3.2 SOME DETAILS
• The GT code is made up of a string of digits which identify specific attributes of a part.
• If the digits of a GT code are unrelated, it is a polycode, and each digit may be looked up independently.
• If the digits of a GT code are related, it is a monocode, and they must be looked up in sequence.
• It is possible to have a hybrid GT code which is a combination of polycode and monocode.
• When selecting what the GT digits represent, the guidelines are,
• They must differentiate products
• Must represent non-trivial features
• Only critical features should be encoded
• Function should be encoded
• Every digit should be significant
• Parts can be encoded using
- process flow
- tool axis
- tolerance
- function
- material
- shape.
3.2.1 Optiz Code
• One example system is the popular Opitz code, developed in a German university by H.Opitz.
• This code uses a sequence of 5 digits, 4 digits, and 4 letters, such as ‘11223 4455 ADEA’
- The first five digits are the form code (identify shape). See the table for form codes.
- The next four digits are the supplementary code - used to represent non-form details such as tolerances, materials, etc.
- The last four letters are the secondary code, used to represent production operation types, sequences, or other functions chosen by the manufacturer.
• The Opitz code for a part is constructed from the first digit on, as shown in the tables below.
3.2.2 Decision Tree
• Decision trees are developed to be specific to typical product line, or manufacturing facility.
• To develop one of these trees we draw a tree that shows alternate possibilities for a part, and then number the options (care must be used to leave options not anticipated).
• Part of an example decision tree is given below. This can be expanded as it applies to a particular manufacturer or industry.
