molding basics

[MBG]

What is the best way to learn about molds? I am in a machining school that teaches about cnc and manual machining but really nothing about molds. I have also leanred a little about edm molds and been on a tour through a couple of mold shops. But what is the best way to learn more about molds?

Please help
I tried this before but no results

[mxtras]

Exactly what do you want to mold?

I think the process is basically extremely simple but the processes to achieve the mold are determined by the complexity of the part and the materials to be molded (Plastic, plaster, etc.).

Molds to make boats or bathtubs from composites are relatively easy - in this case, the model is the tricky part - the mold is made from a model (not always but let's keep this simple). Molds to injection mold plastics or urethanes can get tricky depending on the part and the properties of the material.

Is there a specific mold you wish to investigate?

Scott

[MBG]

specific mold. Not really anything specific right now. I have some things in mind. But I would be willing to do anything to start learning.

I would like to learn about plastic and composite molds. Really mainly composites right now. Are the two much different in molding?

Thanks for the help so far

[ynneb]

You have asked a "How long is a piece of sting" question.

Do you want to cast concrete, plastic, resins, iron, alum, pressure filled, vacuum filled, rotational hollow casting, positive casting, negative casting, lost wax, etc.

If you have a specific item let us know and I am sure we could point you in the right direction.

I have done a little with concrete and pourable resin moulding, I do know some other methods too.

Maybe you dont want to tell us what it is you have in mind, but i am sure you can give us a rough idea without any of us stealing your good idea

[MBG]

I would most likely be intersted in learning how to do composite (fiberglass/carbon fiber) and plastic molds.

[MBG]

I researched it deeper. I would like to learn how to do vacuum bagging technique

[MBG]

and maye some resin transfer molds

[ynneb]

Try this for starters Vacuum veneering ( Free plans)

[MBG]

Originally Posted by ynneb Try this for starters Vacuum veneering ( Free plans)

thanks do you go on any messenging service? AIM or YAHOO?

[OCNC]

Originally Posted by MBG and maye some resin transfer molds

grpguru.com If you're serious check out their DVD.

[MBG]

I found out that what I really want to do. I belive the process is vacuum bagging.

ocnc I will check it out

[mxtras]

Plenty of experience (from a few years ago - not currently into that area).

What questions do you have? SCRIMP is pretty straightforward and simple but it's also kind of a pain in the butt. The hardest part is getting the bagging film in position without pinholes, tears or punctures. I would recommend using a Nylon bagging film if it is compatable with your resin. You can find Nylon bagging film that can stretch up to 400%.

If you are making small runs of highly stressed parts, or parts that need to look smooth on both sides, like a rotor blade, you need vacuum bagging otherwise it is just an option. It has added expenses such as bagging film, vacuum source, seperation vessel, sealing tape, fittings and hoses. It takes a few casts to get it down correctly and you can waste resin if it's not done well.

I, personally, don't really care for vacuum bagging but some parts and budgets leave no real alternative. Plan on scrapping the first three or four parts until you get the timing, catalist mix and the vacuum port position correct. If you release the vacuum too late, you can suck the resin right out of the filiments in that local area near the port. Too early and you don't fill out the part. It's almost an art to get things right consistently, but it's an art you can teach yourself, I guess, it just may take a few parts to get it right. if they are big parts then it could get expensive really quick.

There are so many methods and each method of composite manufacture has it's merits. There is usually one method that will stand out for each particular project.

?? - fire away!

Scott