Homebrew PCBs

On Tue, 02 Jan 2007 18:12:50 +0100, twb8899 <twb8899@...> wrote:

>> The Diacro machine is smaller but I have formed .125" ABS
>> parts 6" deep with this machine. My molds are made from hardwood and
>> sometimes I solder pieces of circuit board laminate together to make
>> the shape needed. Most of the molds I use are positive molds but I
>> almost always use negative (cavity) molds for the deep parts.
>
>
> I did not know plastic that thick can still be vacuum formed, good  
> to know!
>
> ST


I used to work at a plastics company making their vacuum boxes for  
mold forming.   Got pretty good at it if I do say so myself.




The trick with getting a deep mold to work is using what they called  
a "clip" box, an upper vacuum chamber box with lexan viewing ports on  
the sides.

You heat the plastic sheet, typically no more than 1/4 inch thick,   
turn on the vacuum to the upper box and watch as it makes the soft  
plastic balloon up.   Then you flip the vacuum to the mold and the  
plastic collapses down and forms to the mold, which has lots of 1/64  
inch vacuum holes drilled in it.

If you don't use this technique to stretch the plastic first, the  
thickness of the finished part will be uneven over a deep mold.     
You could have breakthroughs or weak spots.


I did some of the mold work too.   Gosh, I love that Butcher's Wax.    
We had it in sheets 1/4 inch thick and you could build forms out of  
it for casting or fiberglassing.


Speaking of enclosure design, if you have a sign supply company  
nearby, they have Celtec boards.   It's something like a foamed  
plastic, very useful.


I've assembled stuff out of Celtec with Gorilla glue and screws.   As  
I recall, you can bend it by applying a little heat.   A friend  
loaned me a "hot strip" a while back.

You just clamp it to the plastic, plug it in, and when it's time to  
bend it, Celtec will pretty much bend on the that line.    I used it  
to whip up some brackets for holding household water filters, it was  
fun.


Corian, the countertop stuff, has some real potential too.






















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