Product category:
Milling cutters
News Release from: Walter GB | Subject: Insert milling cutters
Edited by the Manufacturingtalk Editorial
Team on 12 December 2001
Inserts replace HSS rippers to up
productivity
By progressively switching from regrindable high speed steel ripper cutters to Walter insert tooling BAE Systems has gained productivity increases through the improved feed rates.
By progressively switching from regrindable high speed steel ripper cutters to Walter insert tooling, including TiN-coated tools, BAE Systems has not only slashed tool stock levels and costs at its Samlesbury site but it has also gained productivity increases through the improved feed rates and surface finishes now available In one case - the machining of forged light alloy centre fuselage intake frames - the use of Walter tooling has enabled cycle times to be reduced by at least 25 per cent
This article was originally published on Manufacturingtalk on 20 Jun 2001 at 8.00am (UK)
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BAE Systems' machining business unit at the Lancashire site is a centre of excellence within the company for the specialist production of complex machined details on components up to three metres long, mainly milled from light alloy or titanium.
Since the mid 1990s, the site has progressively rationalised its tool stocks by moving from regrindable HSS cutters to inserted types supplied by Walter GB of Redditch and, by comparison, traditional massive stocks of cutters have now been replaced by a few storage cabinets.
For the last six years, Walter cutters have been used exclusively for roughing on titanium, and a good example of the cycle time savings and surface finish improvements made possible by the new tooling concerns Airbus A320 titanium engine pylon brackets machined from a Ti forging.
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The use of a specially profiled porcupine cutter has allowed the roughing of an angled wall to a 1mm finishing allowance with a passably smooth finish.
It was previously necessary to rough the wall in a staircase pattern to a 3mm finishing envelope.
As a result, finish machining of the feature has been reduced to a 'clean-up' operation on a five-axis machine that now takes just 20 per cent of the overall eight-hour overall cycle time.
It was previously necessary to complete the component on a five-axis machine and finishing accounted for 50 per cent of the overall machining time.
Mark Wilson, a BAE Systems' manufacturing engineer, comments: "The change to Walter inserted cutters brought with it a much better level of machining consistency.
When we bought the first machine of what became a seven-machine FMS with three five-axis and four four-axis machines, it soon became apparent that 8 and even 10 per cent cobalt HSS ripper cutters were unsuitable for rough machining titanium in many applications.
"Tool life was poor, leading to a high regrind requirement and, as the HSS tools were reground, there was progressive loss of performance.
This could cause tool burn-out and hot spotting on the material - leading to the part being scrapped.
In contrast, the Walter tooling provides fully consistent performance." The machining demands at Samlesbury can be severe.
The Eurofighter wing attachment brackets, for example, comprise two forgings which are electron beam welded together after machining.
There is an overall stock removal requirement of 13mm but on some forgings it is necessary to undercut an overhanging flange - and this demands stock removal to a depth of 30mm while maintaining a volumetric tolerance of +/-0.2 mm.
Batch sizes are usually tied to economic batch quantity considerations so small parts are often machined in batches of six to 12 while larger parts may be produced as one-offs.
The machine shop is very highly automated with three major FMS systems and a number of multi-process cells for specific component families.
All programming is done off-line and downloaded via DNC according to computerised production scheduling.
While for some years Samlesbury's principal workload has been Airbus sub-contract work, the advent of the Eurofighter Typhoon and the company's involvement in the Joint Strike Fighter programme has meant that military aircraft work is now in the ascendancy.
One of Samlesbury's key products for Typhoon is sets of three centre fuselage intake frames, which are machined from light alloy forgings of around 180mm thick.
Each component is an elliptical shape with large diameter holes either side of the centre line - through which the air intakes pass.
Extensive ribbing on both sides provides the desirable combination of stiffness with low weight.
To produce these parts, BAe Systems has invested in four high-speed router/profiling centres capable of accommodating parts up to 3 metres by 2 metres.
Each machine is equipped with a 65kW/18,000 rev/min HSK 80 taper spindle.
"Although the parts are machined from light alloy the material is actually quite hard compared to automotive aluminium - around HRC 40 - and very a brasive," comments manufacturing engineer Dave Birkenhead.
"We were keen to use inserted tooling following the successful experience on the FMS, and conducted trials with a number of suppliers looking at insert life, stock removal and finish.
Ultimately we ordered the Walter F3040 integral taper routing cutter for roughing, using the 40mm (twin blade) and 50mm (triple blade) sizes.
"We've stayed with solid carbide below 40mm diameter because on this material the cost benefit of inserted tooling has not been so great." However, the combination of the new machines with the Walter tooling has helped to bring machining time on the frames down from 200-250 hours to around 80 hours.
Mark Wilson concludes: "Every tool has to earn its place and in this case the Walter cutters proved to be ideal.
"In general, we've been happy with the performance of the Walter tooling.
In addition, standard items are usually available next day and there is an acceptable turn-around on special tools.
We operate with consignment stocks of inserts, so there are no supply problems." .
(This was Manufacturingtalk's Top Story on 11 December 2001).
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