>
SUBCONTRACTING MEDICAL
Advantage titanium
In response to the growth in demand for the use of surgical grade titanium in preference to 316
stainless steel for trauma related components, Mollart Engineering, in conjunction with its tooling
partner Botek and a specialist supplier of cannulated tube to the medical industry, has developed a
drilling process for producing holes in the difficult-to-machine material that creates a totally new series
of options for component supply. Solutions reports.
T
hrough the Chessington-based operation of Mollart nails by the hollow bar method thus avoiding any need for drilling or
Engineering the medical industry can obtain a fully machining the bore.”
developed deep hole gundrilling system for creating As a result of the new methods on femoral and tibial nails, Mollart’s
the holes in trauma nails, for which some 30 machines application engineering team has now developed a process for to govern the output of the machine.
have already been delivered worldwide. producing much smaller bone screws which, like other trauma products, Also problems of tool life, part geometry and surface finish also
Companies also have the option to have components produced are beginning to move away from 316 stainless steel in favour of titanium. exist. “The development of gundrilling will offer the same capability to
complete within the subcontract machining service provided at Traditionally, stainless steel bone screws are mainly produced on lift productivity and ensure quality through geometric, size and surface
Mollart’s Chessington, Surrey and Resolven, South Wales facilities sliding head lathes where the complex thread form, screw head and finish,” concludes Mr Mollart.
or obtain precision machined thin wall drawn tubing from the through hole are produced in a single cycle. However, like femoral
material supplier. In this form it has the bore finished to size and is nails when produced in titanium the drilling of the central hole – often
> MOLLART ENGINEERING
able to meet the stringent geometric tolerances and surface finish just 2mm diameter and between 40mm and 120mm in depth – tends www.mollart.com
requirements demanded by the industry.
The change to the highly specialised grade of titanium Ti-6-4 ELI (6%
aluminium, 4% vanadium) in favour of the traditional 316 stainless steel
has already led to 80% of the US medical industry changing to the new
material due to the advantages it offers. Indeed, latest figures are
showing some 200,000 trauma screws are now being produced a
year and this number is predicted to achieve high levels of growth as
the global medical industry progressively adopts the new material.
Ups and downs
Surgeons are keen to use titanium due to its greater levels of purity,
biocompatibility, high strength to weight ratio and resistance to
corrosion. There is a far lower risk from material fatigue against
stainless steel that can lead to breakage and the composition of
titanium means it has the ability to flex in the human body. The
material also eliminates harmful toxins being released when exposed
to body fluids for long periods of time.
However, the downside in meeting the growing demand for
surgical grade titanium are the problems related to machining and
›
The UK’s premier
especially the drilling of deep holes. For trauma components depth
to diameter ratios of 40:1 are common as parts such as femur and Subcontract Manufacturing Show
tibia nails can require through holes to be produced in excess of
400mm in depth. While the tensile strength of titanium is ideal for its
intended application in the human body, this forces down the speed
the material can be machined using conventional tooling.
Covering everything from plastic mouldings to heavy engineering, electronics
“As a result, machining times become long and expensive and tool
and full design and build services - from design and prototyping to finishing
costs escalate due to the demands of the process and shortened life
and testing...
in service,” says Guy Mollart, managing director of Mollart
Engineering. He describes how titanium is a very poor conductor
which means it is slow to dissipate any heat generated in the cutting
process causing welding at the edge of the tool. In addition, its low
modulus of elasticity can cause slender workpieces to deflect if care
• 30% year on year growth in visitor numbers
is not taken in the machining process.
He continues: “These factors reduce the viability of traditional style
• Unrivalled visitor quality
twist drills on longer holes, not only due to the restrictions imposed
because of very low penetration rates in the material but more
importantly, in achieving, let alone maintaining the high precision
demands for accuracy, geometry and surface finish.”
He outlines how very detailed development of the gundrilling
process involving tool geometry, drill point support, carbide grades,
feed, speed and coolant pressures overcome these limitations and
allow a component such as a tibia or femur nail to be drilled in a
single pass to 18mm diameter with a penetration rate of 12mm per
minute. “Such is the technology that a gundrill will maintain a
concentricity and straightness within 0.015mm TIR over a depth of
400mm,” he explains. “Other long holes required for trauma
components as small as 6mm can be successfully drilled in 13mm
diameter titanium with just a very thin 3.5mm wall thickness.”
Collective thinking
Subcon exhibitors benefit from a complimentary PR package and year-round
Central to Mollart’s development programme to meet the meticulous
demands put on its titanium products by the medical industry was
exposure on the Subcon web site and ‘Manufacturing Talk’
the very close association with the specialist tubing supplier and its
drilling tool partner, Botek. Between them they created a process
whereby the central bore of the trauma components is gundrilled
For further information on exhibiting email jonathan.clark@centaur.co.uk or call +44 207 970 6742
and can be supplied ‘as machined’ to customers to add further
value processes as part of their component supply to surgeons.
The hollow bar method involves the creation of bar lengths of
›
Make new contacts
›
Forge new partnerships
›
Win new business
1,000mm with all the potential stresses removed, any flexing potential
of the material that can build up eliminated and the bore totally finished
ready for any final special processes that may be required. In creating the
bar length, the material is initially turned involving several passes over
www.subconshow.co.uk
its length to de-stress the material which is then gundrilled on a Mollart
machine to create an 18mm diameter through hole. This bore is then
finish honed in order to remove any traces of pick up or machining marks Media partners & supporters:
that could be amplified and lead to surface cracking and eventual failure.
The material is then mounted on a mandrel by the tubing supplier
and drawn to produce the high quality femur or tibia tube to the
specified diameter ready for further processing. As Mr Mollart states:
“One orthopaedic company is already producing a third of its femoral
www.pesmag.co.uk
Production Engineering Solutions • March 2010 33
Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36