Visual Inspection: Can Visual Inspectors be Evaluated?

C

cortiz01

#1
Hello everybody!
My question is if someone knows a method to check if visual inspectors are ok to do the job or not. In my plant we have a lot of people checking visually and we still have defects detected after this inspection, I know 100% visual inspection is not 100% effective, but I would like to know which inspector is better than other...:thanx:
 
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Coury Ferguson

Moderator here to help
Staff member
Super Moderator
#2
First, you need to verify their competency, second, if they are color blind, third, that they have reasonable vision acuity to a known standard.

That would be the first three things that I would evaluate them on, in my opinion.
 
S

silly girl

#3
Couldn't you do a measurement system evaluation? I am no statistician, and it probably depends on but I think the process is something like this:

  • Take a random selection of parts from production
  • Have each inspector inspect each part at least twice (making sure they don't know they are re-inspecting the same part)
  • Assess the variation between inspectors and within inspectors

Hmmm well, anyway I don't know if this could work for attribute inspection... perhaps a statistician will reply.

Silly Girl
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#4
use a Kappa test with known good and bad units. % of bad should equal the current defect rate.
The Kappa will test both the inspectors repeatability within themselves and between other inspectors.
I use it to qualify new inspectors, new inspections or inspection criteria and and as a recheck on an annual or semiannual basis (like a calibration of a gage. in fact I put the inspectors in the calibration system so I have the reminder and the record...)
I have attached a spreadsheet that I use for the math - it's not simple. also there is a good article on this at:

http://www.asq.org/pub/qualityprogress/past/1995/may.html

"When Quality is a Matter of Taste, Use Reliability Indexes" by David Futrell

you have to be an ASQ member to view the article I think...
 

Attachments

Miner

Forum Moderator
Staff member
Admin
#5
Excellent suggestion!

Kappa is a specific type of Attribute MSA. Any of the Attribute MSAs shown in the AIAG MSA manual would be suitable, but the Kappa analysis would be my recommendation also.
 
D

David Hartman

#7
The Third Edition of Juran's Quality Control Handbook defines a method for measuring an Inspector's accuracy (evolved in 1928 by J.M. Juran and C.A. Melsheimer).

I have used this method in the past for what we referred to as Inspector Effectiveness Audits. Perhaps it might be of use to you.
 

Helmut Jilling

Auditor / Consultant
#8
I use reading glasses, as many 50 somethings do. When I audit an older guy (like me), I sometimes ask them to read some small print to me (a control plan or drawing) to see if they read read small print. If they reach for reading glasses, I ask how they can see small visual defects, and we evaluate the audit trail from there.

It is a common oversight. Color blindness is a problem as well.

PS: the website www.4readers.com sells bifocal reading glasses which are full size and suitable for low impact safety glasses. Best part is they are $6.95!
 

gard2372

Quite Involved in Discussions
#9
Hello everybody!
My question is if someone knows a method to check if visual inspectors are ok to do the job or not. In my plant we have a lot of people checking visually and we still have defects detected after this inspection, I know 100% visual inspection is not 100% effective, but I would like to know which inspector is better than other...:thanx:
Cortiz,

Please refer to this link it may help.

http://Elsmar.com/Forums/showthread.php?t=16929

Even a common visual inspection has a certification in NDT (Non-Destructive Testing). I have attached a link to a Q&A article on the Jager Eye Tests we had to perform annually.

http://www.asnt.org


A Certified Level III NDT can train and certify personnel to the Level I or II for VT Visual Testing if you situation warrants it.

Here are a few more links with Visual Testing Certification and Requirements. I found this website at the beginning of my NDT training several years ago when I was an inspector and it helped me to understand many aspects of inspection I would not have otherwise thought of.

Visual and Optical Testing (VT)
Visual inspection involves using an inspector's eyes to look for defects. The inspector may also use special tools such as magnifying glasses, mirrors, or borescopes to gain access and more closely inspect the subject area. Visual examiners follow procedures that range from simple to very complex.

(Source NDT Resource Center © Copyright 2001 Iowa State University
All rights reserved)

http://www.ndt-ed.org/
 
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