Chapter 5 Review Questions
Answer each question in paragraph form using complete sentences. Answer them as completely as possible using your own words, since they are potential examination questions. Also, clearly number your answers with the corresponding question number.
5.2 What is the difference between a continuous variable and a discrete variable? Illustrate with examples.
5.4 What is the difference between a continuous control system and a discrete control system? Illustrate with examples.
5.5 What is feedforward control?
5.8 What is the difference between an event-driven change and a time-driven change in discrete control?
5.9 What are the two basic requirements that must be managed by the controller to achieve real-time control?
5.10 What is polling in computer process control? Illustrate with an example other than one covered in class or the textbook.
5.11 What is an interlock? Illustrate with an example other than one covered in class or the textbook.
5.12 What are the two types of interlocks in industrial control?
5.13 What is an interrupt system in computer process control? How is an interrupt different than polling? Illustrate with an example other than one covered in class or the textbook.
5.23 Describe five forms of computer process control in use today. Be sure that your descriptions clearly distinguish one form from another.
Chapter 6 Review Questions
REVIEW QUESTIONS
7.3 What is the right-hand rule in NC and where is it used?
7.4 What is the difference between point-to-point and continuous path control in a motion control system?
7.5 What is linear interpolation, and why is it important in NC?
7.6 What is the difference between absolute positioning and incremental positioning?
7.12 Name six part characteristics that are most suited to the application of numerical control.
7.14 What are four advantages of numerical control when properly applied in machine tool operations?
7.15 What are three disadvantages of implementing NC technology?
PROBLEMS
7.3 An end milling operation is performed on an NC machining center. The total length of travel is 800 mm along a straight-line path to cut a particular workpiece. Cutting speed = 1.5 m/s and chip load (feed/tooth) = 0.09 mm. The end milling cutter has two teeth and its diameter = 12.5 mm. Determine (a) the feed rate and (b) the time to complete the cut.
7.4 A turning operation is to be performed on an NC lathe. Cutting speed = 2.2 m/s, feed = 0.25 mm/rev, and depth = 3.0 mm. Workpiece diameter = 90 mm and its length = 550 mm. Determine (a) rotational speed of the workpiece, (b) feed rate, (c) material removal rate, and (d) time to travel from one end of the part to the other.
7.5 A numerical control drill press drills four 10.0 mm diameter holes at four locations on a flat aluminum plate in a production work cycle. Although the plate is only 12 mm thick, the drill must travel a full 20 mm vertically at each hole location to allow for clearance above the plate and breakthrough of the drill on the underside of the plate. Time to retract the drill from each hold is one-half the feeding time. Cutting conditions: speed = 0.5 m/s and feed = 0.10 mm/rev. Hole locations are indicated in the following table:
Hole number
xcoordinate (mm)
ycoordinate (mm)
1
25.0
25.0
2
25.0
150.0
3
150.0
150.0
4
150.0
25.0
The drill starts out at point (0,0) and returns to the same position after the work cycle is completed. Travel rate of the table in moving from one coordinate position to another is 600 mm/min. Owing to effects of acceleration and deceleration, and time required for the control system to achieve final positioning, a time loss of 3 seconds is experienced at each stopping position of the table. Assume that all moves are made so as to minimize the total cycle time. If loading and unloading the plate take 20 seconds (total handling time), determine the time required for the work cycle.
Chapter 7a Review Questions
REVIEW QUESTIONS
7.3 What is the right-hand rule in NC and where is it used?
7.4 What is the difference between point-to-point and continuous path control in a motion control system?
7.5 What is linear interpolation, and why is it important in NC?
7.6 What is the difference between absolute positioning and incremental positioning?
7.12 Name six part characteristics that are most suited to the application of numerical control.
7.14 What are four advantages of numerical control when properly applied in machine tool operations?
7.15 What are three disadvantages of implementing NC technology?
PROBLEMS
7.3 An end milling operation is performed on an NC machining center. The total length of travel is 800 mm along a straight-line path to cut a particular workpiece. Cutting speed = 1.5 m/s and chip load (feed/tooth) = 0.09 mm. The end milling cutter has two teeth and its diameter = 12.5 mm. Determine (a) the feed rate and (b) the time to complete the cut.
7.4 A turning operation is to be performed on an NC lathe. Cutting speed = 2.2 m/s, feed = 0.25 mm/rev, and depth = 3.0 mm. Workpiece diameter = 90 mm and its length = 550 mm. Determine (a) rotational speed of the workpiece, (b) feed rate, (c) material removal rate, and (d) time to travel from one end of the part to the other.
7.5 A numerical control drill press drills four 10.0 mm diameter holes at four locations on a flat aluminum plate in a production work cycle. Although the plate is only 12 mm thick, the drill must travel a full 20 mm vertically at each hole location to allow for clearance above the plate and breakthrough of the drill on the underside of the plate. Time to retract the drill from each hold is one-half the feeding time. Cutting conditions: speed = 0.5 m/s and feed = 0.10 mm/rev. Hole locations are indicated in the following table:
Hole number
xcoordinate (mm)
ycoordinate (mm)
1
25.0
25.0
2
25.0
150.0
3
150.0
150.0
4
150.0
25.0
The drill starts out at point (0,0) and returns to the same position after the work cycle is completed. Travel rate of the table in moving from one coordinate position to another is 600 mm/min. Owing to effects of acceleration and deceleration, and time required for the control system to achieve final positioning, a time loss of 3 seconds is experienced at each stopping position of the table. Assume that all moves are made so as to minimize the total cycle time. If loading and unloading the plate take 20 seconds (total handling time), determine the time required for the work cycle.
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