[PSUBS-MAILIST] Acrylic bubble port construction techniques?

[Nathanael Henderson <jude@pconline.com>]

    My question isn't the obvious one, ie. 'how do I.'   Rather, what I'm
wondering is if certain methods are dangerous (would compromise the
structural integrity of the plastic.)

    The most immediate option that springs to mind is milling from a big
solid block of cast acrylic.   I can't imagine any objections to the
strength of the resulting product, but it would be a bit expensive to buy
a huge block just to carve out most of it, plus the considerable headache
of trying to mill out the dome (a lathe of some sort perhaps.)

    Second option:   A laminated block.    You could cut rings of acrylic
out of thinner sheet and fit them together into a rough dome shape, fusing
the sheets with solvent 'glue' (methyl chloride?).  Advantage:   Easy to
obtain sheet acrylic, reduced cost, easier final finishing of the dome.
The big question:   How would the laminated aproach affect final strength
of the plastic?   Probably safe with sufficient de-rating, but I'd feel
better hearing from somebody more knowledgeable.  :-)

    Third option:   Thermoforming, particularly force forming onto a mold.
Probably the cheapest route in terms of plastic costs, but would require
more elaborate equipment and be less predictable in terms of the final
thickness of the plastic.  Limitations on the size/thickness of the dome.

    Fourth option:   Conventional casting into a mold using acrylic
resins.   Advantage:  Efficient, high quality high precision resulting
product.   Ideal for mass production, but possibly very high cost of
equipment to produce them.  Probably not practical for a once-off.

     Fifth option:  Dammit, go buy one.  :-)    How expensive are
commercially manufactured domes?   (Any size prices would be usefull.)