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News Release from: Mike Page - editor's feature articles | Subject: High speed and highly dynamic machine tools
Edited by the Manufacturingtalk Editorial
Team on 13 September 2007
Is it a high speed machine tool or
highly dynamic?
One local area of minor confusion for some, when visiting a German machine tool exhibition and talking about machining, is the difference between 'high speed' and 'highly dynamic', writes Mike Page.
When you visit the EMO 2007 international machine tool show in Hannover, Germany, next week, you may get confused between what a 'high speed' machine tool and 'highly dynamic' machine tool can do The German way of defining machining tends to talk about 'high speed cutting' (HSC) and 'high speed production' (HSP)
You can have either, or both, in one machine.
With HSP, mainland Europeans get excited about 'highly dynamic' machining.
* HSC - most of us know what high speed cutting is.
For some, it means that if a milling cutter is to rotate at more than 10,000-12,000 rev/min, you need to balance it and the holder.
In theory, HSC cuts and removes chips before the cutter gets hot.
Most of the generated heat is contained in a very hot chip, which is flung from the cutting tool/workpiece interface and does not get the chance to even think about transferring that heat to either the tool or the job.
Simplistic, I know, but that is what happens.
It means too, one can cut some metals at HSC rev/min, with a shallow depth of cut, without using coolant, or just using a fine mist.
Then, because the tool may be machining at 12,000 to 30,000+ rev/min, and at a high cutting feed rate, metal removal rates can be impressive.
Make sure the system clears the chips efficiently! The mould and die guys and the aerospace folk like HSC.
The latter tend to be more cautious, but they use it.
If the workpiece metal gets upset at high metalcutting heat inputs, then HSC may be the answer.
At EMO, talk to Cincinnati Machine, Correa, DMG, Innse, Forest Line, Mori Seiki, Soraluce, Waldrich, Zimmermann and the many others who will update you on HSC as far as milling is concerned.
* HSP - high speed production, and its 'soul mate', highly dynamic machining (let's call it HDM), is really zapping a spindle head and/or the pallet or table around as fast as possible.
The idea is to kill 'down time' or 'air cutting time' to squeeze yet more seconds from the overall cycle time.
Linear motors were talked about in a 'white paper' last week.
Linear motors are very good at moving things around very quickly as are the latest ballscrew - and even some precision rack+pinion - drives.
Even more importantly, their acceleration/deceleration rates are impressive.
Indeed, talking about a machining centre with fast axes traverse rates up to 90m/min or more is fine - looks impressive.
But the real key is the 'G' factor.
Ask yourself how, in a machine tool with a working envelope of, say, 1m3, any axis traverse is going to reach 90m/min and then stop? Many machining centres in the 1m-1.5m3 machining envelope at EMO 2007 will have acceleration/deceleration rates of 0.25-0.5G.
Some may have 1G.
A small number may boast 1.5-2G - and boy! They can move! The latter will be great for say drilling, reaming and boring multi-hole patterns in jobs like internal combustion engine cylinder heads, complex valve blocks and the like.
So good, in fact, they can be a better bet than a multi-spindle drilling/reaming head.
That is why some transfer line and rotary transfer (dial in US parlance) machine builders use 2- and 3-axis HDM machining units instead of multi-spindle units.
If a drill breaks in a multi-spindle head, the line stops.
If it breaks in a single-spindle HDM head, quick attention from a tool changer has the line going within seconds.
It will be worth checking up too - assuming HDM is in your interest - to find out what happened to the 1990s 'Hexapod' ideas.
EMO 2007 will be a great show, and the western users of production machine tools will be checking up on HDM.
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