c. Provide one reason/motive for designers using coupler curves to size a mechan
ID: 1766584 • Letter: C
Question
c. Provide one reason/motive for designers using coupler curves to size a mechanism. When do we have a crank-shaper? (Hint: think about the link sizes) When do we use a crank shaper? d. What are the advantages and disadvantages of the three joints discussed in class? (Hint: pin joint, slider joint, and half joint) e. t. What is one criterion that you need to ensure when determining the rotatability of the system? (Hint: order of connection does not matter) What is rotatability? What is revolvability?Explanation / Answer
c) Couple points or coupler curves are used by designers to find useful curves in the mechanism. According to shape of the segment useful curves can be easily found out and the coupler point acts as the output of the linkage. Also when used in four bar mechanisms the equation for coupler curves can be derived and the dimensional needs for these mechanisms can be obtained and also straight line motion can be produced.
d) A crank shaper is a shaper that uses a mechanical crank to actuate a ram and helps in the shaping process. The crank shaper works based on the quick return mechanism. The mechanism uses crank and slotted link.
We use crank shapers to machine a linear flat tool path along a workpiece. It cuts the workpiece using the tool carrying ram and shapes the workpiece.
e) Pin joint- Advantages - It is quicker and a lot cheaper. Movement is faster
Disadvantages - The pin gets damaged over time. And when this happens joint becomes loose.
Joint loses strength
Half joint -- Advantages - Works well when forces are applied. Strength and effectiveness can be improved.
Disadvantages- Joint gets damaged over time when exposed to water.
f) For all twist angles in the range the excess of the sum of the frame and input twist angles over Pi should, in absolute value, be greater than that for the coupler and follower twist angles; the difference between the follower and input twist angles, in absolute value, should be greater than that for the coupler and follower twist angles . Rotatability is the ability of a mechanism to be able to rotate , it is the ability of a link in a mechanism to make a full revolution according t placement of other links.
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