Linear EDM halves mould tool cycle times

A two-shot injection mould specialist is building on its success by halving the cycle time of its toolmaking process through the use of the latest linear EDM technology.

Chesham, UK-based two-shot injection mould specialist Euromoulds is building on its success by halving the cycle time of its toolmaking process through the use of the latest linear EDM technology.

Richard Powell, managing director of Euromoulds, started the business in 1986, growing it into the 12-employee, GBP 1.1 million turnover concern it is today.

Clever management has steered the company into a relatively niche area of injection moulding - the two-shot process.

This is the ability to produce complex mouldings from two different polymers at the same time during one machine cycle, and has the benefits of creating mouldings with more than one colour, or with different materials combined in one moulding.

The benefits of the process are far-reaching and include the elimination of post-moulding processes to join separate mouldings together or apply colour to components.

This in turn reduces labour input and cycle times accordingly.

To complete a multi-component tool requires the capacity to trial tools and Euromoulds has two twin-shot presses for this purpose - a 2000kN (200 tonf) Arburg and a 1000kN (100 tonf) Krauss Maffei, both with a rotary unit.

The most crucial element in two-shot injection moulding is the design of the tool, which features moving components.

For the process to run efficiently the tool must be designed so that both moulded parts can be created in the same tool.

This is achieved by machining moulds that have two separate component cavities and can be rotated through 180deg so they line up with the two injection units.

In the first step of the process a pre-moulded part is created in the first cavity.

The tool then opens to allow the necessary rotation through 180deg to the secondary position.

When the tool closes again the pre-moulded part is in the second position so that it can be finished with the second injection.

During this second phase another pre-moulded part is being produced in the first position - hence the process is a continuous cycle.

Advances in EDM provide benefits Creating tools with these capabilities is where Euromoulds prefers to exploit the benefits derived from using Sodick linear EDM and milling technology.

"The machines we've bought have replaced some older models," explains Powell.

"Spark erosion technology has really moved on - tools that were taking eight weeks to manufacture not so many years ago, today take two weeks.

And with regards to linear milling, this is helping us reduce hand finishing massively.

The days of spending a morning cleaning an electrode to go into a job are long gone." In combination with its linear CNC milling machines and wire eroders, the company uses Unigraphics solid modelling software, NC Graphics' Machining Strategist and Cimatron to help manufacture the high precision mould tool components.

Powell says the chief benefits of linear motor technology are speed, accuracy and repeatability.

Yet initially he was not convinced.

"I was fortunate enough to go to Japan in 1998 to see linear technology in development at Sodick," he says.

"At the time I did not think it would be the next step change in EDM.

It was going so fast that it just did not look right.

I could not help but think the speed would compromise quality, but I was wrong." Competitive Advantage Today, Euromoulds' armoury of advanced technology is helping the company successfully secure new two-shot injection moulding business in the face of stiff global competition.

Typical examples of the types of moulding produced by Euromoulds are bicycle handles requiring a soft grip area, as well as triggers, knobs, dials, switches and thin-walled surgical masks for anaesthesia applications.

The latter are manufactured from clear polypropylene and soft white TPE (thermoplastic elastomer) for the face contact area.

Euromoulds has targeted the medical sector purposely and Powell says the company is now widely recognised as having the equipment required to serve this growing industry.

Euromoulds has recently completed a new range of surgical masks in various sizes for a leading medical supplier.

The advantages over silicon or single material masks are cost, patient comfort and the ability for the surgeon to see the patient's mouth during use.

Two-shot injection moulding greatly simplifies the production process and promotes the moulding of high-value added products.

Typically chosen for moulding TPE over a thermoplastics substrate to improve the tactile, ergonomic and cosmetic features of a product, the two-shot process has become very popular in a broad range of markets from medical devices to power tools.

Most raw materials can be used: the resin is in pellet form before processing.

Painting, which can rub off, is also eliminated, enabling most piece prices to be kept quite low.

The company can produce two-shot, single-shot and liquid silicon tooling using traditional cold sprue feed, multi-plate feed or any hot runner system that the customer may specify.

Exemplifying Euromould's expertise at producing 'conventional' injection mould tools is a vacuum cleaner impeller for Dyson, a long-standing customer of the company.

This particular product requires a complex 3D die-sinked mould that Powell says is twice as quick to produce on linear machines.

"In fact we would not even have attempted it before," he adds.

"It would be impossible to achieve the finish required by Dyson." Investment is critical for success Powell also highlights ease-of-use as a critical factor in the selection of Sodick machines, as well as the back up provided by Sodi-Tech EDM.

Yet undoubtedly the overriding feature of choice is the linear motors.

"I feel that Sodick has taken the lead on technology where perhaps some of their competitors have not," he says.

"Investment in the latest technology is absolutely critical to our pattern of continuous improvement.

We have been fortunate enough to secure some lucrative contracts and these have allowed us to re-invest a high percentage of profit back into the business - we have spent money on capital equipment every year since our inception.

It is vital not to stand still.

So often I read that the acquisition of new equipment is seen as 'the last piece of the jigsaw'.

I view it differently - I see every new machine as the first piece of a new jigsaw and I firmly believe this is one of the reasons we are competing successfully in a tough global market.".

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