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Norman
Noble, Inc. utilizes
specialized metal finishing processes during the
manufacturing of medical devices & implants,
aerospace components, and commercial parts. In addition,
our proprietary metal finishing capabilities are
used for
the most challenging applications.
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Automated
Microtube Flushing |
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- High powered
(13,000 psi) acid flushing system.
- Capable of
processing hypotubing with a minimum diameter of .004” ID and maximum length of 69”.
- Processes all types of metals including stainless
steel, nitinol, and cobalt chrome.
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| Purpose: Metal
removal, remove stress risers, corner rounding, edge sharpening,
deburring, providing high luster, removing heat effected
zones and micro-cracks, and often improves the products
fatigue life.
Process: The
NNI EP process utilizes various engineered
blends of acids that are designed to dissolve
the components of the part’s material,
when the part is connected to a positive
electrical charge, placed in a bath of
engineered acids, in the presence of a
negatively charged counterpart, miracles
can happen.
The part then becomes the anode, the counterpart becomes the cathode.
Ions flow from the part to the cathode, in a somewhat disproportionate
manner. The irregularities such as corners, burrs, and protrusions
become high current density areas, these polish the fastest. Low
areas or middle areas polish slower. ID’s will only polish
if there is exposure to a cathode.
During polishing, the acids become saturated with the dissolved
metals and metal salts from the parts that have been polished.
During repeated use, the solution approaches its equilibrium point
and then begins precipitating out additional metals and salts to
the bottom of the EP system as sludge. The majority of the metal
in the solution plates to the cathode.
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Considerations:
- Oxygen
is liberated at the anode, and hydrogen is
liberated at the cathode. Therefore, EP will
not cause hydrogen embrittlement of the parts.
- EP
can improve fatigue life by removing cold working
stresses, or heat effected zones on the cut
surfaces, smoothing stress risers, removing
micro-cracks, and rounding corners.
- NNI
can also modify the EP effect to sharpen edges
and points.
- The
EP effect when done properly, can improve a
finish typically 2 fold, or more if tolerances
allow. i.e., a 8Ra will be reduced to a 4Ra.
- Proper
EP can greatly reduce the possibility of bacterial
growth on critical surfaces.
- An
area to attach the rack should be identified
prior to RFQ.
- Typically,
part designers target .0008” to .0010” inch
removal per surface, if maximum fatigue life
of the product is a concern.
- Parts
typically need to be back figured by NNI engineering
to allow for the material that the customer’s
design requirement needs to be removed.
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NNI
typically is always prepared to passivate all 300 and 400
series Stainless steels, 17/4, titanium, nitinol.
Purpose: Passivation
treatments improve the surface condition of
stainless steel by dissolving iron that has
been imbedded or exposed in the surface during
forming or machining. If allowed to remain,
the iron can corrode and give the appearance
of rust spots on the stainless steel. Our passivation
line is validated to remove all surface iron
from 304, 316, titanium, and soon Nitinol will
be validated also.
Our validated processes are certifiable to ASTM A967.
Passivation treatments also improve the surface condition of nitinol
and titanium by dissolving iron that has been imbedded or exposed
in the surface during forming or machining, and allowing the Nitinol
or titanium to grow a thicker protective oxide layer, providing the
maximum corrosion resistance.
In addition, NNI can also perform passivation per: AMS-QQ-P-35 (Replaced
QQ-P-35), AMS 2700, ASTM A-380, ASTM B-254, MIL-S-5002, ASTM B600.
Process: This is not
a rust removal or coating process, this is a deep cleaning with various
concentrations of nitric acid and temperatures. NNI’s passivation
solutions are replaced weekly. This level of diligence is unheard
of in the industry. The passivation is designed to maximize the inherent
corrosion resistance of stainless steel, titanium, and nitinol parts
post-machining. |
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A
very clean, machined, polished or pickled stainless steel
part automatically acquires
some oxide film from exposure to oxygen
in
the atmosphere. While this natural passivation provides a thin protective
oxide layer, it is not robust. Even if the parts are shiny and bright,
stainless steel parts may still tarnish in a short time. This invisible
oxide layer is found to be extremely thin, from 1 to 10 millionths
of an inch. During the nitric acid passivation process, a nitric
acid solution dissolves all contaminants, sulfides, and loose iron
allowing the metal to grow a robust protective oxide film that completely
covers all surfaces of the part to the maximum possible thickness.
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Pickling
of stainless steel, titanium and nitinol.
Purpose: Pickling
is a treatment for metal surfaces that remove
oxides, impurities, stains, rust or dross.
Process: This
is accomplished by dissolving the
stain or oxide, along with the
base material. This generally leaves
the grain boundaries of the material
exposed, and a somewhat |
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matte
and uneven surface. Pickling can be used to slightly
change the parts dimensions, or chemically machine
.0000” to .0020”.
Considerations: Back
figuring may be required if dimensionally tolerances are
relatively tight.
Heavy etching can cause grain boundary ditching, which may be undesirable
in designs that require a specific fatigue cycle life. |
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Small
Diameter Tube Cleaning
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| Purpose: Cleaning
and/or de-drossing the inside of Stainless Steels and Nitinol
Tubes. |
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Process: Proprietary.
NNI Custom built this machine to wash, descale, flush clean,
and dry small tubes up to 5’ long, and ID’s
as small as .0050”. |
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NNI
uses a solvent called trichloroethylene (TCE). Typically
parts are steel, brass, aluminum, or stainless.
Purpose: To
totally remove any grease, grime, oil, or even
moisture from parts.
Process: Room
temperature parts are immersed in hot TCE that
is in a distilled vapor state, this causes
the TCE to condense on the surfaces, to melt
off any grease, oils, or even |
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moisture.
NNI also has hot TCE with ultrasonic action to cavitate
contaminates out of surface pores and internal
features. Note: TCE is an EPA regulated
solvent and is expensive to purchase and use compliantly,
but in my experience, nothing degreases better.
Considerations: Chlorinated
solutions should never be used on titanium
or nitinol. |
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Abrasion
or Bead via Cabinet, Tumble, Precision CNC, or Micro-Blast
CNC.
Purpose: To
provide desired surface texture and/or corner
breaks. I.e., matte, rough, bright, removing
slag or dross, oxide removal, and corner rounding. |
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Process
for Abrasion or Bead: Varieties
of different abrasives and beads are available, and need
to be chosen for the application.
Abrasive blasting is accomplished by propelling a graded abrasive
media into a stream of compressed air or nitrogen, and focused thru
a nozzle at a fixed positioned in relationship to the part(s). The
abrasive material is directed at a targeted area to accomplish a
specific task. Spent media is continuously drawn out of the work
chamber via a vacuum and then sent through a filtration area to a
dust collection system. |
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Bead
Blasting is similar to abrasive blasting, except beads
lightly peen, cold work, or plastic level the surface with
graded beads consistent sizes.
Eight main parameters control most blasting processes:
1. The type and size of the media chosen.
2. If the abrasive once, or for a period of time.
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3.
Velocity of the air flow.
4.
The media flow rate.
5.
The
Stand-off or distance from the nozzle from the
part(s).
6.
The nozzle’s diameter.
7.
The
operator’s or CNC machines precision and
repeatability.
8.
Good
scheduled equipment maintenance.
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CNC
Bead Blasting and Aluminum Oxide Blasting
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| Machined
parts are placed onto either a static or rotating fixture,
the nozzle(s) are then positioned, and the parts are blasted
with fixed parameters and CNC movement. Finished parts
will be deburred, and have consistent texture. |
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CNC
(X, Y, Z, and A axis’s) Micro Bead Blasting and
Aluminum Oxide Blasting
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| Small
or intricate machined parts are placed onto either a static
or rotating fixture, the nozzle(s) are then positioned,
and the parts are blasted with fixed parameters and CNC
movement. Finished parts will be deburred, and have consistent
texture. |
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| Machined
parts are placed into screened barrels, the nozzle is then
positioned, and the parts are blasted with fixed parameters.
Finished parts will be deburred, and have consistent texture. |
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Machined
parts are placed into the blasting cabinet, the nozzle
is hand manipulated, and the parts are blasted with fixed
parameters. Some variation may be experienced. |
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High
Energy Finishing and Dry Tumbling
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Purpose: to
remove burrs, and/or add luster.
Process: Machined parts are placed in a hexagonal,
sealed barrel, with media, water, and soap. The barrel is then placed
into a turret with 4 other containers. This process is similar to
a carnival ride.
Rotation of the large turret creates a centrifugal force on the media
and parts inside each barrel. This force compacts the load into a
tight mass causing the media and parts to slide against each other,
removing burrs and creating desired finishes. This action also reduces
the cycle time needed to complete the finishing of the parts by up
to a factor of 30 over conventional vibratory and barrel tumbling.
Results with this centrifugal barrel finishing are consistent and
predictable, every time.
Considerations: The
expected Fatigue life of the parts must be considered
prior to exposure to High Energy Finishing. |
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Purpose: to
remove burrs, and/or add luster.
Process: This is similar to High Energy Finishing,
but with much less energy.
This process uses cyclic vibration causing rotation to move the media
around and thru the parts. This can be performed wet or dry.
Considerations: The
expected Fatigue life of the parts must be considered
prior to exposure to Vibratory finishing.
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Microburnishing
is like using a wire brush, but without a handle.
Purpose: to level burrs, and/or add luster.
Process: is a process by which variously shaped smooth
metal media is rubbed on the metal surfaces. This process flattens
the high spots by causing a plastic deformation flow of the metal
surfaces and corners. Typically the corners will only slightly round,
and exhibit displaced material compressed on the edge. Passivation
is recommended post burnishing, to removed loose iron. Very little
material is removed, in normal use, only a few ten thousandths of
an inch off corners. This process will not remove heat affected zones.
Burnishing economically improves the surface finish, and provides
some work hardening of the surfaces. |
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More
Information About Medical Coatings and Plating
Specifications
|
Revised
and Updated
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The Pocket
Guide to Plating Specifications was developed by
The Electrolizing Corporation
of OHIO and is available to you free of charge
by clicking
here and filling out the request form.
A
majority of the processes listed
in this reference guide are
provided by The Electrolizing
Corporation of OHIO. |
Contents
|
The Electrolizing
Corporation of OHIO's Pocket Guide to Plating Specifications
contains references to specification documents
and requirements.
This Pocket Guide is
not, however, meant or intended to be an authoritative or
comprehensive statement of particular specifications, procedures
and requirements, or to present all applicable specifications. |
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