Hi Mark,

No actually I am just across the channel in Brittany, France. I will try to find that guy you are mentioning...

Thanks !

https://www.youtube.com/watch?v=HfrFaKDsJxc

Surface finish is not such an issue as it can be re-worked after.
In fact, I am not really trying to make the most perfectly looking parts...they are for racing bikes so yes, looking decent is nice, but being quick to build and reliable is more important. And the thing is that I do lots of small but different parts. And it feels (but I may be wrong) that infusion would take me a lot of time for parts that can be quite small, especially when I want to make a few...

Too bad that I cannot just give it a shot to see how I get it to work and decide after. Infusion no problem to try, I have more or less all I need to give it a shot...but pre-preg, there is the oven issue and my kitchen oven does not sound like a good idea (-:

I agree with what Mark said.  The prepreg is more equipment intensive and the material is more expensive.  Debulking multi-ply layups is more time.  You'll also need to consider high temperature capable tooling which is an added issue.  Building an oven isn't a huge deal - but buying a used industrial one may be safer and cheaper in the long run.  Beware the unattended home made oven!

You can probably infuse on the tooling you are already using for wet layup... maybe.  Unless you have very nice tooling surfaces (or metal molds) you may find infusion gives you a better surface finish too - just more resin.  You didn't mention core, but infusion is more core friendly for non-honeycomb stuff.  

Thanks a lot for your reply !!! I am leaning towards pre-preg maybe...because I do make complex shapes and I must say that the wet lay-up can be quite a lot of work. Also yes, pre-preg seems to be a little less toxic, less waste...easier in my garage ! I have no issue with the slightly higher costs (because it does seem that after a bit of a learning curve, I would be faster at setting it up...and so save a lot of my time !), and I know someone who can then spray a very good finish afterwards so even if my parts are not the best aesthetically speaking right off the mold, it should be fine. Storage in a freezer is not an issue either...the real one is the oven...the Easy Composite oven would be awesome (I don't have access to an autoclave)...but it is pricey...

THanks !

There are, as you'd probably expect, lots of different pro's and con's to weigh-up when deciding what process will work best for you

With pre-preg manufacture, I'm guessing that you'll be looking at out of autoclave processing, unless you have access to an autoclave?

This process can deliver parts that are probably the most optimal in terms of strength versus weight, although infused parts won't be significantly far behind. For many, using pre-preg feels more straightforward and 'cleaner' as you don't need to handle and mix resins. It can also offer a somewhat easier approach to producing parts that have some complex shapes to them or require split-moulds to deal with return edges etc. Another benefit is the in-built heat tolerance and this might be a desirable feature for you? Infused parts can be post-cured (which would also require a good oven set-up) but not quite to the same temperatures and you'll likely need to deal with resin shrinkage afterwards that'll leave them looking quite 'bumpy'.

On the flip side, getting good cosmetic results can be challenging and a lot will depend on your skill and access to reliable materials that work well with oven-only curing. If you intend to clear-coat your parts, this might not be such a concern but many people find that there can be quite a steep learning curve towards getting reliable results, with some trial and error a possibility. Tooling and fabric costs can also be higher, but some of this would be offset by the fact that you wouldn't need separate resin and there'd likely be a small saving on other bagging materials. There is also the need to buy a good sized curing oven that can precisely control the heat, but many people who have the necessary skills and confidence have made their own relatively cheaply

Once you've mastered the basics of infusion, it can be quite a flexible process that offers the chance to use a greater range of fabrics than are usually available in pre-preg form. You can also opt to use polyester or vinylester resins, if you're willing to compromise a little part strength and this would save on material costs. You tend to waste a little more fabric, due to a bit more overlapping onto wider mould flanges but, generally speaking, dry fabric would be less expensive that pre-preg material

It can take a little while to develop your bagging skills and it can take a bit longer than learning to envelope bag moulds, as per pre-pregs. Lay-up time can also take a bit longer and can be a bit more fiddly. If you use some of the more stable surface fabrics and a good spray-tack, it is possible to cut and joint separate pieces really well where necessary for good cosmetics. If ambient temperatures aren't always ideal, you can make a fairly simple 'hot box' to help with curing. 

It is possible to use split-moulds, but it can be a little more challenging to design the moulds if you don't want to resort to envelope bagging the whole thing. Pre-preg use has quite an advantage here insomuch as the natural fabric tack can help on inverted returns. You don't need to worry about resin seepage onto the reverse of a mould if using an envelope bag 

Infusion does offer the opportunity to use an in-mould coating prior to laying down your fabric, though, which is not really possible with pre-pregs due to the processing temperatures. This can give your parts more UV resistance and the option to carry out minor surface repairs without losing the gloss finish. A compressor and dedicated cup gun sprayer would be required for good results, but it can be a good alternative to post-production spraying that can be a bit more technical to get good results from and more costly.

I'm sure that others might add a few more pro's and con's based upon their experience, but both methods can produce really great quality parts. I guess that you'll need to weigh-up what features do and don't work for you in terms of the parts that you'd like to make and how they'll be used. Getting a good oven set-up is key for pre-pregs, though and it'd certainly be a useful thing to have even if you opt to infuse later. 

 

 

Dear all,

Have been making carbon fiber parts for race motorcycles...the old way (wet layup, etc...). Trying to get things improved and nicer...so there will be some time and $$ investment ! So would you suggest me to move toward Pre-preg or infusion ?

Thanks for  hour help !