14. COMPOSITES

INTRODUCTION

The goal of this assignment is design a 3D mould with the limitations of 3 axis machining, and select and apply suitable material and processes to create a composite part.

Students should have:

Shown how you made your mould and created the composite

Described problems and how you fixed them

Included your design files and ‘hero shot’ photos of the mould and the final part

Read and linked to the material safety data sheet (MSDS) and technical data sheet (TDS) for the resins that you’re using

MOLD AND MILLING

I used SolidWorks to do my design for the molding. I did the shell of a turtle on the top of a rectangular cube.

With the program Modela Player 4 I opened the design in stl and I configured it.

1. Model
1.1. Size and oritentation: If it necessary you can scale the design, depending on the material you had. Also you can selected the top surface.
1.2. Origin: Place the origin on our desing.


2. New process creation: define the characteristics of the molding.
2.1. Type of process: Roughinng to remove most the materail and to shape the mold, and Finishing to obtain a better precision on it.


2.2. Select the cutting surface.


2.3. Select the tool.


2.4. Select the area: is possible to mold all the area or chose a specific area.


2.5. Select the type of tool path area: is possible to mold in X, Y or X+Y, the last one it will spend more time; also the countour lines it is very useful to do the Finishing or if there is a round shapes.


2.6. Set the cutting parameters.


2.7. Save the process.


Is possible to watch the endings of each process.

In my case, I did a Roughing and Finishing with the same tool (the 3.18 mm diameter tool). When it finished I cut the excess material with a cutter.

MIXING EPOXY

For the composite adhesive I used SUPERSAP ONE resin and hardener. The safety data sheet does warn of skin irritation and allergic reactions and cautions against breathing the vapours. For these reasins, we have to work with the resin in a spacius and well ventilated area and using gloves.
On the technical data sheet explains the right mix ratio of 2 parts Epoxy to 1 part hardener and stiring the mixture in plastic cups enough to get the correct colour and viscosity.

LAYERS COMPOSITE

First I wraped the mold with a layer of non sticking polypropylene plastic sheet plastic (green plastic). Continuously, I added four layers of lycra netting (I used it because the details of my design are very small) with the mixing epoxy. After that, I put a respirative layer (blue plastic) and a absorbent coton layer. Before to put it to the vaccum machine it is necessary wraped all it (to protect the machine) with a layer of plastic (transparent plastic). In the next photos we can see the process; I put in the vacuum mahcine, I turned on it, it begins to do the vacuum machine amd finally when the vacuum machine ends to do the vacuum. At minimum it has to be 8 hours in the vaccum machine.

The dots that will appear on the absorbent coton layer it is the excess of resin, and it is a good signal. It will be a problem if there is not dots (it means that it has not enough resin), or if the absorbent layer was full of resin (it means that it has too much resin).

As we can see in the image it would be better if the details of the turtle shell had been done with more depth and width.

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week 14