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An affordable alternative to JB-Weld and BBQ paint?Thursday, July 31. 2008Cheaper alternatives to Cerastil for securing nichrome heater wire to extruder barrels may be in the offing... Nearly two years ago when Adrian invented the Mk II extruder, the basic enabling technology for Reprap and pretty much any other low cost 3D printer project you'd care to name, he dealt with the problem of attaching the nichrome heater wire to the extruder barrel by wrapping the wire in PTFE tape, a very unsatisfactory solution. I found insulated nichrome wire which helped matters a bit but that was never quite a satisfactory solution and before too long we were experimenting with things like BBQ paint, which I still use, and JB-Weld, a high temperature epoxy which is in wide use in the Reprap community. The problem is that BBQ paint has to be refurbished about every hundred hours and JB-Weld simply perishes in a similar time period. Recently, Chris Palmer (Nophead) discovered Cerastil, a German high temperature ceramic cement, which gives wonderful results but costs about $200/kg. The problem with Cerastil is that the minimum size is a kilogram and you only need a few grammes to attach nichrome heater wire to your extruder barrel. A few weeks ago I went hunting for a cheaper alternative to Cerastil. I ran across an American firm, Cotronics, which offered what may be a close match for Cerastil for about $50-60/kg. I took delivery on some this afternoon. 
I will be trying to use Resbond 989FS to build up one of my thin-walled extruder tubes within a week or two. Resbond 989FS seems to be slightly superior to Cerastil H-115 if the spec sheets are to be believed and much, much cheaper. On the negative side it comes premixed and the bucket is listed as having a shelf life of 6 months at room temperature. I immediately put it in a ziplock bag and tucked it into the fridge to see if I could do better than that. While cheaper, Resbond still comes in what amounts to 1 kg lots, which is enough to finish hundreds of extruder barrels. Cotronics was kind enough to send across their catalog, however, and paging through it I discovered that they had another product, Thermeez 7020, which isn't quite as strong, but handles heat equally well and, more importantly comes in both standard caulking tubes for about $18 and in 4 oz tubes for $26.50/(package of 3). That last looks to me like it may be about what an individual Reprapper might want to be using.  Check out the pic. Those are, unless I am mistaken, heavy duty nichrome heating coils that they are applying that Thermeez to. That speaks well for it's applicability for our purposes. Now. Who's going to buy and try this stuff? Me again? :-) Trackbacks
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I should really go find that bucket of (cheaper than that, if I recall correctly, or at least smaller) furnace cement from the hardware store I got a couple years back for making perlite-cement refractory insulation and try that...
Not sure if it's exactly this type, but this is the sort of thing:
http://www.woodstove-outlet.com/blackpint.htm
Has anyone tried Kapton Tape?
http://www.kaptontape.com/5_Mil_Kapton_tape.php
500 F? Pretty much the same problem as you have with PTFE tape. The nichrome hits something like 1,400 F at red heat. Red heat with the nichrome in the extruder barrel is a regular occurance where the nichrome exits the barrel into the air.
I've used fibreglass and plaster of paris to great effect.
Also tried making a perlite/cement replacement for the PTFE cylinder - not so successful.
Vik :v)
Let us know how it goes. I also found "flue tape" made by 3M that claims to be good to 600F (315C) - this implies it isn't PTFE based. All else being equal, I prefer tapes to mixes because they're reversible.
I might up a roll and test it for suitability if nothing better (cheaper) surfaces by the time I get to building my extruder.
Hence the interest in ~$5/pint cement that's supposed to stick to metals and is good to 2000F (and is regularly used with gardening perlite to melt things like aluminum), and is available at home improvement stores (at least here in the US)
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