As Mollart Engineering explains, the signing of an aerospace partnership with multi-million pound potential for turbine shaft production saw the company’s workforce go the extra mile to meet the customer’s delivery expectations.
Mollart Engineering has won a major international aerospace partnership contract for producing key operations on a family of turbine shafts that could progressively build-up to be worth £4 million a year within three to four years for its Chessington site.
“We had to produce sample parts for final approval which meant we needed total support from our workforce that were involved in the project,” begins director, Guy Mollart. “Over the Christmas period they showed their dedication by giving up parts of their holiday to come in and ensure the customer would take delivery directly after the break.”
Operations director Mike Pragnell explains how the contract was secured which involves working closely with the forging supplier. “It was our ability to combine three essential elements of our business in deep hole drilling and the associated tooling development expertise for special bore production and our large capacity turning and boring capability. However, most influential in the customer’s mind, was the security of our track record with other blue-chip customers to machine very difficult alloy materials that are used in ultra-high functionality and demanding applications.”
An initial proving trial was performed in September that involved machining the first of the alloy steel free issue forged components some 2,200mm overall length and weighing up to 800kg in the raw, that were supplied in the rough turned and heat treated condition. Following the successful machining operations it took some three months to carry out evaluation which included a strict, full quality audit of the Mollart business. This was followed with sample part production before Christmas leading to the issue of the first production batches involving two parts per week.
Prior to machining on Mollart’s Weiler E90 CNC lathes with 6m bed length, each high cost forging has to be fully qualified by Mollart engineers to determine there is no distortion from heat treatment and it will fully clean up when turned and bored.
The forged blank is basically a tube with a trumpet-shaped end having a 50mm thick flange of 500mm diameter at the mouth of the cone shape which is merged into the main body of the turbine shaft that has to be profiled turned to 160mm diameter. A main bore is some 84mm diameter by 1,800mm deep from the flanged end and a further bore is produced 44mm diameter to a total depth of 1,900mm.
The part is then relocated and a bore of 70mm diameter is counterbored to 96mm diameter. There are also a series of steps, cones, and internal/external tapers to the conical end of the shaft that have to be machined. Currently overall production time is running at 40 hours per shaft.
As part of the contract, Mollart’s engineering team developed a special ejector drill head, cartridge and insert design to produce the main 84mm bore as well as the special conical forms required at the bottom of the bore.
Said technical director, Chris Barker: “Due to the material, chip flow from the 84mm bore is critical as we have some 14mm of stock to remove. We also have to account for the abrasive nature of the heavy scale from the heat treatment process in turning and boring operations.”