Product category:
Machining centres - all types
News Release from: KERN Micro- und Feinwerktechnik GmbH & Co. KG | Subject: High precision machining centres
Edited by the Manufacturingtalk Editorial
Team on 20 July 2007
Machining centres are 'ultra-precise'
A machining centre has been developed for predominantly prototyping and small batches while another, also to be shown at EMO, produces 'ultra precise' parts in medium and large batch quantities.
At the EMO 2007 exhibition Kern machine tools will be showing its high precision machining centres in Hall 12, Booth E42; they include the following * prototyping - the Kern Micro machining centre produces prototypes and small batches
This article was originally published on Manufacturingtalk on 26 Jan 2006 at 8.00am (UK)
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* Medium and large batch - the Kern EVO produces 'ultra precise' parts in medium and large batch quantities.
For those requiring automation, Kern the EVO machine has options on tool magazine capacities and a choice of automatic workpiece changers.
* High accuracy - Kern Pyramid Nano has set new standards with a positioning scatter according to VDI/DGQ 3441 of PS +/-0.3 micron (300nm).
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The symmetrically constructed, thermally stable and vibration dampening Kern Armorith base enables accuracy to be achieved across a working envelope of 500 x 500mm.
** How high accuracy is achieved - Kern has tested various drive alternatives thoroughly.
In comparison with linear drives Kern has shown that hydrostatic drives are superior as they do not create the 'whipping cogging' effect.
Hydrostatic guideways lift the table 18 micron so there is no metal to metal contact and no wearing parts.
The oil in each guideway is temperature controlled, so even if one axis is being moved faster and further than another axis - there will be no accuracy differences between the axes.
The hydrostatic guideways also play an important role in improving the surface finish that customers expect on their components.
The machines are available with two spindles.
The HSK25, 6.4kW spindle has a speed range of 500 to 50,000 rev/min and the HSK40 11kW spindle has speeds of 200 and 36,000 rev/min.
A Z-axis temperature controlled guideway system houses the spindles.
This dissipates any heat through 360 deg.
Kern will also show a 2-axis trunnion type table for the first time at EMO.
The table accepts either System 3R Magnum or Erowa Power chucks as the spindle.
These systems provide automatic workpiece changing and an accurate means of workpiece location.
A temperature controlled torque drive powers the 2-axis table.
The Kern Pyramid Nano has a wide variety of automation capabilities with a tool magazine holding up to 95 tools and an integral workpiece changer with 20 positions.
Alternatively, external changers with pallets up to 280 x 280mm can be provided.
The Pyramid Nano machine benefits from Kern's experience of unmanned machining to very high accuracies in its own subcontracting division for many years.
** Defining precision - Kern said that all machine tool manufacturers offer 'precison' - but asks: 'what defines precision?'.
Kern said that the British Standard, DIN, the newly introduced Euro norm EN and standards on other continents have no clear definition of the word 'precision' or 'accuracy'.
Many manufacturers of machining centres do not state accuracies in their brochures, while others only state the measuring system resolution.
Within Europe there is DIN VDI/DGQ 3441, which offers clear definitions for accuracy and repeatability with variations between European and Asian standards adding to customer confusion.
At EMO, Kern will introduce its own definition of precision.
The company said that what is achieved in a machined workpiece defines the accuracy of its machines.
This accounts for miss-positioning of the axes, spindle run-out and cutter 'push-off' (that is, the reaction force of the workpiece material's characteristics in rsisting, or pushing back the cutter away from the wokpiece - Ed) - all factors competitor manufacturers do not take responsibility for.
Such accuracies have been proven on test pieces for NASA US for its Kern machine purchases.
The Kern definition of accuracy (on the workpiece) is as follows: * <= 10 micron = 'micro' precision * <= 3 micron = 'ultra' precision.
* <= 1 micron = 'nano' precision.
Highlighting these exceptional accuracies, Kern will show the Kern Micro, the Kern EVO and the Kern Pyramid Nano with workpiece precisions of <= +/-2.5 micron, <= +/-2.0 micron and <= +/-1.0 micron and positioning scatter of PS1.0 micron, PS0.5 micron and PS0.3 micron respectively.
* Kern at EMO 2007, Hannover, Germany, September 17-22, Hall 12, Stand E42.
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