Sprocket Science | Page 6

How to build the best automatic chain oiler in the world...

This month - the Mould Tooling

Hand carved from obsidian on the thigh of a cuban maiden ?

Not exactly.... more EDM eroded from diamond hard swedish steel!

Plastic injection moulds are incredibly complex devices in themselves, requiring specialist design, construction and operation but thats just the first part of the story.

A lot of the design and build process requires knowledge of not just what the parts are to be made from but also what they will be used for.

Eash resin (as the granular plastic beads that go into injection moulding are termed) has its own set of properties which include what its resistant to - such as UV and corrosive agents, to how quickly it cools and how much it shrinks when it does so.

So the "Tooling" as the mould is known needs to be designed to produce a part of a specific size not when its made but after its cooled- clever stuff!.

The resin we use is called Acetal, its an engineering resin made by Dupont chosen not least because its strong, resistent to UV, oil and a whole host of chemicals.

Not only that, its capable of being precisely machined and maintaining stability in both high and low temperature applications.

Just what we need!

Even after all the precision that goes into making the mould tooling, its not enough to simply assemble what comes out of the machine. Each valve body must be CNC machined to a tolerance of 5 microns to achieve the precision fit primary seal, more about that next month!.