- Carbon rims using the HP-RTM process
- Compact complete solution with sophisticated production equipment
- MX press with 10,000 kN, RIM-Star Compact 8/4 HP-RTM dosing system, two robots and tooling
Golf clubs, bicycles – and now also automotive: Taiwanese composite specialist Advanced International Multitech (AIM) is expanding its portfolio with KraussMaffei to include high-pressure RTM. High-quality carbon rims are produced on a complete system with sophisticated molds.
Anyone who plays golf and pays attention to weight has (almost certainly) already held an AIM product in their hands. The company has a market share of around 80 percent in the carbon golf club sector under various brand names and is also successful in cycling. Various composite technologies have been part of the standard repertoire for around 30 years. When AIM wanted to enter the automotive sector, however, KraussMaffei’s expertise was needed: for the first time, a high-pressure HP-RTM / High Pressure Resin Transfer Molding system was to be put into operation.
Compared to low-pressure processes, HP-RTM requires more complex dosing technology, but then delivers consistently good components with particularly precise surface quality – and with shorter cycle times. The latter is particularly important in the automotive industry. With the system, the AIM team initially wanted to get to grips with the new technology, as Tyson Hsiao (R&D Manager) explains: “Fredrick Su, our sales partner at KraussMaffei, listened carefully and then put together a package with which we can map both high pressure transfer molding and wet pressing and compression RTM for small production series in an HP-RTM cell. That convinced us.”
A concrete project was quickly found: Carbon rims, which tend to occupy a niche in the automotive sector – albeit an extremely lucrative one because it is in the high-price segment. A mix of materials is common here: a rim body made of CFRP (carbon fiber-reinforced plastic), to which the wheel spider made of aluminum is bolted. These wheels are around 20 to 30 percent lighter than those made of pure aluminum and at the same time around 20 percent stronger than steel rims. Sporty, ambitious drivers can accelerate faster thanks to the reduced weight and, as less unsprung mass follows the bumps in the road, the driving experience is also more pleasant. But if you want to adorn your vehicle with carbon rims, you have to dig deep into your pockets: €10,000 to €15,000 per set is common.
Overall competence from KraussMaffei
When it came to realizing the AIM project, KraussMaffei demonstrated its overall expertise: Project manager Thomas Eilhammer actively supported the customer and coordinated the comprehensive package comprising an MX press with a clamping force of 10,000 kN, the RIM-Star Compact 8/4 HP-RTM metering system, two robots for metering and handling with various grippers and a complex mold solution. He is still enthusiastic: “The system, including the enclosure, is very compact at 16 x 12 meters and all the components are perfectly coordinated. That is simply our strength as a full-service provider.”
René Ring’s team at the Georgsmarienhütte, Harderberg site was responsible for tool development: “We work with a master mold and use several tool packages for the different rim diameters. This makes the customer very flexible.” The process then looks like this: A carbon preform manufactured by the customer is placed over the inner core of the tool and four sliders, which form the round outer contour of the rim, move together. The press closes and the epoxy matrix material is metered in via a distribution star. After a hardening time of around 15 minutes, the mold opens, the slides open and an ejector ring pushes the rim body, which has shrunk to the core (diameter 20 inches), upwards. The tool is designed for rim diameters from 18 to 22 inches and a width of eight to 12 inches. The finish is achieved via a series of downstream processes.
The know-how is in the tool
The many moving parts in the mold posed the greatest challenge: sealing the entire system at a high internal pressure of around 60 bar. Normally, the press force alone seals a mold and the horizontal sealing surface is only located between the upper and lower part of the mold. In the rim project, the undercut and C-shaped part contour requires the four slides to be able to demold at all, plus the movable ejector ring. In order to maintain the vacuum in the mold and prevent the thin material from escaping, the team relied on the greatest possible manufacturing precision and a good concept. The locking force is generated by four cylinders on the upper side of the master mold; locking elements attached underneath move into recesses on the slides and block them. Due to the mold temperature of 120 to 130 degrees, it was necessary to protect pneumatic and electronic components with insulating panels.
The tool weighs a total of 4.9 tons. It was completed in Harderberg in 2023, then sampled at the KraussMaffei technical centre in Munich, optimized once again and finally delivered to the customer with the entire system. As a rim has to be one thing above all else – namely round – René Ring’s team is particularly proud of one figure: “We have a concentricity precision of less than 2/100 millimetres.” And there is another remarkable fact: the first shot already delivered a good part.
The carbon rim has already been on display at the leading composite trade fair JEC in Paris and Tyson Hsiao praises the good cooperation: “It was important for us to have an experienced full-service provider for HP-RTM at our side who is equally proficient in plant, process and tool technology. This allowed us to concentrate on our part, the production of the carbon blank. As a result, one cog fitted into the other.”
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