OldSynths

HI again, Richard,

I've been kicking around the idea of molding up some other (non-
musical) parts for awhile, and this little episode has finally pushed 
me over the edge.  I went ahead and ordered some molding silicone, 
release agent, and black urethane casting resin.  I imagine I'll have 
all the "fixins" by next weekend.  Naturally I had to order enough to 
make 200 slider knobs, but if I have good luck with my parts I'll be 
glad to make you a copy of yours... although all that shipping back 
and forth across the pond could make this a very long process.  I've 
been working with composites for a number of years, although this 
will be my first venture into do-it-yourself injection molding, so 
I'm looking forward to the new challenge.  My slider knob has a 1mm 
thick white (pointer) line that runs horizontally around its 
circumference that adds a bit more challenge to the project... I'm 
thinking I'll make an initial cast part into which I can mill the 1mm 
slot around its middle (it's nice to have a machine shop at hand) and 
use that to create a new exterior mold, then use an actual knob to 
mold the rear, with the notch for the slider shaft.  One advantage to 
this approach is that the parting line will be at the exact back of 
the knob, so any flash will be removed invisibly.  Once the black 
part is released from the mold I can apply some white casting resin 
to the slot, sand away the excess and polish off the whole thing once 
it's all cured up.  A ton of work to duplicate a 50 cent part, but at 
least it will be right.  I just hope the casting resin's black 
matches the black of the original knob.  We'll see.

 <marv>


--- In oldsynths@yahoogroups.com, "RMC" <rmc@r...> wrote:

> if I do get anywhere with making a mould, I will let you know. 
Thanks for 
> getting in touch - at least we both know we aren't alone in our 
feeble 
> quest!
> 
> Cheers
> 
> Richard Craven
> England