Main focus of this seminar: process integration, lightweight construction and functional surfaces. “These are the most important growth drivers in the automotive
industry and the key for more efficient processes and a better ability to compete,” stated Gilles Lefevre, Managing Director of Engel Thailand, during his keynote speech. Then Mr. Michael Fischer, Sales Manager Technologies of Engel and Mr. Thomas Rothmayer, Head of Competence Center of Borouge captured the attention of the participants. Innovative technologies and case studies instead of sales talk and promotion. This was very well received by the international audience of more than 120 participants. Here the first part of our recap covering the different injection moulding technologies to produce multi-component parts.
A wide range of basic production methods are available to produce multicolour or multiple component moulded parts. A combination of these basic production methods with other production technologies (e.g. thermoforming) and a high degree of automation then enable the production of sophisticated multi-component parts in one single production cell, such as Engel foammelt, Dolphin or Varysoft. First an overview (clickable) about the different and most common “basic production methods”, and then Engel specific technologies.
- Transfer Method
- Rotary Table Method
- Turning Platen Technology
- Index Platen Method
2) Engel Specific Technologies
- optimelt (among others)
Basic Production Methods
The part/preform is “transfered” from one station to another by robot, e.g. to insert metal parts or transfer moulded parts within an injection mould, or between two injection moulds on two machines.
Rotary Table Method
ROTARY TABLE METHOD
The transport of part/preform is accomplished by rotation. The rotary table is part of the machine. Special rotating media supply lines ensure that the injection mould is provided with the required resources (temperature control, sensors, electric system, optional hydraulics).
Turning Platen Technology
TURNING PLATEN TECHNOLOGY
A two-platen injection moulding machine is combined with a rotary module on a sliding carriage. Injection moulding units are mounted on the platens. The horizontal rotary module carries the central part of a double-daylight (stack) mould.
Index Platen Method
INDEX PLATEN METHOD
The transport of part/preform is accomplished by rotation. The index platen is generally an integral part of the mould (therefore only the mould is rotating). Indexing platens are lifted from the master mould after each injection cycle, rotated and reinserted.
Engel Specific Technologies
Engel foammelt is a physical foaming process using the MuCell technology. Here either nitrogen or CO2 is injected into a specially adapted plasticising unit during plasticising. Due to the pressure in the plasticising cylinder, the gas dissolves in the plastic melt and is not released until after injection.
Process step 1
Process step 1: The plasticizing process takes place after injection of the previous shot and during the mould cooling phase. With the needle valve nozzle closed, the melt builds up in the space in front of the screw. Gas injectors introduce nitrogen in its supercritical fluid state” into the metering zone during the plasticizing process.
Process step 2
Process step 2: The mould opens and the part is demoulded. The melt for the next shot is kept under pressure so as to ensure a uniform melt temperature. This is a prerequisite for the optimally uniform foam structure of the moulded part.
Process step 3
Process step 3: The mould closes. The needle valve nozzle opens and the melt is injected. During injection, the finely dispersed gas in the melt nucleates and expands to produce a microcellular foam.
Process step 4
Process step 4: The melt expands to fill the mould, forming a solid outer skin and a microcellular foam core of extremely uniform structure.
- lightweight moulded parts due to lower density
- sink marks and war page are minimised due to the “internal” homogenuous post pressure.
- smaller machines with lower clamping force can be used
- negative compression further ensures a uniform cell distribution in the foam structure
- loadhog lid: 1,700 ton machine is sufficient for foaming the part, compared to 3,000 tons which would be necessary to produce the solid/compact counterpart
- climate control panel: can be additionally IMD decorated
- HVAC doors / interior door trims: PVC skin, back injected with PPT20
- fan: made of PA6.6, 8% weight savings, 27% shorter cooling time, 33% shorter cycle time
In this context also the instrument panel of the Golf 7 was mentioned which is produced by using “foaming by decompression stroke” featuring low density and higher bending stiffness of the part.
The Dolphin process allows the production of multiple component interior parts with soft-touch surfaces in automobile interior applications, without intermediate steps. It is a combination of 2-component injection moulding (rotary table method) with MuCell foam injection and compression technology.
Injection moulding of the substrate (carrier), typically made of glass fibre reinforced PBT. After completion of the cooling time, the injection mould is opened and the core side is rotated into injection station 2.
a) Injection of nitrogen saturated melt onto the carrier (thermoplastic polyester) by a second injection unit.
b) After a defined delay time to allow the compact outer skin to cool, the clamping unit is opened by a defined compression stroke. The nitrogen dissolved in the polyester is released from the solution and foams the core of the polyester layer. This system provides the technical basis for precision opening (negative compression), which is the precondition for controlled foaming.
- cost-effective alternative to parts moulded in multiple step processes, such as lamination with PU or TPE foils, or in place foaming with polyurethane foam.
- covers of instrument panel (Actros truck of Daimler): first series production
- foldable panels: visibility on both sides, Dolphin and the carrier structure
(In total up to 12 different moulds were used in one injection moulding machine for the Actros project)
This process allows the manufacturing of multi-dimensional, soft-touch components for automotive interiors. Premium parts can be produced in single-step production by injecting a PUR foam layer between a thermoplastic carrier and a pre-heated decorative film.
A dashboard produced by using the varysoft process
- single-step production of sophisticated parts consisting of thermoplastic carrier, PUR foam layer and decorative film
- undercuts in the component design is possible
- passenger airbag cover: ABS/PC Mucell foamed carrier with a PUR foamed middle layer (0.2 g/cm3) and in-mould grained TPO skin
To replace steel and aluminium with lightweight components: Organomelt is an integrated, automated thermoforming and injection moulding process for lightweight thermoplastic composite sheets with a multilayer reinforced structure. The Organomelt process is now in the process of further development in order to be used with thermoplastic tapes with UD continuous fibre reinforcement.
- 5-step process in one production cell: heating, forming, consolidation, backmoulding and trimming
front end module (Audi A8)
break pedal (ZF Friedrichshafen): weighs only 355g (50% weight reduction compared to steel pedal) and goes now in series production for Porsche. This part also received the “Composite Innovations Award 2011”
Engel optimelt (coinmelt)
This process is a combination of injection moulding and injection-compression moulding. During injection, the mould and/or the mould cavities are kept open by a defined gap. Expanding the flow diameter in this manner reduces the filling pressure, shear strain and the orientation of the polymer molecules. After filling, the injection mould is closed to final dimensions (=compression stroke). Running the method in heat and cool technology the mould temperature control is very important as the mould is hot during filling and about 30-40 degree C colder during holding.
- The pressure on the melt during compression is lower than in injection moulding and acts homogeneously on the whole cavity (“coining”). The resulting internal stress in the moulded part is low. Parts feature low torsion, homogeneous distribution of properties and extremely precise surface contours.
- optical parts / lenses: thick lenses are usually moulded in multiple layers to reduce the cooling time. In addition, possible sink marks and defects can be compensated by the 2nd layer.
Mr. Michael Fischer also provided a short overview about the Engel clearmelt technology for the production of thermoplastic parts combined with PUR in one cell, the “In-Situ Polymerization” and further development project which will be hopefully topics of another edition of the Automotive Days in Bangkok.