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The debate continues over the appropriate technology for die and mould manufacture. The key to high productivity, argues Sandvik Coromant, is high speed machining - as long as it's used properly. （图片） Cutting tool company Sandvik Coromant champions the virtues of high speed machining (HSM) over electrical discharge machining (EDM), particularly in die and mould manufacturing.
'HSM can deliver outstanding productivity and the accuracy necessary for good economy in die and mould manufacture,' says Martin Pollard, Sandvik Coromant's Business Development Manager with special responsibility for the die and mould sector.
'It should also be remembered that the life cycle of products produced by dies and moulds tends to be shorter, making a faster, more flexible manufacturing process even more important for the future. And the closer blanks become to the near net shape of the die or mould, the more we predict that HSM will continue to grow in importance.
'Another important factor concerns modeling and prototyping of dies and moulds made of easy-to-machine materials. These can be undertaken with cutting speeds as high as 1500 to 5000m/min and at very high feeds. Here HSM really comes into its own.'
Sandvik Coromant makes the case for applying HSM in die and mould manufacture by highlighting reduced machining times - in some cases as much as halved.
Also, higher precision, reduced lead times, reduced number of process stoppages, the elimination of or very little need for manual finishing work and reduced try-out times.
Key criteria for maximizing the effects and benefits of HSM include the need for dedicated manufacturing equipment. To implement HSM effectively, it is necessary to combine the use of dedicated machine tools and controls with cutting and holding tools that have been specifically designed for HSM.
The Sandvik Coromant Capto is a genuinely universal solution suited to lathes, turning centres, drilling and milling machines. The system is extensively used in the die and mould industry with its coupling being extremely strong with regard to stiffness and resistance to deflection.
In productivity terms, it has a repeatable accuracy of ±20µm in X and Y axes, virtually eliminating the need for measuring cuts - another significant time saver.
Being self-centring and balanced by design, the Capto's polygon coupling minimises run out and gives the insert a correct centre height to ±2.0µm. The toolholder clamps into the turret with just a half turn of an allen key.
Another Coromant tool holding system that is increasingly applied in die and mould is CoroGrip, a system that covers all applications from super finishing to heavy roughing.
One holder can clamp all types of tools from face mills to drills and a wide range of proprietary collets can also be used with the holders.
All CoroGrip tool holders are individually balanced and the symmetrical clamping forces in the system maintain its low run out even in the most arduous roughing conditions.
Coromant's CoroMill Plura range of solid carbide tools are particularly useful in these conditions as experienced by die and mould manufacturers.
'CoroGrip and Plura are a perfect match' says Pollard. 'The advanced machining capabilities of Plura and the high precision of CoroGrip chucks offer a highly stable combination.
'Plura has been specifically designed for HSM applications with tool geometries and its grade family profile allowing the best possible productivity in all work piece materials.'
So, how does Coromant's argument for using HSM in preference to EDM work in practice?
To prove its point that HSM offers the more productive solution, engineers at Coromant have undertaken a direct cost and speed comparison between the two technologies. This is based on a recent application for the manufacture of a mould for a shoe sole.
The contrast between traditional production habits and the newer HSM technology produced some significant cost savings. Machining time with HSM was just over half that achievable with EDM.
The HSM operation was undertaken using an optimised CNC programme using NC-SPEED software and a range of, predominantly, Sandvik Coromant Plura R216 cutting tools.
Based on £60.00 per hour machining time the EDM route - manufacturing the roughing and finishing electrodes, machining the finished part and final polishing was £400.00. Using HSM, the mould was finish machined in just 2.8 hours (£170.00), producing a cost saving of £230.00 on machining time alone and freeing up the machine tool for further use.
Furthermore polishing was eliminated. The EDM cost did not include the cost of raw materials for manufacturing the bespoke electrodes whereas the cutting tool cost could be amortised across a very wider range of machining operations, further reducing the cost.
Machining operations to achieve the finished mould involved periphery and flat roughing, semi-finishing operations and the contouring and grooving necessary for the precision finish machining.
In conclusion, Martin Pollard says: 'The optimum combination of dedicated tooling and advanced application technology is fundamental for obtaining the best HSM manufacturing economy in die and mould making.
'More demanding materials and ever-faster machine tools put a great onus on the correct tooling solutions.'
1/11/2005
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