Machine Tool Measurement Assures Quality On Custom Milling Machine

F. Zimmermann GmbH's aerospace industry customer tasked them to develop a bespoke portal milling machine to manufacture complex titanium suspensions for aeroplane control surfaces. The new system needs to handle the programming of production paths, all milling operations and on-machine component inspections. In taking on the challenge, Zimmermann chose Hexagon's Machine Tool Measurement solutions for its custom build to manage in-process and final quality inspections of the manufactured parts.

Zimmermann is a technology leader known for its large high-performance portal milling machines and horizontal machining centres. The export-oriented machine builder has delivered more than 550 machines to 37 countries worldwide. In addition to supplying standardised machines that guarantee customers an efficient high-precision milling process, Zimmermann also develops and produces individual custom-built milling solutions to address more complex and unique application challenges.

One of Zimmermann's aerospace industry customers required a unique portal milling machine with several new functions and benefits. The customer needed Zimmermann to select and run-in the specialised machining toolset, program the production path of the component and finally, enable measuring on the milling machine itself.

"We have more of a bespoke or made-to-order character – we are not a mass manufacturer," says Steffen Nüssle, Sales Director Export, Zimmermann. "But our machines’ modular design usually allows us to adapt them to specific customer and application requirements relatively easily; several custom-built milling machines are already in use at an Asian aircraft supplier. But this new order went far beyond what we had delivered so far."

The component that Zimmerman's customer needs to produce is an approximately 1.5-metre titanium suspension for aeroplane control surfaces. A particular machining challenge is a series of twelve holes in lugs located one behind the other on the workpiece over a length of 990 millimetres. Here the customer demands high precision, prescribing for the 17-millimetre bore diameter the tolerance H7, meaning an allowed hole variance of 18 microns. In addition, the variance in concentricity of the bores must be less than 50 microns over the entire component length. High precision and accuracy are also required for the bore lugs, which need to be perpendicular to the component surface.

In its new machine, to ensure the quality of the component, Zimmermann decided to use Hexagon's latest generation radio-wave touch probes with HxGN NC Server, which enables PC-DMIS metrology software to be used to measure parts directly on the milling machine. The chosen probe allows measurement with a cross-probe insert, which is necessary to measure the bores. PC-DMIS is an industry-leading metrology software that supports diverse measurement needs on systems from CMMs to portable measuring arms and laser trackers.

HxGN NC Server has helped Zimmermann's customer automate production by enabling their operators to easily create and execute fully automatic PC-DMIS measurement routines on the milling machine at any stage of the production process. This is especially valuable when working with a tough, difficult-to-machine material like titanium.

In-Process Clamped Part Inspection Avoids Measurement Deviations

In-process measurement of the component is performed directly in the clamping to avoid measurement deviations due to spring back or warping. The system detects tool engagement limits or tolerance violations in good time, before the production of cost-intensive scrap. Next, all finished parts are again inspected on the machine tool, with some going forward for final quality inspection on the customer's CMM to complete their quality assurance process.

In addition, the approximately X=8500 mm x Y=3900 mm machine size gives the customer the security of having an available measuring solution should they need to manufacture larger components in the future. The size of their CMM would not constrain them.

"We’re focused on building high-performance milling systems for our aerospace customers that reliably achieve outstanding precision," says Nüssle. "This is why we’ve used HxGN NC Server with PC-DMIS for this special build and on many other machines – the software is well-established and proven in quality assurance. We have complete confidence in the system's measuring performance and its contribution to boosting productivity for users of our machines."

HxGN NC Server automatically executes the required measuring programs and generates PC-DMIS reports when measuring routines are executed. A machine operator must only press a button, and the Titanium component will run autonomously through all production and inspection steps until the creation of the final measuring protocol. No other operator action is necessary.

PC-DMIS simplifies the acceptance of measurement results throughout the entire quality process and enables direct comparison with the customer's CMM measurements. Zimmermann and their customer highly value this ease of use and simple user experience. "Having a unified experience across all measurement operations, from the milling machine on the shopfloor to the CMM in the quality room, makes things easy for the operator," says Nüssle. "And it's a big benefit not to have to train operators on multiple software tools."

"The bottom line is that with Hexagon's support, we have successfully built a turnkey, high-performing milling solution including a proven machine tool measurement system for a demanding and now delighted customer."

For more information: www.hexagonmi.com

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