Part of designing a mechanical iris diaphragm is knowing what’s the best material to use for iris blades. Material choice is important for a number of reasons, such as; environment, durability, cost, and ensuring a smooth operation.
Choosing the right approach
A particular issue arises when designing an iris with a very small minimum aperture. The blades tend to all become compressed and fight for space, as there’s not enough space for them to all physically occupy. Your options in this situation usually are:
- Use less blades in the design
- Use thinner blade material
- Increase the design’s minimum aperture
- Lower the friction
Friction is an important factor in your material choice. For example, Aluminum is a great material for an iris housing, but it has a high coefficient of friction – which is not ideal for iris blades, unless it can be coated.
Un-coated materials, such as stainless steel, brass, blue tempered spring steel, or steel shim material are all good options.
Reducing friction further
Graphite coatings are helpful in reducing friction – if you don’t mind a bit of dusting. You could also anodize aluminum, which would help. Otherwise you’re into plastics…
Unsure on how to make your blades / leaves? Take a look at Iris diaphragm blade making tips and tricks.