See the technical article on Centrifugal Iso-Finishing on surface finish and it's effect on engine components in the Motorsports Industry terms of performance improvement. Contact D. A. (Dave) Davidson at ddavidson@deburring-tech-group.com for additional information or help with free sample finishing.

1. APRIL 2018 A property of Gardner Business Media
ADDITIVE
MANUFACTURING
3D printing in
a job shop pg. 62
CNC
TECHNOLOGY
Five-axis
fine-tuning pg. 64
DATA-DRIVEN
MANUFACTURING
The value of machine
monitoring pg. 76
Getting to a
Better Grind
pg. 68
mmsonline.com

2. MMS APRIL 201868 mmsonline.com
AUTOMOTIVE MACHINING

3. Camshaft Grinding, Finishing
Modern Machine Shop 69
Evolution of Performance
Camshaft Grinding, Finishing
Comp Cams has made numerous improvements to
its CNC camshaft grinding process. The company has
also implemented what it calls its “Micro Surface
Enhancement” finishing technology, which works in
tandem with its enhanced grinding process to further
improve camshaft longevity and durability.
Oftentimes, grinding lobes and bearing jour-
nals is the final step in machining an engine’s
camshafts. This is still the case for a number of
offerings from Comp Cams, a leading manufac-
turer of aftermarket camshafts and valvetrain
components for race, show and street vehicles.
The Memphis, Tennessee-based company has
continued to adopt new grinding technology over
the years, and now has nine computer numerical
control (CNC) grinding machines using carbon-
fiber-hub, cubic-boron-nitride (CBN) wheels that
are profiled and trued on the machines using
rotary diamond wheel dressers. It also recently
has introduced a new lobe and bearing-journal
finishing
process
for one of
its most
popular
roller-lifter
camshaft
lines that
not only
makes the
camshafts look better, but more importantly,
extends their lives by reducing abnormal, prema-
ture lobe wear. The kinetic finishing process
does this by removing tiny peaks of material left
behind after grinding while also minimizing
the amount of side-to-side waviness across the
surface of a camshaft lobe, thus increasing the
effective surface-bearing area between a lobe and
its mating lifter’s roller. This lowers the amount
of localized stress the camshaft lobes experi-
ence during operation, minimizing the number
of microscopic imperfections that could even-
tually propagate and become problematic on a
macro scale.
Comp Cams calls its finishing process Micro
Surface Enhancement (MSE), and it is currently
available as a standard feature for the roller-lifter
camshafts it offers for popular General Motors LS
engines (introduced in 1995 for use in a variety
of rear-wheel-drive vehicles) as well as custom
racing applications for an added cost.
That said, MSE proved not to be a cure-all.
In developing and refining the MSE process,
the company realized it made sense to circle
By improving its CNC grinding
processes and adding its new Micro
Surface Enhancement (MSE) finishing
technology, Comp Cams has not only
improved the look of its camshafts for
LS-type GM engines like the one on
the bottom left, but more importantly,
improved their longevity.
DEREK KORN | EXECUTIVE EDITOR

4. MMS APRIL 201870 mmsonline.com
AUTOMOTIVE MACHINING
back to further refine its grinding process to
generate a better overall camshaft lobe surface
profile and finish thereby maximizing the bene-
fits that MSE offered.
Circling Back
Comp Cams is no stranger to the pages
of Modern Machine Shop. In 2011, I visited with
Billy Godbold, valvetrain engineering group
manager, who explained how the company had
developed a process to turn and mill custom,
powder-metal camshaft cores for racing appli-
cations complete from barstock using a twin-
spindle/twin-turret Okuma LT300-MY turning
center. (Camshaft cores have their primary
features machined, but still require subsequent
heat treating and grinding operations.) After
learning a bit about MSE recently, I decided a
return trip was warranted.
For a number of years, Mr. Godbold and his
team have been researching various finishing
processes to improve camshaft lobe and journal
surface quality. He says some camshaft manu-
facturers (Comp Cams included, largely for
custom racing camshafts) perform belt sanding.
However, it is challenging to get a belt to provide
uniform pressure on a lobe. This can cause a
lobe’s surface to become even more wavy, and
the lifter’s load to be applied only to a lobe’s
high spots. Plus, belt sanding does not remove
any remaining burrs on a lobe’s side edges. In
addition, this is still largely a manual process
requiring a skilled operator, so it is not easily
scalable for higher-production applications.
It is also possible to acid-etch the surface of the
lobes, which anneals and softens the iron in their
surfaces, and then to polish the surfaces with
media to smooth them. However, the etching
Comp Cams has nine CNC camshaft grinding machines.
Eight of these are Okuma GC-34 NH models.

5. Camshaft Grinding, Finishing
Modern Machine Shop 71
doesn’t affect the carbide in the iron lattice struc-
ture of the steel, so the process can leave behind
peaks of carbide, which become stress risers, or
points of localized stress.
A third option is micro peening. This kinetic
energy process blasts the lobe surface with micro
media, but it can create tiny craters that have
stress risers around their circumference. Also,
it is challenging to clean out all the media from
camshafts after the micro-peening process.
Ultimately, Comp Cams discovered a manufac-
turer of centrifugal-barrel finishing machines and
worked with the company for a couple years to
tailor that type of kinetic energy finishing process
to its camshafts. (Mr. Godbold withheld the name
of said equipment manufacturer.)
The machines (Comp Cams has two) operate
on a Ferris-wheel-like principle. Each has four
drums, or baskets, into each of which a single
camshaft and the polishing media are manually
loaded and enclosed. These drums rotate in the
opposite direction of the barrel rotation. During
operation (typical finishing time for a camshaft is
15 minutes), the combined rotation of the barrel
and drums creates two tons of force on the media
and camshafts in the drums, and this force is
distributed equally on the camshaft surfaces to
evenly polish them.
Although some applications of this finishing
technology use organic material as the polishing
media, Comp Cams determined that denser,
ceramic-composite media and higher rotational
speeds worked best for its steel camshafts, not
only to remove any peaks and to minimize wavi-
ness across the camshaft lobe because of the
uniform force that is applied, but also to provide
a high luster. The process also deburrs the side
edges of the lobes and journals. In addition,
the company found that this process, with a
very dense media, served to impart compres-
sive stresses into the surfaces, which slightly
strengthens them. MSE’s rust-preventive qual-
ities also made it no longer necessary to coat
camshafts in as thick of an oil as the company
used to do prior to packaging.
That said, while MSE proved to be an effec-
tive finishing process, precise measurements
using an Adcole 911 camshaft inspection device
and Zeiss Surfcom Flex 50A skidless profilometer
showed that even further improvements could
be realized by making changes to the grinding
TOP: One camshaft installs in each of an MSE centrifugal
barrel finishing machine’s four drums. These drums
contain the media that polishes the camshafts, too.
BOTTOM: The combined rotation of the barrel and drums
creates 2 tons of force on the media and camshafts in the
drums. This force is distributed equally on the camshaft
surfaces to evenly polish them.

6. MMS APRIL 201872 mmsonline.com
AUTOMOTIVE MACHINING
process to generate a higher-quality surface prior
to MSE finishing.
Grinding Through Improvements
Today, Comp Cams’ eight Okuma GC-34 NH CNC
camshaft grinding machines and single Landis 3L
camshaft grinding machine use carbon-fiber-hub
CBN wheels instead of steel-hub CBN wheels.
Although these lightweight wheels are much
costlier, they offer improved vibration damping,
repeatability, predictable performance and
less-frequent dressing (dressing is required after
every 20 to 30 camshafts). The company found
that using steel-hub CBN wheels on its rigid
grinding machines sometimes caused camshafts
to vibrate during grinding.
Comp Cams uses a variety of wheel brands
depending on the camshaft being ground and
performs tests to measure the electrical current
during a grinding operation when selecting
grinding wheels for a given application. Higher
current means that more pressure and heat are
created during grinding, which could cause
burning, so the company looks for wheels that
grind with the least amount of current. It also
added scrubbers to its grinding machines that
shoot high-pressure streams of coolant across
the face of the wheel during operation to remove
any swarf buildup. Cleaning material out of
the voids in the wheel surface reduces grinding
pressure (and risk of burning the camshaft lobe
and journal surfaces) as well as the frequency of
dressing operations. Grinding tests proved that
As Mr. Godbold notes,
if you are trying to
improve a process but
cannot measure to verify
that improvements are
being realized, you are
ultimately just guessing.
Skidded and Skidless Profilometers: What’s the Difference?
According to Zeiss Industrial Metrology, the primary
principle of a skidded profilometer is that its diamond
stylus and the skid datum are independent of each other
and are in contact with the part surface when the trace
is made. The surface texture is measured by the change
in the diamond’s position relative to the plane of the
skid that follows the surface. Because of this, any form
or long wavelengths are filtered out, and the remaining
data is roughness only. Typical skidded profilometers
are portable, cost less and incorporate short traverse
movement. In addition, they are robust enough for shop-
floor use, have good vibration damping characteristics
and are generally easy to use.
As manufacturing techniques and surface analysis
became more advanced, a more capable “skidless” profi-
lometer was developed. The primary principle of a skidless
trace is that the diamond stylus and datum are interde-
pendent. The diamond tip is solely in contact with the part
surface at the time of measurement, and surface devia-
tions are measured in reference to the diamond’s position
against a straight datum built within the instrument’s drive
guide. Skidless profilometers can analyze surface profile,
waviness and roughness. These devices are more accurate
and repeatable than skidded models, but are also more
expensive due to the precision datum guide, multi-speed
driver and higher-resolution probe.
The top image shows a skidded profilometer;
the bottom shows a skidless profilometer.

7. Camshaft Grinding, Finishing
Modern Machine Shop 73
even less current was drawn when scrubbers
were used, because wheels could grind more
freely when they were not loaded with swarf.
The company also settled on Castrol Syntilo
9974 heavy-duty synthetic metalworking fluid,
which Mr. Godbold says is costlier than many
other fluids, but it offers high, consistent
lubricity with no need for a lubricity additive.
In addition, the company went so far as to
decouple coolant mist collectors from machines.
Originally, the grinding machine mist collectors
were mounted directly on the machine enclo-
sures. However, it was determined that the
mist collectors’ electric motors caused a slight
amount of vibration that resulted in a small bit
of measurable chatter in the ground camshafts.
Now, the mist collectors are mounted on a frame
separate from the machines.
Addressing the Dress
The final big change was refining and optimizing
the wheel dressing process. William McIntyre,
a manufacturing associate engineer for process
development at Comp Cams, says the company
received a good bit of input from Okuma and
various grinding wheel manufacturers in devel-
oping its wheel dressing routines. As he explains,
the first step in refining the dressing process was
to get the speed ratio of the dressing and grinding
wheels to the recommended 75 percent to mini-
mize the risk of dressing chatter. In other words,
the surface feet per minute (SFM) of the rotary
diamond dresser was adjusted to be 75 percent of
the normal SFM of the CBN wheels to provide the
proper pressure on the wheels, enabling proper
surface fracturing. He says it is important not to
reduce the grinding wheel speed during dressing
They also feature scrubbers
that shoot high-pressure
streams of coolant across the
face of the wheels during
operation to prevent swarf
buildup that would otherwise
increase grinding pressure as
well as the frequency of
dressing operations.
All nine of Comp Cams’ CNC
grinding machines now use
carbon-fiber-hub CBN wheels.

8. MMS APRIL 201874 mmsonline.com
AUTOMOTIVE MACHINING
because it can adversely affect grinding wheel
concentricity, making it more difficult to balance
at the normal rotational speed.
Comp Cams grinds so many types of material
and surface profiles in lobes that it has multiple
different dress parameters it uses depending on
what’s best-suited for a given application. Mr.
McIntyre notes that it can be challenging to deter-
mine the appro-
priate dressing
wheel transverse
rate across the
grinding wheel.
This rate is kept
slow, but not so
slow as to cause
burning on the
flanks or ramps of the camshaft. Too slow of a
transverse rate will not open the wheel grains
properly, so the wheel will ultimately burn the
camshafts during grinding.
In dialing in the dressing processes for
each application, the company tested ground
camshafts at set integrals to check for lobe
surface topography, lobe profile and burning.
Using a carbide disk that emulates a lifter, its two
Adcole 911 camshaft inspection devices record
the translating lifter motion for each lobe every
0.1 degree as it rotates the camshaft, meaning
3,600 data points are collected in a single rota-
tion to a radial resolution of 1 micron. Comp
Cams takes three measurements for each lobe
(at the middle and on either side). This device
records the motion of the lifter, determines if the
lobe is convex or concave, and performs a fast
Fourier transform (FFT) algorithm to check for
grinding chatter.
While the Adcole 911 is used to determine
follower motion 360 degrees around lobes, the
Zeiss Surfcom Flex 50A skidless profilometer
measures lobe profile and surface finish longi-
tudinally (side-to-side) across the lobe surface.
It does this using a pointed diamond stylus that
drops into any valleys and moves over any peaks
in the surface to determine actual surface topog-
raphy to a resolution of 0.000002 inch.
The profilometer is also used to check for
appropriate lobe crown on roller camshafts.
This skidless profilometer
is used to measure the
roughness of camshaft
journal and lobe surfaces
as well as their waviness.
It can determine actual
surface topography to a
resolution of 0.000002 inch.
THE RACE IS ON
Visit gbm.media/comp to learn
how Comp Cams became more
effective using its twin-spindle/
twin-turret lathe to machine
small batches of custom racing
camshaft cores.

9. Camshaft Grinding, Finishing
Modern Machine Shop 75
Mr. Godbold says that the surfaces of the lobes for
roller camshafts should be slightly convex (with a
bit of a crown in the middle), because the rollers
on the mating lifters are also slightly convex. By
having both mating surfaces slightly convex, the
pushrod load (which can reach approximately
2,500 pounds for LS engines) tends to cause each
surface to flatten a bit. Comp Cams shoots for a
lobe crown of just 0.0001 inch.
The company also uses Profile Master data
analysis software from Digital Metrology
Solutions to process and report the data gathered
by the profilometer. Mr. Godbold says the soft-
ware’s graphical interface is valuable in clearly
communicating to manufacturing and quality
control personnel how changes to the grinding
process affect the end product.
To check for burned surfaces, Mr. McIntyre
created a test station in which camshafts are
first dipped in a bath of nital, an etching solu-
tion that is a combination of alcohol and 8
percent nitric acid, and then dipped in a bath
of alcohol and 8 percent hydrogen chloride to
deactivate the etching. This process will cause a
significant color change of any burned surfaces
because different material hardnesses react
differently with these solutions.
Product Improvements
The various modifications of the grinding
process ultimately enabled it to serve as
“pre-polish” step on lobe surfaces prior to MSE
processing. This enabled Comp Cams to use
smaller media in the MSE process, because not
as much material removal or surface pressure
(as bigger media would provide) were required
to remove material peaks and minimize profile
waviness. Plus, bigger media tended to create
new valleys in the lobe surface anyway, which
would also reduce bearing area, meaning a
second MSE operation with smaller media
would have been required.
MSE was put into production in October 2017
for the company’s LS engine camshafts and intro-
duced at the SEMA show in Las Vegas, Nevada,
later that month. Comp Cams plans to offer MSE
for other camshaft lines down the road. Mr.
Godbold says the bearing area for the compa-
ny’s camshafts was approximately 10 percent 15
years ago and 15 percent 10 years ago. Now with
refined grinding and MSE processes, the company
is achieving 50 to 70 percent bearing area and
reduction in peak roughness of 65 percent to
more effectively spread the load on camshaft
lobes, lowering the stress they endure during
operation for improved durability and reduced
valvetrain noise.
The key in all this, however, was having the
capability to precisely measure various lobe
features as the company worked to improve
its camshaft manufacturing process. As Mr.
Godbold notes, if you are trying to improve
a process but cannot measure to verify that
improvements are being realized, you are ulti-
mately just guessing.
| Adcole Corp. | 508-485-9100 | adcole.com
| Castrol Industrial | 877-641-1600 | castrol.com
| Okuma America Corp. | 704-588-7000 | okuma.com
| Zeiss Industrial Metrology US | 800-327-9735
zeiss.com/metrology
The image above depicts a camshaft lobe
surface before the MSE process, while the
image below shows it after the MSE process.
The uniform force generated during MSE
removes many material “peaks” and minimizes
waviness across the camshaft lobe.