Horological Meandering

Kong
[Moderator]
7855

• Show profile
• Show other posts

I can only explained from ...

my previous plastic injection molding experience.

It is not necessarily accurate to say machining approach is higher cost, as the one with the mold incurred tooling and machine cost too.
I don't have the any figures, so I could not advise accurately.  Will explain with processing steps.

Starting with the molding approach, taking example from AP ....

(details are at this post : www.network54.com )




1) Accurately placing the carbon fibre into mold, as a deviation of just +1 gm, the thickness will increase by 0.6cm or 6mm.





2) Heat the carbon fibre in the mold to a certain temperature then transfer over to a high tonnage press.




3) Pressing the mold and hold till the temperature dropped to the determined level, then removed out of the press.




4) Open the mold and remove the molded unit....




5) The molded unit.  Remove the binder material (white).




6) Machine to final dimensions using diamond and high-speed steel cutting tool.


From above schematic view, using the molding approach, still required many steps and also a final machining step.


As for structural strength (which you termed as 'quality & longer life'), it does not mean that molding is lower, as the design/shape
of the case , the thickness of the walls will determine the more suitable process. 
For thicker walls, both molding or direct maching approach could be used.  However for thinner walls design, most likely direct machining
of a solid block of carbon fibre would yield better strength.

Another consideration to adopt molding approach is for higher production quantity. Since the 'rough shape' is already molded, it will require
less machining to get the final dimension piece.

For direct-machine approach, the fabricator need not have the knowledge of the molding processes and also the heating and press equipment.
However, their production quantity should be a lot more lower, as it will require lots of high cost diamond or high speed steel cutters.

Hope you can follow my rant, otherwise got to talk to you over the phone

Kong