KraussMaffei (Munich, Germany) reported on Feb. 21 that its equipment is being used to manufacture thermoplastic body panels and composite structures in the passenger cell for the new all-electric BMW i3 passenger car.
The equipment includes injection molding machines with swivel plate technology and machinery for high-pressure resin transfer molding (HP-RTM). "That is our contribution towards a new generation of vehicles in order to facilitate the breakthrough for lightweight construction and electromobility," says Nicolas Beyl, president of the Reaction Process Machinery Segment of KraussMaffei.
The i3 is the first production passenger vehicle to be manufactured primarily of carbon fiber composites, including and especially in the passenger cell that surrounds the passenger compartment.
KraussMaffei has supplied BMW with injection molding and reaction process machines, including two double-swivel plate machines that are fully automated with two industrial robots. Weighing 400 tonnes, each MX 4000-17200/12000/750 WL is 24m/79 ft long, 9m/30 ft wide and 7m/23 ft high. The thermoplastic outer shells of the BMW i3 are produced on these machines, which have a clamping force of 4,000 tonnes, at the BMW plant in Leipzig, Germany.
Using the "joining in injection molding" process, the outer door shell and its substructure are injected in a single pass, are joined as the two swivel plates turn and are bonded with a third plastic component. “The combined work processes ensure very high dimensional accuracy of the parts," says Frank Peters, vice president sales of the KraussMaffei brand.
In addition to the sidewall panels and the rear bumper, the hood of the BMW i3 comes from a KraussMaffei injection molding machine. "They are produced on the most complex machines we have ever developed", emphasizes Peters. ”We showed a great deal of commitment in accepting the challenge to contribute the most innovative machine technology which places maximum demands on availability. I am proud of what our team has achieved."
In addition to injection molding technologies and automation solutions, the Reaction Process Machinery Segment is involved in the BMW i3. Twenty machines for high-pressure resin transfer molding (HP-RTM) supply reactive resin components for the carbon fiber composite supporting structures, for example the side frame, at the BMW plants in Leipzig and Landshut. HP-RTM allows fast-reacting resin systems to be processed in order to attain short cycle times. High-pressure injection produces a high degree of fiber wetting. A 10-man team from the KraussMaffei Reaction Process Machinery Segment set out to improve metering technology and provide mixing heads with the possibility of adding an internal separating agent. The experts worked under high pressure to meet the specific requirements relating to chemistry and the process. "We are now the only manufacturer of metering machines on the market who has this experience under series conditions," says Beyl.
In order to produce fiber-reinforced parts with an epoxy matrix in larger series, KraussMaffei enhanced high-pressure resin transfer molding (HP- RTM) for series use. In this process a self-cleaning, high-pressure mixing head injects the resin into the closed cavity and saturates the fibers inside under high pressure and with precise stipulations of the duration and temperature so that the resin and hardener are fully networked. Compared with the autoclave process or vacuum infusion, the advantage of automated production is that the cycle times are reduced from up to 24 hours to minutes depending on the complexity and size of the component.
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