www.TK560.com

[jdougn]

[spektr]

Hobby machines running thin low temp plastics can use hardibacker type stuff and get away with it. Get away with it is the correct term because as we all know, it isnt the ideal material. The oven will have a finite life determined mostly by the worksmanship of the builder. It will neeed replacement at some point in time if you run it a lot.

You have to acknowlege the limits of your machine and accept the fact that it isnt a miracle worker. I see lots of guys wanting to do thicker stuff like 3/16th ABS or more. You need to be a few rungs up the learning ladder to get there. TJ machines are the simplest and least capable. Single sided machines (1 oven) like protoforms are an order of magnatude better, but still have limits you need to understand.

Its all about knowlege.

PERSONALLY, TJ machines with the coils sitting above the hardibacker are a lot better use of hardibacker as the heat radiates up and away from the unit. The bottom of the oven and its hardibacker cools because it is exposed to room temp air from below it against the convection direction (up) Protoform style machines with top ovens are a lot harder on the hardibacker because the fences trap heat and the hardibacker heat soaks faster.

Lets keep this simple because I can do complicated in a heartbeat.
My daily use machine is a lot more capable. Scaleable top and bottom heat. top and/or bottom platen, vac and plug assist top, plug assist bottom. And PLC'd
If I can dream it up I can make it.

Scott.

[Fredo]

Here's another site for hige temp insulation http://www.armilcfs.com/pages/Boards_Specs.htm .They seem to have about everthing................Fredo

[spektr]

Thanks Fredo......

[puppetworks]

Hi all,

This is an old post but its one of only 4 that pop up with 'ceramic fiberboard' in them and it seemed to be the definitive one.

I've built a 2'x3' vacuformer based on the proto-form design. I ordered 'ceramic fiberboard' from a construction supplier. cost $70 shipping included. It is kinda like suspended ceiling tile material, but made of almost a glassy wool substance. without much trouble you can push a nail clean through it. Is this the right stuff? I have the nicrome wire tight against the fiberboard with pennies used as washers and split cotter pins to fasten it.

[kayaker43]

Some pennies are copper coated zinc and melt at around 875F,.. nothing like a shower of molten metal on your plastic sheet to liven up the day. People send me pictures of their plans built machines and some are in carpeted basements!! Sharing ideas is good, but not all ideas are safe to share.

I would use 1400F as a minimum temp when shopping for an oven board material. A lot of people guess at building nichrome elements and being a little off could mean 1500+ wire temps. I read hardibacker was only rated at 375 or something like that?? Many so called "high temp" boards are only good to 1000 or so. None of them will catch fire, they just crack or weaken considerably. I have to buy 2000 lbs from the UK to get exactly what I want. You can find several good choices from Mcmaster Carr but they all cost more than my kits and if you can't pick it up, the freight charges will kill you. I ordered one sheet and it came by truck in a crate and cost $120 just for shipping!!

For the last 15 years I've been looking for an affordable source of material for the oven kits I sell. I follow up on every lead I read on forums or elsewhere, and never really found anything cheap that I'm comfortable using in my kits. Aside from some rare surplus deals, the good stuff is all expensive. All the cheaper options I've found were either too low temp, too dense or too soft, too thick or too thin, and none were cheap enough to be worth compromising performance.

Another aspect to consider is the thermal mass which is related to density. Thick or dense materials mean long warm up times and reduced output. All refractory brick or kiln linings are like that.
_________________
Doug Walsh
www.build-stuff.com
Hobby-Vac and Proto-Form machine plans

Also other plans books and videos for people who like to build things

[puppetworks]

Thanks for the reply.

I hope I didn't come across as endorsing pennies as washers. Not a good plan. I ought to mention I'm from Canada and our Pennies are made of steel now. There were some older American pennies in there too. Were.

The fiberboard I used was $70 for 6 sqft. Seemed pricy enough to me. I'll have to talk to the supplier and get a real answer on what the boards specs are. It is pretty light weight so the thermal mass ought be low.

Is there an odor when you run your oven? From the oven I mean. Not the plastic.

[kayaker43]

I think some US pennies are copper plated zinc but I may have that wrong?

Some boards use an organic binder that smokes the first time. More than that and I would suspect its not up to the task. When its cold you might poke it a little to see if its losing any integrity in the burned area? Most of the materials I've tried make no smoke or smell at all but do discolor a bit where the coils touch.

That price is much less than half what I would expect to pay for the good stuff.
_________________
Doug Walsh
www.build-stuff.com
Hobby-Vac and Proto-Form machine plans

Also other plans books and videos for people who like to build things

[Culvan]