Matter

This page discusses different kinds of matter, concentrating on their behavior in various fabrication regimes. Most of the discussion is specific to laser engraving and cutting, but that may change over time.

Plastic, etc.

Many types of plastic do not work well with laser cutting and engraving. For example, some plastics burn, melt, or give off Chlorine gas (!). Some types of rubber also contain Chlorine; unfortunately, I haven't found an easy way to distinguish the bogons.

Acrylic Glass

Acrylic glass (PMMA) is a bit pricy ($14 for a 24" x 18" x 1/8" sheet at TechShop), but it engraves nicely and produces a very robust result. The original surface is glossy; engraved surfaces are rough and whitened. Opaque sheets work better for sighted users, but a blind user has no reason to care.

Although relief engraving at high power causes acrylic to warp, careful use of power and speed settings can mitigate this. Fastening the piece to a flat surface (e.g., with tape) can also keep the warping under control during the engraving process. Finally, the finished Utile can be placed in a flattening jig and heated to acrylic's glass transition temperature (e.g., 250 degrees F).

I'm planning to experiment with Duraplex, an "impact modified" form of extruded acrylic sheet. Although it is more prone to burning or melting than (say) cast acrylic, its superior impact resistance is appealing, given the amount of handling that the tiles are expected to endure.

Wood, etc.

Note: Be very cautious about using exotic woods. You really don't want to be breathing (or emitting) toxic smoke! Nor do you want to poison the folks who are handling your finished products.

Finishes

For convenience, it would be nice to use a finish that is water based and does not require mixing. However, this may not be an option.

Various finishes protect the wood, but most do not strengthen it. TMI's stabilizing resin (applied under a vacuum and heat-cured) appears to be an exception.

Hardboard

Smooth white hardboard wall panel (1/8") is extremely inexpensive ($13 for a 96" x 48" x 1/8" sheet at Lowes, with free cutting!) and the white coating provides good visual feedback (on one side) for sighted users. However, small features (e.g., braille dots, walls) are fragile, so it can only be used for engraved (rather than relieved) features.

Plywood

As described in the Ultimate Guide to Baltic Birch Plywood, birch plywood is a very nice material:

Baltic birch’s core is unlike traditional plywood you may be used to seeing: the layers of inner plies are 1.5 mm-thick solid birch veneer, cross-banded, and laminated with exterior grade adhesive. It's a recipe that results in a void-free core with a number of advantages, which is why in the U.S. we've discovered that the material is fantastic for thousands of projects in woodworking.

Birch plywood is about 2/3 the cost and weight of Acrylic glass ($10 for a 24" x 18" x 1/8" sheet at TechShop). It works nicely and produces an attractive and reasonably robust result. Wood can a bit tricky to engrave, tending to char, smoke, and catch fire. However, this can be mitigated by making multiple passes at low power, etc.

It has been suggested that I look into plywood that has a central core of MDF (medium-density fibreboard). MDF engraves more consistently than wood, because it has no (glue-filled) gaps.


This wiki page is maintained by Rich Morin, an independent consultant specializing in software design, development, and documentation. Please feel free to email comments, inquiries, suggestions, etc!

Topic revision: r9 - 27 Nov 2015, RichMorin
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