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DFA Evaluation Procedure
Every part must be included in the analysis such as labels,
protective caps. Reference : Lucas Engineering and Systems Page 19 of 22 S. Venkannah Factory Automation MECH 3135 The indices must be used in context with the company
resources and experience
Where large number of components are involved, it may
be convenient to sub divide the analysis into sub
assemblies. Care must then be taken during Functional
analysis as component in one sub assembly may also be
required in other sub assemblies.
The Step by Step Approach.
1. Understand the product design specification
Opportunities for automation
Product family potential
2. identify every part by number and name
3. start with a major functional item and work outwards
through the mechanical interfaces to assign every part a
4. calculate design efficiency, then ;
if the product exists continue to 5
if the product is new but > 60% continue to 5
if the design is new and the efficiency is less than
60% redesign the product before continuing Reference : Lucas Engineering and Systems Page 20 of 22 S. Venkannah Factory Automation MECH 3135 5. Determine the likely feeding method for every part and
assign an appropriate index
6. Draw the assembly sequence flowchart
7. Determine the gripping index for automated assembly
8. Allocate fitting indices
9. Allocate non assembly process indices
10. Identify areas for attention
i. Design efficiency < 60%
ii. Handling indices >1
iii. Auto feeding indices >1.5
iv. (∑feeding indices /A parts) >2.5
v. Gripping indices > 0
vi. Fitting indices >1.5
vii. (∑fitting indices /A parts) >2.5
11. Redesign using prompts from 10
12. Re-evaluate new design.
Cost of Assembly (C) ∝ Cp/Nt + Ca/Na + Cm
Now Cp ∝ Np∑(Cf + Cg+ Ci + Cfx)
Cp- Te total capital cost of the assembly system
Reference : Lucas Engineering and Systems Page 21 of 22 S. Venkannah Factory Automation MECH 3135 Nt – the total number of assemblies produced during the
life of the system
Np – The number of parts in the Assembly
Ca- the annual cost of operating the system
Na – The annual production of the system
Cm – cost of labor per assembly
Cf – the feeding cost of an individual part
Cg- the gripping cost of an individual part or sub assembly
Ci – the insertion cost of an individual part or sub
Cfx- the cost of any fixing operation Reference : Lucas Engineering and Systems Page 22 of 22...
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This document was uploaded on 03/12/2014 for the course MECHANICAL 214 at University of Manchester.
- Spring '14