Re: [CAD_CAM_EDM_DRO] plastics

At 09:34 PM 1/12/02 -0000, you wrote:

>Forgive me for raising a question which is not specifically related to CAD
>or CAM but I have a problem which is perplexing me and preventing me from
>finishing my mill !! ;o)
>
>I have been making a new mouthpiece for my euphonium out of acrylic
>(perspex, lucite?) and I have turned it from a solid 2" diameter rod. When I
>finished it and polished it it looked the bees knees and I was delighted
>but, since I have been playing on it for a few days, it has developed a
>network of fine cracks around the narrowest portion of the bore. I am
>assuming that these must be due to vibration from the sweet musical notes
>but, since such plastic mouthpieces are made and sold commercially in the
>US, I assume that they shouldn't be there and are probably due to stresses
>already in the plastic.
>Does anyone know if there is a way to stress relieve plastics after
>machining?

Acrylic is particularly sensitive to stress-corrosion cracking. If you
polish the acrylic and avoid stressed areas like self-cutting threaded
screws) you may be able to avoid it. It goes without saying (but that's
never stopped me) that you should avoid any exposure of acrylic to solvent
or even solvent fumes.

Best regards,
Spehro Pefhany --"it's the network..." "The Journey is the reward"
speff@... Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
/.-.\
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