Mistake Proofing and Poka Yoke

Quality Series

© 2009 Factory Strategies Group LLC. All rights reserved.

Outline

• • • • • • What is Mistake Proofing?

Everyday Examples Effectiveness & ROI Error Proofing and SPC Inspection Techniques Types of Poka Yokes 2

Everyday Examples

3.5 inch diskettes cannot be inserted unless diskette is oriented correctly. This is as far as a disk can be inserted upside-down. The beveled corner of the diskette along with the fact that the diskette is not square, prohibit incorrect orientation. Fueling area of car has three error-proofing devices: 1. insert keeps leaded-fuel nozzle from being inserted 2. tether does not allow loss of gas cap 3. gas cap has ratchet to signal proper tightness and prevent overtightening.

New lawn mowers are required to have a safety bar on the handle that must be pulled back in order to start the engine. If you let go of the safety bar, the mower blade stops in 3 seconds or less. 3

Poka yoke & SPC

Successive checks or Self-checks Source Inspection X-bar chart (measurement data)

use to sort out defects, will not improve the process use as corrective action for special causes

p-chart (attribute data)

special case of np chart, ad hoc design, will also sort out defects use to eliminate specific types of defects 4

Individually, mistakes are rare

• Task Type • ▫ ▫ ▫ ▫ Detection of deviation or inspection Alpha input per character Numeric input per character Assembly per task element As a group they are common Probability 0.07

0.008

0.003

0.00007

▫ ▫ ▫ ▫ ▫ ▫ Research study #1 (Harris) Research study #2 (Rook) Research study #3 (Voegtlen) Research study #4 (Headlamps) NASA mishaps FAA Maintenance problems Data from “Human Reliability Data - The State of the Art and the Possibilities” Jeremy C. Williams, 1989 CEGB >0.80

0.82

0.60

>0.70

>0.50

>0.94

5