Page 605 - Sensors and Control Systems in Manufacturing

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Cha p te r
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load a workpiece precisely on a pallet or install limit switches and
other sensors to identify the workpiece and check its position. Since
location need not be precise, sensors in robot loading will be easier to
arrange. The force sensors will optimize the cutting speed whatever
the material, and for a robot, will ensure that a component is installed
with the correct amount of force. The use of such sensors and control
systems will allow planning of manufacturing operations to be auto-
mated, with such programming as is needed done off-line.
A lathe or milling machine would be equipped with adaptive
sensors and control systems on the spindle, to adjust the speed for
turning, drilling, tapping, and milling. In that case, the vision sensors
would be used to identify the workpiece for the robot. Lathes and
milling machines can already be programmed off-line, and with
vision sensors, the robot could be programmed in the same way, with
the sensors adjusting the position and size of the gripper or changing
the gripper to suit the workpiece. Also, the controller could assess
whether a new set of chuck jaws is needed, and if so, instruct the
robot to change it. Thus, without the need for in-line programming
and adaptive control the lathe or milling machine would be able to
machine a wide variety of components completely unmanned.
Just as the productivity of lathes and milling machines has
improved, quantitatively and qualitatively, so other machines can be
improved through sensors and control systems. For example, several
machining centers have an extra attachment to allow machining of
the fifth face, whereas some machines made by Mandelli Machine
Tool, Italy, can machine the fifth face without the need for an attach-
ment. This is a worthwhile development, since it reduces downtime.
With the introduction of modular universal machining centers for
turning, milling, boring, and grinding operations, manufacturers will
encourage more moves in this direction. In some cases, handling
equipment to permit the fifth face to be machined without the need
for a full resetting operation is also likely to come into use, as are the
laser welding and laser sensor measurement systems on the machine
tool itself.
But the major developments will continue to come in sensors and
control systems, computers, and software. In the next stage, the com-
puter at each flexible manufacturing system might have access to an
“expert” system, which is in effect a huge database. Included in the
database are data concerning all the components to be produced—
input from the CAD system—such as machining methods for differ-
ent speeds, surface finishes, and tolerances. In fact, the database will
be a complete encyclopedia of machining. This will be updated con-
tinually and directly from the CAD system and from a remote data-
base on machining (Fig. 11.10).
Once sensors and control systems are perfected, this will allow
machining to be performed without programming. When the work-
piece is fed into the system, a vision sensor will identify it in detail.