COMPUTER NUMERICAL CONTROL MACHINES
CHAPTER LEARNING OBJECTIVES
Upon completing this chapter, you should be familiar with the following:
Set up CNC lathes and milling machines.
Develop CNC lathe and milling machine programs using CAD/CAM.
As the hardware of an advanced technology
NC MACHINE SAFETY
becomes more complex, new approaches to the
All safety rules that apply to conventional machine
processing of materials into useful products come into
tools also apply to NC machines. Always wear
common use. This has been the trend in machining
appropriate eye protection. Remove all rings, bracelets,
processes in recent years. Parallel development in other
watches, necklaces, and loose clothing that may be
technologies such as electronics and computers have
caught by moving or rotating equipment. Always wear
made available to the machine tool designer methods
and processes that can permit a machine tool to far
Always keep the work area around the machine
exceed the capabilities of the most experienced
clean and clear of obstructions. Do not use compressed
machinist. To state it very simply, the MR rate has gone
air to clean the machine or the area around it; chips can
from the horse and buggy days to the space shuttle days
become dangerous missiles. Never use machine
surfaces as worktables. Use proper lifting methods to
This chapter will give you some information on the
handle heavy workpieces. Take measurements only
impact numerical control (NC) has had in the field of
after the spindle has come to a complete stop. Never
machining. It is only an overview and cannot be
handle chips with your bare hands.
expected to take the place of a programming manual for
Before you start the machine, make sure the
a specific machine, on-the-job training, or MR "C"
work-holding device and the workpiece are securely
fastened. When changing cutting tools, protect the
With the development of NC, a variety of input
workpiece from damage, and protect your hands from
media has been used to convey the information from the
sharp cutting edges. Make sure cutting tools are
print to the machine. The most common types of input
media used in the past were magnetic tape, punched
Do not operate any machine controls unless you
cards, and punched tape. However, most of the new
understand their function. All NC machines have
machines are controlled by computers. All of the
electrical compartments; keep the doors closed to keep
machines on board Navy intermediate maintenance
out dirt and chips. Only authorized technicians should
activities (IMAs) are computer numerical control
perform maintenance or repairs in these compartments.
To avoid damage to the machine or workpiece,
There are many advantages to using NC machines.
check the tool path by making a dry run through the
The greatest advantage in NC machining comes from
program; that is, let the machine make all the
the unerring and rapid positioning movements possible.
positioning and cutting moves without a cutting tool
An NC machine does not stop at the end of a cut to plan
its next move. It does not get fatigued and is capable of
uninterrupted machining, error free, hour after hour. In
Above all, follow all safety precautions posted on
the past, NC machines were used for mass production.
the machine and any listed in Navy Occupational Safety
With the introduction of CNC, a qualified machinist can
and Health (NAVOSH) Program Manual for Forces
program and produce even a single part economically.
Afloat, OPNAV Instruction 5100.19B.