Just Say No..?

[Vipersan]

Not yet there but bloody close I think ...
Here are some photos of my first attempt to cast a replacement cam component in liquid plastic ...
If successful it would of course have to be drilled out ...
As expected air bubbles trapped in the confined space of the silicon rubber mold are causing problems ...
These 'bubbles' can be clearly seen in the first component made..
luckilly the part is easily removed and does not stick to the mold thus once cleaned it can be re-used if handled gently..
rgds
VS

Time to invest in some disposable syringes I think ...
These of course could only be used once per session ...(the more molds I have on the go the better)
..but would allow sufficient 'mixed' plastic to be drawn up and injected under pressure into the mold ...and maybe less air bubbles resulting..
just an idea as yet ..
we shall see...
...also adding a hole at the top of the mold and inserting a plastic drinking straw would help to allow trapped air to be forced out.

 

[Vipersan]

Looks like I may never perfect this technique for making small plastic gear parts ..
My mold making skills have significantly improved as well as the ability to run the process without much mess ..
In this case the part produced is my best yet ..
but still not perfect although it is useable in an emergency..
Basically the problem appears to me micro bubbles of gas being released in an enclosed space (within the mold) which rise unable to vent around the more complex areas of the structure (teeth) ...all this during the curing process ..and even after I have used the syringe pump to force the liquid plastic though and out of the mold several times to be drawn back in without bubbles after these have been expelled as much as possible.
So even after several passes through the mold and venting completed leaving what I think is just liquid plastic in the mold ..
micro bubbles of gas (not neccessarily air) are being released from the liquid during curing ..
These of course cannot escape..
cest la vie..
but at least I gave it my best shot..
rgds
VS

 

[Vipersan]

2 more images ..
hit my max of 10