New Part: Bicycle seat (3 of 3)

posted in: Carbon Fiber | 2

Last part of this process. Now we have to make the piece of carbon fiber. While it seems a simple step, you have some details that will not make it so obvious.

We start from the last entry: the Mould. After unmolding, I should make sure that the surface is perfectly smooth, which happened to a very light sanding with wet sandpaper 500 grit. This leaves almost polished surface. Then, clean it well with soap and water and then with acetone to wipe any dirt or grease that may cause the mold release wears off. One wrong step, and the whole process be damaged. It pays to be thorough


As with mold, I proceed to prepare all the material that I will use, and once you have everything at hand, I proceed:


– First, I apply generously mold release into the mold. 7 layers
– I mix the resin and paint the entire mold well with her. Extend it with a brush evenly.


– I apply the first layer of carbon fiber. This I have to apply very carefully, as it will be seen that, so no wrinkles, try not to move the plot, and copy the entire surface well without deforming.
– With the brush, compact well the resin throughout the cloth has to be well soaked
– Next layer of fiber, this time I’ll use a super heavyweight, whose fiber orientation is in + -45 °, and is extremely durable. This is used in boats, and trust that these three layers gives him suficient stiffness. More compact resin and again, so it is all well soaked


– Proceeding in the same manner with the other layers, so that the last one is a fiber layer as the first, for which the smooth finish is decent.

– For the last layer, I will apply a coat of Peel Ply. It is a Nylon cloth, which is used to facilitate removal of excess resin, when the vacuum is applied, and also leaves a rough finish, if we continue later laminating. No need to sand


– When I said last layer, not to say that it was over, far from it! Now we have to prepare to apply entire set vacuum and facilitate the absorption of excess resin. That’s what I’m going to use a sheet of plastic micro perforated, which comes packed with a layer of fiberglass. This allows the resin to pass through the micro holes of the plastic, to finish filling a blanket retainer, but without allowing the blanket from sticking to the end piece, which is fundamental.


– This is the layer of plastic micro perforated. And just above I applied a layer of retaining blanket that looks like a sheet of cotton, but has very good absorption properties.

– In this image can be seen perfectly as the resin begins to transfer the micro perforated plastic film, and then we see the retaining blanket

– Now if we’re done with the whole package, just need to put it in a vacuum bag.

– As its name suggests, is nothing more than a plastic bag, but it has to be resistant to temperatures around 80 degrees, and be strong enough to not bore with some small edge, of course, no leak. Inside I put the tube vacuum pump (which coincidentally fits a motor old fridge) But I added a tube which are used for winding cables, so that over, and when the vacuum is done, create a kind channel to ensure that air is drawn evenly throughout the part. In the following video this is best appreciated.


– In this picture it looks like the channel allows the generation gap fairly uniformly, and as the resin will transferring micro perforated plastic retainer soaking the blanket. Now I have to put the whole set in an oven, and comply with the periods of curing of the resin.

– Yes, I agree that it may seem unprofessional, but with a simple cardboard box and a heater bathroom, I have come to reach temperatures up to 70 °, more than enough for the resin to cure in an hour or little more .

So far the lamination process. The following steps correspond to the creation of the piece itself, shaping the carbon surface by sanding and work.
Once the cured resin is demolded, and as with the mold, the piece goes smoothly. Here we see the amount of resin that has soaked blanket retainer. If not for her, all this excess resin would have accumulated in the piece, increasing its weight.

After removing the retaining blanket and the other layers that do not serve us, we have the final piece. The result, for the first piece that I make independently and on my own, more than acceptable. The only failures due to not having autoclave or more powerful vacuum pump, the fiber has not been well adhered to the mold, generating small pockets of air, which meant surface defects. If we were to paint it would not be a problem because it can be repaired, but if we leave carbon look, I’ll fill with resin and sanded again.

Now comes the dirty, tedious job of all, clean up and sanding the piece until the desired shape. As I said before, because the vacuum was not perfect, the surface has many pores, so it will be sanded and hit a coat of resin to cover them. This process is inherent in almost every piece carbon fiber finish whenever you want carbon view. There are always small pores to be plugged with more resin. After the resin applied, and let it dry, re-sanding. In this step you have to be careful, because if you sand too much, we risk destroying the first carbon layer, and the finish will look deteriorated. The trick is sanding as the dust is white (resin) if it begins to be black, is that we are removing carbon.

4 layers of resin and sanding later, we have this result:

As you can see, the finish is matte, ultimately sanding with wet sandpaper grain 500 The piece is ready for his last operation. Lacquer. This can be performed either with gun or spray, regardless of method, you must have some experience or practice before, it is a very delicate operation that marked the final part quality. If we had applied lacquer may drip, if we do not, stay grainy. So you have to implement the just and necessary, and uniform throughout the piece.
Updated March 30, 2014:
Finally assemble irons to mount on the bike. So I settled on a bike, and my good friend Jose Antonio made ​​guinea pig …
Their impressions: the saddle perfectly fulfills its function. It is comfortable, durable, but hard. Logically it would lack some flexibility, which can be fixed with some perhaps less carbon layer, to deform and somehow “dim”. But most importantly: It works!
prueba sillin 1
prueba sillin 3
prueba sillin 2

2 Responses

  1. Vallekano

    Hola tocayo,

    Lo primero felicitarte por tu máquina y los resultados que estás obteniendo. Yo llevo años con la idea de la CNC en la cabeza pero nunca he tenido sitio. En los próximos meses seguramente ya tenga el huequecito y me lance a construirla. Mientras tanto han pasado muchas horas de Solidworks y muchos diseños y presupuestos. Como tu la idea es hacer una de MDF y luego con ella y si le cojo la gracia ir haciendo y sustituyendo la madera por aluminio. Tenía pensado hacer una máquina muy similar a la tuya solo que pensaba invertir más en las guías y usar raíles soportados. Pero viendo tus resultados la verdad es que estás consiguiendo gran calidad con esas guias caseras…y son mucho más baratas. Bueno, soltado el rollo va mi pregunta :). Has echo alguna prueba de mecanizar aluminio? Porque sería interesante saber si tu máquina lo admite, aunque sea a baja velocidad. Esto pensando en construir con esta CNC una v2 en aluminio. Bueno, gracias y sigue compartiendo tus pinitos en este mundo que te seguimos.

  2. Oscar Terrer

    Hola Oscar!
    La verdad es que la idea inicial del proyecto era acabar con una fresadora en aluminio, ya que para romper mano, preferia no gastarme mucho dinero, y de la de madera se pueden aprovechar muchisimas cosas que si o si te tienes que gastar en una de aluminio. Ahora que ya tengo el know how, podria ponerme a diseñarla y construirla, pero… falta el dinero, cosa importante. Mientras sigo aprendiendo cosas con la de madera, entre ellas, me falta probar a mecanizar aluminio, como bien dices. Lo tengo en tareas pendientes, cuando lo consiga, colgare los resultados, no lo dudes. De todas formas, si quieres construir una V2 de mi maquina, consultame todo lo que necesites! sin compromiso. para mas detalles, contacta conmigo a traves del correo