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‘Only grinding is considered for that.’
Tim Kern and Wolfram Hermle about the role of Haas CNC grinders in the aerospace industry

Tim Kern, demonstrations manager, and Wolfram Hermle, software development manager at Haas. Photo: Kraas & Lachmann

Tim Kern, demonstrations manager, and Wolfram Hermle, software development manager at Haas. Photo: Kraas & Lachmann

Haas Schleifmaschinen GmbH (with its US daughter Haas Multigrind LLC in Warsaw, IN) is a great partner for manufacturers in the aerospace industry because the Multigrind® grinding machines made by Haas in Germany master the most demanding grinding tasks with flying colours.

Where are the Multigrind® CNC grinding machines used in the aerospace industry?
Wolfram Hermle: Haas users machine a variety of workpieces ranging from IP (intermediate pressure) compressor blades through to HP (high pressure) turbine blades, HP vanes or HP shroud segments for aircraft engines. These are all components in the high-pressure area of an aircraft turbine which are exposed to extremely high thermal and physical stresses. Here, we are dealing with very demanding materials which are hard to machine. Only grinding is considered for that.

How do you see Haas’ position in the aerospace industry?
Tim Kern: We encounter a lot of technical expertise – from engineers and technicians who know what they want. In comparison to medical equipment, the technical specifications are much tighter in this sector. We have the technical ability to meet the high requirements which prevail in this sector – with our grinding software, our CNC grinders and our experience. That spreads by word of mouth.

Precision to one one-thousandth of a millimetre. Grinding a shroud component for aircraft turbines. Photo: Herbert Naujoks

Precision to one one-thousandth of a millimetre. Grinding a shroud component for aircraft turbines. Photo: Herbert Naujoks

What are the technical challenges when grinding aero engine components?
Wolfram Hermle: Our customers want absolutely reliable, absolutely robust processes with which they can achieve reproducible quality. One component should be just the same as the next.
Tim Kern: These challenges from aero engine makers are just what we like to hear. Where possible, we only clamp a component once, then measure it and machine it in a single operation to produce the finished item.

Having to re-clamp several times costs time …
Wolfram Hermle: … and money and, above all, precision. Fewer clamping operations also means that the workpiece spends less time waiting around, thus shortening the cycle times. You have fewer half-finished, expensive components lying about, require less effort for quality assurance and measurements and need less staff, as they don’t have to operate five machines – just a single grinding machine.

What does quality assurance look like at Haas?
Wolfram Hermle: At Haas, we work with a variety of measurement technologies, including three-two-one measurements to exactly locate the workpiece in space. In this type of measurement, we have three points to define the plane, two other points then define the axis and the third point is then on the workpiece itself. In itself, this is nothing completely new, but so far it has not been common practice to use the integrated three-two-one measurement when grinding. Especially not in the way that we further process the result of the three-two-one measurement with our Multigrind® Horizon grinding software. This automatically adapts the grinding program to the workpiece’s exact position in the working space.

Which software module does a user from the aerospace industry need?
With the Multigrind Horizon® 3D-CAD package and the 3D-CAM package, users can cover about 90 per cent of all grinding tasks in turbines. If users also want to machine teeth for drive functions, where sliding fits are important, then they will also need the package for rotationally symmetrical workpieces. All of the measurement functions and the dressing technology to dress the tools in the process are included in the basic package.

The complete machining of turbine blades with the Haas sandwich clamping process. Photo: Herbert Naujoks

The complete machining of turbine blades with the Haas sandwich clamping process. Photo: Herbert Naujoks

To what extent does the casting of high-pressure compressor blades affect the dimensional accuracy of the part?
Tim Kern: Casting is expensive and time consuming. The caster is responsible for the position of the part in this bismuth holder. That means that the process decides whether I get a good part or an expensive reject.
Wolfram Hermle: With the three-two-one measurement and the Haas sandwich clamping, we have the technical ability to compensate for casting tolerances. When measuring a compressor blade, if deviations such as a visually imperceptible warp are revealed, then the measurements will be introduced into our grinding program. We correct casting faults in the grinding process. This permits optimum efficiency to be achieved for the engine.

What sort of materials are we dealing with for turbine components?
Tim Kern: Alloys, titanium, titanium aluminium alloys, aluminium alloys and ceramic coatings. These are all materials which can withstand the enormous physical stress within a turbine. Important characteristics here include low weight, high operating temperature and tensile strength.

How do you see the role of the grinding software in the overall grinding process?
Tim Kern: Our grinding software is becoming ever more important and powerful, especially in the high-precision area where one one-thousandth of a millimetre is important. Our Multigrind® Horizon can generate a lot more than grinding paths. It is a genuine CAM system, a grinding programming system, a tool management system, a robot-handling program, an interface to a measurement system and, last but not least, operating software which is really easy to use. Our grinding software is so flexible and has so many facets that both the designer in the development department as well as the operator of the machine can work with it – each at their own user level.
Wolfram Hermle: Working with varying rights or user levels has the advantage that a validated grinding process as required by the FAA (Federal Aviation Administration in the United States) cannot be changed by an unauthorised person. This means that the Multigrind® Horizon ensures traceability at all times of who changed what and when in the grinding process. This documentation of absolutely everything is mandatory in the aerospace industry.

What do aerospace industry customers attach the most importance to?
Tim Kern: Our users want a grinding process which has been properly run in and which will produce faultlessly from the very first day. This means developing robust processes and then automating them. And the processes should work just as well in the United Kingdom as in France, China or the United States.

Tim Kern, Wolfram Hermle, thanks a lot for talking to us.

At Haas, Tim Kern is responsible for demonstrating the machines and for setting up the grinding processes on customer premises. His specialities include the grinding of medical implants and instruments as well as machining parts for the aerospace industry.

Wolfram Hermle manages the software development at Haas. With the Multigrind® Horizon software, he and his team have developed a completely new type of grinding software whose advantages are particularly appreciated by users in the aerospace segment.

Tim and Wolfram are looking forward to your comments or questions here in the blog or send send them an e-mail

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