Quality Control

The function of quality control is to monitor specific project results to ensure that the results match the standards that were set for the project. The quality control function utilizes a number of techniques to accomplish this. Many of these tools and techniques are rooted in the concepts of probability and statistics.

Figure 4-2. Deming's fourteen points.

• Constancy of purpose

• Drive out fear

• Adopt a new

• Break down barriers


• Eliminate need for

• Eliminate slogans,


targets, and the like

• Only consider total

• Eliminate management

cost, not price

by standards and quotas

• Improve constantly

• Remove barriers to

pride of workmanship

• Initiate OJT

• Institute education

and self-improvement

• Initiate leadership

• Get everyone involved

Many times statistical methods are used in project quality control. These techniques can improve the performance of those involved in quality control by allowing less than 100 percent inspection of all of the products produced.

As a result of a good quality control program recommended corrective and preventive actions will be generated as well as recommendations for the repair of defects and inspection methods for the later repaired defect.


Inspection is carried out by the observation of attributes or measurements. An item that is supposed to be a certain size can be measured directly, and the data regarding its dimensional size can be collected. All items accepted will be within the acceptable allowed tolerance on the item.

Items may also be inspected by attribute. In this technique the item to be inspected is made to fit or not fit into a specially designed gauge or special measuring device. If the part fits into the ''Go'' gauge and does not fit into the ''No Go'' gauge, then the part is acceptable. If the part does not fit into the ''Go'' gauge or fits into the ''No Go'' gauge, the part is considered to be bad. All attribute inspections have a yes or no outcome.

Attribute sampling has several advantages over measurement methods. In attribute sampling the inspection is fast and cheap, and there is little room for mistakes on the part of the inspector. Measurements take a certain amount of skill and concentration. As such, measurements are prone to human errors stemming from fatigue and boredom.

For example, suppose a motor shaft has a design tolerance of 1.5 inches and an allowable tolerance of plus or minus .015 inches for its diameter. This means that an acceptable part will have to be between 1.515 and 1.485 inches.

To test this attribute, a gauge is constructed with a hole that has a diameter of exactly 1.515 inches. This is a ''Go'' gauge. Parts that have a diameter of less than 1.515 inches will fit into this gauge, and those that are larger than 1.515 inches will not fit.

Another gauge is constructed with a hole of 1.485 inches in diameter. Parts that fit into this gauge will be unacceptable, since their diameter is less than 1.485 inches. This is the ''No Go'' gauge.

The inspection of shafts is quick, easy, and nearly foolproof. A part is taken and first applied to the ''Go'' gauge. If it passes this gauge, it is immediately put into the ''No Go'' gauge. If it fails to fit this gauge, it is an acceptable part.

Was this article helpful?

0 0
Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

Get My Free Ebook

Post a comment