From the material selection we have decided to choose polystyrene as the material for the clips. We feel polystyrene is the best choice as it is the closest fit for our requirements of strength and cost. It has a higher yield stress than the maximum stress that is applied to the clips, and a suitable elastic modulus for the force requirements. It also has the lowest cost from the selection of available materials due to the above constraint.
From the Process Selection, there are no primary processes. The secondary processes are injection moulding and conventional machining. The process that would suit our product the most, in our opinion, would be injection moulding. It would be the most efficient as it would match the manufacturing process for the body.
Body
For the body, we decided to choose polystyrene for the material also. This makes the overall manufacturing of the auto-syringe more efficient as it matches the material of the clips. This reduces the cost also as the material can be bought in bulk. Polystyrene also fits the requirements for the body as it is light and cheap.
From the above Process Selection, injection moulding is the primary process. The secondary processes are compression moulding and conventional machining. We have decided to choose the primary process for the body as we feel it will produce the best product for our design.