I believe I've acknowledged that uniform heating does not follow from uniform air temperature, and that the rate of heating depends on the velocity.
I've said so myself, repeatedly.
My point is that while heating rates for different regions of the sheet will be different, depending on air...
IRstuff, I'm not sure what you're trying to tell me.
I understand that in a pure convection oven (no direct infrared), heating rates will vary with uneven airflow. However, as long as the airflow is nonzero everywhere and the air is continuously mixed and redistributed, all temperatures should...
I may indeed go with radiant, using nichrome coil. That's the easiest route to something that works fairly well.
What I'm trying to figure out is whether a convection oven would give better results, and how hard it is to construct a good enough convection oven. Ideally, I'd come up with a...
Dwight,
Thanks for the link, but I've been there (and various sites about robotics, RC model building, prop and costume making, etc.), and there isn't much depth of engineering knowledge out there in the hobbyist world. (With a few exceptions, like Doug Walsh.)
But perhaps your point is...
I have consider injecting polyurethane, but I don't currently see how to do it with simple, cheap machinery and very simple tooling. I can currently vac form thin sheets, including foam sheets, and if I could simply laminate them a la vacuum bagging, that seems acceptable for many purposes...
Harry,
I have several applications in mind, all of which require a certain rigidity and light weight. (And ideally the ability to take whatever paint you want and not have it crack or flake off because the lightweight plastic flexes too much.)
One example would be for RC model planes. Hollow...
I've been thinking about vacuum-forming a sandwich construction in three vacuum forming steps, applying a spray adhesive in between.
The idea is to construct something stiff and light, similar to foamcore board, in the desired shape, using a thin layer of HIPs or ABS followed by a thin layer of...
BTW, what's a good place to get relatively small quantities of EVA foam sheet cheaply?
I've been vacuum-forming Foamies from the craft store, but it only comes in limited thicknesses (2mm, 3mm, and 6mm) and sizes. (I can only find the 6mm in 9x12 sheets, which are way too small. I can find...
DIY vacuum forming is popular among Star Wars fans who make their own stormtrooper costumes, etc. They might be of assistance, too.
http://www.tk560.com has flip-flop vacuum table plans and a discussion board where people talk about alternative designs (e.g, over-and-under configurations, gas...
OK, this is sounding doable...
As I understand it, high-end commercial convection ovens for heating plastic generally blow the air 1 to 5 meters per second.
I'm guessing that they top out a 4 or 5 meters/second because the limiting factor is the thermal conductivity of the plastic, not the...
Is there a simple generalization about the effect of velocity on heat transfer when using simple forced convection across a sheet? How does the velocity affect the heat transfer---e.g., almost linearly, or not nearly linearly, or what?
I want to be able to heat a 2 x 2 foot sheets of 2 to 6...
