Z94.12.3 P - Manufacturing Automation & Computer Control

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PAPER TAPE. A continuous strip of paper in which holes can be punched to represent data.

PARABOLIC INTERPOLATION. A high order of interpolation producing contoured shapes by having the cutting tool travel through parabolas or portions of parabolas.

PARITY. A means of testing the accuracy of binary numbers used in transmitted, recorded, or received data. A self-checking code is used in which the total number of 1's or 0's is always even or odd.

PARITY CHECK. A computer checking method in which the total number of binary 1's (or 0's) is always even or always odd. It is either an even-parity or odd number of bit patterns to signify a character; thus, all characters are added, modulo 2, and the sum checked against a single, previously computed parity digit, i.e., a check which tests whether the number of ones in a word is odd or even. Synonymous with odd-even check and related to check, redundant and to check, forbidden combination.

PART PROGRAM. A complete set of data and instructions written in source language for computer processing or written in machine language for manual programming for the manufacturing of parts on an NC machine.

PARTS EXPLOSION. A list or drawing of all parts used in all the subassemblies of an assembly or product.

PERIPHERAL EQUIPMENT. Auxiliary machines and storage devices which may be placed under control of a central computer and used on or off line to provide a system with outside communication; for example, tape readers, high-speed printers, CRT's magnetic tape feeds, and magnetic drums or disks.

PHASE SHIFT. (1) A time difference between the input and output signals of a system. (2) A change in the phase of a periodic quantity. (3) A change in time relationship of one part of a signal waveform with another, with no change in the basic form of the signal. The degree of change varies with frequency as a signal passes through a channel.

PHOTOCELL (PHOTOELECTRIC CELL). A solid-state photosensitive electron device in which use is made of the variation of the current-voltage characteristics as a function of incident radiation.

PHOTOSENSOR. A photo-sensitive electric device incorporated in an electric circuit and used for controlling mechanical devices; also referred to as an electric eye or photocell.

PLOTTER. (1) A device which will draw a facsimile of coded data input, such as the cutter path of an NC program. (2) A visual display or board on which a dependent variable can be drawn automatically as a function of one or more variables.

POINT-TO-POINT CONTROL SYSTEM. An NC system which controls motion only to move from one point to another without exercising path control during the transition from one end point to the next.

POLAR COORDINATES. (1) A mathematical system of coordinates for locating a point in a plane by the length of the plane's radius vector and the angle the vector makes with a fixed line. (2) Either of two numbers that locate a point in a plane by its distance from a fixed point on a line and the angle this line makes with a fixed line.

POLLING. (1) Refers to an important multiprocessing method used to identify the source of interrupt requests. When several interrupts occur simultaneously, the control program makes the decision as to the one which will be serviced first. (2) Refers to a technique by which each of the terminals sharing a communications line is periodically interrogated to determine whether it requires servicing. The multiplexor or control station sends a poll which, in effect, asks the terminal selected "do you have anything to transmit." (3) A flexible, systematic, centrally-controlled method of permitting terminals on a multi-terminal line to transmit without contending for the line. The computer contacts terminals according to the order specified by the user, and each terminal contacted is invited to send messages. (4) Refers to centrally controlled method of calling a number of points to permit them to transmit information.

POSITION ANALOG UNIT (PAU). The unit which feeds analog information about the position of a machine slide to the servo amplifier for comparison with positional input information.

POSITIONING/CONTOURING SYSTEM. An NC system that is able to contour in two axes, without buffer storage, and position in a third axis for operations such as drilling, tapping, and boring.

POSITION SENSOR. A device used in measuring a position and converting the measurement into a form which facilitates transmission.

POSTPROCESSOR. 1. A computer program that takes a generalized or centerline output and adapts it to the particular machine control unit/machine tool combination that will machine the part. 2. Refers to a set of computer instructions which transform tool centerline data into machine motion commands using the proper tape code and format required by a specific machine control system. Instructions such as feed rate calculations, spindle speed calculations, and auxiliary function commands may be included.

PRECISION. The degree of exactness with which a quantity is stated. Contrasted with accuracy; for example, a quantity expressed with 10 decimal digits of precision may have only one digit of accuracy.

PRESET TOOL. A cutting tool placed in a holder so that a predetermined geometrical relationship exists with a gage point.

PRINTED CIRCUIT. (1) A circuit in which interconnecting wires have been replaced by conductive strips printed, etched, etc., onto an insulating board. It may also include similarly formed components on the baseboard. (2) Refers to resistors, capacitors, diodes, transistors and other circuit elements which are mounted on cards and interconnected by conductor deposits. These special cards are treated with light-sensitive emulsion and exposed. The light thus fixes the areas to be retained and an acid bath eats away those portions which are designed to be destroyed. The base is usually a copper clad card.

PRINTED CIRCUIT BOARD. A board on which a predetermined conductive pattern, which may or may not include printed components, has been formed.

PRINTER. An output device that prints or types characters from parallel or serial entry.

PRINTOUT. A printed output of a system giving all data that has been processed by a program.

PROCESS CONTROL. (1) Automatic control of industrial processes in which continuous material or energy is produced. (2) Pertaining to systems whose purpose is to provide automation of continuous operations. This is contrasted with numerical control, which provides automation of discrete operations.

PRODUCTION. (1) The manufacturing of goods. (2) The act of changing the shape, composition or combination of materials, parts, or subassemblies to increase their value. (3) The quantity of goods produced.

PRODUCTIVITY. The quality or state of being productive. As applied to manufacturing, it means the measured output of goods from a productive facility relative to some standard, norm, or potential maximum.

PROGRAM. (1) The plan or procedure for the operation of a machine or process especially when the machine is a computer. (2) A set of instructions arranged in proper sequence to cause the desired operations.

PROGRAMMABLE CONTROLLER (PC). A solid-state control system which has a user programmable memory for storage of instructions to implement specific functions such as: I/O control logic, timing, counting, arithmetic, and data manipulation. A PC consists of central processor, input/output interface memory, and programming device which typically uses relay-equipment symbols. A PC is purposely designed as an industrial control system which can perform functions equivalent to a relay panel or wired solid state logic control system.

PROM. (1) Programmable read-only memory is generally any type which is not recorded during its fabrication but which requires a physical operation to program it. Some PROMs can be erased and reprogrammed through special physical processes. (2) A semiconductor diode array which is programmed by fusing or burning out diode junctions.

PROPORTIONAL CONTROL ACTION. Refers to designed control action in which there is a continuous linear relation between the output and the input. Such a condition applies when both the output and the input are within their normal operating ranges and when an operation is at a frequency below a limiting value.

PROTOCOL. A former agreement between two communicating devices. It defines how data is formatted what the control signals mean, how error checking is performed, and the order and priority of various types of messages.

PUNCH TAPE. An input/output medium in the form of punched holes along a continuous strip of nonmagnetic tape. The tape is used to record and store data and/or programs and/or job control statements (Syn: perforated tape).

PUNCHED CARD. (1) A card of constant size and shape on which information is represented by holes in specific positions. (2) A piece of lightweight cardboard on which information is represented by holes punched in specific positions.

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