Intelligent manufacturing halves airfoil production time

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Doncasters Precision Castings manufactures industrial gas turbine airfoils. The company has seen considerable growth in demand for its machining services, which has led to a significant investment of over £2 million in Mazak products.

Intelligent manufacturing halves airfoil production timeThe company previously used three-axis machining centres, but the processes were time consuming and required highly skilled operators and hard fixturing. To eliminate errors and increase productivity, the company invested in three Mazak VORTEX i-630V/6 vertical machining centres.

Ollie Macrow, Engineering Manager at Doncasters explains: “When you are dealing with £10,000 Inconel castings the machines must be correct. Costs are another concern: in addition to the cost of the casting there is time and tooling cost. Additionally, certain components are not reworkable, so if it’s wrong, it’s scrap.

“Our challenge was to replace fixtures with simplified, modular-type systems and reduce human interaction in the setting process. This is because hard fixturing is expensive; requires high skill level and requires maintenance.”

The company had limited experience with probing, so Renishaw’s input was vital. The machines were equipped with Renishaw RMP600 high-accuracy probes, featuring patented RENGAGE strain gauge technology. They were useful because of the ability to deliver unrivalled submicron performance when applied to complex 3D shapes and contours.

Renishaw recognised that MSP’s NC-PerfectPart and NC-Checker software in combination with the RMP600 probe was the best option before cutting.

The initial step is to ‘map’ the machine tool to create a benchmark. NC-Checker assesses the probe performance prior to carrying out five-axis checks of the machine tool. This ensures that probing and machining performance is within set tolerances prior to part setup and metal cutting. The machine check can run regularly as it only takes a few minutes to complete – ensuring the machine operates within set parameters and produces accurate parts.

Complex shapes

NC-PerfectPart solves the problems created by poor part alignment on the machine tool, which is particularly important on components with free-form, complex shapes and those subject to five-axis machining. Setting up parts can be time consuming and difficult to achieve accurately and consistently, this is overcome by probing the part with the RMP600 using a program created from the component’s CAD file.

From this measurement, an alignment is created to eliminate errors in part positioning. This is uploaded to the machine control and compensations are automatically calculated to produce a part program perfectly aligned to the part. Set-up is automated, meaning that fixturing is no longer critical, manual set-up error is eliminated and time required to set components is reduced.

Furthermore, material condition, pallet loading systems and temperature, can be accounted for early on, reducing the risk of producing bad parts. After metal cutting, NC-PerfectPart can confirm the accuracy of the finished component prior to it being removed and inspected on a CMM.

Before the addition of the RMP600 and MSP software it would take 4 hours to set and machine a typical industrial gas turbine nozzle. Now that same part can be probed, machined and checked in under 2 hours – a 50 per cent productivity increase.

On more complex components, the machining time could be up to 8 hours and required the presence of a highly skilled operator. These parts are now produced in the same 2-hour cycle as simple parts, generating even greater savings.

Macrow explains: “When we first decided to buy the machines, we sat with Mazak and said, ‘How are we going to do this?’. They didn’t think it was possible with our current set-up – Renishaw and MSP provided the solution we needed. I feel that we would not be successfully machining castings without their help.”

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