| by Dirk Dusharme
Make it smaller, faster, cheaper,
easier and more accurate. That's what today's (and yesterday's
and tomorrow's) metrology customers demand. Everyone knows
that semiconductor devices continue to get smaller and faster,
with more computing power in less expensive packages. What
many consumers may not consider is that, pushed by shrinking
computer chips, mechanical devices also continue to shrink:
Computer-aided fuel injection allows more precise control
over fuel flow, which in turn creates a need for more precisely
machined fuel injectors; pacemakers, once cigarette packet-sized
boxes carried outside the body, are now so small they're
embedded in the body.
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To review recent advancements in metrology software
would take a book rather than a few paragraphs. But
there's one key driver for all the advancements: "With
the economy fluctuating, it's difficult to keep operators
up to speed," explains Dave Genest, director
of marketing and communications at Brown & Sharpe.
"You're always training. The software has to
be simple. It's even more important than the [hardware]
technology."
Enterprise Metrology Solutions from Hexagon Metrology,
Brown & Sharpe's parent company, is a suite of
advanced software tools available with PC-DMIS. Depending
on installed options, EMS allows PC-DMIS to create
inspection programs directly from native CAD languages
for CMM, vision and even probe-fitted NC machine tools.
PC-DMIS will control and take measurements from equipment
across the enterprise and provide reports via the
Web.
With outsourcing becoming more prevalent, maintaining
supplier quality is critical. Origin International
Inc. gives its customers the means to monitor part
quality across all of its suppliers. To do this, Origin
installs CheckMate software on the CMMs of its client's
suppliers. SoftFit software provides root cause and
GD&T analysis to deal with out-of-specification
dimensional issues on supplier- or manufacturer-made
parts.
Once implemented and personnel trained, the Origin
software allows CAD-based CMM dimensional data to
flow to and from all participants over the Internet
or dedicated networks. The manufacturer can control/standardize
the data required, decide what gets measured and how,
and provide the supplier with CMM programs that will
run on any DCC CMM. Some of the benefits are accurate
and consistent supplier dimensional data from all
participating suppliers at all stages, from part design
to manufacturing or assembly; reduced timeframes to
determine and fix out-of-spec parts; and instantaneous
communication of dimensional data.
Partly in response to the new ISO 9001:2000 standard
that requires determination of measurement uncertainty,
Carl Zeiss Industrial Measuring Technology has introduced
Offline Virtual Coordinate Measuring Machine, a new
option for its Calypso CAD-based software. Previously,
all accuracy specifications of coordinate measuring
machines consisted exclusively of data obtained on
comparison standards. OVCMM allows operators to determine
the measurement uncertainty for every measured feature--a
central requirement of the ISO 9001:2000 standard.
Each record indicates the captured measurement uncertainty
next to the actual value. The main uncertainty factors
of the CMM, the probe, the workpiece, the measuring
strategy and the environment are all included in the
OVCMM measurement.
Zeiss is also addressing automation with its new
Flexible Automation and Control System, and Application
Automation Interface. These products supervise all
the devices in the process flow. For instance, it
can control a robot loader to place parts on the CMM,
tell the CMM to measure the part and then tell the
loader to unload the part.
"Even people with medium-sized companies are
using it for cost savings," says Jose Torres
of Zeiss. "They can use half the staff with a
simple pallet loader and can save money."
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To keep technology and innovation rolling, metrology equipment
manufacturers must continuously develop the means of measuring
our shrinking universe. But higher measurement resolution
and accuracy aren't the only issues. Pressure from low-cost
foreign manufacturers means that measurement equipment must
not only measure increasingly smaller parts, but it must
also do it faster and with fewer people involved in the
process. Moreover, faced with high employee turnover, today's
metrology customers demand operator interfaces that are
easy to learn.
Following is a look at some of this year's new metrology
products, chosen because they typify metrology equipment
makers' response to customer demands. This is by no means
a comprehensive list; there are literally hundreds of cutting-edge
products from dozens of leading metrology companies released
each year. Use the following information as a brain tickler
for the current state of measurement technology and what
it can do for you.
Many industries--particularly electronics and medical
device--are driving the need for high-accuracy large-envelope
vision measurement. Both require micron and even submicron
measurement accuracies at ever-escalating production speeds.
"Customers are pushing for yield," explains
Mike Metzger, measuring department manager at Nikon Instruments
Inc. "For example, medical device manufacturers are
building stents at a remarkable rate. Production capabilities
are higher than they've ever been. The ability to build
things accurately and repeatably is higher than it's ever
been. Metrology has to keep up."
Nikon has addressed the need for large-envelope high-accuracy
measurement with the VMR-H3030 CNC video measuring system.
Equipped with a maximum magnification module, the product
features a final magnification range of from 36X to 4,320X
when displayed on a 17-inch high-resolution monitor, a field
of view of 4.7 by 3.5 mm at 36X to 0.04 by 0.03 mm at 4,320X,
stage scale resolution of 10 nm (0.01 mm),
accuracies from 0.6 mm
and a working distance of from 32 to 9.8 mm, depending on
magnification. The product also features a through-the-lens
laser focusing system that allows the instrument to scan
parts at 1,000 points per second, greatly increasing inspection
throughput when measuring profiles of 3-D precision parts.
Submicron accuracy and repeatability has been around for
a while, but stage-accuracy and other mechanical issues
have limited submicron accuracies to workpieces of less
than about 10 X 10 in. As the need grows for precision measurement
of large-envelope parts such as printed circuit boards and
flat panel displays, look for vision-based machines to provide
submicron accuracies over distances of 30 inches or more.
To increase throughput in 2-D measurements, vision-based-equipment
manufacturers continuously push the envelope on depth of
field--the maximum distance from top to bottom that a device
can remain accurately focused.
"For a long time, customers have been wishing for
something that's going to provide much quicker and easier
measurement of parts that exhibit depth and different types
of features that need to be verified with a single parts
program," explains Frank Demski, Mitutoyo America Corp.'s
vision products manager.
Because high accuracy once meant higher magnification
and lower depth of field, it also meant focusing on a feature
at one height, performing a measurement and then changing
Z-axis position and focus to measure a feature at another
height. "That took time," says Demski. "Now
we've just come out with a special telecentric lens that
allows us to develop a vision machine that has both wide
field of view and long depth of focus. With Quick Image,
a workpiece up to about 1 X 1 in. is entirely visible in
the field of view. And, the part can be up to 0.9 in. in
depth."
Quick Image is basically a manually focused 0.2X fixed-magnification
device that provides a field of view of 29.5 by 22.2 mm.
The user has control over measurement resolution and therefore
depth of field. At the maximum 22 mm depth of field, the
Quick Image can measure an object with a height variation
of about 0.9 in. and a minimum feature width of 300 mm
with an accuracy of 8 mm.
Measurements of 5 mm
accuracy are possible if the depth of field is reduced to
1.2 mm.
"Once you create a measurement program for a specific
workpiece, the operator can grab a sample from the production
line, place it on the Quick Image stage and instantly measure
100 percent of the part features and get a report, all without
any stage movement or focusing," says Demski.
Customer requirements for measuring small or fragile parts
are pushing traditional touch-probe equipment to the limit.
To measure fragile parts with critical surface boundaries,
Optical Gaging Products Inc. has developed the Feather Probe,
a 100 mm diameter stylus
that uses proprietary technology to determine when the probe
has contacted a surface. The probe requires less than one
milligram of force to acquire a data point and is ideal
for measuring microminiature components and parts that can
be deformed by traditional touch probes (e.g., rubber parts
or solder paste). The Feather Probe is a specialty probe
that can be used on any OGP measurement system that accepts
traditional touch probes.
Mitutoyo's UMAP is another product to measure microfeatures,
in particular, microholes. The product was developed to
measure the orifices of fuel injectors but can be used for
any small feature, such as optical ferrules or medical device
parts.
UMAP consists of a vision system with an accuracy of 1.4
mm and resolution of
10 nm. The vision system positions UMAP's touch probe over
the microfeature to be measured. The touch probe is a 2
mm or 12 mm long stylus with a 30 mm
tip. The system uses piezoelectronics to excite the probe
at an ultrasonic frequency and then detect a change in the
signal frequency and amplitude, indicating that the probe
has contacted the workpiece's surface. With a contact force
measured in micronewtons (1 micronewton is about 0.1 mg
force), the system can also be used when ultralow contact
force is required. Of course, the vision portion of UMAP
can be used as a traditional stand-alone vision system.
Until a technology comes along that replaces touch probes
for accurate measurement in hard-to-reach places, look for
touch-probe technology to continue evolving toward smaller
and smaller probes.
One key feature of most high-precision stage products
is a 10 nm resolution specification. For measuring machines
that have a moveable stage, this specification defines the
ability to accurately identify the location of the stage
in the X, Y and Z axes. This is dependent upon stage construction
and the linear scales attached to the stages.
Heidenhain is a leading international manufacturer of
precision measurement, and its scales are used in a variety
of dimensional measurement equipment. Heidenhain recently
announced the release of a linear scale, the LIF 400 series.
Although the scale's 8 mm
line spacing and 10 nm resolution aren't unique in the industry,
several other features address customer needs in linear
scales.
One problem with scales is that, on startup, the stage
electronics don't recognize where the stage is located and
must traverse the entire length of the scale in order to
find the stage's home or index position. A special homing
track on the LIF 400 series tells the machine which direction
to move the stage in order to most quickly reach the index.
The product also features optical limit switches instead
of magnetic switches. Linear motors used with most measuring
machines interfere with magnetic switches if the two get
too close together. On the LIF 400, optical switches allow
the scales and motors to be right next to each other, facilitating
the construction of smaller machines. Finally, a unique
scale construction eliminates the peaks and valleys between
a scale's lines that can fill with dirt. The result is improved
accuracy and reduced maintenance.
As the requirement for even higher precision stages at
reasonable costs pushes the market, look for higher precision
scales to become more mainstream.
There was once a definite line between vision-based systems
and traditional probe-based CMMs, usually a tradeoff between
speed and accuracy. Customer demand has caused the line
to blur considerably.
One type of product hyped at this year's Quality Expo
was the multisensor vision system. In addition to their
vision capabilities, these products generally also include
touch probes, laser scanners or other probe types, allowing
the machine to quickly measure large features, while providing
high-accuracy measurement of critical dimensions. A multisensor
machine swaps one probe for another as measurement requirements
change on a particular workpiece.
The intent is to meet the customer's need to balance inspection
throughput requirements with accuracy requirements for workpieces
of most any size, says R. Stephen Flynn, senior vice president
of marketing and sales for Quality Vision International,
the parent company of OGP, RAM Optical and View Engineering.
"Multisensing is a real value," says Flynn.
"You can completely measure a part without having to
restage it on a number of different machines. And, a single
setup improves accuracy."
SmartScope Quest 650 Multi-Sensor Metrology System is
the latest multisensor system from OGP. It has a measuring
envelope up to 24 by 26 by 16 in., 10 nm resolution, 1.0
+ 4L/1,000 mm accuracy
and can utilize video, laser, touch probe, continuous contact
probing and other probing technologies.
Of course, large volume for a vision system is tiny compared
to a large CMM such as those from Brown & Sharpe, Mitutoyo
or Zeiss. But companies that measure very large parts on
such CMMs can also benefit from multisensor technology.
Although not necessarily called "multisensor,"
most large-envelope CMM manufacturers are incorporating
noncontact measuring probes such as cameras or lasers in
addition to touch or scanning probes.
The advantage is obvious when measuring large structural
components that also contain critical dimensions, says David
Genest, director of marketing and communications at Brown
& Sharpe, which provides various noncontact sensors
for its large CMMs, such as its Global series. "The
advantage is that you can match the right type of probe
with the right application," he explains. "For
big parts, like an aircraft structural component, you could
zoom over the top with a noncontact probe and then, if you
need precision measurement of prismatic features, you could
use a touch probe."
The Global series CMMs can measure parts up to about 78
by 157 by 59 in. and with accuracies starting from 4.5L/200
mm.
Each year, the line between CMM and vision systems gets
blurrier. Look for these two to eventually merge into one
integrated technology.
Advancements have also been made in form and surface measurement
equipment. Driven in part by the automotive industry, Corning
Tropel has announced two new products that provide greater
speed and accuracy in this area.
The ThetaForm was developed to meet the need for high
production volume, high-accuracy measurements on rotationally
symmetric forms (e.g., valves, pistons, etc.), according
to John Bruning, president of Corning Tropel. "As next-generation
technologies are implemented on manufacturing floors, sealing
and bearing surfaces will undoubtedly require lower form
tolerances," says Bruning. "Conventional measurement
technologies no longer have the accuracy and speed necessary
to control a high-volume production process."
Although accurate, traditional touch-probe form measurement
devices are slow. The ThetaForm uses dual interferometers
to perform noncontact measurements with accuracy in the
submicron range. A part that might take 20 minutes to measure
on a touch-probe device takes about two minutes on the ThetaForm.
In addition, it collects about 100 times more data than
a touch-probe system, meaning a more accurate representation
of the form.
Another product, Tropel's Lasercheck, was designed for
in-process surface roughness measurements. Although the
Lasercheck's technology isn't new, advancements in product
packaging allow the device to be used for inline process
control, says Andrew Kulawiec, director of metrology operations.
"There's nothing else that does 100-percent inspection
of parts while moving by on a conveyor," claims Kulawiec,
"The Lasercheck takes 10 individual roughness measurements
per second. You can integrate this into the control system
to provide process feedback or pass/fail."
Along with advancements in dimensional measurement, much
has been done to increase throughput and accuracy in noncontact,
nondestructive technologies.
Ultrasonic evaluation is usually associated with one-sided
thickness measurement, particle size measurement or subsurface
fault detection, but this technology continues to grow as
its uses widen, particularly in the area of real-time inline
process control.
The Ultrasonic Process Analyzer by UTEX Scientific Instruments
Inc. allows users to make inline measurements of the physical
properties of polymers and food products. Using a patented
ultrasonic technique, the UPA can measure such properties
as the blend ratios of two or more polymers, cooking cycle
measurements for food processing, cure rates of polymers
like those used in contact lenses, and physical properties
such as viscosity, molecular weight and particle size.
Before this, such measurements were taken offline, says
Matthew Oleskiw, marketing manager at UTEX. "You would
take a sample from the process, run it to the lab--of course
it's curing all the while--and then put it into the lab
equipment to measure."
Inline monitoring of a production process using the UPA
system means real-time information can be used to adjust
process controls faster. This reduction in testing time,
and improvement of the accuracy of the measurements, means
that product quality improves while costs due to production
waste go down.
UTEX and other nondestructive equipment manufacturers
believe that many companies don't think of nondestructive
methodologies like ultrasonics when considering measurement
equipment. For instance, noncontact form and density measurements
can be taken on contact lenses while they're curing.
"There's a lot that we can offer," says Oleskiw.
"We need to open the realm of how NDT and metrology
fit together."
The demand for tighter tolerances and networkability has
driven metrology companies to design equipment that measures
faster with ever-increasing accuracy and communicates more
easily with the manufacturing environment. As traditional
technologies like touch probes continue to evolve and newer
technologies such as ultrasound, interferometry, laser,
radar and vision become faster and more accurate, the applicability
of these technologies increasingly overlap, giving users
more options when selecting metrology equipment. Now more
than ever, users can select from among several technologies
to find measuring equipment that meets their specific needs
of accuracy, throughput and cost.
Dirk Dusharme is Quality Digest's technology editor.
Letters to the editor regarding this article can be sent
to letters@qualitydigest.com.
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