Ch10-Motion Study-q

Review Questions 10.1 What is motion study? 10.2 What is work design? 10.3 What is a therblig? 10.4 Identify some of the ineffective therbligs. 10.5 What is the term sometimes used for the kind of analysis involving therbligs in a task? 10.6 What are the general objectives of micromotion analysis? 10.7 Name some of the principles of motion economy that deal with the use of the two hands. 10.8 Why are smooth continuous curved motions better than straight-line motions when performing manual work? 10.9 What is the lowest classification of hand and arm motions? 10.10 What is the difference between eye focus and eye travel? 10.11 What advantage does the use of the legs have over the use of the arms? 10.12 What is a gravity feed bin and what is its advantage over a simple tray? 10.13 What are the desirable adjustments on a chair designed for the workplace? 10.14 Why are multiple-function tools better than separate tools for each function?

Problems Therbligs 10.1 The plumber, kneeling on the floor next to the sink, reached for the monkey wrench in his tool kit, pushing around a few other tools before grasping the wrench and picking it up. He then moved it to the pipe beneath the sink, positioned it onto the pipe fitting, and turned the fitting one-third of a rotation to loosen it. Once loose, he put down the wrench and continued turning by hand. Four rotations were required before the fitting was free of the mating pipe threads, during which he had to grasp and regrasp the fitting ten times due to the limited rotation ability of his own wrist. Write a list of the therbligs that comprise this motion sequence and label each basic motion with a brief description.

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10.2 The secretary reached for the envelope with her right hand, picked it up and exchanged it to her left hand. She then reached for the letter opener with her right hand, picked it up, positioned the blade under the sealed lid of the envelope, and proceeded to slit the top of the envelope open. Still holding the envelope in her left hand, she laid the letter opener aside, and reached into the envelope with her right hand, pulled out the document, and began to read. Write a list of the therbligs that comprise this motion sequence and label each basic motion with a brief description. 10.3 The grocery store checkout clerk picked up the item from the checkout table and moved it across the bar code scanner. Immediately, the scanner audibly responded that it had successfully identified and recorded the item. Since this was the only item the customer had brought into checkout lane, the clerk punched one of the buttons on the cash register to print out the sales slip. While the register printed, the checkout clerk placed the item into an open plastic bag in front of him, picked up and closed the bag, and handed it to the customer. Write a list of the therbligs that comprise this motion sequence and label each basic motion with a brief description. 10.4 Sitting at her desk, the writer reached for the mechanical pencil, picked it up, positioned it, and then began to write on the pad of paper. After finishing one sentence, she lifted the pencil, and read the sentence. She then put the pencil aside and reached for the rectangular eraser nearby. Grasping and positioning it, she erased one of the words in the sentence. Write a list of the therbligs that comprise this motion sequence and label each basic motion with a brief description. 10.5 For the previous problem, identify some areas for possible study that might improve the method, indicating the nature of the improvement that might result. 10.6 The worker reached for the small part a short distance away in the workplace, picked up the part, and placed it in a vise. The worker then rotated the screw handle of the vise three turns to hold the part between the vise jaws. In rotating the screw handle, he had to grasp and regrasp the handle six times due to the limited rotation ability of his own wrist. On the final turn, he applied additional torque to tighten the vise. Write a list of the therbligs that comprise this motion sequence and label each basic motion with a brief description. 10.7 For the previous problem, identify some areas for possible study that might improve the method, indicating the nature of the improvement that might result.

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10.8 The assembly worker reached for an Allen wrench in the workplace, hesitating momentarily while searching for the correct size from the group of Allen wrenches lying there. Finding the correct size, she picked it up and positioned it into the hexagonal socket of a screw that had previously been hand-turned into a threaded hole in the work unit. She then twirled the Allen wrench handle with one continuous finger and wrist motion until the screw had been rotated seven turns. At this point she gripped the Allen wrench handle with her hand and tightened the screw the last quarter turn. Write a list of the therbligs that comprise this motion sequence and label each basic motion with a brief description. 10.9 For the previous problem, identify some areas for possible study that might improve the method, indicating the nature of the improvement that might result.

Principles of Motion Economy 10.10 Charles Dickens continued working well into the night, writing with his quill on one piece of paper after the next, the only light provided by the lone candle in front of him on the desk. (a) Identify some of the principles of motion economy that seem to be violated by Dickens’ method of working and workplace. (b) Make recommendations for improving the work method and workplace. 10.11 The assembly worker is performing a repetitive manual task consisting of inserting 8 plastic pegs into 8 holes in a flat wooden board. A slight interference fit is involved in each insertion. Each work cycle consists of her picking up a board from the stack of boards located on the left side of the worktable (about 15 inches away from center, where they are placed by a material handling worker), performing the 8 insertions, and then placing the assembled board into a rack that is next to the starting stack. Her first step in the work cycle is to reach for the top board in the stack with her right hand, pick it up, and exchange it to the left hand. While holding the board in her left hand, she picks up the pegs from a tray about 10 inches away in front of her with her right hand and inserts them into the holes in the board, one peg at a time. The rack holding the completed boards has a capacity of six assemblies. When the rack is full, the worker gets up from her worktable, picks up the loaded rack, carries it to a pallet located on the floor three feet away from the workplace, and places it onto the pallet. The pallet only holds four racks on one layer. A material handling worker riding in a forklift truck must periodically take the pallet away and replace it with an empty pallet. Because of delays by the material handling worker, the assembly worker is occasionally forced to stop working

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and wait for the pallet exchange to occur. (a) Identify some of the principles of motion economy that are violated in this work cycle. (b) What recommendations for improvement would you make? 10.12 Sitting in front of her all-wooden desk in her all-wooden chair, the author reached for her wooden pencil, picked it up, positioned it, and then began to write on the pad of paper. After finishing one sentence, she lifted the pencil, and read the sentence. She then put the pencil aside and reached for the eraser nearby. Grasping and positioning it, she erased one of the words in the sentence. She then laid the eraser aside, picked the pencil up, made a correction, and continued writing. Periodically, she would repeat this sequence of writing, erasing, correcting, and then continuing to write. After working in this way for about two hours, she went and took a nap. (a) Identify some of the principles of motion economy that are violated in this work sequence. (b) What recommendations for improvement would you make? 10.13 The Calm Seas Cruise Ship Line wants to analyze the method used by its stewards to clean each of the passenger cabins on its ships. The current method used by a steward to clean one cabin is the following. First the steward knocks on the cabin door with his right hand to determine if the room is empty. Given no response, the steward reaches for his master key in his pocket, unlocks the door, opens it slightly and yells “housekeeping.” If there is still no answer, he walks into the room to look around. After looking around, he goes back out into the hallway, and pushes his cart into the room. He then goes back into the hallway for his vacuum cleaner and carries it into the room. His first cleaning step is to vacuum the room and adjoining bathroom. He then strips the bed linen, puts it into the hamper on his cart, goes back into the hallway and walks down to the closet where the fresh bed linens are kept. He picks out a set of linen, carries them back to the room, and proceeds to make the bed. Next, he walks into the bathroom, picks up the used towels and carries them out to the cart hamper. He then goes back into the hallway and walks down to the same closet as before to obtain fresh towels for the room. He brings the towels back and places them onto racks in the bathroom. From his cart, he obtains fresh soap items for the bathroom. His final cleaning step is to pick up any trash items that may have been left in the room by the passengers. (a) Identify some of the principles of motion economy that are violated in this method. (b) Besides the principles of motion economy, what other deficiencies in the method can you identify? (c) What recommendations for improvement in the method would you make?

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