Integrated Data‑based Process Chain Optimisation+

Thermocouples say when metal arrives, but not how fast. A melt volume flow sensor based on Lorentz force velocimetry was therefore developed for the low-pressure casting process: magnet assembly, force measurement and thermal protection were designed and built at the utg, referenced against a laser distance sensor above the riser tube, and then installed in the furnace for the casting of a complete stator housing.

The sensor makes the filling of a part observable while it happens. It supports the validation of mould filling simulations, and in production it opens a route to monitoring: a clogged slot nozzle or a contaminated riser tube changes the signal before it changes the part.

Machining does not only release residual stress, it writes a new one into the surface layer. For every parameter combination the machined surfaces were measured by X-ray diffraction using the sin²ψ method, parallel and perpendicular to the cutting direction, for both material conditions.

To reach below the surface, material was removed from selected specimens by electrochemical etching in small steps, with a measurement after each step. The resulting depth profiles show how far into the part the mechanically affected zone reaches – the quantity a distortion model needs as its machining-side input, and one that is rarely available for aluminium cast alloys cut with sharp diamond tools.

The deep holes were first developed on a simplified model with three bar cross-sections, then transferred to the stator housing itself. The trials ran on a machining centre under minimum quantity lubrication throughout, with thermography of the drilling operation, force and torque recording, and inspection of the finished bores.

In parallel, a finite element model of the process was built in which the two-fluted tool is represented by helical heat sources, validated on the simplified geometry against the measured temperature fields and then applied to the thin-walled and the thick-walled region of the housing. The material condition turned out to matter for process stability, which places the heat treatment ahead of the deep-hole operation in the sequence.

High-entropy boride and carbide coatings were developed by physical vapour deposition and deposited on indexable inserts of an Austrian tool manufacturer – a low-temperature, gas-free process route chosen for its energy and environmental profile, and one that also opens the door to sensor functions on the tool surface.

The coated inserts were characterised and then run in cutting and milling trials against uncoated references, with the condition of the cutting edge documented before and after. The trials identified coating adhesion, rather than coating hardness, as the property to work on next.

Together with a tool manufacturer, series-related precision boring tools for roughing and finishing were rebuilt into measuring instruments. Strain gauges sit in the tool body where the load path of the cutting edge passes through it; a telemetry unit with wireless transmission, an inertial measurement unit aligned with the axis of rotation and a rechargeable battery are housed in the tool itself – without giving up the internal coolant supply that aluminium machining depends on.

The positions of the gauges were worked out beforehand on a finite element model of the tool body, with the cutting, feed and passive force applied as separate load steps, so that each channel responds to the component it is meant to see.

Before the tools could be trusted, each channel was calibrated on the machine against a reference dynamometer of known behaviour: a connecting element transfers a defined load into the cassette seats, the load is raised in steps, and the response of every strain gauge is recorded – for the roughing and the finishing tool separately.

The tools then went into analogy components before touching a project housing: turned aluminium rings that reproduce the bore of the stator housing, machined with the same tools and parameter sets. From there the work moved onto the cast housings themselves, in the HSK-100 spindle of the machining centre, with the acquisition triggered automatically from the NC program so that the recording starts and stops with the cut – the form the concept would take in series production.

A thin-walled casting reacts to the way it is clamped, so the workholding became part of the experiment rather than an accessory to it. For the cast housings a fixture was built at the IfW: a base plate with spacer bushings that pick up the machined support faces and positioning bores, and clamping claws that hold the part for the boring passes.

Alongside it, the IFT used a fixture in two configurations whose part supports are instrumented with force sensors, so that the load the clamping actually applies is recorded together with the cutting data instead of being assumed. For the deep-hole drilling trials the ISF added a fixture with an adapter plate for the measuring equipment, a thermographic camera on the outer wall and eddy current sensors seated directly in the stator bore to follow its displacement during the cut.

On these setups the housings were prepared in a defined sequence – support faces, positioning bores and the bearing seat first, then the stator bore in roughing and finishing passes with the sensor-integrated tools, then the deep holes and threads.

Two housings that differed only in the immersion direction during quenching were run through an identical machining sequence with the same cutting parameters. The stator bore was then measured on a coordinate measuring machine in two states: with the part still in the fixture, and after unclamping. Roundness profiles were recorded at several heights in the bore and evaluated for diameter, roundness and cylindricity.

In the fixture the two parts are indistinguishable. They separate only on release, and in opposite directions – the part quenched with the thick side first holds its form, the other loses it. That is the experimental counterpart to the distortion simulation, and the reason an in-fixture measurement is only meaningful when the history of the part is known.

The interface analysis in the project showed that a central project database would not transfer to industry, where the stages of the chain belong to different companies. The exchange was therefore built on Asset Administration Shells to the IDTA specification and implemented as a working demonstrator in Eclipse BaSyx.

The shell of a workpiece carries a traceability submodel whose references point at the casting, heat treatment and machining runs that this individual part passed through, addressable on the shop floor by QR code; the shell of a process carries its sensor, simulation and quality submodels. Data are referenced, not copied, so a machining company can release a quality result without releasing its process data. Since BaSyx derives an OPC UA address space from the same definition, no second mapping is needed for machine-level communication.