CASE STUDY

Porsche 911 air control box components exploded view

Classic Porsche 911 Air Control Box

For many decades this air control box distributed air through the cabins of various Porsche 911 models

This ingenious design is entirely modular, employing 5 base parts which in different configurations make up a left and right hand assembly consisting of 7 components each. Unfortunately neither this assembly nor any of its components are available from the manufacturer. Good second hand ones are rare and expensive and typically sold as complete units, often with defects which only become apparent when disassembled.

It is wasteful to buy a whole replacement unit when only one or two of the components need replacing but aren't available individually. We set out to solve this problem.

The first step is a high detail 3d-scan

The process starts by 3d scanning the part in the highest possible definition. Point density and dimensional accuracy is crucial and for that reason we use high-end industrial scanning equipment. We also take thorough physical measurements during the process.

We normally find a good example without defects but in this case some bits were missing. There's a lot of symmetry and repetition between the parts so this was no issue as we could fill in the gaps using CAD.

If any mistakes are made during this step then the end result will not fit as intended so we could easily spend a few hours scanning, examining and measuring a part to ensure that subsequent steps will be based on accurate and complete data.

Cracked Porsche 911 air control box scan

CAD design

A new design is created in CAD using the data points gathered so far. It's at this point where decades of hindsight comes in handy. Weaknesses in the original design. which may not have been apparent when these cars were new, can now be addressed by tweaking the design as needed. This is done subtly to minimise any changes to the appearance of the part and of course always keeping in mind that it needs to fit as well, or better, than the original.

Manufacture

As with any high quality part, the challenge is to make it as strong as possible while adhering to the original dimensions. The originals were made from a Bakelite--like material and, while being extremely rigid and heat resistant, it also means that they were brittle.
With this in mind it's essential that the replacement parts are not only rigid but also durable and impact resistant.
The material of choice is therefore nylon PA12 which is tough, heat resistant and unlikely to become brittle or crack over time. It also maintains its dimensional accuracy irrespective of humidity or temperature, which is important as only one or two components will typically be replaced, meaning that our parts will almost always have to fit in with original parts.