Moulding lightweight parts
Many industries see lightweight construction as a "problem solver". The objective is to reduce the weight of the parts while also improving their mechanical properties. ARBURG processes such as physical foaming with ProFoam, the fibre direct-compounding process (FDC), also in conjunction with thermoplastic composite sheets, and Particle foam Composite Injection Moulding (PCIM) are used.
Long glass fibre-reinforced lightweight components
In innovative fibre direct compounding (FDC), continuous fibres are trimmed and added directly into the liquid melt. This is a cost-effective alternative to processing fibre-filled compounds. With the FDC process, the fibre length, fibre content and material combination can also be adapted flexibly and on an individual basis to influence the part properties in a targeted manner.
A hydraulic ALLROUNDER 820 S with a clamping force of 4,000 kN produces high-strength lightweight joints for household goods made of long glass fibre-reinforced PA. The consistency of the shot weight, and therefore of the fibre content, is displayed via a weight monitor integrated into the automation system, with the measurement result being controlled as a process parameter in the SELOGICA control system. A linear MULTILIFT V robotic system deposits the finished parts on a conveyor belt.
Lightweight construction with fibre reinforcement
ARBURG offers the new ProFoam process for the physical foaming of thermoplastics. The plastic granules are mixed with a blowing agent in a granulate lock upstream of the injection unit. This means that fibre-reinforced plastics are no longer subject to additional shearing.
ProFoam enables lightweight, robust and low-distortion parts to be injection moulded with a homogeneous foam structure. When glass-fibre reinforced materials are used, a longer average glass-fibre length is generally produced in the component than with conventional compact injection moulding. One efficient example is a kinematic housing for a automotive interior application, which, weighing 361 g, is around 13% lighter than a comparable compact part.
Foamed part combined with plastic
Particle-foam Composite Injection Moulding (PCIM) combines a foamed insert with a polymer component. By melting the surface of the foamed insert in a defined manner when injecting the plastic, a lightweight part is produced with a durable mechanical connection, dispensing with the need for downstream assembly steps.
The centrepiece of this compact and flexible automation solution is a hydraulic two-component injection moulding machine which, in a single process step, produces a finished model wheel comprising a foamed EPP tyre and injection moulded PP rim overmoulded with TPE. The new mobile Agilus six-axis robotic system (Kuka/fpt Robotik) is used for handling, and moves along an additional linear axis arranged transverse to the machine. The flexible seven-axis solution permits more dynamic movements and mould entry that is 43 % faster. The result is shorter cycle times and higher productivity.
Powerful combination: Long fibres and organic sheets
A lever is used as an example to show how the new Fibre Direct Compounding (FDC) process can be combined with the overmoulding of two continuous-fibre reinforced thermoplastic inserts of different thicknesses (thermoplastic composite sheets). The result is a high-strength composite component which can be used as a substitute for metal.
A six-axis robotic system picks up the two continuous-fibre reinforced thermoplastic inserts (organic sheets), which are of different thickness, and heats them gently in a two-sided heating process, before transferring them into the mould at a precise forming temperature. A servo-hydraulic ALLROUNDER 820 S overmoulds the organic sheets with long-fibre reinforced PP and, in a cycle time of 40 s, produces a component with additional functional and reinforcement elements that is over 500 mm long and weighs just 200 g. This corresponds to 62 % weight savings compared to die-casting.