New Part: Bicycle seat 2 of 3

posted in: Carbon Fiber | 0

I continue with the fabrication process. Even though this has no relation with CNC machining, I see this interesting, in order to see how a carbon fiber part is done, from the idea to the last laminate layer and finish. And I’m on it:

Once the model is finished as you can see in the last post, the Master, or 1:1 model of the final shape, it’s ready to work with. So I will start by putty the defects, and round the corners of the model, in this way, when you go to apply the fiber will be much easier to take the form

The first thing I need, putty and sand it, and liters of acetone (always good to have everything clean. Putty and sanding And …
Here is also an attempt to soften the very basis of all, and round the junction between the output surfaces and base.

Not much to explain here, is perhaps one of the most tedious tasks, sanding and sanding and putty defect. The better the putty is applied, there is less sanding. First give the shape, removing material with a 40 grit or 60, removing excess, and giving a general way.
Then apply finer sandpaper, followed with a 180, for example, until you remove scratches from the previous grit, and so what you’re left with the smoother surface possible.

This last image is the result of 4 applications of putty and sandpaper, until the last was a 500 grit water, leaving the almost perfect surface. Obviously, where there is more work, is on the surface of the seat itself, the rest, if not perfectly polished, no matter, because of the part will not use.

The next step, one of the most important, is the application of the release. I’ve used that can see in the picture, so generous. The instructions advise least 3 layers, allowing to dry between them. I applied at least 7. I do not want to risk.

After applying the release agent, you can start rolling the mold. I advise having absolutely ALL the material at hand, and ready to apply. It is important to forecast all the tools that are to be used, and mentally review the process steps to avoid haste and poorly made​​.
You had it all ready, so we continue with the process: First, apply Gel Coat. It is an epoxy based paint is ideal for copying the surface, and with very good grip to the resin and fiber. So generate a surface where later apply the carbon fiber will be tough and durable, and copied to the last detail. With a brush and carefully apply a generous layer


Now comes the important thing. You have to let the gel coat catalyzes a little. And starts to get hard. Thus, as we apply the resin and not drag the gel coat, because almost be hard, but do not let it harden completely, with a half hour is enough. So now you can start, resin, and fiberglass MAT, the hairs, until we say enough. I estimate that every two layers makes a millimeter, and the die has stiffness, at least 3 or 4 mm will be needed. I’ve also taken to implement more fiber in areas where you may need more in the corners or edges


This is the final result, we now have to wait for the resin to cure.

Once cured, must demolding, which always makes me a little nervous … I will have well-defined surfaces out? will have applied the release agent right? the response has been positive, as it has unmolding the first and almost in one fell swoop:


As seen in the images, the result is magnificent. This mold is perfect, and has gone very stiff. You will not have deformation or by time or by weakness. Obviously, the images already clean, but you have to take the radial and review all sides, and sand the surface to not hurt, as the stiff fibers are like knives.

In the next post, the piece of carbon fiber …