The test was intended for use with applicants and incumbents for jobs where knowledge and skill in the area of CNC operation is a necessary part of job activities. Job analysis activities conducted during development of this test revealed that an applicable title is Nesting Operator as defined in the Dictionary of Occupational Titles (U.S. Department of Labor, 1991).
007.362-010 NESTING OPERATOR, NUMERICAL CONTROL (aircraft mfg.) alternate titles: computer-numerical-control nesting operator; pattern data operator.
Operates computer to lay out graphic display of parts to be machined in optimum arrangement (nest) and generate control media for numerical-control drilling, routing, and cutting machines: Reviews shop orders to determine job specifications and nesting requirements. Sorts shop orders into groups according to compatibility factors, such as quantity and shape of parts, and type, size, alloy, and gauge of material to be machined to produce nest that maximizes material utilization and minimizes machine setup and operation. Enters computer commands to retrieve stored parts data and graphic displays such as simulated patterns or templates, and displays and manipulates part images on computer screen into optimum arrangement. Calculates and codes machine controlling criteria, such as table movement, type and size of cutting and drilling tools, spindle location, and machining start point, feed rate, and speed, utilizing knowledge of numerical-control machine operation. Enters commands to title and store nest layouts in computer memory and to build and maintain source files. Keys in commands to transfer nest data, listings, or layouts to other media, such as hard copy, tape, or floppy disk, or to route nest data by direct link to direct-numerical-control machines. Loads and unloads disk packs, tapes, or floppy disks. May operate digitizing equipment to produce patterns. May discuss nesting or machining problems with machine operators or other personnel.
Norman Bleier, author of a popular text on CNC, was asked to list significant areas of job knowledge for CNC Operators. He then wrote a series of multiple-choice questions in each area. This resulted in a series of 60 questions in 7 areas as shown in Table 1 below.
CNC OPERATOR TEST
FORM CNC-2RBC (2009)
A. General Knowledge – 8
B. Coordinate Systems – 15
C. Interpolation – 9
D. Tape Code and Program Structure – 8
E. Tool Compensation – 5
F. M-Codes – 3
G. Operations – 12
Total # of Questions – 60