Micro-machining centre simplifies mould making

The accuracy of a 5-axis micro-machining centre is simplifying the production of injection mould tools used for producing microfluidic devices

As one of the UK’s top ten academic research centres, Cardiff University and in particular its Manufacturing Engineering Centre (MEC) continually conducts advanced scientific projects. Within the MEC department, the MicroBridge Project has been set up to create a link between the latest technology and industry.

The aim is to boost the UK’s manufacturing competitiveness.

The MEC has received GBP 7.5 million over five years with 50% of the funding provided by the UK Government’s Department of Trade and Industry (DTI) and the Welsh Assembly Government (WAG) with the rest being provided by industry and commercial income.

The investment in state-of-the-art equipment is continually ongoing with a previous funding programme providing a 5 axis HSPC micro-machining centre from Kern.

The Kern machining centre at the MEC plays a vital role in an environment where micro and nano machining operations are conducted daily.

The Kern HSPC has been supplied to the MEC with two spindles, one standard one at 42,000 rev/min spindle and an additional 90,000 rev/min one.

The machine also has a 4th and 5th axis dividing head.

* Injection mould tools for microfluidic devices – the Kern has recently been employed by the MEC to produce injection mould tools for microfluidic devices.

The accuracy of the Kern HSPC has simplified the production of the mould tool, said MEC.

Microfluid devices require micro channels moulded on a surface and these channels are produced by free standing walls machined on the mould tool.

A recent microfluid mould tool for examining drops of blood required channels machined at 20, 30 and 40 micron wall thickness.

Whilst the wall thickness is a challenge, the 200 micron depth proved the more problematic issue with this particular application.

MicroBridge Operations manager, Dr Robert Hoyle, explained: ‘With regards to machining we had to employ micro machining strategies to ensure the free standing walls would remain intact.

Using 0.6mm diameter end mills we had to machine at the full 200 micron depth making small cuts on one side of the wall and then the other to gradually achieve our 20, 30 and 40 micron wall thicknesses’.

The mould has initially been developed to produce small batches of microfluid moulds.

The moulds are machined in brass mainly for its ability to remain intact under such difficult machining conditions.

The ability of the Kern HSPC to deliver such extreme accuracies in this demanding application is credit to the HSPC polymer concrete base that offers vibration dampening qualities superior to cast iron machine tool bases by up to 2000%, said Kern to manufacturingtalkmold.wiki.

The reluctance of the base to react to changes of temperature and vibration enable the Kern to achieve surface finishes that are normally difficult to achieve by milling.

The rigidity of the Kern HSPC and stability of the feed motors can increase tool life by more than 25%.

This feature is of particular importance when machining to micron tolerances with cutters below 1mm diameter, said Kern.

* MicroBridge project – the MicroBridge project started in September 2005 but was converted to a spin out company in October 2007.

The MicroBridge project ihas been renamed MicroBridge Services – a company with the remit of commercially exploiting the MEC micro and nano machining capability for the benefit of UK industry.

Dr Hoyle said: ‘The MEC is a centre where ‘mechanical engineers continually make things smaller’, we have to focus upon the precision required for true micro machining.

So when the MEC was looking for a machining centre, the Kern stood out as the most accurate and best machine available to meet our specific needs’.

Working to deliver ground breaking technology to industry; the MEC works with the drug delivery, microsurgery and the diagnostics arena of the medical sector as well as optic, lens, electronics and aerospace industries.

This involves machining non-silicon materials, glass, polymers and a variety of metals.