Definition Defect Mapping - Here is my definition

John B.

Registered Visitor
#1
Hello all.

Here is my definition of Defect Mapping: "A problem solving tool used to visually identify and track physical locations and types of defects on a product."

Does anyone use Defect Mapping? If so, how? On what kind of processes are you using Defect Mapping?

Any advice?

Gratefully,
John
 
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Miner

Forum Moderator
Staff member
Admin
#2
We use it under a different name (concentration diagram). It is useful for analyzing soldering defect (e.g., bridges) locations on a PCBA. You could also use it to study the locations of molding defects (nonfills, knit lines), casting porosity, etc.

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#4
Hello all.

Here is my definition of Defect Mapping: "A problem solving tool used to visually identify and track physical locations and types of defects on a product."

Does anyone use Defect Mapping? If so, how? On what kind of processes are you using Defect Mapping?

Any advice?

Gratefully,
John
Hello John. I am new to Elsmar Cove and was poking around and saw your post. I know it has been a long time but I thought it couldn't hurt to add my comments. Defect mapping in my experience is used heavily in industries such as paint processes, casting, weld inspections, stampings and other processes where defects are usually attribute/visual/functional and it is important to know the location as well as the type of defect. For example, in a foundry application, it would be common to keep track of how many castings are being produced with a particular defect, such as porosity or shorts (unfilled section). It is important not just to know what defect is occurring, but also where the defect is recurring over a period of time/production runs. Knowing the recurring Casting measles.png location of the defect as well as type allows a process or tooling or quality engineer to have a much better idea of what the root cause is. For example, if I map short material locations over time by marking the location of short material on an image of my part, that would lead me to how I might change my gating, injection pressure, or other process factor that would affect shorts in a specific area. Or if I map "thin" areas on parts I am painting, if I see from my defect map/concentration diagram of where thin has occurred over some time, it will give me clues as to how to adjust my paint robot pattern, nozzle angle, part orientation, etc. The value is in being able to map defects on a single image of your part (CAD image, line drawing, digital photo) and see if a pattern emerges in the type/location of defects. Below are a couple examples of defect maps. The one on the left represents an image with a grid laid over it (like a 10 x 10 grid) with counts in each grid location of the number of defects in that grid area. The larger one is more of a defect "scatter" where individual defects from many parts are mapped on a single image.

inspect trunk car conc diagram.JPG Inspect Concern Scatter screen shot.PNG
 

John Predmore

Trusted Information Resource
#5
I used a Concentration Diagram to solve my first problem for Red X certification. The die casting department had a big reject problem due to porosity. The castings had to be 100% visually inspected or else assemblies downstream would fail leak test and result in more expensive scrap. As I recall, this problem was costing them $75K/month. The engineers had spent weeks studying scrap parts, trying different settings, all in an attempt to minimize porosity voids. The voids which intersect the center bore were the biggest concern.

The Quality Engineer from the die cast department and I went through the scrap pile with a piece of graph paper, and in 10 minutes, we had prepared Diagram A on the left (I no longer have the original, so this is a re-creation). I remember our conversation, "It looks pretty random to me." Then, in a flash of genius, I suggested we turn the picture 90°. He measured the depth of the porosity voids with a ruler and a flashlight, and in 10 minutes I had prepared Diagram B. My friend looked at the picture and said "Oh my gosh, do you know what that means?" I said I could see it was not random, but I didn't know what it meant. He said the problem was the bung. I said I don't know what a bung is. He said the bung is the slug which forms where the two halves of the die cast mold come together. All the porosity was at the dividing line between the mold halves. The solution was to re-make the mold cavity and move the bung an inch higher. That way, any porosity which formed was in a non-critical area.

The morale of the story, the concentration diagram alone was not enough to see the answer, the quality engineer's knowledge of casting was not enough to solve the problem, but put those two together and we solved a $75K problem in 20 minutes. Turning a random problem on its side for a new perspective was also key to this success. I often say, "random" is more a statement of our ignorance than any useful description of the problem. I also say, if your quality people can solve a $75K problem in 20 minutes with proper tools, why would you have them do anything else?
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Last edited:
#6
John, That was a great real world case study. Not only highlighting the collaboration of individuals with different expertise working together to solve a problem, but also how having timely information presented in a meaningful way leads to a rapid determination of root cause. By the way, you left out the part of the story where you were given a large bonus based on the substantial cost savings...
 

John Predmore

Trusted Information Resource
#7
Still waiting for that bonus, but I was rewarded in other ways. This was the beginning of a 4-year career as a full-time problem solver. Most engineers will tell you they solve problems, but solving the company's problems was my full-time job for 4 years. I got good at it . I was very fortunate and learned a lot. I am pleased to share with others on Elsmar.
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#8
“It’s amazing the things you can see when you look”. Yogi Bera
Graphical visualization of the Problem is the most critical tool we have s problem solvers to detect the non-random pattern.

This diagram is also called a measles plot.

One of the first reported uses of this approach was by Dr. John Snow during a major cholera outbreak (The broad street pump).
 

Miner

Forum Moderator
Staff member
Admin
#9
“It’s amazing the things you can see when you look”. Yogi Bera
Graphical visualization of the Problem is the most critical tool we have s problem solvers to detect the non-random pattern.

This diagram is also called a measles plot.

One of the first reported uses of this approach was by Dr. John Snow during a major cholera outbreak (The broad street pump).
John Snow's map. Blue = public water pumps; Red = cholera cases

1611324074743.png [/QUOTE]
 
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