Sme membership webinar_08.19.15_final-1

Isotropic Finishing for Surface
Integrity and Part Performance
The webinar will start at 2:00pm (EST)
Brought to you by SME Membership
August 19, 2015

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• 1 hour webinar: 45 min + 15 min Q&A.
• Attendee phones will be muted during the webinar.
• During the presentation, you can log your questions in the Q&A window
of the WebEx screen.
• The presentation will be recorded. A web link to the recording will be
emailed to attendees within 24 hrs by SME.
• If you have any difficulties, please email nlowell@sme.org
Webinar Housekeeping Rules

Today’s Webinar
Isotropic Finishing for Surface Integrity
and Part Performance
SME Speaker:
Dave Davidson
SME Advisor: Machining/Material Removal
Technical Community
SME Speaker:
Jack R. Clark, President
Surface Analytics, LLC, Fort Collins, CO
Faculty Affiliate: Colorado State University

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What are Isotropic Surfaces?
Why are they important?
.

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Isotropic Finishing Bearings (IFB)
2-D and 3-D surface views

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Isotropic Finishing: Definition
• In contrast to machined or ground surfaces Isotropic surfaces are
non-directional or random in character.
• They do not exhibit the surface pattern of parallel lines, grooves
or notches common to all machining methods
• This is a desirable surface characteristic functionally as the overall
amount of surface available for bearing loads can be increased
dramatically and machining notches which provide potential
failure related crack propagation points are attenuated
substantially.

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Centrifugal Isotropic Finishing (CIF)
– How it works…
• Rotating Turret
• Counter-rotating barrels
• High Internal G-Forces
• Rapid media turnover and
slide zone

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CBF Advantages:
• Very high speed processing
• Quick change over capability
• Different parts can be
processed simultaneously in
different chambers
• Compartmentalization or
fixturing possible
• Very refined surfaces possible especially
in sequential processing

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CBF Isotropic Finishing - Bearings
• Bearings require
substantial processing to
produce low-micro-inch
surfaces needed for
optimal load bearing
capability.

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Hands-Free Surface Finishing
of 3-D metal printed parts
• 3-D metal printed parts of
various alloys were received in
their printed condition.
• Profilomic and areal data
collected from a sampling of
the part specimens
• Indicated an initial surface
roughness of 350+ micro-
inches.
• CIF process reduced surface
profiles on these tested
samples f to a range of 12 – 15
micro inches Ra.

Centrifugal Isotropic Finishing of
Laser cut stainless steel
Stainless Steel,
laser cut using
nitrogen as the
shielding gas.

Extreme Finishing
• Flame-cut foundry steel
castings, with as-cast and
flame-cut surfaces.
• Demonstration experiment
to validate surface profile
reduction on extremely
rough surfaces.

Heat-treat scale removal, edge-contour,
burnishing automotive parts
• These heat-treated
automotive stampings
require cleaning and edge
contour on exterior and
interior edges.
• CIF high-intensity finishing
processes with smaller
media used as the process
was able to achieve
specifications for radiusing
the inside edges of the
part that conventional
processing could not.

Small Part Finishing: Metal
Injection Molding
• Metal Injection molded parts
typically exhibit a rough surface
condition that can pose a severe
challenge when the part is
destined for the mass consumer
market and has a requirement
for very smooth or polished
surfaces to meet cosmetic or
aesthetic criteria.
• On small parts such as these cell-phone hinges conventional buffing
and polishing techniques are inadequate given their potential for
creating bottlenecks and production constraints to production of
large numbers of parts.

CBF Isotropic Finishing
Dental Applications
• Dental laboratories have long
faced severe bottlenecks and
production constraints in the
finishing of dental parts such
as cast chrome partials, full
dentures and full cast crowns.
This finishing bottleneck often
limits a dental technician’s
production rate to three to four
pieces every 1.5 hours when
manual finishing is employed.

CBF Isotropic Finishing – Carbide Tooling
• Two process tracks have been
developed for improving tooling
with edge and surface
preparation. One process that
has been developed utilizes
non-abrasive materials to
burnish edges and surfaces.
• The other track uses dry
process media material in
conjunction with polishing
abrasives to develop more
refined and consistent tooling
edges that are more
predictable. This type of
processing adds service life and
improves cutting performance

Medical Device Finishing
• In the medical industry, the
fine isotropic finish produced
by CBF machines is a
requirement.
• Processing metal implants in
centrifugal finishing machines
helps reduce complications
within surgeries and
procedures.
• Centrifugal machines are also
used by companies that
produce other medical
devices.

Isotropic Surface Generation on Roller Bearings –
Before and After, SEM and 3D views compared.
(As ground vs. CBF Finish)
Photos by Jack Clark, Surface Analytics, jclark@surfaceanalytics.com | SME MMR Tech Community

Meeting the Lean Deburring Challenge at MacKay
Mfg. Co. Spokane, WA
Typical Hand deburring
operation prior to
implementation of high speed
centrifugal isotropic finishing
and cellular flow for deburring
and finishing operations.
This batch method can lead to
uniformity problems and have
uneven stress distribution on
parts that can lead to
premature part failure in many
cases.

High speed isotropic finishing
in cellular flow environment replaces most hand finishing…

Parts can be processed in bulk

Parts can be processed in
Compartments with Fixtures

High pressure finishing can remove machining or
milling marks for ultra-smooth surfaces

Smaller parts with difficult to access
geometries can be finished…

Isotropic vs. Conventional Ground Surfaces
SRa= 1.05
SRz = 19.31
SRpk = 2.50
SRk = 2.38
SRvk=2.42
SRa= 0.435
SRz = 5.65
SRpk = 0.17
SRk = 0.45
SRvk=1.33

Diesel Camshaft and Roller Tappet
High Wear Interface

Failure!
• When the form and roughness of
each component is not compatible,
FAILURE is guaranteed!

Complex Cam Roller Profile

Which Cam Roller Will Survive?
IMPCO
CBF As
Ground
Super
Finished

As Ground
 High Ra
 Large Rz/Ra ratio = 6.5:1
 Poor SRvk/SRpk ratio = 1.9:1

Cross Hatch
 Better Ra
 Very Large Rz/Ra ratio = 9:1
 Better SRvk/SRpk ratio = 2.4:1

Super Finished
 Low Ra
 Large Rz/Ra ratio = 7.1:1
 Poor SRvk/SRpk ratio = 1.5:1

CBF Finished
 Best Ra
 Best Rz/Ra ratio = 6.1:1
 Better SRvk/SRpk ratio = 2.1:1

Draw and Iron (D&I) Aluminum
Can Punch and Die
• The punch drives a sheet of aluminum through a progressively
smaller and smaller pack of dies to thin the material and form the
can.
• If the surface finish of the punch does not retain lubricant and vent
air, the newly formed can cannot be “stripped” off the punch
damaging the can.
• If the finish on the dies is not such that they produce a “bright
looking” can, it will not be marketable.

Can Punch
Conventional Grind
 Good Ra
 Excellent SRvk/SRpk ratio = 4.1:1
 Unpredictable can release

Can Punch
Conventional Grind
• The texture of the grind
limits the lubricant flow
and restricts air flow to
support release.
• The Texture Aspect
Ratio (Str) reveals a
small included angle
that is not good for
lubrication distribution.
Even though the roughness and
Bearing Ratio are “good”...

Can Punch
CBF Finished
 Good Ra
 SRvk/SRpk ratio = 1.4:1
 Predictable can release

Can Punch
CBF Finished
• CBF allows for excellent
lubrication
flow/retention with
excellent air infiltration
for good release.
• The Texture Aspect
Ratio (Str) reveals a
random finish that has
proven to be excellent
for release in many
similar applications.
Roughness was optimized by
varying abrasive grit/binder, and
CBF compressive loads.

Spinal Implant Manufacturing Issues

Concave Spinal Implants
• Form variance must be controlled.
• Overall shape can cause unpredictable in wear.

Convex Spinal Implants
• Each step of the forming of the part must be monitored.
• Turing and super finishing artifacts remain after final
polishing.

Wear Analysis
• Wear on Convex Implant.
• Original spherical form will be
removed for wear analysis.

Convex
Concave
New Part “Couples”
•As manufactured mating parts
must be uniform over the entire
contact area.
•Machining process have
produced forms where the two
surfaces only touch in the areas
indicated by the arrows.

Worn Part “Couples”
Concave
Convex
•The resultant wear on each part
indicates that the original form
did produce high loads and,
therefore, premature wear.
•The high wear area is indicated
by the arrows progressing to less
wear in the centers.

Implant Surface Finish Varies
• All surfaces are 4 - 7 nm SRa and 42 – 68 nm SRz
• None are Isotropic Finished

Isotropic Finishing Summary
• Deburring and surface conditioning of complex machined
parts is one of the most troublesome problems faced by the
metalworking industry.
• High-energy surface finishing can drastically reduce finishing
and deburring costs.
• Isotropic Finishing:
– Extends tooling and part life.
– Improves wear resistance.
– Reduces fatigue failure.
– Ensures part-to-part uniformity.

Questions?
Dave Davidson
Presenter
Thank you!
Jack R. Clark
Presenter

Thank You for Attending
Dave Davidson
dryfinish@gmail.com
Jack R. Clark
jclark@surfaceanalytics.com
SME Membership | http://i.sme.org/home
One SME Drive | Dearborn, MI 48121 USA | www.sme.org
Next SME Membership Webinar
3D Printed Carbon Fiber
9/15/15 3:00pm - 4:00 pm (EST)
Register at SME Member X-Press
https://www.xpressreg.net/register/sme/start.asp

References
• "The Effect of Surface Finish on Functional Surface Performance". Dr. M.B. Grant, Director of
Corporate Metrology, Cummins Engine Company. (SME Paper, presented at the International
Grinding Conference, 1990)
• Metal Finishing Magazine, 3 May 2006. Co-authored with Michael Massarsky, PhD, and David
A. Davidson, “It's the Finish that Counts”.
• “Expanding the Limits of Interferometric Measurement for Automotive Applications”. Jack R.
Clark author ( XI. International Colloquium on Surfaces, Chemnitx, Germany, 2004).
• SME Medical Manufacturing 2008 Annual, pp. 91-93, “Metrology Keeps Hip”.
• Products Finishing Magazine, posted 1 January 2015. Co-authored with David A. Davidson,
“Isotropic Mass Finishing for Surface Integrity and Part Performance”.
• "It's the Finish that Counts"
• http://www.slideshare.net/dryfinish/its-the-finish-that-counts
• "The Role of Surface Finish In Improving Part Performance":
• http://www.slideshare.net/dryfinish/november-2012-f4-deburring-1-final?related=1
• "Free Abrasives Flow for Automated Finishing":
• http://www.slideshare.net/dryfinish/october-2013-f2-deburring-1?related=2

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