Product category:
Vertical machining centres (VMC)
News Release from: 600 Centre | Subject: Fanuc T14iB Robodrill vertical machining centre
Edited by the Manufacturingtalk Editorial
Team on 03 July 2002
VMC package revolutionises electrode
machining
A high speed VMC and application specific engineered package has had a major impact on the speed and efficiency with which complex 3-D copper and graphite electrodes can be machined.
"It is the best electrode machining solution on the market," is how Mike Malby, managing director of the MH Group Plc, summed up the Fanuc T14iB Robodrill vertical machining centre with its 600 Centre developed electrode machining package Installed in the West Sussex factory of group company MH Mould Tools some 15 months ago, this high speed vertical machining centre and application specific engineered package has had a major impact on the speed and efficiency with which complex 3-D copper and graphite electrodes can be machined for forms and cavities in plastics injection mould tools
This article was originally published on Manufacturingtalk on 22 May 2001 at 8.00am (UK)
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As Mike Malby outlines, the new Robodrill has cut his machining times by some 20 per cent, improved quality and provides a reliable, unmanned capability at night for round-the-clock working.
"When you are producing up to 100 different electrodes each week; fast, accurate and efficient machining is a prime requirement," he insists.
He follows on to describe how the 600 Centre of Shepshed near Loughborough supplied package of high speed spindle, 14-station tool turret and advanced control and software allows highly intricate 3-D electrode forms to be produced which just could not have been tackled before.
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He said: "The 700mm long table means that we can multi-fixture up to six electrodes at a time and run them through the night with no-one around." Unusually, both graphite and copper are machined wet using a dielectric as the cutting fluid on the Robodrill.
MH has found this causes far less problems in terms of dust build-up and prevents the production system becoming clogged.
The practice of wet machining with dielectric also prevents any abrasive particles causing damage to the machine's bearings, ballscrews and moving elements.
And, as well as being easier to manage, wet machining is far more environmentally friendly by eliminating any problems caused by airborne dust.
In addition, this technique has the added advantage for MH as it impregnates the electrode with dielectric during the cutting process.
This enables a finer level of surface finish to be achieved during the actual erosion process, about which Mike Malby comments: "The electrode tends to cut sweeter." Multi-flush type nozzles have also been installed on the machine to flush away all the graphite dust and this goes directly into a special cyclone separator to centrifuge the solid matter.
MH Mould Tools has been using the wet machining technique for several years on its larger electrodes or multi-electrode type tools.
However, as the purity and quality of copper alloy has progressively improved, the trend has been to change over to this material for any smaller electrodes.
Based in Bognor Regis, MH is recognised as a leading designer and manufacturer of plastics injection mould tools for the electronics, automotive, white goods and aerospace sectors.
The company has 'World Class' toolmaking status achieved in 1998 as part of the GTMA initiative to benchmark UK toolmaking companies and regularly invests in the latest production equipment.
It also has multiple stations for designing and draughting while programming terminals for 2 and 3-D surfaces are linked by a DNC network to all the CNC machines in the machine shop.
Key production equipment at MH includes: the Fanuc Robodrill T14iB, for high speed electrode manufacture and various high speed vertical machining centres, for roughing out 3-D profiles/cavities which sometimes involves hard metal cycles.
System 3R pallet-type tooling is used throughout from electrode machining through to the actual erosion of cavities, so that ultra-precise location is assured from machine to machine without the need to establish separate datums and set-up locations for each new job.
Full 3-D measuring and inspection equipment ensures that tools are 'ready to run' before in-house trials.
Virtually all 2-D electrode forms tend to be wire eroded as this is quicker and more cost-effective than milling and less material is wasted.
All the complex 3-D electrodes are now machined on the Robodrill which is programmed off-line using NURBS-based software and a 3-D modelling package.
These electrodes are then used to produce plastics injection mould tools for a wide range of components including: hand sets for aircraft in-flight entertainment, fascias and consoles for cars, various refrigerator parts and retail display lighting elements.
When the decision was made to replace an original eight year old Robodrill for electrode machining Mike Malby's team looked very closely at several different machines, before finally deciding the Fanuc Robodrill T14iB best met the all-round needs.
As Mike Malby maintains: "In terms of performance, accuracy, capacity and cost, the Robodrill was by far the most suitable machine on the market.
We also were very conscious that we had eight years of trouble-free operation with our previous machine and so we knew from experience that Fanuc machines were extremely reliable.
And when we compare the latest version, they are a good six times faster than most of our other vertical machining centres." The company produces a wide variety of single copper and graphite electrodes, in sizes ranging from 1 mm dia up to around 500mm by 400mm, that the cycle times enable the machine to run out of normal hours unmanned.
So, to take full advantage of the situation, the T14iB was specified with a sub-table in order that multiple fixtures, and therefore electrodes, could be set up.
Typically, this means that up to six components can be loaded and with average machining times of around one hour, this provides sufficient material capacity for extended 'lights out' machining.
As a matter of course, electrodes requiring longer cycle times tend to be machined at night to ensure maximum productivity and almost continuous production with the spindle running at its maximum speed and with feed rates between 700 and 1,000mm/min.
Depths of cuts tend to range between 0.5mm for roughing to 0.1mm for finishing.
One job which highlighted the performance of the latest Robodrill was an ultra-thin electrode for a large mould tool to produce drop-down lighting consoles on a new model of car.
Machined from a 152mm by 101mm by 55mm deep solid block of copper, the aerofoil styled form finished up just 0.7mm thick by 45mm deep and within a tolerance of 10 microns.
Mike Malby confirms how the Robodrill accurately produced this form.
"It particularly maintained a very high level of surface finish on the face of the thin section," he said.
While on a graphite electrode required for an in-car CD player facia, small upstandings, which were less than 1 mm apart, were also machined successfully.
Mike Malby recounts: "Both these jobs would have been extremely difficult and very time consuming to produce on any other machine in the factory.
And in the case of the mould tool for the CD fascia, we would have had to produce separate electrodes for the upstandings.
However, being able to machine them all together on a single-piece electrode is typical of the advantages we have gained from the 600 Centre machine.".
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