8 GD&T: Application and Interpretation Copyright Goodheart-Willcox Co., Inc. This helps develop a positive attitude among those who must produce the parts. The most important advantage for involving people from various disciplines is that part cost will be reduced. The design will be producible, machine programming will be made easier through better applied dimensions, tool design will be facilitated because of better specifi cation of functional relation- ships between features, and inspection will be better directed because of a clearer understanding of part requirements. These are only a few of the benefi ts that can be realized by designing through teamwork. Sometimes, it is tempting to complete a design through an individual effort. The temptation is probably caused by an apparent increase in effi - ciency during the design process. However, this apparent improvement in effi ciency may be mis- leading, especially when considering the time spent on changes that may occur after production has started. Changes may be necessary because of errors and oversights that an individual can make when working alone. It is important to stress that working with a design team does not always reduce effi ciency. A design team can work together and be effi cient. Effi ciency can be achieved through close cooperation and a willingness to achieve a common goal. A close-working team will be effi cient when compared to one individual trying to defi ne all the design attributes without the involvement of subject matter experts. Professions and Trades Affected by Dimensions Designers and design engineers are obviously affected by dimensions and tolerances because they must apply these requirements on the product defi - nition, whether on model geometry or in a draw- ing. A thorough knowledge of standard practices is required to make sure the information shown on the product defi nition conveys what is actually intended. Careless or uninformed application of toler- ances can result in part requirements that are overly restrictive, thus forcing the part cost to increase. Incorrect application of tolerances can also result in inadequate control, resulting in parts that will not assemble or will not function properly. A complete understanding of how to apply tolerances enables the design requirements to be applied in a clear manner, with meanings that are supported by one or more national standards. This is important no matter where parts are to be produced. Manufacturing engineers and machine planners are often the people who decide how parts are to be produced. They must review the product defi nition and make decisions based on the shown tolerances. The dimensioning and tolerancing knowledge of the manufacturing engineer can have a signifi cant impact on whether or not parts are made effi ciently and correctly. Inadequate knowledge can result in an overly cautious approach therefore, processes that are more accurate than needed might be used. This increases the product cost. Inadequate knowledge can also result in requirements that do not receive enough attention during fabrication, and the pro- duced parts may therefore not meet requirements. Machinists and machine programmers create the computer programs and operate the equipment that produces the parts. These are the people who produce a real part from the information communi- cated on a model or a drawing. If they understand the requirements, they can produce the parts with the greatest amount of effi ciency. If they do not understand the requirements, there is little chance of obtaining functional parts at the lowest possible cost. Misunderstood or missing requirements can result in either excessive or inadequate care in the completion of fabrication steps. Inspectors verify that parts are produced in compliance with specifi ed requirements, including dimensions and tolerances. If inspectors have a good understanding of dimensioning and tolerancing principles, they will accept good parts (those within allowable tolerances) and reject bad ones. Tool designers design the jigs, fi xtures, and other machining tools that are required to produce parts. Proper understanding of the dimensions and tolerances is required to correctly design the tools. Tolerance specifi cations often dictate how a part must be located in a machining tool. If the tool designer does not understand the product tolerances, incorrect location methods might be designed into the machining tool. This could result in ruining all parts produced with the tool. Correct understanding of the requirements improves the chances that the tool design will be correct. Fabrication of a good-quality product depends on a knowledgeable team. It is important that all peo- ple involved in the design and fabrication process work together to develop a full understanding of the standard practices. A knowledgeable team can pro- duce a product of which they can be proud. Knowledge of standard principles and careful application of that knowledge can also reduce the risks of product liability. Product liability should be a concern to all who work on a design or its pro- duction. Individuals as well as their companies are sometimes held responsible for errors.