New lightweight solutions for the automotive industry today must meet numerous requirements-they must provide opportunities not only for the weight reduction of the final component, but also for the cost reduction of the final component. Therefore, they need to use materials that are reasonably costly and that they have the potential to be recycled.
Although thermoplastic composites meet these requirements, processing challenges have been hindering their application.
A new type of thermoplastic composite material pre-forming technology and corresponding processing equipment developed by South Korea's EELCEE company called "QEE-TECH" is said to provide a lightweight solution to meet these challenges.
QEE-TECH technology can form the complex three-dimensional preforms required for thermoplastic composite parts, and reduces the cost and time required for mass production of thermoplastic composite parts. The equipment used was manufactured by QEESTAR, a joint venture between EELCEE and Robostar, a robotics company based in Gyeonggi, Korea.
To demonstrate the joint venture's evolving capabilities in this technology, EELCEE implemented a demonstration project with a car supplier that supplies door modules.
Viscosity is too large to process
Compared to the corresponding thermoset materials, the relatively high viscosity of thermoplastic polymers is a major cause of processing problems.
"The high viscosity of thermoplastic resins imposes strict requirements on the impregnation method, and subsequent molding operations place strict requirements on the integrity of the preform and the mold," said Queein Chang-Manson, CEO of EELCEE.
To solve this problem, the company is forming a prepreg fiber structure, and then putting the prepreg (prepreg) into a mold and overmolding it, so as to impregnate continuous fibers outside the mold, Then put this prepreg into the mold to solve the problem of poor impregnation of continuous fibers in the injection or compression mold.
"By encapsulating unidirectional fiber and fabric composite inserts in injection molded and compression molded parts, QEE-TECH technology brings significant advances in design space for mass-produced thermoplastic composites and facilitates "Multiple functions are integrated into the components," she explained. "This gives designers freedom of design, allowing them to place expensive high-performance continuous fiber materials only where necessary, while using lower cost, Low-performance, free-flowing materials ensure freedom of shape to optimize cost and performance. "
In a series of applications, EELCEE has proven that it can reduce weight by 20% to 30% (up to 50% in special cases) and reduce costs by 10% to 20%.
In 2013, EELCEE won the JEC Innovation Award during the JEC Asia show. The award-winning product at that time was a thermoplastic bumper system produced by the molder Hanwha Group for 3D QEE-TECH technology for Hyundai Kia Motors.
Automated process
Automated layup, forming, cutting and infiltration. The fully automated QEE-TECH device uses a fixture that is fixed on a rotatable, sliding, and / or tilting table. The device can quickly lay the material into a desired three-dimensional shape. After the preform obtained thereby is automatically cut and pre-impregnated, it enters an injection molding or compression overmolding operation.
This three-dimensional preforming process can be completed in a cycle time of 60s (picture from EELCEE company)
QEE-TECH's three-dimensional pre-forming equipment is designed to allow the production of complex shapes with multiple functions and customized structural properties in a single operation step.
This fully automated process begins by pulling multiple continuous carbon or glass rovings or tows from a single bobbin and passing them through a series of dies to use the appropriate resin (such as PA, PP, ABS and PEEK, etc.).
"When strength is the focus of consideration, glass fiber has proven to be the preferred alternative, but if high rigidity is the primary requirement, carbon fiber may be the preferred material," Chang-Manson said.
During the infiltration process, the material passes through a preheating furnace. In the next step, the homogeneous molten tow is deposited on a fixture that is fixed to a rotatable, sliding, or tilting table robot. During the deposition process, a pressure roller applies pressure to the tow.
In short, the production unit uses three robots-a head robot system for depositing materials, as well as a desktop robot system and a support robot system.
By quickly laying into an ideal three-dimensional shape, an open, customized three-dimensional skeleton (prepreg) is prepared. Through a jet system, the deposited material is cooled. Then, the finished solid composite preform is automatically cut and then enters an overmolding operation.
This fully automated preform production facility can be synchronized with an integrated overmolding operation to enable efficient lamination at temperatures up to 400 ° C. This three-dimensional pre-forming process can be completed in 60 seconds.
"QEE-TECH technology is designed for mass production of structural components." Chang-Manson emphasized, "Each production unit provides a cycle time of less than 1min., And can produce 10,000 to 300,000 components per year."
Generally, conventional structured or short-fiber-reinforced polymers (PA, PP, PET, ABS, etc.) are used in overmolding operations, especially injection molding or compression molding.
"This is a non-isothermal process," Chang-Manson explained. "The insert is preheated to a temperature just below the melting temperature, and the overmolded material is heated above the melting temperature. As a result, the injection pressure is achieved. In order to achieve low porosity and good adhesion between the insert and the overmolded polymer, the cycle time is the same as ordinary injection molding. "
According to reports, when integrated into a production line, this preforming process does not have a negative impact on the cycle time of overmolding (the same as injection molding). The preform production unit can also be integrated into other composite production technologies such as RTM and thermoforming.
Composite door module
Assemble the "backbone" of continuous fibers. QEE-TECH equipment can quickly lay out the main structural strength parts of the door module (upper left) to create some sheets that can be combined in a mold into an open, customized three-dimensional skeleton. When incorporated into an integrated production line, this preforming process does not affect the cycle time of the overmolding process (picture from EELCEE)
EELCEE cooperated with South Korean auto parts manufacturer Duckyang Industrial Co., Ltd. and MS Autotech to jointly develop a composite door module. This research was supported by the Ministry of Trade, Industry, and Energy (MOTIE) and the Korean Academy of Science and Technology (KIAT).
"The value of this concept is primarily that it offers the opportunity to reduce weight, cost, and subcomponents for metal door modules of the same price range. By using continuous fiber preforms to locally reinforce thermoplastic composite doors, you can Achieve weight loss of up to 20%, "she added.
For this module, EELCEE has adopted a so-called "M-Tow" proprietary system. This is a braiding system that encloses a unidirectional ribbon fiber tow with a suitable fiber braid and / or polymer, so that the tow can be deformed by heat during the subsequent automatic layering process, Without any loss to the consolidation of the composite, no polymer bleed out. It also allows braided tows to be self-supporting during any form of three-dimensional layup.
Use continuous fibers only where needed. The door of this thermoplastic composite made of QEE-TECH three-dimensional preforms consists of only 6 parts, compared with 17 parts for steel doors. This overmolded preform can be seen on the open door frame (picture from EELCEE company)
The QEE-TECH process also allows customers to pave a variety of 3D preforms for specialized load introduction and load distribution. With proper design, the number of sub-components can also be reduced-this thermoplastic composite door module consists of only 6 parts, compared to a traditional steel door module consisting of 17 parts.
"When developing this component, you need to consider all the factors of the entire value chain, including: production process and mold design, after assembly and end of life." Chang-Manson pointed out, "Introducing inserts to the local can improve performance, but this is bound to Increases complexity. So it's important to define 'where performance is prioritized to minimize complexity'. "
The redesign of the door is not only focused on weight reduction, but also on engineering strength. In order to verify the reliability of the process and the performance of the product, EELCEE has performed extensive tests on various preforms using different material combinations and shape configurations.
"Our partners are very satisfied with the prototype parts produced," Chang-Manson said. "They are dimensionally stable and look good for mass production."
It is said that Hyundai Motor Co., Ltd. is closely following the door project and is considering using this technology in production.
After the trial is complete, EELCEE plans to contact other OEMs.