Schabmüller taps into Mapal’s aluminium machining expertise

Presenting a rear axle housing (from left): Stephan Streck, Mapal technical consultant; Eugen Bien, Mapal application engineer and Helmut Häckl, managing director at Schabmüller Automobiltechnik GmbH

Germany-based Mapal has taken care of tool management at automotive supplier Schabmüller Automobiltechnik GmbH (SMI) for some time. However, in a more recent development, the tooling supplier has taken over CAD/CAM programming for components, including simulations, and with a growing requirement for aluminium machining, Schabmüller values this full-service solution.

SMI in Großmehring, near Ingolstadt, has been an automotive supplier since 1988 and has increasingly specialised in the efficient manufacture of large series components. The parts are installed in vehicles made by a number of automotive brands, including Mercedes, Porsche, Audi, BMW and Jaguar. SMI operates predominantly as a Tier Two supplier with major customers that includes Aludyne and Strojmetal, which directly supply the automotive industry as an aluminium foundry and forge.

Until a few years ago, the manufacturer produced cylinder head covers for the Volkswagen 3.0-litre V-group engine in quantities of up to 320,000 a year. The components, for which SMI also handles installation, are still produced, but while the volume of these has decreased, alternative orders have replaced them, making the company less dependent on the internal combustion engine.

Managing director Helmut Häckl, said: “Demand for suspension parts has provided us with an opportunity to diversify ourselves in a new direction. Our business has developed and pursued precisely this goal.”

Whole new experiences
However, the new components have also posed challenges for Schabmüller, too. Particularly in the case of components for for electric vehicles (EVs). As it is still a fledgling technology, projects are sometimes postponed, originally planned quantities are not reached, or additional changes are required at short notice before series production begins. Mr Häckl said “Up until the end, the OEMs gather experience in load tests for vehicles that are becoming increasingly heavier due to the weight of the batteries. This means that certain components are designed in a more stable way to cover all borderline situations.”

Pictured right: SMI manufactures hub carriers in pairs on a double spindle machine from SW. The image shows the use of disc milling cutters with indexable inserts from Mapal

Stephan Streck, technical consultant at Mapal, explained using the example of a hub carrier. As issues with stiffness arose during driving, almost at the last minute, another surface had to be machined and a stiffening rib added to rectify the problem. SMI has to plan the production requirements and prices for the components before their exact design is known, which is a challenge. Mr Häckl added: “Cycle time is the decisive factor for getting an order.”

To get a better grip on these short-term changes and continue optimising overall production, Schabmüller decided to bring Mapal on board at the CAD/CAM programming phase. Mr Häckl explained: “We have a very cooperative partnership with Mapal and always appreciate its rapid response times. So we felt good about expanding our cooperation to CNC programming and simulation.” Mapal tailors t services to the client’s needs. These include tool scheduling, pre-adjustment, dispensing and reconditioning, technical support for series production, tool and cycle time optimisations, and tool life optimisations.

SMI stopped programming itself back in 2018 and Mr Mr Häckl pointed out that for CAD/CAM it requires specialists three or four times a year for new projects so cannot justify employing someone itself. Schabmüller has used the machine manufacturer’s services for programming from time to time since then. However, there was no option for 3-D simulations, so while this was tolerated, SMI knew that not all options for optimising cycle times were being utilised.

Now that Mapal is involved from the beginning, this has changed. NC programming, simulation and tool management are now perfectly intertwined. For instance, simulation data is included in tool planning, which helps detect potential collisions at an early stage. It is possible to respond immediately to component changes by the OEMs before the start of production. Modifications are made in the 3-D simulations before the tools are finished. Mr Streck explained the importance of simulation: “If you do not catch adverse changes in good time, costs can run into the five figures.”

Plays a key role
Simulation also plays a key role in optimising machining. For instance, it shows approach angles that can be used to improve material removal. Data from the computer can also be used to reduce tool wrapping. Mr Streck said: “This type of detail is much easier to detect in simulations than looking through the window into a machine.”

Pictured left: production at Schabmüller mainly takes place on multi-spindle machines. Hub carriers are machined by SW on a double spindle

The suspension parts SMI now manufactures involved a shift in material from die cast aluminium to forged aluminium. Forged parts have much higher load indicators than cast parts. The higher stability is required in particular for electromobility. However, this also increases machining requirements to achieve the desired cycle time. Material removal and thus the volume to be machined are much higher here, which requires adapted milling strategies.

The material properties have also changed, as Mr Streck explained: “Compared to aluminium cast parts, the forged material has a much lower silicon content. This means that the chip does not break well, long chips are produced in machining, and we need to deal with smeared blades. All of Mapal’s aluminium machining expertise is required to find solutions here.” Schabmüller currently uses forged aluminium to produce some of the hub carriers, steering knuckles and control arms made in Großmehring.

Another aspect of improving processes is Mapal bringing new tools on board as soon as they are available and promise benefits. As application engineer Eugen Bien noted, the new indexable insert milling cutter NeoMill-Alu-QBig was used at Schabmüller before it even officially came on the market.

This new indexable insert milling cutter from Mapal stands out for its top performance in high-volume aluminium milling. It is designed for use at speeds up to 35,000rev/min to achieve the maximum possible material removal rate. For a tight fit despite high centrifugal forces, screws with increased tensile strength are used to hold the indexable inserts firmly in the prismatic seat. Mapal has fitted the tool body with a fine balancing system to protect the machine spindle and achieve high surface finishes where possible. In addition, focus was placed during development on low cutting forces and highly precise indexable inserts.

From the three coatings available, ­Mapal technicians chose a diamond coating for the machining of mould casting at Schabmüller. During operation, the machine operator rotates the indexable inserts with their two cutting edges directly on the machine. Mapal retips the milling cutter in the setting room. One benefit of the ductile solid carbide inserts of the NeoMill-Alu-QBig in comparison to the milling cutters with brazed PCD blades used before: they break out less quickly when there are sand residues from the casting mould on the raw part.

Achieved shorter cycle times
However, there is another aspect that is decisive for the user, as Mr Häckl affirmed: “In production, we achieved shorter cycle times with the NeoMill-Alu-QBig, as we were able to attain greater values for cutting speed and feed. For this, we were readily willing to accept shorter tool lifes.”

Pictured right: in the warehouse system, Mapal provides all tools needed for a component via the tool management. For hub carriers, 45 to 55 different tools are required

Switching to the NeoMill-Alu-QBig required a different milling strategy and higher central chip density. The values measured by Mapal are testament to the success achieved as a result. The adjustments implemented with higher cutting parameters, the switch from circular milling to helix milling, and the improved machining conditions resulted in a cycle time saving for this machining operation of 54%. The new tool made it possible to increase the feed per tooth from an average of 14 to 32mm.

In the comprehensive tool set for machining a hub carrier, the NeoMill-Alu-QBig is one of the few standard tools, but it plays a crucial role for the cycle time, as Mr Bien put it: “Use of the NeoMill-Alu-QBig constitutes around 30% of the total machining time.” The focus is on the roughing of the component, but the tool also produces surfaces in finished part quality.

The hub carriers set high requirements for the machining strategy. For Porsche and AMG, Schabmüller produces around 97,000 of these each per year from cast or forged parts, for which cycle time of six minutes for two components is required on the double spindle. The tool sets for this consist of 45 to 55 tools. For the most part, these are client-specific custom tools. Most of them, such as drills, step drills and fine boring tools, are only used for one or two machining operations. The role of the simulation is to keep non-productive time for all the different tools to a minimum and ideally to start each machining operation once only.

Schabmüller currently has around 150 employees and is growing constantly. Work was completed on a third hall recently. Originally designed for the production of large quantities of cylinder head covers for VW, part of the double hall is currently used for other purposes. Schabmüller machines a large amount of the starting material to produce top plates for electric vehicle batteries. Rear axle housings are being produced for another automotive manufacturer in a second project.