Five-axis CMM inspection saves time

Scanning probes speed up form-data collection and feedback
to machining cells, reducing CMM fixturing and cut probe calibration time
dramatically at Kawasaki’s US manufacturing plant.
 

KAWASAKI’S US small engine manufacturing plant in Maryville
is utilising two 5-axis scanning probe systems to reduce CMM inspection and
probe calibration times, and speed up QC feedback for machining of small engine
components.

The 5-axis Renishaw Revo systems, installed on Mitutoyo
Crysta-Apex 121210 CMMs, replaced two PH10 articulating heads using SP25
scanning probes on traditional 3-axis CMMs.

The Revo-equipped CMMs have cut inspection times by half or
more on scanning intensive applications, eliminated the need for custom probe
configurations, cut probe calibration times from six to seven hours to about 45
minutes, and added new capability to collect large amounts of form measurement
data, improving part quality.

Of primary importance, the Revo systems have increased
inspection throughput, data quality and flexibility of the QC department.
Kawasaki’s 800,000 square-foot Maryville plant produces approximately 500,000
single and twin-cylinder air-cooled or water-cooled engines per year, with 50
machining lines typically arranged in a U-cell pattern.

“Primarily, it’s one-piece production with machining lines
running a part through multiple processes at a high rate,” JC Watts, Quality
Control Technical Group Supervisor at the Maryville plant, explained.

“We’re running similar tolerances that automotive powertrain
uses for high-end products, and there are probably four or five critical
processes for our aluminium parts and 15 for the steel parts,” Watts added.

“It is not uncommon to find tolerances in single digits in
microns for form, and 0.05mm true position.”

The QC lab inspects 125 different mass-produced parts, as
well as vendor parts and those produced for engineering development.

5-axis scanning
advantage

“When I started here, we had a couple of 3-axis CMMs with
PH10 articulating heads and SP25 probes, and another CMM with a fixed probe
head,” Watts explained.

“We were frustrated with having to make probe configurations
and being limited to what we could do even with the articulated heads. We had
so many different probe configurations that calibration times of six to seven
hours took a bite out of our inspection throughput, too.

“We wanted to do better than what the industry considered
the norm, so we looked at several options and the 5-axis Revo system appeared
to be the fastest and most flexible available.”

The Revo 5-axis scanning probe head can collect up to 6000
data points/sec. It is engineered for high-speed precision measurement of
contoured surfaces and complex geometries requiring high-volume data collection
to validate fit and form with high accuracy.

It uses two rotary axes (one in vertical plane and one in
horizontal) for infinite rotation and positioning. Five-axis software drives
the measuring head and synchronises its motion with the linear axes of the CMM.

Look-ahead algorithms drive the probe path and CMM in
coordinated continuous motion. The head adapts position while measuring on the
move, maintaining stylus tip contact with changing contours at scanning speeds
of up to 500 mm/sec.

“Though our SP25s were scanning probes, we were doing 95%
touch probing because scanning was too slow with a 3-axis CMM,” Watts said.

“To accurately collect enough data points to measure the
geometry of a bore 80 to 100mm in diameter and 150mm in length, the SP25 probe
took so long we limited those inspections to machine set up or special
requests.

“Now on every crank case we measure, the Revo does a spiral
scan of bores and the system outputs the values to software.

“We also send a graph of the data points to our network that
can be used by anyone in QC, engineering or production. What would take 3-4
minutes with an SP25; we’re measuring in 10 seconds with the Revo.”

The Revo scanning heads have all but eliminated the need for
touch probing. Now 95% of inspections utilise scanning, with no “time penalty”
as before.

The Revo probe can also do “head touch” probing or be used
for traditional machine-touch probing when the situation calls for touches.

“With scanning inspections, our production and engineering
people have a lot more confidence that the data is valid,” Watts added.

“With touch probing it is easy to get one speck of dirt that
causes an out-of-round condition if you’re only sampling seven or eight points.
It can throw the location of that circle off.

“The Revo scanning capability allows us to catch form errors
much more quickly, without a time penalty on our inspections. It has definitely
made us more proactive in catching quality problems early in the game,” Watts
said.

Fewer probe
configurations

With Revo, the Maryville operation now has two probe
configurations that measure all of its mass production parts, reserving custom
probes in a changing rack for a few special applications.

“We were able to eliminate the large ball stylus
configurations because of the large approach angle the Revo creates between the
stylus and the work piece.

“During scanning it maintains the approach angle which
allows a large cylindrical feature such as a cylinder bore to be measured with
the same stylus used for measuring a 5mm bore, with no chance of shanking the
stylus.”

Special configurations for vendor parts have also been
eliminated because the infinite positioning angles of Revo allow measuring of a
part without special fixturing or consideration of which probe to use. With so
few probes, calibration time has dropped to around 46 minutes. Now QC
technicians monitor the calibration instead of calibrating every shift.

Flexibility of the system has also proven to be a time-saver
for Kawasaki. “We can measure any part on either machine with a limited amount
of fixturing and no special calibrations,” said Watts.

“We measure all our parts on three types of fixturing. The
probe orients itself to the part after it’s initially aligned.”

Kawasaki programs all of its inspection routines in-house
using Mitutoyo’s Mcosmos 3.1 software. The upgrade to Revo instigated a shift
to parametric and modular programming of inspection routines through in-house
development of coding. This allows a program to be used for a part family.

“We might have 30 different crankshafts, for example, but
because everyone has the same features, only a different size or location, we
can use the same inspection program to measure all the parts,” Watts stated.

He said the transition from 3-axis to 5-axis programming is
not difficult, and a programmer with limited ability can still program Revo
inspections as 3-axis.