Mold making for CF shaped tube

[IanA]

I am planning to make shaped large diameter CF & aramid tubes for automotive use. Have a variety of sizes and shapes to do – all with bends in them. I am looking for a more cost effective method of making split molds than CNC aluminium.

Mold should be able to withstand repeated cycles of the application of internal pressure - up to 2 bar in an inserted bladder, overall vacuum and heat up to 150C in an oven.

I would appreciate any tips on any mold making materials that could cope with the above.

 

[rstupplebeen]

I have used high temp 3D prints and wood molds at that temperature and pressure. Your definition of repeated cycles should be defined better is that 10 or 10K? What tolerance do you need and what is the overall size of the finished part? A company like

http://www.protomold.com/ProtomoldProcess.aspx

may be able to help you. I hope this helps.

Rob Stupplebeen

 

[MikeHalloran]

Silly me, I thought the market for cold air tubes was just about saturated.

P.T. was right; it's like a river..



Mike Halloran
Pembroke Pines, FL, USA

 

[IanA]

Many thanks for your advice. I have checked out other threads on the site on this subject.
I have alum versions of all of the shaped tubes that I want to replicate in CF. They are air intake and intercooler pipes. They range from 76.2mm to 63.5mm and about 2mm thick walls- A total of 7 tubes. Some need to cope with up to 2.5 bar pressure in service.

I was planning to:-
Use Resin Film Infusion method in split molds - A resin film against the mold to avoid pin-holing and a film between a CF sleeve and one or two aramid sleeves, using an internal pressure bladder.
Consolidate job in vacuum bag to assist resin flow and using an ordinary oven to heat to around 120C.
I am aiming for a flat 'semi-dry' finish to the CF.

Need a molding material suitable to form a split mold and that will cope with the above process and be reusable.
Production quantities circa 20 of each tube.
Longest shaped tube is 400mm.

I have checked out CNC alum molds and cost is prohibitive so need a more economical means of forming such molds for which I have the plugs.

I have only worked in FRP previously for car panels. I would appreciate any guidance to suitable mold materials and any suggestions re my planned production process.

 

[johnkmcguire97]

I would make composite molds using the aluminum tubes as a plug. For information on this, go to

http://www.fiberglast.com

Look in the "learning center" tab, "free online brochures", and "mold construction". A well made composite mold is good for at least 100 parts if you take care of the tool properly and its much cheaper than a CNC aluminum mold.

If you are working with resin films and doing an oven cure, you will need tooling resins that can withstand the temps. I have made a few composite molds using tooling epoxies from Airtech with excellent results. They have tooling epoxies that have an intial cure at room temp and then a post cure to give a service temp up to 400F. They will also provide step by step guides on how to use their products.

 

[Compositepro]

Composite tooling is becoming a popular replacement for metal tools. It can be lower cost with shorter lead times, and the thermal expansion better matches your parts. Bismaleimide resins will generally last much longer than epoxy.

However, composite tools are usually used for vacuum-bag molding where the cure pressure does not place mechanical loads on the mold.