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Fab Academy 2016

Week 14 - Composites
This weeks assignment is to create a 3D mold and produce a fiber composite part in it.

The plan


I will be using a very cheap material like soft wood or high density foam to make the mold and then create a fiber composite using Epoxy resin and woven rovin cloth. The vaccum sealant bag for used in the process will be made using vaccum bag film and sealant tape.

Things used for this assignment



Epoxy resine was hard to source and after searching for a while, I was able to procure epoxy resing and harnder from Sharon Eningeering Enterprises in Kochi.

The wooden block was taken from a construction site nearby to FabLab Kochi. I had trouble finding a large 30cm x 30cm block. In order to complete this project, I am planning on producing a smaller fiber composite part with a smaller wooden block.
For this assignment, I'm making a simple soap tray using Epoxy resin and woven rovin fibre.
composite

I cut a part out of the wooden block to create a shopbot-ready wooden block which can be screwed to the shopbot's sacrificial plywood layer for milling.

composite

This is a very cheap and soft wooden block which weighs around quarter a kilogram. That's far less than what a machinable wax block of the same volume weighs.

composite
Designed a simple mold in autocad. Exported the same in stl format.
composite
Imported the stl file in vcarve. I adjusted the zero plane on top and centered the object

composite
In toolpathe generated rough finish and fine finish. Combined both together and saved it into a gcode file

composite

Machined rough finish on shopbot.

composite

Followed by fine finish.

composite

The resin and harnder needs to mixed in 10:1 ratio

composite

Mold, sealant tape, resin, hardner and rovin cloth.

composite

The plan is to use three layers of this woven rovin cloth to create a hard fibre.

composite

10 part resin and one part harnder mixed in a displosible cup.

composite

I marked the edges of the mold on rovin using temporary marker.

composite

Three pieces of the rovin material were cut in the same size to be applied as three layers.
composite

Cut another peice of the vaccum bag film.

composite

Placed the vaccum bag film on top of the mold.
composite

Dipped the rovin cloth in the resin-hardner solution, squeezed it gently and applied it on the top of the mold over the film.

composite

I sticked sealant tape on four sides of the vaccum bag film.

composite

A piece of the breather fabric was cut and placed on top of the three layers of rovin dipped in resin solution.

composite

Above the breather fabric layer, aother layer of vaccum bag film was placed and pressed together carefully with the sealant material on four sides. The end of the vaccum cleaner available at FabLab was attached to a smaller nozzle using masking tape and inserted at the side of the vaccum bag trough the sealant tape.

composite

Vaccum cleaner was switched on and once the layers were tightly pressed, the nozzle entrance was sealed by pressing top and bottom layers of sealant material while the vaccum cleaner was working. This ensured that air is not trapped inside vaccum bag. Now the bag is set aside to get cured. The curing time is between 8 hours for this particluar resin.

composite

After setting it aside for 8 hours, I extracted the produced fiber part. I cut the extra edges using a normal scissor. Now the fiber is solid, hard and sturdy.
composite

For the time being I will use this soap tray to keep some batteries. :-)

Mold files:
DJ.composite.dwg
DJ.composite.stl