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Scottish Plastics and Rubber Association Scottish Plastics and Rubber Association

Advances in Moulding

ARBURG Freeformer for additive manufacturing

The November SPRA meeting ‘Advances in Moulding’, sponsored and presented by SPRA Corporate Member, ARBURG Ltd, attracted an audience which represented a complete cross-section of the polymer community, with teachers, students, academics, designers, material suppliers, machinery suppliers, moulders and OEMs.

Martin Grimshaw (Northern Sales Engineer for ARBURG) kicked off with a presentation of the newly launched Freeformer, ARBURG’s innovative contribution to additive manufacturing,  Like other additive manufacturing techniques such as 3-D printers, LSA etc, the Freeformer is controlled by a solid modelling file, which is broken down to a layer structure.  Unlike other Fusion Deposition Modelling (FDM) systems, the Freefomer uses standard granular feed and conventional screw plasticisation. 

ARBURG Freeformer build area showing the 2-component nozzle area
The novel feature is a piezo driven nozzle which delivers tiny droplets of melt at a rate of 100 per second from an aperture as small as 150 microns.  Unlike 3-D printers, the nozzle is fixed and the build table moves (in 5-axis in one version), depositing the droplets of melt layer by layer to build up the finished part. 

The current Freeformer can produce parts within the dimensions of 230 x 130 x 250 mm from ABS, polyamide or polycarbonate.  The cycle time for a matchbox size component would be around 2 hours.  Although the surface finish is not like a conventional moulding, the mechanical properties are better than other additive manufacturing prototypes, with a claim of 85% of the strength of a conventional moulding.

Martin Grimshaw (ARBURG) (centre) with Neil McLaren (left) and Bruce McLaren (right) from McLaren Plastics Ltd
The Freeformer is a compact machine, which can pass through a standard office door, requires no pneumatic supply and is designed to be plug-and-play.  ARBURG has a two-component version, ideal for soft touch components for example, and developments are in hand to cover more grades of thermoplastics.

Several of those present had seen the Freeformer at K2013 and commented on how well it had been received.

In the second presentation, Simon Wrighton (Sales Director for ARBURG) looked at a number of advances in moulding, all with a common theme of production efficiency.  Customers are becoming focussed on energy consumption in moulding but the solution does not lie just with developments in injection machine technology but with a more holistic view of the manufacturing process and with production planning and product design.  Increasingly moulders are using specific energy consumption (kWh/kg of product) as their measure of efficiency.  Improvements can be as simple as moving heaters and chillers closer to the machine to cut down heat losses from hoses, coordinating tool changes and minimising downtime by careful production planning.

cube mould
Simon gave several examples of clever product design and mould design, utilising multi-station moulds and robotics to cut cycle times.  The ‘cube mould concept’ with a 4-sided mould tool, rotates about a vertical axis.  While the melt is injected on the first face (clamped), mouldings on the second face (unclamped and open to the atmosphere) are cooling, overmoulding injection of a second melt takes place at the third face (also clamped) and finally the parts are removed robotically from the fourth face.  The cube mould dramatically reduces cycle time and increases energy efficiency.

(left) Long fibre moulding, showing glass roving feed. (right) Benefits of long fibre reinforcement of themoplastics
For fibre reinforced thermoplastic moulding using fibre filled granules, the fibre length is seriously reduced in the compounding of granules, plasticisation in the screw and in the shear conditions in the mould feed system.  ARBURG’s solution is to delay the introduction of the glass fibre until after melt preparation of the base thermoplastic and feed chopped rovings half way along the cylinder.  This achieves longer fibres in the finished moulding, which gives better strength and impact resistance.  The big advantage for automotive manufacturers is that components can be lighter without sacrificing strength, with a knock on effect on fuel efficiency and greenhouse gas savings.

Simon Wrighton (ARBURG) explaining a long fibre reinforced moulding to Fergus Hardie (Hardie Polymers) (right)
Other examples of production efficiency from taking a holistic view of manufacture were packaging and labelling in-line with the injection moulding machine, pouring polyurethane robotically and foaming in-line with the moulding process to produce mouldings with integral PU foam seals and two-station overmoulding of lenses to achieve high optical quality with reduced cycle times.

The mixed audience responded enthusiastically with questions, during and after the presentations.  The opportunity for informal discussions and networking was also evident after the formal close of the evening.

Report by Tom Campbell, SPRA Council Member, November 2013

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