impressed in fact that he volunteered to do some destructive testing to see how good the welds were. He fixed a 3/4 piece of steel rod in the bench vice and used another piece of 3/4 rod to try and tear the welded pipe apart. One weld broke pretty easily. It was a weld on which I had tried minimum heat. You could see at the torn cross-section that some of the end was still shiny and had not even melted from the heat of the skillet. The other welds were so strong that the poly pipe gave way before the weld did. Pretty impressive. But I can see just how much better it would go with a device that was along the lines of the Mini-mac. So could Howard. He showed me some online sources for 'cartridge heaters' that came in various wattages and temps. They ran about $35 each. He also said that he'd mill out a chunk of aluminum for the cause. That's no small favor. It's good to have friends in high places...

Before I left I introduced my Teflon skillet to Howard's bandsaw.


This will give me non-stick surfaces for fusing the poly pipe.

On the way back home, I stopped into Goodwill to look for resistance-heating devices I could savage to heat my home-made polyethylene fusion machine(AKA: 'Mini-Hack'). I had plenty to choose from: hair dryers, clothes irons, waffle irons and finally I found just the thing... a mini electric sandwich maker:


This device drew 600 watts, which I properly guessed ran 300 watts per side:


I got really lucky because it even has a temp regulator. Who would have guessed that sandwiches cook at the same temp as the fusion temp of polyethylene


UPDATE NOTE:
On subsequent posts you will see information volunteered by a reader with far more polyethylene welding experience than I will ever have. Owing to his suggestions, I have passed over the mini-sandwich maker's thermostat because it doesn't allow the heat to go high enough. I have instead decided to go with an electric skillet temp controller because it allows temperatures up to 450 degrees F. I have also wrestled with the fabrication of a simple-to-make answer to a device like the Mini-Mac:


Let there be no mistake, this is a really well-made piece of equipment and a professional ought to trust his work to nothing less. However the price of the Mini-Mac and heater is about $2000, so resourcefulness must prevail.


So here is my current thinking on how to de-technify a device to precisely join poly pipe for fusion welding:


In the background is the jig for centering the pipe. I built it on a large L-bracket. The smaller angle was welded in place first, before cutting out the section from the middle, thus assuring that the two sections would be in line. Since my house is small and well-insulated, it will require a pretty small loop field, so I'll be able to get by with just 3/4" pipe. The operation will require two people, one to hold the heating iron, the other to hold the pipe in place and to apply force on the pipe when the fusion temperature has been reached.In the foreground, bottom-right is the electric skillet heat control (temp control goes over 450F), in the mid-ground, middle left is the heat-cell which I made from the band-sawed Teflon skillet and the 300 watt mini-sandwich heating element. I'll post more detailed photos in a couple of days.

Still have a few mechanical problems to solve before the Mini-Hack meets the poly pipe. I ordered 200 feet of poly pipe five days ago, should arrive in about a week.

[EDIT: Here is a picture of the finished fusion tool. Lethal voltage just a fraction of an inch away from my fingers. This must get fixed before it is plugged in.]




Regards,

-AC_Hacker

P.S.: I just located some good, free industry literature. The Plastic Pipe Institute (there is such a thing) has a book called Polyethylene Pipe Handbook which can be downloaded chapter at a time here:
Handbook of PE Pipe

...of special importance is the chapter on "PE Pipe Joining Procedures" located here:
http://plasticpipe.org/pdf/chapter09.pdf

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Last edited by AC_Hacker; 06-30-13 at 10:04 AM.. Reason: in-line images, new ideas, new progress...
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