Castings for electromobility

Fraunhofer IFAM has been working on electromobility and the casting of electric drive components since 2008. The focus is on the development and testing of new casting concepts and design methods for electric motor castings. The field of expertise has been expanded to include the analysis and evaluation of castings for the body construction of electric vehicles, with a particular focus on giga-casting.

Research and development activities focus, for example, on the casting of tubular or hollow structures in housings for cooling electric motors, batteries or power electronics. Especially for asynchronous machines, our experts develop measures to optimize cast rotors. The patented Fraunhofer concept of the cast coil opens up completely new possibilities for increasing the performance of electric drives compared to conventionally wound wire coils for automobiles, pedelecs, eBikes or scooters. The requirements for subsequent transferability of the developments to series production are always taken into account.

Our interdisciplinary, close cooperation between the fields of "casting technology" and "electromobility" creates an optimal constellation of know-how that enables a holistic view of manufacturing aspects with a focus on casting technology, structural design and electromagnetic design for the successful production of components for electric drives.

Our main areas of research:

• Housings for electric drives, batteries and power electronics
  
• Casting of tubes and hollow structures
• Cast rotors for asynchronous machines
• Cast coils
• Giga-casting in body construction of the future

Housings for electric drives, battery, fuel cell and power electronics

Engine block, transmission housing, oil pan - all these castings have met the same fate with the rapid transformation to electromobility and are being replaced by housings for the stator, battery, fuel cell, or their power electronics in the electric drive. Fraunhofer IFAM is accompanying this transformation and offers scientific support, innovative concepts, and proven solutions for the casting of housing components.

One focus is the identification and evaluation of technology trends and market potential for new housing concepts. In addition, the focus is particularly on the use of alternative, recyclable materials, the dismantling capability of housings and the recycling of the materials used, as well as the Life Cycle Assessment (LCA) from the production to the use phase of new housing concepts.

Fraunhofer IFAM offers extensive know-how in the technological competence for casting tubes and hollow structures made of aluminum, copper, or steel using fillers for stabilization - and without! Our many years of experience in hybrid and composite casting complement this area of expertise, enabling us to cast tubes and hollow structures onto the aluminum housing with the aid of a form-fit or material-fit connection instead of having to recast them completely.

Our range of services:

• Design and concept development for electric drive housings
• Process and tooling concepts for casting production
• Casting of tubes and hollow structures
• Composite casting with sheets and profiles

Casting tubes and hollow structures

For the electrification of vehicles, the focus is on three assemblies: the electric motor, the battery and the power electronics. Electric drives are becoming increasingly powerful with reduced size, which requires increased heat dissipation via liquid-carrying cooling channels within the housings of all three assemblies. In order to be able to cover the quantities required on the market, these housings are mainly manufactured using the aluminum die casting process. One of the greatest challenges here - to date - is the casting of the necessary cooling structures or cavities in the die casting process. The preferred solution is the single-shell housing, which is currently only possible by using technically complex, limitedly available and also cost-intensive lost cores (e.g. as a water-soluble salt core) or by casting in steel tubes.

Fraunhofer IFAM is working intensively on the development of technology for casting hollow aluminum structures. Compared to steel tubes, these offer advantages such as higher thermal conductivity, an adapted coefficient of thermal expansion, low weight, and freedom from corrosion.

One focus is on simulation-based prediction and analysis of the "collapse behavior" of the tubes to be cast in, as well as the stabilizing effect of any fillers and stabilization concepts.

In addition to the casting of prefabricated hollow structures such as tubes or other semi-finished products, Fraunhofer IFAM specializes in the casting of additively manufactured "3D printed" hollow bodies and structures made of aluminum. This can be used, for example, to realize internal support structures which, based on bionically motivated geometries, in addition to having a high stabilizing effect (up to 1,000 bar holding pressure in the die casting process), can also optimize thermal heat dissipation and thus cooling performance of the housing.

Our range of services:

• Casting of tubes with / without fillers
• Casting of tubes with form-fit / material-fit connection
• Novel filler concepts and materials for stabilization in the die casting process
• Additively manufactured hollow structures for use in the die casting process
• Structural-mechanical design and simulation for tubes to be cast in place
• Thermal simulation of the casting process for pipes to be cast in place
• Test tools for die casting tests
• Test rig for measuring the thermal performance of cast-in tubes
• Complete quality test chain for prototypes

Cast rotors for asynchronous machines

Rotors cast from aluminum or copper are used in so-called asynchronous machines in which the rotor is driven by the electric field of the coils and transmits the force generated in the electric motor to the rotor shaft. These rotors are preferably manufactured using the die casting process, in which a stack of sheets is inserted into the die casting tool and axially continuous grooves located therein are infiltrated with electrically conductive molten metal.

Fraunhofer IFAM provides support for the entire process chain for developing rotors for asynchronous machines. In collaboration with the "Electric Drives" department, rotors are electromagnetically designed, simulated, and evaluated, sheet metal packages are designed, and prototypes are produced using laser cutting. In preparation for casting production, concepts are developed and evaluated with regard to the design of the laminations and tooling. The casting of the rotors can be carried out either by die casting or low-pressure casting on the Fraunhofer IFAM equipment. The world's only full-body computed tomography can be used to analyze and evaluate the casting quality in the slotted rotors, while the measurement and evaluation of the electrical performance of cast rotors is made possible by special performance test benches. Only assured material and product quality provides stable series production and enables electric mobility to achieve the highest performance and driving pleasure.

Our range of services:

• Casting of rotors in aluminum die casting or low pressure die casting
• Design of laminations and short-circuit rings
• Design for gating systems and tooling concepts
• Imaging failure analysis, quality assessment and performance testing

Cast coils

A wide range of requirements are placed on the windings of electrical machines. On the one hand, the maximum performance of the electrical machine should be achieved by a high slot fill factor and thus the best possible utilization of the available installation space. On the other hand, the best possible cooling of the conductors must be ensured and the occurrence of additional losses due to current displacement must be avoided. There is an overarching desire for cost-effective and automatable production and assembly of the coils.

Fraunhofer IFAM has developed a process which allows coils for electrical machines to be manufactured by casting. The coil geometries with flat conductor arrangement which can be manufactured using this process offer decisive advantages over conventionally manufactured windings. The casting production can be carried out either by die casting, low-pressure casting or investment casting and the coils can be cast from copper as well as aluminum.

Our range of services:

• Casting of coils as prototype or small series in die casting, low pressure casting and investment casting.
• Coils made of aluminum or copper
• Different dimensions (from 30 to 700 mm conductor length)
• New coil concepts, e.g. with integrated cooling structure
• Electromagnetic simulation and design of coil geometry
• Economic feasibility studies

Giga-casting in the automotive body shop of the future

With the transformation to electromobility, it is not only the automotive industry that is currently undergoing the greatest change in its history. In the die casting production of large-format structural castings for car body construction, so-called giga- or mega-casting has triggered a technology boom and a race of unprecedented magnitude to clamping forces of up to 12,000 tons. The focus is currently on large-format car body structures and battery housings as cast products.

Fraunhofer IFAM has been dedicated to the analysis and evaluation of these technology concepts since the emergence of giga-casting in the summer of 2020 and is active in two main areas: technology analysis and sustainability evaluation.

The giga-casting concept challenges globally established design and production methods for car body construction by casting highly integrated large castings in one piece from aluminum, thus replacing entire car body segments that were previously joined from many individual sheets and components. Fraunhofer IFAM is dedicated to the optimization of material and product quality, reparability, and crash safety of large castings. An important component is the analysis and evaluation of the possibilities for using secondary alloys in order to meet the increasing requirements for greater sustainability.

A large consortium of several Fraunhofer institutes is developing holistic solutions for the evaluation of new car body concepts for the automotive industry. Fraunhofer IFAM is focusing on large casting technologies. The aim is to establish methods, processes, and technologies with which ecological sustainability can be methodically evaluated and technologically ensured in a conflict of objectives with technical performance and costs.

Our range of services:

• Technology assessment and potential analyses
• Use of secondary alloys
• Alternatives to giga-casting