Aerospace Industry Case Study


The company is a leading international manufacturer of high-precision alloy components which are designed to operate in the most demanding of conditions. The company’s products and processes serve the aerospace, industrial gas turbine, specialist automotive and petrochemical markets and their core areas of expertise include new product development, precision casting, forging, fabrication, machining, superalloy production and the supply and manufacture of automotive stud welding equipment.


The Rolls-Royce Trent 700 is an axial flow high-bypass turbofan (fig1) with three coaxial shafts and is used to power the Airbus A330 aircraft. The fan has 26 blades and is powered by a 4-stage low pressure turbine, while the 8-stage intermediate pressure (IP) compressor and 6-stage high pressure (HP) compressor are both driven by a single stage turbine. The single annular combustor has 24 spray nozzles.


The company were involved in making the engine casing for the Rolls-Royce Trent 700 that covered the compressor and combustor sections of the engine. In a bid to reduce manufacturing costs, the complex casing (Ø3.5m) was made as a casting out of nickel base superalloys rather than being machined from solid. Casting would significantly reduce the amount of final machining that was required following the heat treatment process. However, the fixture that they had originally designed to hold the casing during the heat treatment was deemed inadequate by virtue of the fact that there was significant movement of both the fixture itself and the casing which resulted in unacceptable levels of distortion.

(Fig 1 - Rolls-Royce Trent 700 Engine Casing)


Fabwell sought to design, develop and manufacture a new, alternative fixture consisting of two parts (i.e. a top and bottom section) that could securely hold a high precision and geometrically complex Trent 700 engine casing as it was undergoing heat treatment.

The technological baseline and status at the start of the project

As the existing fixture for holding the engine casing was inadequate and had failed to prevent excessive movement from occurring during heat treatment, an alternative solution needed to be found and for which a dedicated development programme had to be undertaken.

Work done

The project commenced with an assessment to review the furnace operation, its dimensions and space constraints; the temperature and heat treatment process; the issues relating to the existing fixture design; the size and geometric complexity of the engine casing; as well as the properties and behaviour of the material for constructing the fixture etc.; so that a suitable design, development and implementation strategy could be identified. As part of this process, Fabwell travelled to the customer site to take measurements of the engine casing and of the furnace interior (BEIS guidelines paragraphs 27b, 31g and 36).


Based on the knowledge gained and following a critical assessment, a technical scoping exercise was conducted for the new fixture along with creating a detailed technical road map on how the project was to be executed.

Fabwell subsequently undertook an iterative design exercise with the aid of CAD software to explore a number of possible configurations for the bespoke fixture. The two part fixture was machined from solid 310 stainless steel to a tolerance of +/- 2mm with special cut-outs created on the bottom section to allow the engine casing to be positioned and fixed. The combined weight of both sections was around 2000kg.


Furthermore, a special ring was designed and machined to enhance the strength of the fixture and hence counter the issues faced with the previous fixture design, whereby special ribs that had been welded, broke during the heat treatment. A second removable ring was also created to help position the various 50mm sections or legs of the casing such that they converged on a central point without having to be joined together as was the case previously. Drawings of the fixture are shown below in figs 2, 3 and 4.


Fabwell conducted on a rigorous in-house testing and validation process to prove out the principle of operation and ensure the bespoke fixture met the desired technical specification with regards to its size, weight, fit, form, ease of assembly and accuracy. The dimensions of the fixture were first verified on a CMM followed by a quality inspection (BEIS guidelines paragraphs 27c and 39). Further temperature tests with the cast engine casing in situ were carried out by the customer at their premises and signed off for use.

(Fig 2 - Base Fixture)

(Fig 3 - Top Fixture)

(Fig 4 - Inner Ring Detail)