Applications and operating
modes for surface roughness analysis are changing. Although
coordinate measuring machines are commonplace on the shop
floor, you’re likely to see more surface-measuring
devices appearing there, measuring surface roughness or
contour practically in real time. Just as likely, you’ll
see these same surface-analysis devices operating automatically,
thanks to computer numeric-controlled technology.
CNC surface analysis has found a place in the manufacturing
cells of first- and second-tier automotive suppliers, where
the demand for automation and in-line operation is highest.
Automated, in-line form measurement is also increasing among
power transmission components and electronic parts manufacturers.
It’s become a standard for industries that manufacture
components with safety- or finish-sensitive requirements,
have high added value or require 100 percent inspection.
As a general rule, the higher the tolerances for metal-to-metal
contact parts, the more in-line measurement you’ll
find. The same goes for large parts because new technology
has made it easier to bring the measurement function to
CNC surface roughness measurement isn’t a revolution
in quality assurance; it’s just the next logical step
in developing and applying surface-analysis equipment. For
the same reason that manufacturers have moved coordinate
measuring machines and other dimensional measuring devices
to the plant floor--the need for real-time measurement integrated
into the workflow--more surface-related measurements are
showing up on part prints. The obvious benefits of in-line,
automated inspection to process control are especially important
given increasing demands for improved productivity and higher
accuracies. If a print specifies a parameter to a given
tolerance, then the faster and closer to real time you can
check that parameter, the better--for quality, process control
and the bottom line.
Several engine manufacturers have begun integrating surface-roughness
testing into their engine-deck milling operations to ensure
that mating parts seal properly in the finished engines.
Originally, these manufacturers performed surface-roughness
testing to satisfy ISO 9001 or QS-9000 requirements, but
they’ve found that automated, in-line surface measurement
can reduce the incidence of seal failures.
The interest in automated form measurement is chiefly
due to its higher speed and ability to execute complex measurement
routines. Additionally, today’s measuring devices
are robust and user-friendly. Good ideas tend to proliferate,
and as the number of shop floor surface measurement applications
increase, so does the range of instruments tailored to specific
CNC-driven surface analysis is the result of increased
productivity demands on the shop floor as well as the need
to perform complex measuring routines on multisurfaced workpieces.
The automotive market, its supply chain and the aerospace/defense
industries require flexible but fast surface analysis equipment
that can work in harmony with diverse manufacturing processes.
The near-machine models of today’s form measuring
equipment don’t require the clean-room atmosphere
and pinpoint temperature control of older models. The new
breed of affordable shop floor surface- analysis instruments
perform as well at 60° to 80° F as a 1990-era lab
instrument in a temperature-controlled clean room. They
measure at submicron levels right on the plant floor, next
to a machining or turning center.
Given proper setup--which is critical for the CNC surface-roughness
measuring machines--near-machine form measurements can be
one-keystroke operations for each measurement. Typically,
the time needed per surface measurement on the floor is
about one-quarter or less than that required in the lab.
Essentially, the cost disappears because operators make
each measurement within the existing machine-cell cycle.
Measuring with CNC machines is so quick and simple that
it becomes feasible to increase the inspection frequency--even
to 100 percent. With proper setup, near-machine form measurement
requires no more skill than it takes to secure a part.
Surface analysis has also proved useful for nonmetallic
parts more often associated with noncontact measurement.
With the higher accuracies now possible with larger surface
equipment, optics have partnered successfully with surface-roughness
analysis. For example, the finishes on medical devices,
especially implant components, are a critical attribute
both to ensure FDA compliance and the devices’ long-term
If your organization adheres to an industry standard,
the sooner you change to shop floor form measurement, the
better off you’ll be. For example, companies that
make automotive OEM parts with roundness, contour or surface-roughness
callouts on their prints will need real-time form measurement
to meet ISO 9001 or ISO/TS 16949 standards. And unless they
meet those standards shortly, they’ll be bumped off
the qualified suppliers list.
But aside from ISO 9001, ISO/TS 16949 and other mandates,
deciding when to move to real-time form measurement is really
up to you. The key is to look at the cost-benefit ratio
in terms of your market’s quality expectations, i.e.,
the economic payoff to your operation in light of today’s
lower prices. In some cases you should also look at product
liability risks, especially if you’re running a job
shop where customers’ prints specify form-related
standards that you’re simply ignoring for now. Although
at one time you perhaps couldn’t afford to use real-time
form measurement, today the dilemma is whether you can afford
How do you start moving toward CNC surface-analysis measurement?
What equipment and functions should take the highest priority?
From a process control standpoint, first look at the parameters
you must measure. Multifunctional equipment such as Mitutoyo’s
CS-3000, which can measure surface roughness and contour
with one pass and using one detector, saves time and money
through increased productivity and reduced setup time. From
a part-function standpoint, however, the priorities are
different. If you produce a lot of flat or contoured parts,
moving surface measuring equipment out to the machine early
in the production process will increase productivity over
the long run.
What should you look for when selecting equipment? First,
remember that you’re buying a multipurpose, CNC-controlled
production device, not a general-purpose lab instrument.
Focus on the most cost-effective machine for the part-auditing
task at hand. You’ll want to consider speed, versatility
and flexibility. Also, focus on the most capable unit that
will reliably achieve the resolution needed to meet present
and anticipated print specifications covering form measurement.
A resolution of 1 µin. is often more than enough for
shop floor surface measurement. Consider multidetector equipment
for productivity as well as ease of use.
Don’t waste money on resolution or neat features
that you’ll never need on the plant floor. Dollar
for dollar, you’re better off with focused, in-line
form instruments placed right in the cells than with a single,
overqualified instrument placed where it can be shared.
What’s ahead for real-time surface measurement?
Progressive manufacturers of high-volume finished and contoured
parts are making room for surface analysis measurement solutions
on their shop floors. They’re demanding machines with
speed and the ability to automate complex routines. The
leaders will invest in both benefits, the followers just
Real-time surface measurement, especially automated solutions,
are expected to expand at least sixfold during the next
five years. This new technology is also expected to pay
its way through product cost savings and increased yields,
as well as ISO 9001 and ISO/TS 16949 compliance.
Bill Wilde is marketing manager for Mitutoyo America.
He has been with the company for 10 years and is responsible
for marketing strategy, branding and strategic planning.
Visit the Mitutoyo Web site at www.mitutoyo.com.