Corin Group Introduces Vertical machining
centre to reduce lead times
Medical implants and instrumentation manufacturer has
introduced 'lean' cell-structured machining systems - including high speed
machining - to reduce overall manufacturing lead times
Link
http://www.manufacturingtalk.com/news/siz/siz235.html
Medical implants and instrumentation manufacturer, the Corin
Group, has introduced lean, cellular production techniques, which have
transformed individual component machining times, as well as overall lead times.
Newly-established routines have also streamlined production through reduced work
handling and separate set-ups.
In addition, investment in another area has eliminated costly
outsourced machining operations and allowed the company to take full control
over its processes.
By establishing cell machining incorporating a Fanuc Alpha T21E high speed,
24,000 rev/min vertical machining centre (VMC), has, for example, been able to
demolish lead times on hip replacement 'cups' from three days down to just one
day.
Also, Corin invesed in two Fanuc Alpha wire EDM machines, to bring back in-house
previously sub-contracted wire edm work.
Production manager, Trevor Buggins, at Corin explained that the Group's global
reputation had been built around a policy of continual improvement.
It impacts every department of the 200 plus-employee company, which in more
recent times, has attracted increased business from countries such as Japan,
North America, Turkey and Venezuela.
Corin produces a wide range of products for the medical sector, hip, knee,
ligament and spinal replacement items, as well as 'instrumentation packs' that
provide surgeons with a complete set of tools for the appropriate task.
The company processes stainless steel, titanium and cobalt chrome alloys, for
example, in various quantities to meet its growing forward order book and stock
demands.
A 'flagship' product, the Cormet Hip Resurfacing system, combines the principles
of conservative arthroplasty with metal-on-metal bearing technology to provide a
solution for patients with osteoarthritis or rheumatoid arthritis.
It is in producing the components for Cormet that the Fanuc Alpha T21E VMC has
been used to impressive effect.
* Cell manufacture - formerly produced with a variety of other products on a
range of five machines at various locations around the shopfloor, the Cormet
product is now machined in cells: one for femoral components (available in 40mm
to 56mm outside diameters), and another for processing batches quantities of 100
cobalt chrome 'cups'.
These are first turned before entering the machining centre for a variety of
milling and finishing operations.
On each cup, the Fanuc Alpha T21E initiates a probing cycle as a datum using its
Renishaw MP700 optical probe before machining three circumferential slots
approximately 3mm long by 1mm wide and 1.5mm deep.
These are used by the surgeon to hold and push the cup, without it deforming,
into the patient's hip.
After machining there is a sequence of face polishing, laser marking, honing and
linishing, followed by shot blasting and cleaning.
Fitted with Renishaw NC3 non-contact tool detection system, the Fanuc Alpha
T21iE VMC is a very capable short cycling machine with a 24,000 rev/min spindle
and 54m/min rapid traverse rate.
Chip-to-chip toolchange time is 1.8s.
The VMC's FS-31iA5 CNC system provides 1,000-block look ahead, nano
interpolation and NURBS smoothing for precise profiling and the VMC a
repeatability of +2 micron.
Corin's engineers had compared the Fanuc Alpha VMC with two other similar
capacity machines by using a strict capability study criteria followed by
tooling trials.
It had been chosen over competitor products, said Buggins: 'Because not only did
it satisfy our capability demands but it is also compact, robust and very
cost-effective'.
* EDM operations - the two Fanuc Robocut Alpha-OiC wire EDMs are used in the
production of a diverse range of instruments, comprising around 30 different
instrumentation sets, to match the different sizes of hip replacements produced.
Once installed, the machines immediately enabled Corin to eliminate the high
weekly cost of around GBP 1,000 of wire EDM outsourcing and the vagaries of lead
time, for example, that can arise from such supplier-dependency.
Capable of handling workpieces of 650mm by 570mm by 250mm and weighing up to
400kg, the Fanuc Robocut OiC machines have X- and Y-axis strokes of 370mm by
270mm, U- and V-axis strokes of 120mm and a Z-axis stroke of 255mm.
Employing linear drive technology for high-precision machining, and the ability
to cut precisely with ultra-fine 0.05mm wire, the machine fully integrates with
nano-interpolation techniques giving 10nm absolute positioning and enables
surface finishes to be machined within 0.04 micron.
* Nano interpolation - nano interpolation also has the effect to smooth the
action of the axis drives and eliminates any accumulation of axial movement or
error.
The result is, exact position calculations are made at 0.001mm from program
command that are 100 times greater than a normal wire EDM.
Like every machine installed on the shopfloor, the Fanucs receive
offline-created programs via a DNC network, said Corin.
Buggins said that the level of back-up, training and support provided by the
machine tool supplier, 600 Centre, was 'excellent'.
Each machine was specified and chosen using what he described as a 'production
drumbeat', where it was deemed that a component should spend a maximum of 10 min
at each station.
Buggins explained: 'This has enabled us to implement value stream mapping
processes throughout the shopfloor.
In the case of Fanuc Alpha T21E VMC cell, this has enabled overall lead times to
be reduced from three days to just one day'.
The success of cellular manufacturing in reducing lead times through, for
example, less inter-machine handling and separate set-ups, has caused Corin to
investigate the use of similar routines in other shopfloor areas.
