Molecular Decomposition Process

2. INTRODUCTION
Molecular decomposition process is an
electrochemical grinding process that
has been refined to enable:
- The removal of increased amount
of material while maintaining
workpiece temperature to within
1ºF.
- Reduced mechanical force to the
workpiece.
- From roughing operations surface
finishes achieved measure at 6 to
8 Ra µin.
- Finishing operations are able to
achieve surface finishes of 1 Ra
µin or less.
The MDP can be outlined as follows:
- Isolation of workpiece and spindle
from balance of equipment.
- Power supply design to address
power surges or brown outs from
external power sources.
- Electrolyte management system
that cleans particulate (anode
mud) separates particulate from
the balance of electrolyte through
controlled filtration maintaining
uniform electrolyte conductivity.
This filtration process provides a
valuable benefit in the elimination
of heavy metals such as arsenic and
hexavalent chrome (making the
designed system environmentally
friendly).
- Electrolyte formulation specifically
maintained to assist the total system.
- Controls of perishables through
specific wheel formulation designed
to address, conductivity, resistance,
abrasive type and concentrations of
abrasives.
- Within the operation of the MDP
system, wheel life is increased
requiring less time in dressing
particular forms within the
perishables thereby increasing the
spindle time in the area of part
production.
- Combining all of the actions within
the system is done through controlled
algorithms that enable operation of
the MDP equipment to happen
in the background. This permits
operation of the MDP equipment
from any level of expertise.
Within the MDP system the workpiece
is isolated from the balance of the
equipment and power is passed through
the conductive workpiece making the
workpiece the anode within the MDP
system. The isolation of the spindle and
conductive “Voltron” grinding wheel
are employed to enable the grinding
wheel to be the cathode within our
electrochemical cell. See Figure 1.
Molecular Decomposition Process =
Electrochemical Assisted Precision
Form Grinding
Super-finishing of forms required to generate geometry like that of the involute of a gear is
a multi-step process where gear blanks are roughed, heat treated, and ground to precise
tolerances allowing for additional stock removal to occur in another value added process
to generate super-finishes to less than 1 Ra µin. A solution that enables the rough and
finish grinding to occur that produces super-finished surfaces to less than 1 Ra µin while
maintaining precise geometries is Molecular Decomposition Process (MDP).
By Joseph A. DeAngelo
Printed with permission of the copyright holder, the American Gear Manufacturers Association, 1001 N. Fairfax Street, Suite 500, Alexandria, Virginia 22314. Statements
presented in this paper are those of the Authors and may not represent the position or opinion of the AMERICAN GEAR MANUFACTURERS ASSOCIATION.
Figure 1: Illustration of isolated work piece (anode),
Voltron grinding wheel (Cathode), filtered electrolyte
delivery between the interface of the Anode and
Cathode (work piece and conductive wheel)
Figure 2: The cutting process being the desired
action between an abrasive and a work piece
MAY 2015 39

3. Through the anode to cathode relationship a defined material
removal through a deplating action is present within the electrochemical
cell which seems to soften the material for stock removal and at the same
time prevents softer alloys from adhering to the cathode (conductive
grinding wheel) allowing for a clean free cut of material without
mechanical or thermal damage.
SurfacefinishesresultingfromtheMDPprocessareimprovedthrough
the ability to maintain uniform cutting action. Within conventional
grinding and machining processes the tools utilized to perform the
work introduce the largest potentially uncontrolled variable. Within a
machining operation tools wear from the initial moment the cut edges
are exposed to the alloy being removed. Efforts to enhance cut edge
life require extensive engineering for cutter material, coatings, rake
and cutter geometry all efforts to enable longer life through the cuts.
Similar engineering efforts are performed for abrasives utilized within
grinding wheel production to enable open clean cuts through porosity
of the wheel or high pressure coolant systems that assist in keeping the
abrasive wheel free of alloys or debris being ground. In either case, a
dulling of the abrasive or cut edge translates to mechanical observations
at the surface of the alloy being exposed to the stock removal process
that would typically be referred to as tearing plowing smearing, or
sliding of material. Figure 2 illustrates many of the conditions which
can directly impact the final as machined / ground surfaces.
The cutting process being the desired action between an abrasive and
a work piece (1.1) Balance of conditions illustrates a level of mechanical
deformation at the surface that leads to increased friction (heat into the
work piece). Abrasive stock removal reflected within (1.3 through 4) are
conditions that are least desired that prohibit dimensionally accurate
stock removal. MDP prevents these types of conditions.
The dulling effect of the cutter or abrasive is best illustrated as
reviewed through a scanning electron microscope (SEM) of the surface
of the alloys. Figures 3 and 4 are SEM images of conventional ground
verses MDP ground product. (Note: alloy illustrated within Figures
3 and 4 maintain the same certifications as they are both from the
same bar of stock).
Figure 3 is conventional ground alloy with a 180 grit diamond
abrasive. Ripping tearing and smearing are all present within produced
sample. Figure 4 is MDP ground alloy with a 180 grit diamond abrasive.
Linear lines present are direct translations of geometry that is present
on the face of the 180 grit diamond grinding wheel (cathode).
Benefits of the MDP system are that of true geometry and material
characteristics are present at the surface of the work piece. Any
geometry present on the surface of the perishable wheel directly
translates to the surface condition on the work piece. When super
finishing of specific geometry is being requested, the perishable wheel
is the first item that must be produced with a uniform desirable surface
finish and geometry. The perishable wheel and the grind approach
must be one that will permit the removal or uniform blending of the
surfaces through mechanical action or geometry. It is fair to state
Figure 4: MDP grinding conducted with 180 grit diamond abrasive at a field of view of 25 µm
Figure 5: Cubic boron nitride abrasive conductive wheel, Grit size – 400/500 (19-22
micron average) resin bond copper infused 80% concentration (V192) easily removes 0.01
inches per side in a single pass
A COMMON SENSE APPROACH IN
THE MANUFACTURING OF WORLD
CLASS GEARS
Raycar manufacturing high
quality smooth running gears
offering competitive pricing
and quick turn around.
• CNC GEAR BLANKING
• CNC GEAR SHAPING
• CNC GEAR HOBBING
• CNC GEAR GRINDING
• ANALYTICAL CHARTING
EQUIPMENT
WE WANT THE OPPORTUNITY TO MAKE YOUR NEXT SILENT
GEAR SEND YOUR QUOTES TO:
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6125 11th Street
Rockford, IL 61109
Figure 3: Conventional grinding conducted with 180 grit diamond abrasive at a field of
view of 25µm
Booth #1634
40 gearsolutions.com

4. that if the perishable utilized within the MDP
system has a measured Ra this will directly
impact the final Ra of the work piece. Within
conventional grinding, this level of detail is
easily discarded as the change of cut condition
and the presence of smearing and tearing are
ongoing through the process.
ADAPTING THE MDP PROCESS
TO GEAR GRINDING
Achievable surface finishes of a system are a
result of multiple inputs including, accuracies
of equipment (mechanically and thermally),
life of the perishable tool, and repeatability
through the entire geometry generation or
linear inches of grind.
Gear production is typically performed by
a roughing process (broaching or machining)
heat treatment, grinding operations, gear
form grinding, when required, super-finishing
is achieved by rotary tumbling with some
media and chemistry (mechanical polishing).
The value added process of rotary tumbling
requires dimensional planning with specific
focus on the amount of material removed by
that value added process, where the material
is removed from and which zones are
subjected to more material removal during
the polishing process in order to generate the
required surface finish. Once defined, these
processes are predictable and repeatable and
become part of the process flow.
WHEELS/PERISHABLES
Cubic Boron Nitride wheels within
conventional grinding systems require
precision made hubs that are manufactured
to matching geometries for the desired
profile. These metal hubs are then plated
and the super abrasive is layered onto the
precision hub which is subsequently dressed
and measured to ensure uniform geometries
are achieved.
Aluminum oxide and silicon carbide
wheels can be dressed within the gear
grinding equipment utilizing programmable
paths or formed dressing wheels. Dressing
of these wheels within the gear grinding
equipment delivers the desired profile with
the geometric accuracies of the equipment
directly translated to the perishable and
subsequently to the product being ground.
When grinding multiple teeth, multiple passes
and multiple dresses of the perishable may
be required within the conventional grinding
system to produce uniform geometry.
Whatever the abrasive selection within the
MDP system, the benefits of producing the
conductive wheel is the first item that increases
the overall ability of the perishable to maintain
uniform geometry through the required linear
Figure 6: Solid alloy steel 4140 hardened to 50-52 HRc
ground from solid with applied MDP technology
Figure 7: Roughed alloy 4140 hardened to 50-52 HRc with
aluminum oxide abrasives and applied MDP achieving
material removal rates of 30.3 mm3/mm/s
Figure 8: Roughed alloy 4140 hardened to 50-52 HRc with
aluminum oxide abrasives and applied MDP achieving
material removal rates of 30.3 mm3/mm/s
Figure 9: Gear inspection data provided by Zeiss Gear
Pro involute (z = 41; P = 11.00000"; b = 0.41000"; n
=
20.000°; = 0.000°; X= -0.45046; db
= 3.50249"; df
/da
=
3.50000/3.90660"; bu
/b0
= -0.41000/ 0.00000")
Tooth Ra Rz Rq
#1n 0.83 µin 7.8 µin 1.07 µin
#1f 0.77 µin 5.2 µin 0.93 µin
#2n 0.96 µin 6.4 µin 1.16 µin
#2f 0.61 µin 4.3 µin 0.77 µin
#3n 0.86 µin 5.9 µin 1.07 µin
#3f 0.83 µin 9.5 µin 1.15 µin
#4n 0.61 µin 4.6 µin 0.77 µin
#4f 0.64 µin 4.5 µin 0.78 µin
Table 1: Surface analysis - four teeth inspected left and right side of the as MDP ground gear is reviewed illustrating as
ground geometries achieved with less than 1 Ra µin. Eliminating the need for subsequent value added processes
MAY 2015 41

5. inches of grind. Abrasive selection is more to enhance the overall life
of the perishable to the number of form dresses that would be required
for a desired form. Although wheel life is product specific, testing
conducted has illustrated 5 to 10 times longer wheel life within the
MDP systems as compared to conventional grinding systems.
APPLIED MDP PROCESS BENEFITS
Increased wheel life is a benefit from the applied MDP technology.
This increased wheel life enables uniform geometry for roughing to
finishing with less expensive types of abrasives while maintaining
required dimensional attributes. The increased wheel life and less
expensive abrasives has an added benefit of enabling a gear grinding
system to rough stock from a solid form within a single setup of the
MDP interfaced equipment. Conventional grinding system utilizing a
plated CBN wheel is less desirable for this approach due to the resultant
mechanical and thermal stresses that would be generated within the
product, along with the expense of the plated CBN wheel.
Accuracy and repeatability are achieved within the MDP perishables
through the use of accurate and repeatable tool mounts. These accurate
tool mounts enable the offline dressing of precision forms and provide
repeatable accurate geometries. This method of form generation
consistently provides uniform surfaces onto the form geometry of the
Figure 10: As MDP ground gear being inspected for resultant surface finish
Figure 11: Conventionally ground gear involute surface analysis illustrates “as ground”
condition of 17.90 Ra µin
Booth #1426
42 gearsolutions.com

6. perishable that would normally be viewed
as grinding lay that subsequently affect the
surface finish of the work piece.
Controls of the perishables through
abrasive size, conductivity, and concentration
further enhance the MDP process. As
the grinding wheel is the cathode within
our electrochemical cell, the abrasives are
present to assist in the removal of non-
conductive elements. The electrochemical
action grinding swarf is a fine particulate
(anode mud) that does not adhere to the
perishable during the grinds. This enables
finer abrasives to be utilized for increased
levels of stock removal. Due to the finer
meshed abrasives and refined dressing
techniques, a uniform and consistent surface
is generated onto the form of the perishable
wheel. The extended wheel life gained from
the applied MDP results in an improved
surface of the form being ground with the
applied MDP process, see Figure 5.
The blank:
Material = Alloy steel: AISI 4140, shown
in Figure 6,
- Other steels ground with the MDP
technology that required super-finishing
of 1 Ra µin or better include: Stainless
steel, 303, 304, 420, 440C; Tungsten
carbide 12% cobalt binder; cast iron;
Inconel 617, 625; Carpenter Pyrowear®
53; CPM10V and D2
Reheated to 845ºC (1550ºF), oil quenched,
425ºC (800ºF) double temper, see Figure 6.
Roughing the blank:
Utilizing a 100 grit aluminum oxide abrasive
with form dressed wheel, stock removal
rates from the solid blank grinding 41 teeth
achieving a Q’ = 30.3 mm3/mm/s with the
applied MDP technology, leaving 0.010” per
side stock for finishing passes to simulate
a standard production gear product. The
applied MDP
grinding was conducted with CNC grinder
manufactured by Chevalier and integrated
with MDP by Oberg Industries. Auxiliary
fourth axis employed is a “Hardinge
DD100” direct drive rotary indexer with
repeatability of 2-3 arc seconds.
Figure 7 shows a roughed gear after running
the aluminum oxide abrasive wheel leaving the
0.01” per side stock for subsequent finishing.
Upon completion of the roughing process,
a CBN (cubic boron nitride) abrasive for the
finishing process was implemented. Grinding
full depth with applied MDP removing 0.005
persideformeasurementreviewandfinalfinish
passes.
Upon completion of grinds, dimensional
results are verified utilizing measurement
over calibrated precision rolls online within
the grinding equipment (see Figure 8). Further
dimensional checks are performed first with
Zeiss coordinate measurement machine
matching to modeled geometry and Zeiss gear
inspection equipment for verification of profile,
lead, pitch, and radial runout (see Figure 9).
Surface analysis checks of the as MDP ground
surfaces are performed offline with a Mitutoyo
SJ400 profilometer. Surface finish data (Figure
10) resultant data recorded within Table 1.
Superior surface condition is achieved
through reduced mechanical forces, control of
thermal properties and the ability to produce
repeatable perishable tooling for use within the
MDP system. Allowing the surface integrity
from the MDP grinding wheel to translate
directly to the work piece is a notable benefit
of applyingtheMDPgrindingprocesstogears.
In comparison to an MDP ground gear,
a conventional ground gear had a relatively
rougher 17.9 Ra µin surface finish when
utilizing the same measurement equipment
(see Figure 11 and Table 2).
SUMMARY
By the means of applied MDP grinding
we are able to illustrate, high stock
removal rates, improved perishable life
measured by repeatable geometry and
surface finishes as MDP ground to a 1
Ra µin or better. The equipment utilized
for these tests does not represent the
geometric stability of a precision gear
grinding machine or work holding devices
specifically designed for holding and
grinding of gears. Illustrating further that
the MDP addition to a grinding system
reduces mechanical and thermal forces
required for stock removal in roughing
and finishing operations.
MDP grinding eliminates the need for
subsequent value added processes that
add additional cost or cycle time to
the gear production. Implementation
of the MDP technology for these
test grinds where performed on a CNC
grinding machine produced by Chevalier
equipment not specific to gear grinding
processes. Adding the benefits of MDP
to a precision gear grinding system
would add the benefits of achieving
super finishes to the “as ground” gear
component and add to the types of gear
geometries that could be produced with
the applied MDP technology.
REFERENCES
1. Marinescu, I.D., Hitchiner, M.,
Uhlmann, E., Rowe, W.B., and
Inasaki, I., Handbook of Machining
with Grinding Wheels
2. Korn, D., Low-Force, Low-Heat
Grinding of Tough Materials,
Modern Machine Shop
3. Ungureanu, C., and Cozminca, I.,
About the wear of abrasive tools in
electrochemical grinding
4. Reitz, E., Surface Finishes:
Methods and Metrics for
Production, MDDI Medical
Device and Diagnostic Industry
News Products and Suppliers
ABOUT THE AUTHORS: Joseph DeAngelo is currently the director of technical development at Oberg Industries specializing in manufacturing
solutions for aerospace, consumer/industrial products, defense, medical and energy. This focus began when he was manager of prototype through large
efforts focused on micro-channel technology for energy and trauma plate manufacturing solutions for medical applications. He is a certified precision
tool and die maker with studies in mechanical& electrical engineering technology, specializing in design and build of plastic injection molds, die cast
tooling, class II progressive stamping dies, and turnkey manufacturing solutions.
Tooth Ra Rz Rq
#1n 17.90 µin 125.4 µin 22.98 µin
#1f 17.10 µin 109.9 µin 22.01 µin
Table 2: Surface analysis - one tooth inspected left and right side
MAY 2015 43