Ballbar testing keeps machines in line

Ballbar testing keeps machines in line

THE 325 MACHINE TOOLS THAT SMITH & NEPHEW Orthopedics uses to make medical implants must be flexible and, more importantly, able to produce precision parts to Six Sigma. To ensure they do, the Memphis company regularly tests machine performance with b

Richard Grimes, calibration specialist, keeps Smith & Nephew's CNC machines operating at Six Sigma by conducting routine diagnostics with a Renishaw QC10 ballbar system.

THE 325 MACHINE TOOLS THAT SMITH & NEPHEW Orthopedics uses to make medical implants must be flexible and, more importantly, able to produce precision parts to Six Sigma. To ensure they do, the Memphis company regularly tests machine performance with ballbar systems.

"Since implementing ballbar diagnosis," says Richard Grimes, company calibration specialist, "all the plant's CNC machines operate at true Six Sigma, or 0.0003% failure rate. Cost savings haven't been figured, but the result on our bottom line can be imagined," he says. "We now make better products and have less downtime since we catch problems before they happen."

With a Renishaw QC10 ballbar system, Smith & Nephew's tests typically take about 15 min. The ballbar attaches magnetically between a machining center's spindle and table and track machine movement to ±0.5 µ. A simple CNC circular program allows the ballbar software to calculate machine circularity error, servo-gain mismatch, vibration, stick-slip errors, backlash, repeatability and scale mismatch, as well as machine geometry.

In all, Grimes checks 13 performance parameters, and the company's quality department requires that those parameters combined must not vary by more than ± 0.003 in. "When new equipment comes in, I first test the machine with the ballbar," explains Grimes. "If a machine is moved, crashes, or loses a spindle, I run a ballbar test. Regardless, each machine gets an annual test and isn't used until it meets or exceeds our specs."

While the ballbar's 100-mm length makes it suitable for most of the company's machine tools, Grimes uses Renishaw's 50-mm ballbar attachment for small machines. He also implements Renishaw's Windows-based Ballbar 5 software, which provides an easy-to-use interface, comprehensive on-line help, and three user modes for high-accuracy calibration checks in minimal time. Says Grimes, "The software makes the tests quicker to set up."

Renishaw Inc.

Shop gets unexpected hard-milling surprise

Steve Raiken, president of Reny & Company Inc., says the Mikron Bostomatic VCP 600 not only handles the company's EDM electrode machining but also hard milling die/mold tooling.

WHILE LOOKING FOR A MACHINE TO SPEED EDM-electrode making, Reny & Company Inc. was exposed to the concept of high-speed hard milling. As a result, the El Monte, Calif., moldmaking shop now cuts its electrodes and machines hard molds and dies with the same machining center.

"A couple of years ago, we were looking for CNC EDM capability and were close to making a machine purchase when I realized that EDM wasn't where my backlog existed. It was in fabricating electrodes," says Steve Raiken, company president. The surprise came when Reto Fehr, regional sales manager for Mikron Bostomatic, made a sales call at Reny.

Charmilles was so impressed with Tech Tool's manufacturing know-how, that it is having the shop test its new Offline software prototype. With this software, operators quickly program the QCRi's entire capacity. "It once took up to 2 hr to program jobs using all 90 electrodes. Now it is done in 20 to 30 min with the software," says Donnie Schanz, Tech Tool EDM operator.

The shop adds a CMM to the mix and does all its setup off-line. Operators touch off parts, which are on pallets, and pick up electrode offsets while the machine is running unattended.


Software proves medical marvel

U. Klein reduces programming time for medical components by 80% using Esprit CAM software.

Programming a part used in a knee implant now takes U. Klein 5 hr with Esprit CAM as opposed to a week with its old system.

BY SWITCHING TO A NEW CAM SYSTEM, A CONTRACT-machining shop specializing in components for medical-equipment manufacturers reduces its programming time for complex parts by 80%. U. Klein GmbH's old system took so long to program parts with complicated 3D contours that the St. Ingert, Germany, shop had to turn down many orders. To gain productivity, the shop switched to a solids-based CAM system built upon the Parasolid modeling kernel.

The system, Esprit from DP Technology, accepts solid part geometry directly from U. Klein's CAD files without translation. This substantially reduces programming time. The shop saves even more time by defining a library of tools that can be imported for each job.

"We selected the Esprit CAM system because it provides a solid-modeling environment that defines the most complex geometry and has an open architecture for enormous amounts of flexibility. We import models from our own Solid Edge CAD software as well as nearly all of our customers' CAD software without losing a single entity," says Ralf Merz, CNC programming manager at U. Klein.

"Esprit's open environment lets us use, for example, Microsoft VBA to further automate the programming process," says Merz. "The CAM software also lets us easily create G-code, which is especially useful because we have several machines built to our own designs and specialized machines that make getting offtheshelf post-processors impossible." While some systems rely on third-party post-processors that can cause translation problems and incompatibilities, Esprit has its own universal post-processor, which seamlessly integrates the CAM system, the CNC, and all its machining functions.

"The time savings have been fantastic," says Merz. "For example, on one complicated part for a knee implant, we reduced programming time from one week to 5 hr. Such speed improvements have not only widened our profit margins but have also helped our customers get products to market faster, making the latest advances in implant technology available more quickly."

DP Technology Corp.

The machine also has a freestanding, double-canister filtration system that keeps iron particles out to prolong machine life. And when filters do need changed, it takes less time as compared to other systems, says the manufacturer.

"I get calls from customers for tolerance specs you wouldn't believe," says Falciani. "For example, they want tiny, complicated configurations made from titanium with zero tolerance —- perfect and needed yesterday. Only the Mitsubishi lets me handle these kinds of demands on a regular basis."

He says no other machine has the features that let him work as fast or efficiently. "Resin maintenance alone with the FA20 saves me valuable hours every week," he comments.

Mitsubishi EDM/Laser

CAM software helps save lives

The Jarvik 2000 left-ventricular-assist device includes internal parts machined with toolpath programs generated in Mastercam software.

THE JARVIK 2000 LEFT-VENTRICULAR-ASSIST DEVICE (LVAD) is the result of one researcher's vision and tenacity, supported by his skill in CAD design and his associates' CAM/CNC craftsmanship. From the LVAD development stage, Dr. Robert K. Jarvik benefited from rapid prototypes made accurate and easy with the appropriate CAM software.

About the size of a C-cell battery, the Jarvik 2000 uses a valveless, electrically powered axial flow pump that fits directly into the left ventricle of the heart to continuously pump oxygen-rich blood throughout the body.

"We started to use Mastercam by CNC Software 15 years ago," says Jarvik. "We had been modeling impeller blades for the LVAD and tracing them with 3D pantographs running a tool to cut the blades. Hand machining was excessively slow, and multiple prototyping was impossible."

CNC Software designed a custom program that interfaces precisely with Jarvik's design files for the LVAD impeller. Ten years ago, this interface enabled the sophisticated swarf cutting used by Jarvik to machine the impeller prototypes — more than 50 before creating the one that would pump human blood without damaging the living cells within it.

"Though we use Mastercam to program everything in the shop — mill, lathe, and wire EDM — we don't need more than 4-axis toolpaths. Occasionally, we use our full 5-axis machining," says Jarvik. His shop includes three CNC mills and two CNC lathes, a 4-axis wire EDM, and various grinding and other manual machines supported by a CMM and optical-measuring instruments.

CNC Software Inc./Mastercam

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