Achieving Zero Defects

There are numerous names for it throughout the Engineering and Quality communities. Sometimes the names and meanings of these different chosen names become blurred.

When it comes down to it however, the intent and details of these methodologies transcend any chosen names for them. This blog will discuss the “basic” approaches to preventing defects from getting to your customer, regardless of whether the “customer” is the end user or the next step in your internal process.

In very simple terms a defect is typically the result of making an error during the process.

ERROR = DEFECT in this example.

ERROR FOCUS (PREVENTION)

If we can eliminate or greatly reduce the possibility of making an error we reduce or eliminate the chance of producing or passing on a defect to our customer.

There are a number of tools/ techniques available to eliminate or reduce the possibility of making an error. Examples are plentiful in numerous books on the topic. Here is a small sample of some of these:

• Assembly fixtures with pins in the holes that do not get items placed into them to prevent the Technician from placing components in the wrong locations.
• Modifications of tooling so it does not fit into or onto a part if it is not oriented correctly.
• Modification of part geometry so that it does not fit into a mating part improperly (example would be the old floppy disks with the beveled corner that prevent reversed insertion)
• Amplification of human senses to reduce the chance of making an error such as larger dial faces, lights, alarms, etc…  

DEFECT FOCUS (DETECTION)

If a process cannot be made to completely prevent an error (resulting in a defect) we have a number of other approaches that can prevent these from getting to our customers.

a)      Control Technique – (at the time it is produced)

–         Examples of “control type” approaches would be once a defect was produced the device/ machine/  jig would lock the part in place so that it cannot be processed further (preventing downstream customer contamination).

–         Another example of a “control type” device would be once a defect is produced a “lockbox or containment box” would require a part to be placed into it before processing could resume. There are many great sensor and vision machine applications for this.

b)      Warning Technique – (at the time it is produced)

–         Examples of “warning type” approaches would be when a defect is produced and a light or alarm is sounded that requires someone to capture and remove it from downstream contamination.

c)      Another approach though not as effective as there is some waste that takes place and risk which is “downstream detection technique” utilizing the same above techniques of “control” and “warning”.

–         Examples of this type of approach might be an assembly line track or feeder mechanism that inspects a characteristic (example – outside diameter of a bushing/ shaft/ etc… or presence of a welded component) through contact or non-contact techniques and vision systems.

Again, the intent of this blog article is not to give examples of all types of devices on the market (there are many), but to illustrate the different “basic” approaches”.

Obviously prevention is much better than detection as with detection we have already produced a defect which means we now have risk of contamination (downstream or at the end user) and costs associated with it (rework, scrap, repair). Both of these are forms of waste.

Here is to prevention and keeping our customers happy and us in business.

Mark