carbon fibre case considerations


mclien

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So I have quite some experience with carbon fibers I dropp my thoughts here.

First what have I done so far (with fiber reinforced resin including glas-, carbon-, aramid-, fibers including mixes of it and colored design fabric):

-recumbend frame

-Seats for recumbends (including molds)

-aerodynamic fairungs for recumbends

-rings (jewlery)

-a new backsige for the fossil wrist PDA watch (bugger battery to fit, 3xtimes the capacity with only 2 mm more in thickness)

And here are the considerations for a pandora carbon fiber case:

The original case is designed for a homogen material to fill a mold, which "should" work also (with some modificatioins) when using very short fibres (less than a 1mm in lenght), which results in a stronger case, with a dark grey (nearly black) monochrom color.

But what most people think of when it comes tocarbn fiberis something like this:

http://engineering.iberobike.com/files/2013/09/Carbon-Bicycle-Frame.jpg

(maybe with smaller patterns of the fibre). To get this finish mostly 2 tricks are done: 1. the firbre you see is most likely some sort of decoration on top of the supporting structure (well not only, but does not that much to it). 2. there are parts "hidden" by plain black color (the bottom braket e.g.).

Both is done, because the supporting structure most likely looks like this:

http://taloncycling.com/resources/TriBike+front.jpg

And believe me this is one of the EVERY goodlooking parts.

So when/if one tries to do a pandora carbon case, there are certain thinks to consider:

-fibers don't like to get bend around sharp edges

-they even like less to fill very tiny structures. In fact they most of the time just don't do it (and due to the way the case is produced, it has a lot of these)

So a carbon case means, you have to design the case compleedly different from the existing one.

Rules for that:

-lowest number of parts you can think of

-flat and smooth as possible

-avoid tiny complitated scructures

So what as to to be sacrified for the carbon case (some are more a guess based on my experience, which are far from professional, as in experience and tools/equipment. But still also far from beginners):

-toolless change of battery. Think open up the bottom of the case shoud work. Alternatively: slide it in/out through a rectangular hole in the side of the case.

-arrester in the hinge (I think of some sort of releasable friction here

-nice carbon look on the key/controll surface (well, you know there are more holes than material). Could be either visible straight fibers or colored resin (needs some tries)

and all the things that happens on the way.

But I think it's worth a try, if there is some interest (at least 10 persons I think). As an idea: to get a working mold for the abacus, I had 3-4 molds, which don't worked an went to trash.

Just let me know, if there is some interest to start that chalange
 
I guess we should not mix up the "classic" carbon fibre with carbon enhanced plastic, these are 2 different things. First one is "backed" with layers while second one is basicly normal plastic with pieces of carbon structures in it, it can be injection molded. I think onto that when people want such kind of material for the Pandora 2. It's very durable, usualy used for modern plastic parts of guns for example.
 
Thats what I ment(ioned). The "carbon enhanced plastic" is what I mentioned first (basicly very short fibers, which result in a much stronger case, than one of a non enhanced plastic).

That works with injection molding (to some higher costs, since I guess you have to work with stronger forms and higher preassures. And perhaps with fewer parts per mold.

What I'm talking about gere is the shiny "visible fabric" thing, which is even more duarable material.

My detaild writing in post one refers to this kind of case.
 
The original case is designed for a homogen material to fill a mold, which "should" work also (with some modificatioins) when using very short fibres (less than a 1mm in lenght), which results in a stronger case, with a dark grey (nearly black) monochrom color.
I think this is probably the way to go. The visible fabric thing is probably going to complicate things too much.

I wonder though: is it either very short fibres (<1mm) or long fibres woven in a fabric, or can you do something in between? E.g. 3mm fibres, still injection molded but with more restrictions on the kind of shapes the mold can have? Or does that not exist?

What is the official name of "carbon enhanced plastic"? On wikipedia I can find only this: https://en.wikipedia.org/wiki/Carbon-fiber-reinforced_polymer but I guess that is the "visible fabric" thing.
 
Thats what I ment(ioned). The "carbon enhanced plastic" is what I mentioned first (basicly very short fibers, which result in a much stronger case, than one of a non enhanced plastic).

That works with injection molding (to some higher costs, since I guess you have to work with stronger forms and higher preassures. And perhaps with fewer parts per mold.

What I'm talking about gere is the shiny "visible fabric" thing, which is even more duarable material.

My detaild writing in post one refers to this kind of case.
Yes, I only wanted to make the difference more clear. Many people think about the "shiny fabric" material when it comes to carbon materials but not many people know that there are also "normal" plastic stuff with carbon that can be injection molded like ordinary plastic. It don't has the typical carbon fibre look of course but it is very durable and rigid. Would give a great case for the new Handheld imho. :)
Stuff like this is available even for 3D printers it seems:

http://www.kickstarter.com/projects/1375236253/proto-pasta-gourmet-food-for-your-3d-printer?ref=live
 
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@_wb_:

The wiki article mainly has that "high end" material in focus, which makes most of the material by using the whole fibre lenght, so yes visible fibres possible, but not a must.

To the fibre lenght: I don't know the most actual stade of the production methods, but generally: the longer the fibers are getting, the more you run into troubles with: mold filling (there may be curves and cornes, where fibers build clusters. Like floating wood on a river), choking (longer fibres will do that much more likly), stability/ durability uf the mold (carbon fibers will wear the mold out more fast the longer they get. Grinding and sawing  carbonreinforced plastics "kill" your tools very fast).

Kind of inbetween those are longer fibres (20-100mm lenght), which are not have any specific direction (like felt). Normally you can use that with a mold of two pieces, where the already in resin embedded firbre is put in (by hand) an than ist closed and through this presure (and heating of the mold), the resin is aactivated and backed. Durability and strenght is enbetween teh 2 mentioned types, but looks not nice, so you will use colored resin to cover that.

Maybe I can do pieces of all kind with the mentiined mini mold of mine,if there is enough interest...

@Fusion Power:

Yes, I#m with you about the material. (still ED or some else has to figure out how much this will raise costs). still I can do something simellar, for everyone to look at.
 
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Most of the parts are quite flat, so i was thinking it would get vacuumpressed and then baked if it were 100% carbon. However i got the impresson that it would be some plastic carbon mixture.

It doesnt really depend on any characteristics not found in solid plastic of the dense kind to begin with, but carbon is a nice selling feature, and its lighter.

I like a more smaller fibre/uniform pattern, the interleaving needs some kind of epoxy coating to look presentable, it would be nice if the whole thing was just one solid thing through, not even painted.
 
You ALLWAYS have to put the fibre in some kind of matrix (most likely it is some kind of resin).

What differs is the amount of resin. The ideal version is as follows: Think of a bundle of drinking straws (only the carbion fiber isseveral time thinner than a human hair). If you sort this in the most dense array possible, you get some "rounded trianges" as gaps. If you fill these and have just one molecule of resin between the straws, the you have the absolute minimum of resin that is usable.

The kind of the laminat (crossed fibers or not, dens of package) and the method used, producing it (without any preasure, with acuum, with vacuum and preasure from the outside) define how close you come to that ideal version.

The reason you see the fibre is, that normaly (cristal) clear resin is used as matrix.
 
What is the official name of "carbon enhanced plastic"? On wikipedia I can find only this: https://en.wikipedia.org/wiki/Carbon-fiber-reinforced_polymer but I guess that is the "visible fabric" thing.
The first picture in the articel is yet another thing. There are sheets of diferent thicknesses of carbon fiber reinforced resin. These are build from layers of fibers in different angles to ahive an material with nearly same strenght in all directions (so kind of removes the "best" direction from the fibre). from this pieces are cut (mostly watercutting) in the desired shape.
 
What is the official name of "carbon enhanced plastic"? On wikipedia I can find only this: https://en.wikipedia.org/wiki/Carbon-fiber-reinforced_polymer but I guess that is the "visible fabric" thing.
The first picture in the articel is yet another thing. There are sheets of diferent thicknesses of carbon fiber reinforced resin. These are build from layers of fibers in different angles to ahive an material with nearly same strenght in all directions (so kind of removes the "best" direction from the fibre). from this pieces are cut (mostly watercutting) in the desired shape.
How does the material handle machining for use with screws (tapping)? Does it need to be pre-tapped or can it take threads from a self-threading machine screw?
 
What is the official name of "carbon enhanced plastic"? On wikipedia I can find only this: https://en.wikipedia.org/wiki/Carbon-fiber-reinforced_polymer but I guess that is the "visible fabric" thing.
The first picture in the articel is yet another thing. There are sheets of diferent thicknesses of carbon fiber reinforced resin. These are build from layers of fibers in different angles to ahive an material with nearly same strenght in all directions (so kind of removes the "best" direction from the fibre). from this pieces are cut (mostly watercutting) in the desired shape.
How does the material handle machining for use with screws (tapping)? Does it need to be pre-tapped or can it take threads from a self-threading machine screw?
Not quite sure here. What is clear carbon is a lot more stress for  whatever does the threading. I think normal self-threading ossibly will kill the screw.

The shorter the fibers are, the less stress for the tool.

While talking this about in this thread is kind of useless, because this material is not really usable for a case. And as you have to build molds for that and build the case anyway aou might as well apply inserts also. Or as mentioned before a piece of thread as part of the mold. Onto which the fibre is applied and after sureing you remove the thread-bold and have carbonfibre thread inside the case.

Again, question is how much interest there is for a carbon fibre case, so I can decide if it's worth to go that path not theoretical. (building some material examples of the tiny wristwatch part I did onceshould be easy enought)
 
I would be very interested in a carbon fibre case. I believe ED mentioned that it was suggested to him by some company, so it could be that he already has (or is waiting to receive) a sample of the material and/or a case made out of it. So before you put too much effort in it, perhaps it would be wise to find out what ED already did first.
 
Hm, I can see this works for simple/hollow structures like a shell but a handheld case like the Pandora has alot of compex internal structures like sinks for the screws, various "chambers" for mainboard, stylus including it's holding mechanisms, battery storage including the battery lid etc. Not sure how this is doable with the "usual" carbon fibre fabric stuff. ^^"

I can imagine to put the carbon only over the outside as structural shell to make the case more durable, inside would be "normal" plastic. But I guess this would cost alot. Better skip the carbon fibre fabric stuff completely and focus on carbon enhanced plastic that can be injection molded, like already mentioned. :)
 
Yes, this kind of case is only doable as a custom extra-thing.

On the outside you have to do smooth shell shapes, which e.g. means you possibly can't have a toolless batery exchange. The inside scruktures can be done in a secons step. It is also possible to inject resin in a manual procedure with a clever mold design and the use of vacuum...

Mayby I'm doing it anyway to have it for my own...
 
There is a lot of people claiming this doesn't even work or any benefits of carbon fiber is ruined by 3D printing it.
He did say: "for prototypes". A prototype doesn't need the benefits of carbon fiber, right? It just needs to give you a feel for if you are going in the right direction with your designs.

-God Ginrai
 
There is a lot of people claiming this doesn't even work or any benefits of carbon fiber is ruined by 3D printing it.
He did say: "for prototypes". A prototype doesn't need the benefits of carbon fiber, right? It just needs to give you a feel for if you are going in the right direction with your designs.

-God Ginrai
Well a much cheaper 3D printer could do the same thing.
 
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