Better performance but lower cost in moulding

Better performance but lower cost in moulding

Developments in injection moulding processes continue to improve efficiency and precision and cut costs. European Plastics News looks at the latest advances in in-mould welding, inline sealing, mould steel and micro moulding.

Sonderhoff, the foamed-in-place foam gasket (FIPFG) system and materials specialist, has developed a new Mold’n Seal process that was shown at the open house at Arburg’s German headquarters at the end of March.

Sonderhoff says that compared with its earlier FIPFG systems, Mold ‘n’ Seal, as shown in Lossburg, has a relatively small footprint of 50m2 for the complete production cell. The cell consists of an Arburg 570S injection moulding machine, polyurethane MK600 mixing and DM402/403 dosing equipment, a 6-axis Kuka articulated part handling and gasket material application robot, and line balancing conveyor belt.

The system fully integrates the Mold’n Seal process with the injection moulding machine’s control system as one inline system. A particularly innovative feature is the cell’s use of just one 6-axis robot for part removal and PUR sealing material application. At the sealing stage, the residual heat from the moulding process reduces the curing time needed to form the in-place foamed gasket on the moulded part.

Sonderhoff marketing director Peter Fischer told European Plastics News that in the Lossburg demonstration, injection moulding, part removal and placement for seal application took around 45 seconds.

Following this, it only took another three minutes for the Fermapor K31 seal to become completely cured, eliminating the need for a long balancing belt.

Stoppages for mixing head cleaning are no longer required with the newly optimised K31 polyurethane material in an eight hour production run. During this time, 2,560 parts can be moulded, foam sealed and passed on for further downline processing.

The 40g cover produced in Lossburg was moulded in Tecnoprene A60 K6, a 30% glass fibre reinforced PP from Italian compounder PGroup.

A new means of welding together two injection mouldings within an injection mould has been launched as the Joinmelt process, developed by injection moulding machine producer Engel with mouldmaker Hummel-Formen and welding system specialist KVT. The process was given its premiere on the Engel and Hummel-Formen stands at the VDI plastics in automotive engineering conference in Mannheim in April.

Key to the process is the use of a patented KVT 400oC hot gas welding method under inert gas. The Joinmelt process itself has been patented by Hummel-Formen. KVT claims the process is suitable for all types of thermoplastics, in particular glass fibre reinforced polyamide media ducts in automotive engine compartments, without the bulges conventionally arising from use of other welding techniques.

In the process, two moulded halves are simultaneously produced on left and right sides of a mould. The mould opens after the cooling stage and the movable left half is slid to a position so that the two mouldings face each other. The hot gas heating element enters the open mould area between the cavities and heats the edges of the two mouldings, which are then welded together by renewed closing of the mould. On reopening, the complete welded part is released.

At the VDI conference, Hummel-Formen pointed out the advantages of using Joinmelt, including clean smooth parts free of particles, greater geometric freedom, lower production costs and weight reduction in a “simplification of the production process”.

In the mould making sector, stainless steel mould steel producer Deutsche Edelstahlwerke (DEW) launched its new Corroplast FM steel at the Euromold 2010 fair last December. The new steel addresses the needs of more precise machining capability when making stainless steel moulds, as the number of cavities increases in multi-cavity PET bottle preform moulds up to as many as 192-cavities.

Key to enhanced machining without compromising corrosion resistance has been two years of work spent in optimisation of the steel alloy’s chromium, nickel, manganese and sulphur contents.

According to Jens-Sebastian Klung of DEW’s development, material and process simulation department: “A particular challenge was homogenisation of the structure and the correct sulphur content, which has a positive effect on machining properties, but also decreases performance, especially in the transverse direction.”

The negative effects of the sulphur content were overcome by attention to melting, secondary metallurgical treatment, as well as by minimisation of embrittlement by delta ferrite through thermodynamic calculations. These measures achieved the required enhanced structural homogeneity.

DEW says that the new Corroplast FM steel, with its 290HB hardness and improved microstructure, is available in 1,000mm wide rolled or forged sheet in thickness of between 40mm and 400mm.

In a conference organised by the IVAM microtechnology trade association at the Compamed 2011 fair last November, examples of overcoming challenges in micro moulding medical device and drug delivery components were given by Paul Glendenning, business development manager micro_components and polymer optics at Micro Systems (UK).

Glendenning identified these key micro mould tooling success factors: machining and alignment accuracy, preferential use of three-plate mould systems for auto-degating, and attention to venting. He pointed out that 0.050 - 0.200mm pin gates are used for injection, “unless an attached runner is needed for part handling”.

A new Wittmann Battenfeld MicroPower 15 machine ran on the Micro Systems (UK) stand at Compamed 2011, producing a medical clip as a development part with overall size of 1.5 x 2.6 mm and tooth pitch of 0.3mm. A clip was also produced on the Wittmann Battenfeld stand at the Medtec 2011 fair in Stuttgart in March. The POM part weighed 0.003g and was produced with 4s cycle time in a four-cavity mould supplied by Microsystems (UK).

Micro Systems (UK) has successfully moulded parts with 0.2mm diameter holes in 1.5mm and 0.32mm diameter holes in 7mm thickness “at a compound angle”. Holes as small as 0.04mm diameter have been achieved in thin moulded filter meshes, Glendenning stated.

Applications described by Glendenning included a micro-moulded drug-delivery caplet involving overmoulding in a two-cavity mould of bio-resorbable material. He also described a catheter tip development for a cardiac operation fluid delivery tube in which Pebax plastic is moulded onto a Pebax tube, followed by post-moulding laser drilling to produce a hole in the tip and 600 holes in the Pebax tube walls. Total cycle time amounts to 20s for two catheters.

Dental surgery was represented among Glendenning’s application examples by DFRP’s Smartseal ProPoint obturation device used in root canal treatment. The device applies hydrophilic polymer instead of conventional Gutta Percha, resulting in the first-ever lateral expansion within the root canal to form a complete 3D seal, claims DFRP.

The 43mm long, 0.18mm diameter ProPoint tip is made of a 60% mineral filled polymer that is “radio-opaque” to X-rays in a two-cavity tool. The tip was developed with Bradford University that has received its first MicroPower machine from Wittmann Battenfeld.

Microfluidic and bio-photonic applications were also addressed by Glendenning, with micro-moulding facing challenges as more features are integrated into microfluidic devices, such as use of diffractive optics to shape laser or LED light in, for example, cell interrogation.

With surface nanostructures being used to control wetting ability, “design know-how is needed at the nano level to create functional surfaces on specific materials”, Glendenning concluded.

Wittmann Battenfeld has been active in other application developments with the earlier MicroSystem 50. This has included micro metal-plastic hybrid part moulding, developed together with the packaging technology business unit of roll-clad metal strip producer Heraeus.

But the new MicroPower machine can be equally well integrated as part of a complete production cell producing items such as LED lead frames by overmoulding thermoplastics onto roll-fed metal strips. With cycle time of 5s, the company claims that cost savings of 30 to 50% can be achieved compared to conventional injection moulding machinery used for this purpose.

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This entry was posted on Pondělí, Červenec 25th, 2011 at 10:56 and is filed under plastic injection mould maker. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

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