Couplings speed moulding system setups

SPC multi-couplings provide the failsafe, quick and secure connections for the valve gate controls required by today's complex moulding systems.

Many injection moulded parts are required ready for use straight off the moulding machine; there is no opportunity to cover moulding errors with painting or surface coating.

In response to this demand producers are increasingly employing hot runner moulding systems combined with sequential valve gate controls.

Staubli SPC multi-couplings provide the failsafe, quick and secure connections for the valve gate controls that these complex moulding systems require.

Injection moulders are producing larger and more complex moulded parts, the control of material flow demanded in these applications is provided by the use of hot runner systems combined with sequential valve gate controls.

Hot runner systems provide improved control of the mould filling pattern and reduce scrap by eliminating both runners and sprues due to the material being kept hot in the mould ready for the next component.

Hot runner moulds are typically 10-20% more expensive than traditional moulds but a fast payback can be achieved through the elimination of scrap, the ability to run at faster cycle times and the opportunity to make energy savings.

Valve gate operation is a critical feature in hot runner moulding systems; it controls the flow of molten plastic within the mould.

This allows the mould designer to reduce the thickness of the part where required without causing flow problems and also to position the knit lines, where two or more flow paths meet, in a suitable position on the moulding.

Valve gates also control the material flow around core pins which gives improved hole formation The system is ideal for fill sequencing, processing foamed materials or gas assist moulding.

The valve gate is operated by a moving pin typically actuated by a hydraulic piston which opens or closes the valve controlling plastic flow through the gate.

The majority are hydraulically actuated; the higher pressure allows the use of smaller valve gate cylinders in the tool - for example 3mm diameter compared with10-12mm diameter for pneumatics - and the valve pin is quicker to respond and has less chance of sticking.

Predicting the fill pattern of large multi-gated parts is difficult.

Process simulation and practical experience are normally used to determine gate locations and hot runner bore diameters to balance the material flow.

This method essentially is based on trial and error can be very costly.

A better alternative is sequential filling.

This technique is used to control the fill pattern of multi-gated single or multiple cavity moulds.

The valve gates can be sequenced, opening and closing independently to achieve the required fill pattern.

The sequential fill method reduces differential shrinkage and improves dimensional stability and knit line appearance.

Cycle times can often be improved, warpage and flash are reduced.

Staubli's first application for valve gate connections was on a six gate system used for the production of car bumper fascias; subsequent systems were developed in co-operation with several IMM operators.

Valve gate control systems were also fully incorporated into fully automatic plate systems.

These experiences lead directly onto the introduction of Staubli's SPC203/205 valve gate multi-couplings available today.

SPC multi-couplings were developed by Staubli specifically to address the need for quick and accurate changes of sequential valve gate connections.

These multi-couplings are designated SPC203 and SPC205 and are designed for flow rates up to 2.85 and up to 8 litre/min, respectively.

They connect the hydraulics to the valve gate cylinders in the mould which control the operation of the sequential injection nozzles on the injection moulding machine.

The couplings are very robust and fully capable of withstanding any mechanical damage that can often occur during mould changeover.

The use of a multi-coupling guarantees connection accuracy, eliminating any confusion on which lines have to be connected, avoiding the need to trace back each line to ensure connections are made in the required sequence.

The result is a faster and safer connection.

Mould changeovers can take up to 20 minutes when individual couplings are used, even longer if threaded connections are involved.

This time is reduced to less than 1 minute with SPC multi-couplings.

Space is normally at a premium on mould surfaces so the small footprint of the multi-coupling permits flexibility in mounting the tool side plate on any available location on the mould and the press side is easier to handle.

There are three options available on each model depending on the number of circuits to be supplied: two, four or six, and the plate fixed to the mould will have the corresponding four, eight or 12 plugs.

Each connector is of nonspill clean break design preventing any pollution to the working environment and the circuits.

Connection is only possible in one position preventing misconnection and additional safety options include a keying system to prevent any connection errors where several plates are used with the same mould tool.

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