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Old 10-14-2012, 04:46 PM   #166
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Trying something new...

The last layup for the exhaust shroud didn't work so well, so I decided to try something different; pre-preg.

I cut pieces of plastic a little bit larger then the fabric, then layed the fabric on the plastic. Next I squeegeed epoxy into the fabric.

This is what it looks like before application.








Then I simply grabbed the plastic, folded it like a taco and started to mesage the fabric into the mold. I had let the epoxy sit for about an hour before applying to the mold so it was super sticky, but it wasn't too hard to get it to lay into the mold.




The plastic on the first layer was super hard to peel off. The second was a litte easier, and the third was really easy, but there was a problem. The reason that the plastic was easy to peel off on the last two pieces was because the pieces had cured beyond tackyness. They didn't stick well to the layer below.


I put it all under the heat lamp in hopes that I could get some of the epoxy to flow and stick together a little better, but this only cured it further at this point.


The pre-preg method didn't work very well, and I was so hoping that it would. If only the plastic would peel off easier when the epoxy was tacky. If it did, then this technique cold work very well.

If anyone has any tips on how to do this better, I'm very interested.

No worries, right? We must move forward...

So I applied epoxy to the mold once again and let it get super tacky.

Here I am tilting the mold back and forth to help the epoxy flow through the whole thing instead of pool in the bottom.


Here three layers of fabric have been applied.


I didn't lay the fabric on the long sides down on the flange in hopes that it would help the sides of the mold from pulling off. I guess we'll see...


I think that I may need a vacuumm pump and some bagging materials...

Also, I was thinking that this epoxy was a lot more flexable then the previous epoxy that I was using, but I think now that it just takes longer to cure to its full stiffness.
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Old 10-14-2012, 05:49 PM   #167
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The step you're not replicating, when the epoxy gets to the appropriate point in the cure cycle, you need to deep freeze it to stop the cure. Then you have time to lay it up/press/vacuum.

If you don't freeze it in the right stage of cure you will get that problem.
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Old 10-14-2012, 08:52 PM   #168
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Originally Posted by P B G View Post
The step you're not replicating, when the epoxy gets to the appropriate point in the cure cycle, you need to deep freeze it to stop the cure. Then you have time to lay it up/press/vacuum.

If you don't freeze it in the right stage of cure you will get that problem.
P B G, it sounds like you have some experience with this pre preg stuff. Could you elaborate on the process of making the pre preg material?

When do you know when to freeze it?

I would imagine that you put plastic on the top and bottom before you put it in the freezer. Is this correct?

Thanks for the help, man!!
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Old 10-14-2012, 09:00 PM   #169
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Ha Making it...

I don't make it, BUT - I will say if you find a resin system with a high cure temp, you won't have this issue as much either.

Essentially what you are doing is racing against a resin that is trying to cure. Prepreg materials your concept is that the resin is not going to cure on you in the conditions you are working with.

SO if you layed out your carbon, and used a resin system that needed high temps to cure, and set yourself up with some form of curing oven/autoclave you might be able to do this method more successfully.

The closed I have come to this is to pull a thin plastic over a model of someone's foot, then wet up multiple layers, and layered them, then bagged, and pulled full vacuum, then set under IR oven on low till cured.
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Old 10-15-2012, 08:25 AM   #170
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you may use bagging film instead of plastic to keep out wrinkles

most all of what you are doing is covered over at composites central. start reading and post your project there

I have not done it but a lot of people doing small runs spray clear polyester gel-coat into the mold and lay up epoxy parts to get a bling finish.

also carbon fiber is highly conductive. if you are grinding and cutting take care of electric motors. more than 1 has had a dremel arc out and smoke in their hands. A single thread of tow can snag on a 2-3 prong plug and 7/4 starts early.

to get the detail you want you might have to vac-bag. 2x2 drapes well but hard getting sharpness with hand L/U
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Old 10-15-2012, 08:56 AM   #171
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You would find compression moulding those parts very easy. Someone I know used to make very similar parts, which took about 15 minutes to make and came out pretty much perfect every time. The fact you choose to use epoxy resin system for cosmetic items though, will make things much harder, and even with compression moulding, you will probably still have problems with air bubbles.
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Old 10-15-2012, 12:38 PM   #172
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Quote:
Originally Posted by SkunkWizard View Post
you may use bagging film instead of plastic to keep out wrinkles

I was thinking about peel ply, but I see that "real" prepreg is backed with an embossed type of plastic. I'll see what I can find.

most all of what you are doing is covered over at composites central. start reading and post your project there

I have already signed up. Thanks for the suggestion. BTW, this thread won't change because you all are more fun to share with.

I have not done it but a lot of people doing small runs spray clear polyester gel-coat into the mold and lay up epoxy parts to get a bling finish.

That does sound like a good solution for a smooth clear finish. I think that I'll try to lay up a piece of prepreg with a resin rich first layer and see how that goes.
I'm fond of sanding and finishing the part anyway, so pinholes and small bubbles aren't much of an issue.


also carbon fiber is highly conductive. if you are grinding and cutting take care of electric motors. more than 1 has had a dremel arc out and smoke in their hands. A single thread of tow can snag on a 2-3 prong plug and 7/4 starts early.

That's interesting that you mention this because my Dremel has been running a little, different, if you know what I mean. It very well could be the CF dust.

to get the detail you want you might have to vac-bag. 2x2 drapes well but hard getting sharpness with hand

I have spent some time today looking into a vacuum system. I'll probably build it myself, and of course I'll post the process.

L/U
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Originally Posted by Twin-shocker View Post
You would find compression moulding those parts very easy. Someone I know used to make very similar parts, which took about 15 minutes to make and came out pretty much perfect every time. The fact you choose to use epoxy resin system for cosmetic items though, will make things much harder, and even with compression moulding, you will probably still have problems with air bubbles.
Twin, you elude that using epoxy will cause more problems then using poly. Do you feel that poly is easier to use and if so, what properties of poly make it easier to use?

Thanks, guys!!
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Old 10-15-2012, 01:26 PM   #173
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Unless you are making structural parts, there is no real point in using epoxy. Cost of poly is a lot lower, but ease of use is the main reason, and you would find a low viscosity clear poly casting resin and compression moulding, would be much much easier that what you are doing currently.
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Old 10-15-2012, 05:07 PM   #174
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Transfer molding in a vacuum bag works pretty decent too.
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Old 10-17-2012, 05:56 AM   #175
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I would like to add this simple observation. Whilst it is great to have advice, along of new steps in learning, It is also easy to get overwhelmed. I am not intending to pick on anyone here, so please don't take it as such, But RM, you are perhaps getting too exited, and loosing focus on the simple things. All the different advices are all catalysts. Try to focus on one thing at a time. Like bubbles..... change one thing at a time in your layup teq.....so as to be able to identify what went wrong. I will say this. The heat shield, can be laid up with just mold release.....epoxy...... and then fiber and achieve a bubbleless matrix. I just laid the first layer down on my plug. I use the same materials you do. Lot's of the things that are being recommended are great, but not the root of your problem. So dont set the world on fire, trying to get them as they wont necessary change the results. So Calm down..... have a Coors or two.....re-assess the steps, and change one thing at a time...... You are doing great.
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ebrabaek screwed with this post 10-17-2012 at 11:43 AM Reason: Grammer......grrrrr....
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Old 10-17-2012, 07:29 AM   #176
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Quote:
Originally Posted by Twin-shocker View Post
Unless you are making structural parts, there is no real point in using epoxy. Cost of poly is a lot lower, but ease of use is the main reason, and you would find a low viscosity clear poly casting resin and compression moulding, would be much much easier that what you are doing currently.
I am interested in trying out the poly products. Twin, why the clear casting resin?

I would like to set up a nice little (inexpensive) vacuum system, but until then I have another idea for compression molding. I'll post more on this later.

Quote:
Originally Posted by P B G View Post
Transfer molding in a vacuum bag works pretty decent too.
P B G, how does this work? I did a Google search but didn't find anything close to laying up with composites.

Quote:
Originally Posted by ebrabaek View Post
I would like to add this simple observation. Whilst it is great to have advice, along of new steps in learning, It is also easy to get overwhelmed. I am not intending to pick on anyone here, so please don't take it as such, But RM, you are perhaps getting too exited, and loosing focus on the simple things. All the different advices are a catalyst. Try to focus on one thing at a time. Like bubbles..... change one thing at a time in your layup teq.....so as to be able to identify what went wrong. I will say this. The heat shield, can be laid up with just mold release.....epoxy...... and then fiber and achieve a bubbleless matrix. I just laid the first layer down on my plug. I use the same materials you do. Lot's of the things that are being recommended are great, but not the root of your problem. So dont set the world on fire, trying to get them as they wont necessary change the results. So Calm down..... have a Coors or two.....re-assess the steps, and change one thing at a time...... You are doing great.

I know, I know, one step at a time, but this stuff is too fun and there are so many possibilities.

I have had recent successes however, and I'll post more about this when I get home this evening.

Thanks everyone for all the tips and contributions to the thread! I'm hoping that this info is helping others along the same path that you all have taken, and that I am currently on right now.

Keep it up!!
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Old 10-17-2012, 01:27 PM   #177
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It's been a while since i've been in the shop, but I'm getting back into it with some vacuum bagging for a customer of mine.

Observation and suggestion: We had a team of guys laminating our parts (motorcycle fairings) a few years back. We had one very important goal in mind and without this one goal, all the rest would be null. Flexibility in the parts. The lead laminator made a part out of Valspar gel coat and two layers of 6oz plain eglass and made it nearly as flexible even days later, as our parts that we made with 5x the price epoxy resins. he achieved the goal.

He used a squeegee, the same as used to apply bondo, the plastic/rubber/flexible squeegee to run out the excess resin. This dramatically reduced the amount of resin needed and made a thinner stronger more flexible part.

I mention this as an alternative to bagging that will produce a very similar product. This method isn't intended, in my opinion, for CF parts because they will be primarily cosmetic pieces and pulling the fibers will cause the fabric to become crooked.

this method of hand lay up uses a different type of mold also than what's used for vacuum bagging. Since the flange around the part edge isn't necessary in the hand lay up process, and more to the point, the flange creates a lip that makes the fabric lift at the edges, two different types of molds are needes between the two processes. I have an idea to make a mold that will be usable for both processes, but at this point, it would be a waste of time and money since I will eventually be using one or the other for production.
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Old 10-17-2012, 08:33 PM   #178
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Quote:
Originally Posted by beechum1 View Post
It's been a while since i've been in the shop, but I'm getting back into it with some vacuum bagging for a customer of mine.

Observation and suggestion: We had a team of guys laminating our parts (motorcycle fairings) a few years back. We had one very important goal in mind and without this one goal, all the rest would be null. Flexibility in the parts. The lead laminator made a part out of Valspar gel coat and two layers of 6oz plain eglass and made it nearly as flexible even days later, as our parts that we made with 5x the price epoxy resins. he achieved the goal.

He used a squeegee, the same as used to apply bondo, the plastic/rubber/flexible squeegee to run out the excess resin. This dramatically reduced the amount of resin needed and made a thinner stronger more flexible part.

I mention this as an alternative to bagging that will produce a very similar product. This method isn't intended, in my opinion, for CF parts because they will be primarily cosmetic pieces and pulling the fibers will cause the fabric to become crooked.

this method of hand lay up uses a different type of mold also than what's used for vacuum bagging. Since the flange around the part edge isn't necessary in the hand lay up process, and more to the point, the flange creates a lip that makes the fabric lift at the edges, two different types of molds are needes between the two processes. I have an idea to make a mold that will be usable for both processes, but at this point, it would be a waste of time and money since I will eventually be using one or the other for production.
Hey Beechbum! Thanks for hanging out, man!

Thanks for posting the above info. It's great information, most of which I have come to find out is very true. Take for example my last layup. I didn't press the fabric down to the flanges because it kept pulling at the corner. I'll keep this in mind when I make molds designed for hand laying in the future.

Regarding the super flexable part that your man made... I have come to learn that too much resin is BAD. This is one reason why I was hoping that the prepreg technique would work. I was able to apply, and remove excess resin with a squegee when I was making the prepreg. It seems like it would be easier to control the amount of resin that is applied by using this technique.

As for vacuum bagging compared to hand laying, and the challanges that both present; well I hope to be solving the clamping challange very soon. Read below for more details.
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Old 10-17-2012, 08:43 PM   #179
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Finally a bolt on...

Work has been a little crazy lately with the new 10 hour shifts which hasn't left a whole lot of time to work on the projects and post, but I'm doing my best. Hang with me, people...

With the last lay up of the exhaust shroud, I didn't press the fabric down to the flanges which I was hopping would keep the fabric from pulling at the sharpish corners on the long sides of the mold. Well, this worked.

I poped the part to find out that it looked acceptable. There were no real blemishes besides small bubbles.

I trimmed it up, washed it up, and took some pics.


I'm diggin' it.


Before and after...


I think that it looks pretty good.


I rode the usual 25 miles to work, and when I pulled in, all seemed well. But after being stopped for a few minutes it really started to heat up. The screws especially got really hot. The area up close to the seat really heated up and became plyable. The temp outside was probably around 45 or so, so I can't imagine that on a hot day with bags on the bike, chugging along on dirt roads and trails that it would do much better.

I'll see how it goes over the next week or so with the part and report back, but I might have to go with a high temp epoxy for this application.

One thing that I have been thinking about a lot lately is mechanical clamping. I am really interested in vacuum bagging, and I'm sure that I'll go that route someday, but I need to find a better solution for the right now.

I'll post more about what I have in mind tomorrow, but for now I'll leave you with the following two pictures.





It's about to get dirty, folks!!
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Old 10-18-2012, 02:55 AM   #180
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The easy way to make any small cosmetic parts is to use compression moulding, with 2 piece mould tools. Not viable for one offs really though, and for this its probably best to stay with contact moulding.
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