Pivot: No Entombed PLA. Comparing Female Mold Versus Male Plug for Composite Core Clamshells

Wrote a full post and my browser crashed. Lost it. No auto-save Blogger? 

Don't feel like re-writing it all again right now.

Basically, I've decided not to entomb PLA core structures within the frame.

Rather I'll use 3D printed forms to mold individual carbon composite clamshell pieces which will then be bonded together constructing the first [interior] layer of the frame. Then wrap subsequent carbon composite on top of that hollow structure. 

So, basic process will be:

• In SolidWorks, separate frame into individual clam shell forms sized to fit in the printer.
• Print forms.
• Layup onto/into the forms, remove, finish sand individual clamshell pieces.
• Assemble all individual pieces in the fixture forming the first interior layer of the frame.
• Reinforce seams of clamshell segments to preserve and retain geometric accuracy.
• Remove from frame fixture and perform subsequent full layups over the hollow first layer.

But which would be more appropriate: forming over male plugs or into female molds? Test both.

Decision: Use male cores.

• Printed sections can be larger than female molds. 
• Printed male forms use less plastic. 
• Easier to layup over male forms. 
• Easier to vacuum bag over a male form than into a female mold.
• Parts made over male forms have better geometric control over to mating parts like pivots and bottom brackets. 
• Parts from male plugs have better control of the mating/parting line when assembling the clamshell halves to each other.