Computer Innards for Beginners

Against the Current, No 6, January/February 1987

Art Myatt

IN CASE the sudden appearance of the term “computer” is surprising, a brief ex­ planation is in order.

The common idea is that computers are easily recognizable. When you see a desk top containing a keyboard, some type of tv screen, a box with a slot or two for disks to go in, and maybe a printer, those elements appear to be obviously a computer. But these things are only input and output devices for the computer.

At the heart of the computer is microchip circuitry. The microchips and associated circuitry are the computer. They might be built into the keyboard, or into another box on the desk. They could be in another room, another building, or another city, in which case you are probably looking at a dumb terminal and not an independent machine.

The computer in a machine tool can be buried in the case, protected from the oil and dirt of the shop. The devices that input data to it can be sensors for torque on the spindle, clamping force on the workpiece, a number of directions of motion of the workpiece and the tool, and whatever other aspects of the machine’s operation can be detected.

To give an idea of the degree of sophistication these monitoring and feedback functions have reached, we can look at some recent work done in this field by the National Bureau of Standards.

They have demonstrated that -the flow of coolant in a metal-cutting operation can be used as a coupling medium between the part being cut and an ultrasonic transducer located in the coolant nozzle. The transducer sends out the ultrasonic signal and detects the backscattered ultrasonic energy. Microchips then interpret the backscattered signal to read the surface roughness of the part in process.

Surface roughness is not only a part specification; it can now be used as another way to monitor the condition of the cutting tool. (American Machinist and Automated Manufacturing, p. 37, April 1986)

There is no need for a keyboard if no input from the operator of the machine is desired. One button to start operations and one to stop (just like a non-computerized machine) will suffice.

For output devices, the computer can control the motion of the workpiece and the motion of the tool. No screen or printer is needed if the machine operator is not going to be given any information. Maybe the computer can set off a buzzer when it is time for the worker to exchange the finished part for one to be worked on, and a bell when the tool is dull or broken. The device that loads programs into the computer can be detachable, or simply located elsewhere and connected by a long wire.

January-February 1987, ATC 6

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