CAM software helps make moulds faster

At Essex Injection, the addition of Open Mind's Hypermill CAM software for Autodesk Mechanical Desktop has greatly increased the company's capabilities and reduced turnaround time.

At Southend-based plastic injection mouldings specialist, Essex Injection, the addition of Open Mind's Hypermill computer-aided manufacturing (CAM) software for Autodesk Mechanical Desktop has greatly increased the company's capabilities and reduced turnaround time.

Whereas lead-time from receipt of customer's CAD model to production of first-off mouldings used to be 10 to 12 weeks, this has been cut by at least two weeks, even though the complexity of the mouldings produced has increased significantly and both surface finish and accuracy have improved.

Essex Injection was established 15 years ago by ex-Lesney toolmaker, Eddie Edwards.

From the start, Edwards set out to offer an integrated service for tool development and first-off production under the same roof.

With time the company has evolved to the point where, as well as tool manufacture and prove-out, it also undertakes production moulding of customers' components using a range of plastic injection moulding machines from 25 to 250t capacity.

"Customers appreciate the one-stop shop approach", Edwards confirmed.

"In many cases we work very closely with our clients, providing product development services that can result in very worthwhile savings on costs.

We are committed to invest in facilities to improve the service that we can provide.

We moved into CNC machining in the mid-1990s and for a time used an outside agency to provide CNC programs.

However we always intended to have our own facility".

Essex Injection works for a wide variety of mainstream principals including medical, hi-fi and automotive suppliers.

In addition, it provides tool and product development services for specialist markets such as model railways and pest control, alongside production of around 100,000 bingo counters per day.

The company's toolroom is staffed by six fully skilled toolmakers.

Key CNC machining resources are a Bridgeport machining centre and a Charmilles EDM die sinking machine.

The company also operates a variety of manual equipment.

Almost all of the tooling produced is fully hardened and produced by the classic soft machine/harden/finish route.

John King, the Toolroom Manager, commented, "We use the machining centre to rough out cavities and to machine electrodes.

A high proportion of our tooling has built-up inserts to improve venting.

The nature of the work we do means a lot of the tools are fairly complicated, with sliding cores to allow certain features to be produced.

In addition we produce quite a lot of components with metal inserts moulded in; these are usually manually loaded into the tool so we have to consider the loading/fixturing requirement as part of the tool design".

When the time came to purchase its own CAD/CAM facility, Hypermill for Mechanical Desktop had a head start on alternatives as this was the system used by the agency that had been supplying programs to Essex Injection.

However, Edwards points that, although the company was familiar with the output, there was nobody within the company with hands-on experience of CAD/CAM.

He said, "We knew what we wanted the system to do but were looking for ease of use as well.

As a result we examined quite a few systems.

One factor very much in favour of Hypermill was the local supplier, Trionics, and in particular its sales engineer Len Newman who has given us a lot of technical and applications support.

Because he is also a toolmaker he understands what we want and can lead us through the process of getting there.

Experience with the system has allowed the company to develop a high level of expertise with Hypermill.

One of the benefits has been that it no longer needs to commission patterns.

In many cases, however, the job would be almost impossible to complete without availability of a CAD-based system.

A high proportion of our customers supply CAD models which allows them to incorporate more features into their products", King commented.

"A good example is a job we have done for a model railway track component supplier where the bolt heads on the chairs and the wedges for securing the track have been incorporated into the model.

Because we had Hypermill, it was a moderately straightforward exercise to divide the model up into its constituent features, produce a set of electrodes to generate the mould cavity and produce a pin-type insert to generate the inner form of the chair during moulding.

Without the software and CNC machining we couldn't have done the job at an acceptable cost".

Almost all of Essex Injection's electrodes are machined from graphite, using cutter diameters down to 0.25mm to achieve the necessary levels of detail.

As a rule, the machine is set up to run overnight.

The company has noted that this normally provides enough time to complete the machining process.

Use of the Erowa location system on both machining centre and EDM machine means alignment accuracy is maintained throughout the cavity machining cycle.

King has a high level of confidence in the system.

"Provided that we get the machine set-up correctly, the component that comes off is exactly as we expect.

There is plenty of in-built capability to inspect cutter paths and simulate the machining process but we rarely need to use them now.

The good thing about Hypermill is that you get out of it what you put into it", he said.

"If you have the correct CAD information, use the right shrinkage factor and specify the draft angle properly, then the tool will work".

The view is confirmed by Eddie Edwards: "The machining strategies available with Hypermill provide us with excellent finish in a very acceptable time frame.

When I think back to when I worked on the bench as a toolmaker, I certainly wish it had been available then".

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