“just what the doctor ordered” for medical machine tools

New ballbar technology “just what the
doctor ordered” for medical machine tools
Nemcomed, a division of Avalign
Technologies, is a full-service supplier of
implants, instruments, cutting tools, specialty
instruments, cases and trays for medical
device OEMs. Avalign’s strategy is to be
a “one stop shop” for OEM providers to
the orthopedic, spine and trauma sectors
– aiming to supply everything a physician
needs to perform implant procedures.
Ensuring that machine tools and processes
are capable of producing parts to spec is a
goal shared by customers and the company’s
450+ employees, as well as federal regulatory
agencies. “Obviously, we have to meet FDA
and ISO requirements,” said Eric Arnold,
Manufacturing Engineer at Nemcomed. “But
we also have special customer requirements,
as well a personal interest and pride, knowing
that our products may end up in someone’s
body. As potential patients ourselves
someday, we want to make the highest quality
parts possible.”
The QC20-W wireless ballbar requires just one set
up, and less than 15 minutes, to test the X-Y, Y-Z
and X-Z planes.
Nemcomed manufactures approximately 1000
different parts, many have complex curved or
spherical components.
Using pre-printed
test cards,
Nemcomed keeps
a visual check of
overall circularity
error value status
on all machines
tested.
Case study
Fort Wayne, Indiana, USA – Ballbar analysis
is a proven method for determining machine
tool capability, and is the most practical,
convenient and comprehensive tool for
assessing the contouring accuracy of CNC
machines. Ballbars have been commonplace
at precision machining operations for more
than 20 years, but a Midwest-based medical
device manufacturer, is showing how the
latest wireless ballbar technology makes a
big difference in doing fast capability checks
on small machines, as well as establishing a
benchmark on machines’ volumetric accuracy.
IN505
Wireless operation facilitates use in
small machining envelopes, and allows
fast checks with minimal interruption.
Volumetric accuracy testing adds new
dimension.
Regulatory environment and customer
requirements
As a manufacturer of medical devices,
Nemcomed must comply with both the FDA 21
CFR Part 820 Quality System Regulation and
the ISO 13485 Medical Device Standard. To
qualify machines, the company had been using
a traditional wired QC10 ballbar from Renishaw.
“We test the X-Y, Y-Z and X-Z planes and the
QC10 required a setup for each, so our setup
time was about 1.5 hours,” said Arnold.
The company acquired Renishaw’s new QC20-W
wireless ballbar in 2010, which immediately
had positive impact on part quality and the
company’s bottom line. The new ballbar retains
the principle of using a CNC circular program
and powerful software to quickly diagnose
and quantify machine positioning errors
including servo mismatch, stick-slip errors,
backlash, repeatability, scale mismatch and
machine geometry as well as providing an
overall circularity error value. It also adds new
capabilities. “The wireless ballbar requires just
one setup – less than 15 minutes – for testing in
all three planes,” Arnold said. “More important, it
doesn’t disturb our production setup, so we don’t
have to re-set the machine when we go back to
production mode. We remove the ballbar, insert a
tool and get back to making parts in minutes.”
Wireless operation is also ideal for Nemcomed’s
small machines, Arnold added. “Machine tool
makers understand how much ‘lean operations’
value floor space, so the new machine tools are
designed with smaller footprints,” he explained.
“This results in less interior space to manoeuvre
a wired ballbar, so wireless data transmission is
a big advantage. Safety is also improved by the
ability to fully close the doors on the machine
during the tests.”
Surgical implants and instruments
Nemcomed manufactures approximately 1000
different parts – either implants or the tools used
during implant procedures – and it supplies parts
to the top orthopedic OEMs. The company makes
implants for knees, hips, shoulders, wrists,
elbows, fingers and the spine; tools include
pliers, cutters and wire cutters. The implants are
“family-sized,” with five to six sizes of each part,
and typical lot sizes are 30-40 pieces. Many of
the implants have complex features, such as
curved or spherical components. The company
Nemcomed uses small machines to produce medical
implants and instruments, and the wireless aspect of
the QC20-W makes it easier to manoeuvre in tight
interior spaces.
Nemcomed’s patented Flex-Shaft is used in surgical
screwdrivers, taps and drills.
also makes proprietary products, developed
through internal R&D, and licenses them to
customers. Its Flex-Shaft and Self-Retaining
technologies, for example, are patented and
used in a variety of applications, including
spinal procedures and hip, shoulder and knee
arthroplasties. The Flex-Shaft is applicable to
surgical screwdrivers, taps and drills.
Parts are generally made of stainless steel,
titanium or cobalt chrome, and start as bar
stock or forgings (implants). Raw materials are
processed through a cut-off cell, then move on to
a mill or turning center, depending on complexity.
Speed WITH accuracy
“Shortly after receiving the new ballbar, we had
a machine go out of spec so we tested it, as well
as having the laser interferometer folks come
in and test it,” said Arnold. “Our results were
identical, so we learned then the ballbar would
allow us to test our CNC machines quickly and
with an extraordinary level of confidence.”
This ability to test quickly and accurately led
to the acquisition of a large, quality-focused
customer that required verification of machine
calibration. “The expense of bringing in the laser
interferometer for every machine would have
made it cost-prohibitive to supply this customer
with parts,” Arnold explained. “We showed
the customer the results of the ballbar and
interferometer tests, and they agreed that ballbar
testing would meet their verification requirements.
Basically, the QC20-W paid for itself after testing
just two machines.”
Volumetric testing provides new performance
benchmark
The new ballbar design brings the unique
advantage of testing in three orthogonal planes
through a single reference point, with a single
setup, which allows the accompanying software
to produce a representative measurement of
volumetric positioning accuracy by correlating
all three. Arnold explained this benchmark of
volumetric accuracy is valuable to Nemcomed
because positioning errors can be compounded
by simultaneous multi-axis motion during
contouring. (Note: volumetric accuracy is also
important with large machining volumes and
parts, where tool path deviation is amplified
across longer machine travels).
EDM machines. Maintenance engineers monitor
results in a predictive maintenance program,
tracking a 3-month timeframe for early detection
of errors for optimum efficiency in scheduling
maintenance and repairs.
The ballbar comes with a system case with
spaces for the most popular accessories making
it easy to transport. “We can take it to any of
our four global manufacturing facilities, set it
up quickly and get the machine qualifications
we need,” Arnold said. “Knowing the machine’s
capability before it cuts parts allows us to
minimize scrap and machine downtime. That
gives us high part-quality and productivity while
keeping manufacturing cost down. It’s what Lean
Manufacturing is all about – greater customer
value.” The company completed another
14,000-sq-ft. expansion in November, and as it
continues to grow, Arnold said use of the ballbar
will grow.
www.renishaw.com/calibration
In August 2010, Nemcomed completed a
10,000-sq-ft addition to its Fort Wayne plant,
to consolidate another plant’s operations and
add space for new machines: five new Citizen
Swiss machines and a 5-axis Fanuc Robodrill
to complement its lineup of Mori-Seiki and
Mazak 5-axis mills, Fadal 3-axis mills, Brother
and Fanuc wire EDMs, and a Samsung 3-axis
lathe. The company uses the ballbar on 20
machines, including all of its CNC mills and wire
Nemcomed is a division of Avalign Technologies. The company supplies medical implants and speciality
instruments for the orthopaedic, spine and trauma sectors.
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*H-5650-3142-01
Issued 1211 Part no. H-5650-3142-01-A