Biomedical Engineering Reference
makes rapid assembly (especially by automated systems) virtually impossible. This is
not much of an issue if your device has two components, but if it contains an electronic
printed circuit board then it will have lots. The obvious thing to do is to reduce
inventory, that is, make as many components as alike as possible, for example by using
the same bolt, the same nut, and the same pneumatic fitting throughout. It is obvious
when pointed out, but is so often missed. One should also look at numbers of items. You
may have a lid held onto a box with 20 bolts; are they all required? How many do you
really need? It seems small, but each bolt has a cost and putting in the bolt may cost
even more than the bolt itself!
Another aspect is how your device goes together. Is it easy to assemble or is it difficult? Are
jigs and fixtures required? If so, design them. Can you design out the need for jig and fixtures?
If our device's method of operation depends on good assembly, then this cannot be ignored.
The second aspect is assembly at the point of use. Many of your devices will require some
assembly by the end-user; some may need complete assembly from a box of bits. Do not
forget these people are unskilled in manufacturing - have you considered their assembly
demands in your design? You must imagine yourself in their place; do not just assume it is
easy for them. This is also a really good point to get the end-users in and see if your assembly
protocol is logical.
Table 8.8: 6 σ Seven Wastes Applied to DFA
1. Waste of overproduction
Too many components?
Too many assembly tasks?
2. Waste of waiting
Too complex assembly that requires significant
Specialist operations or tooling required?
3. Waste of transporting
Too many subcontractors required?
Too many site visits required?
4. Waste of inappropriate processing
Too many operations?
Silly, ill-conceived joining methods?
5. Waste of unnecessary inventory
Too many components?
Too many variations of similar components?
6. Waste of unnecessary motion
“Fiddly” assembly methodology?
Ill-conceived assembly protocol?
Too many variations of similar looking components?
No thought of end-user assembly?
7. Waste of defects
No thought of end-user issues?
7(c) Waste of inappropriate systems
Use of confusing technology?