Part Design and Rapid Prototyping for BMC

1
Part Design and Rapid Prototyping for BMC
Reducing the Time to Market for New BMC
Applications
2
Part Design Guidelines for BMCs
3
Design Considerations for BMCs

• Design to optimize inherent properties of
  material
• Use structure as-opposed to mass wherever
  possible
• Keep Line-of-draw in mind to minimize reduce
  or eliminate undercuts and/or trapped steel
  conditions in mold
• Add molding draft based on line-of draw to
  insure minimum wall sections are maintained

4
Wall Stock for BMCs

• Maintain nominal wall stock as consistently as
  possible.
• Use structure wherever possible to increase
  directional strength and/or combine part features

5
Wall Stock for BMCs
Wall Stock Recommendations

• Minimum recommended wall stock 2mm
• Thicker nominal walls required for larger parts
  with extended flow lengths
• Wall stock for small parts can be as low as .5mm
• Dependent on part configuration and material
  selection

6
Wall Stock for BMCs
Parts with Varying Wall Stock
Parts with significant variances in wall stock
can be successfully molded in BMC.

• Avoid multiple thick-to-thin transitions
• Avoid thin-to thick gate placement
• Minimize or eliminate wall stock variations near
  dimensionally critical features

7
Molding Draft
Draft Angle or taper added to vertical surfaces
on a part to allow for release from mold during
ejection.

• Line-of-draw draft angle required on all
  vertical part surfaces
• Minimum recommended draft 1-degree P/S
• The more draft the better!
• Add draft where possible to small vertical walls
• Linear distance vs. angular draft
• Draft vs. tolerances ( draft / - draft)

8
Molding Draft
No-draft Requirements

• Can be successfully molded on BMC
• Eliminates secondary machining
• Commonly used for bearing bores brush-box
  applications.
• Use only where necessary
• Minimal length-of-draw
• Ejector pins surfaces adjacent to feature

9
Undercut Features in BMC Part Designs

• Common in todays BMC part designs
• Complex shapes not a problem
• Multiple undercuts common
• Tooling technology capable
• Linear or rotary (unscrewing)
• Avoid trapped steel conditions
• Consolidate multiple undercuts where possible
  into same line-of-draw

10
Fillet Radii
Blend intersections with fillet radii wherever
possible.

• Increases part strength
• Improves material flow
• Mold construction benefits
• Mold integrity / maintenance benefits

11
Molded In Inserts

• Injection, transfer or compression process
  capable
• Configuration dependent
• Large inserts my require pre-heating

Commonly utilized in automotive and electrical
switch-gear applications
12
Mounting Hardware for BMCs
BMCs are hardware-friendly materials that are
capable of accepting a number of common types of
mounting hardware
13
Mounting Hardware for BMCs
Self-Tapping Screws

• Widely used method of mounting to BMC
• BT-style thread cutting screws recommended
• Thread-forming screws not recommended
• High torque values
• Excellent torque retention

14
Mounting Hardware for BMCs
Mounting Boss Sizing for Self-Tapping Screws

• Wall stock (not boss diameter) to be a minimum
  of 1 1/2-times the screw diameter

• Thread engagement to be a minimum of 2 1/2-times
  the screw diameter
• Pilot hole to be .002 P/S larger than
  root-diameter of screw
• Minimal draft in mounting holes
• Blind holes to be 25 deeper than installed
  screw engagement

15
Mounting Hardware for BMCs
Rivets

• Commonly used to attach non-stressed components
  onto BMC parts
• Used in assembly of household circuit breaker
  housings

• Refer to hardware manufacturers recommendations
  for mounting geometry

16
Mounting Hardware for BMCs
Insert-Molded Secondary-Installed Threaded
Inserts
Commonly used in BMC applications where service
or installation requires multiple assembly /
disassembly

• Insert-molded
• Secondary installation
• Excellent retention in BMCs

Refer to hardware manufacturers specifications
for hole sizing application-specific
information
17
Snap Features in BMC Part Designs
Given the range of flex modulus achievable in
BMCs, snap details are possible provided that
they can be designed with an interference that
can operate within the flex-range of the material
grade selected. Feel free to contact BMCIs
Technical Group if you have a proposed snap
design and would like to review it for
feasibility in BMC.
18
Direct Conversion from Metal Design

• Common in BMC
• Configuration dependent
• May require design modifications to accommodate
  molding of features previously formed by
  secondary machining operations
• Significant savings potential associated with
  elimination of costly secondary machining
  operations

19
Direct Conversion from Metal Design
Vacuum Gearbox Housing

• Direct conversion from metal
• Eliminated nine-(9) secondary machining
  operations
• Implementing as running change
• Minimal design changes
• Annual volume 600K
• Annual savings 690K

20
Part Consolidation Through Conversion
21
Part Consolidation Through Conversion

• Incorporation of multiple part features into one
  design
• Part count reduction
• Lower assembly tooling costs
• Reduced assembly labor
• Elimination of secondary machining operations
• Overall lower assembly cost

22
Surface Finishes Appearance Treatments
As Molded Finishes

• High gloss
• Satin
• Textured
• Colors
• Faux finishes (as molded)
• Paintable
• Platable

23
Rapid Prototyping for BMC Materials
From Art to Part
24
Rapid Prototyping for BMC Materials
Overview The ability to quickly provide
customers with prototype parts in our materials
has proven to be both a valuable sales tool, and
an effective method of shrinking product
development lead times. Since BMC thermosets do
not lend themselves to traditional Rapid
Prototyping processes such as SLA (Stereo
Lithography) of SLS (Selective Laser Sintering),
we have developed our own prototyping process for
providing net-shapes to our customers for
evaluation.
25
Rapid Prototyping for BMC Materials
Process Our process first involves the
pre-molding of plaques, or blocks of the BMC
formulation selected for the application. These
Billets of material are then laminated together
using epoxy adhesives, or parent resin to form a
Blank that is roughly the size and shape of the
part. Lastly, the blank is 3D machined in our
mold shop from the customer part file to produce
a net-shape prototype part. We have used this
process to produce parts as small as a plumbing
fitting, and as large as a stove top frame.
26
Rapid Prototyping for BMC Materials
BMCI In-House Tooling / Prototyping

• Part / product design assistance
• Mold design
• Prototype / production tooling
• Prototype part construction
• Tooling conversion for BMC materials

27
Rapid Prototyping for BMC Materials
BMCI In-House Tooling / Prototyping
Contact Information
Mark Bieberstein Technical Sales Engineer (630)
377-1065 [phone] Mark_B_at_Bulkmolding.com