Q & A: Polished acrylic machining

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Problem

Let’s say I wanted to do some Taig CNC milling on an acrylic or
polycarbonate block. The result needs to have some decent optical
clarity but I expect the tooling will result in a fairly scratched,
milky surface.

Is there any simple answer for this? I know there are plastic polishes
that can kinda buff that out but I’d expect major problems getting a
Dremel buffer wheel into small low spots. Is there any magic cutting
head or something that results in a smooth surface, or some special tool
or chemical for removing them?

Solution

depends on the shape- if its a flat area you can get good results simply by
lacquering the parts, this hides the m/c’ng defects. This technique
can produce good optical clarity on prototypes with little need for excessive
polishing.

you can also use a small torch to feather the edges of clear acrylic,
you have to use with care. A Propane torch is an excellent choice, but as
I said, use with small strokes, and feather the heat to the
material, takes a little practice.

you can try the acrylic cement that is solvent base to try to
restore the surface shining in the machining area you can improve it
disolving in it some of the acrilic chips.

The next option is to get somo chlorinated solvent (chloroform is the
one that I used) and disolve some acrilic plastic on it up to get the
consisitncy of a light oil (is about 10% in weight of acrilic).

with this solution aply it to the surface and allow to dry, take the
normal precautions to the use of solvents (use it away from flames
and sparks and with a good air circulation)

If you need to polish some surface you can use your dental paste
(preference the white one) with a rag or you can use the polish
compound that is use for cars with good resuls if you need to use in
a small hole you can saturate a cotton cord with the polish paste and
past the cord back and for several times and that make the trick.
Jose L Sanchez

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