Chapter 38

Brandon Alcaraz
Flashcards by Brandon Alcaraz, updated more than 1 year ago
Brandon Alcaraz
Created by Brandon Alcaraz over 8 years ago
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ISE 2500 Flashcards on Chapter 38, created by Brandon Alcaraz on 04/29/2013.

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Question Answer
What are some of the advantages of using electrical power in an automated system? Advantages listed in the text are (1) it is widely available, (2) it can be readily converted to other forms of power such as mechanical, (3) it can be used at lower power levels for signal processing, communication, and data storage, and (4) it can be stored in long-life batteries.
What is the difference between a closed-loop control system and an open-loop control system? The difference is that a closed-loop control system includes feedback of data related to the output of the process that is used to make control adjustments. An open-loop system does not have this feedback loop.
What is the difference between fixed automation and programmable automation? In fixed automation, the processing or assembly steps and their sequence are fixed by the equipment configuration. The program of instructions is determined by the equipment design and cannot be easily changed. In programmable automation, the equipment is designed with the capability to change the program of instructions to allow production of different parts or products.
What is a sensor? A sensor is a device that converts a physical stimulus or variable of interest (e.g., temperature, force, pressure, or other characteristic of the process) into a more convenient physical form (e.g., electrical voltage) for the purpose of measuring the variable. The conversion allows the variable to be interpreted as a quantitative value.
What is an actuator in an automated system? In automated systems, an actuator is a device that converts a control signal into a physical action, which usually refers to a change in a process input parameter. The action is typically mechanical, such as a change in position of a worktable or rotational speed of a motor.
What is a contact input interface? a contact input interface is a device that reads binary data into the computer from an external source.
What is a programmable logic controller? a programmable logic controller (PLC) is a microcomputer-based controller that uses stored instructions in programmable memory to implement logic, sequencing, timing, counting, and arithmetic control functions, through digital or analog input/output modules, for controlling various machines and processes.
Identify and briefly describe the three basic components of a numerical control system. The three basic components are: (1) part program, (2) machine control unit, and (3) processing equipment. The part program is the detailed set of commands to be followed by the processing equipment. The machine control unit in modern NC technology is a microcomputer that stores the program and executes it by converting each command into actions by the processing equipment, one command at a time. The processing equipment accomplishes the sequence of processing steps to transform the starting workpart into a completed part.
What are some of the benefits usually cited for NC compared to using manual alternative methods? Advantages of NC include (1) reduced non-productive time, (2) lower manufacturing lead times, (3) simpler fixtures, (4) greater flexibility, (5) improved accuracy, and (6) reduced human error.
A leadscrew with a 7.5 mm pitch drives a worktable in an NC positioning system. The leadscrew is powered by a stepping motor which has 200 step angles. The worktable is programmed to move a distance of 120 mm from its present position at a travel speed of 300 mm/min. Determine (a) the number of pulses required to move the table the specified distance and (b) the required motor speed and pulse rate to achieve the desired table speed. (a)  = 360/ns = 360/200 = 1.8 np = 360x/p = 360(120)/(7.5 x 1.8) = 3200 pulses (b) Nm = vt/p = (300 mm/min)/(7.5 mm/rev) = 40 rev/min fp = vtns/60p = 300(200)/(60 x 7.5) = 133.33 Hz
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