DRAGON INNOVATION, INC.

DESIGN  FOR  MANUFACTURING  (AND  ASSEMBLY)  

COURSE 11: DESIGN FOR MANUAL ASSEMBLYPART 2: BOOTHROYD DEWHURST METHOD

SCOTT N. MILLER | CEO | @DRAGONINNOVATE | WWW.DRAGONINNOVATION.COM

Recommended References

Tutorial: www.dfma.com/support/tutorials.htm

BD Method

•Product cost is directly related to assembly time.

•Assembly time and quality are driven by the number of parts and their ease of assembly.

•BD Method involves analyzing part count and geometry to calculate theoretical assembly time which is compared to the minimum theoretical assembly time to determine design efficiency.

-Method can provide key insights into ways to reduce part count and improve part intelligence.

BD Overview

Factors Affecting Assembly Cost

• Number of Parts

• Ease of:

– Handling

– Insertion

– Fastening

Boothroyd-Dewhurst Method

• Design Product

• Create Assembly Matrix

– Handling: Size, Weight, Orientation

– Insertion: Alignment & Securing Method

• Calculate Theoretical Assembly Time (TAT)

• Calculate Design Efficiency Index: 3s*Min_Parts / TAT

- Iterate to Improve Design

Symmetry: Align & Orient

• Alpha (Align): Max angle the part must be rotated perpendicular to axis of insertion (i.e. “end-for-end”) to repeat its orientation.

• Beta (Orient): Max angle part must be rotated about axis of insertion to repeat its orientation.

- Total Angle of Symmetry = Alpha + Beta

Additional Definitions

• Thickness:

• Length of shortest side of bounding box.

• For (Cylinder or regular polygon > 4 sides) and (D<L), Thickness = enclosing Radius.

- Size: Length of longest side of bounding box.

Ref: Product Design for Manufacture and Assembly, Geoffrey Boothroyd, Peter Dewhurst and Winston A. Knight.

Symmetry Examples

Ref: Product Design for Manufacture and Assembly, Geoffrey Boothroyd, Peter Dewhurst and Winston A. Knight.

Manual Handling

Ref: Product Design for Manufacture and Assembly, Geoffrey Boothroyd, Peter Dewhurst and Winston A. Knight.

Manual Insertion

Ref: Product Design for Manufacture and Assembly, Geoffrey Boothroyd, Peter Dewhurst and Winston A. Knight.

Example

Ref: Product Design for Manufacture and Assembly, Geoffrey Boothroyd, Peter Dewhurst and Winston A. Knight.

Improved DFA

Ref: Product Design for Manufacture and Assembly, Geoffrey Boothroyd, Peter Dewhurst and Winston A. Knight.

dragon@dragoninnovation.com

Full Manual Insertion Table

Ref: Product Design for Manufacture and Assembly, Geoffrey Boothroyd, Peter Dewhurst and Winston A. Knight.