Bulk Molding Compounds,
Inc.
‘Complete
Composite
Solutions’
BMC Injection- Molded Motor Bracket
BMC vs. Die Cast Me
ADVANTAGES
• Reduced Cycle Times / Reduced Manufacturing Cost
• Thermal / Dimensional Stability
• Noise Reduction
• Weight Reduction
• Elimination of Costly Secondary Machining
Operations
• Lower Tooling Costs / Longer Tool Life
• Greater Design Freedom
= 30-50% Cost Savings over Die-Cast Metal
Thermal / Dimensional Stability
RIGIDITY AT ELEVATED TEMPERATURES
BMC Composites vs. Engineering Thermosets
Thermal / Dimensional Stability
BMCs offer significant acoustical insulation over
metals
Automotive valve cover
conversion from aluminum to
BMC
25% Reduction in Valve-train
noise in BMC !
Part Weight
Reduction
Part Weight
Reduction
Lower Specific-Gravity with BMC
• BMC Polyester : 1.7 – 2.05s.g.
• Die-Cast Aluminum : 2.6s.g.
• Die-Cast Zinc : 6.9s.g.
• Reduction In Assembly / Unit Weight
• Lower Raw Material Content $
• Reduction in Shipping Weight / Cost $
No Secondary Machining
• BMC Parts molded GATE
FREE. No Secondary Gate
Removal
• No material overflows
required for BMC. No
secondary trim-die
operation required
• Critical dimensions /
tolerances typically held
as-molded. No secondary
machining operations
required.
Package At Press
Tooling Friendly
BMC Polyesters are very “tooling-friendly” offering the
following advantages over metals:
• 4-5 Times Longer Mold Life
• Higher Cavitations
• Significantly lower PM & Repair Costs
• Allows for use of more complex moving actions (Slides
etc.)
• Allows for use of manifold systems for material delivery
to cavities
Greater Design Freedom
The flow characteristics and
related moldability of BMCs
allows for the formation of
more complex part
geometries.
This gives the part designer
increased freedom to:
• Incorporate the net-shapes
required to optimize the part /
assembly design
• Reduce the number of
components through
consolidation of parts
Motor Bracket Configurations
Commutator End Brackets / End Bells
Fan End Brackets
Clamshell Motors
Motor End Plates
“Cup” Style Motor Housings
Fan / Diffuser End Caps
Brush Plates
Brush Cartridge Housings
Commutator End Bracket / End Be
• Integrated Brush Box Features
• As-Molded Bearing Bore, Brush Boxes & Field
Pads
Fan End Brackets
• Integrated Airflow
Features
• As-Molded Bearing Bore
& Field Pads
• Mounting Points Suitable
for Motor Assembly
Clamshell Motor Housings
As-Molded Bearing Bore
Advantages in Small HandHeld Applications
Weight Reduction
Noise / Vibration
Reduction
Ground-Path Insulation
Motor End Plates
• As-Molded Bearing Bore
• Weight Reduction on Large Motor Configurations
“Cup” Style Motor Housings
• Reduced Number of Components in Assembly
• More Consistent Motor Alignment
• As-Molded Bearing Bore, Brush Boxes & Field Pads
• Integrated Airflow Features
Fan / Diffuser
End Caps
* Accommodates
the formation of
more complex /
efficient airflow
geometries
Brush Plates / Cartridge
Housings
Superior Properties over Thermoplastics
BMC Motor Bracket Materials
BMC Materials currently supplied into motor
bracket applications:
BMC 400
BMC 620
BMC 1412
T40-(18)
T40-(20)
T40-(25)
MCI can custom-formulate materials as-necessary to meet specific application
Case Study #1
Commutator End Bracket Conversion
Aluminum
BMC
Material Cost / Part:
$.19
$.14
Molding Cost / Part:
$.281
$.225
Secondary Gate Trimming:
$.01
-
Secondary Machining:
$.035
-
Scrap @ 3%
$.015
$.011
Total Cost / Part:
$.531
$.376
30% SAVINGS
Case Study #2
Commutator End Bell
Conversion/Redesign
Brush Boxes incorporated into BMC part as 1-Piece Design
Aluminum
BMC
Material Cost / Part:
$.08
$.133
Molding Cost / Part:
$.22
$.23
Secondary Gate Trimming:
$.01
-
Secondary Machining:
$.035
-
Scrap @ 3%
$.001
$.011
Brush Plate (2nd Part):
$.217
-
Total Cost / Part:
$.563
$.374
34% SAVINGS
Mounting Hardware for BMCs
Self-Tapping Screws
Thread-Cutting Never Thread-Forming
“BT”-Style or “Type-23” Style recommended
High-Low thread preferred
Hole diameter +.002” p/s over root-diameter of screw
Minimum thread engagement 2 ½ X screw diameter
Hole depth 125% to 150% of screw engagement depth
Mounting boss diameter minimum 2X major screw
diameter
Design Considerations for
BMC
Minimum Recommended Wall
Stock .070”
Recommended Nominal Wall
Stock .100” - .125”
Minimum draft 1-degree P/S
(Excluding Bores & Brush Boxes)
Consistency of Wall stock
Core-out Thick Sections
Wherever Possible
Fillet Radii Wherever Possible
“Line-of-Draw Features Wherever
Possible
The BMC Advantage
Faster Cycling
Longer Tooling Life
No Costly Secondary Machining
Weight Reduction
Noise Reduction
Dimensional Stability
Design Versatility
BMC offers cost
savings without
sacrifice.