Why is it important to know if a mechanism has a single degree of freedom?
Problem 3.2 Solution: a) Because the DOF of a mechanism is the number of mechanism parameters required to fully define its motion, a mechanism having a single DOF requires a single mechanism motion parameter to fully define mechanism motion. As a result, a single DOF condition provides maximum mechanism motion control.
How many degrees of freedom does a four bar mechanism have?
two degrees
What must be the criteria for designing a double rocker mechanism?
d) One double-rocker mechanism is possible when the link opposite the shortest link is the frame. If l + s > p + q (if the sum of the longest and the shortest link lengths is greater than the sum of the lengths of the two intermediate links).
What is the condition involved in Grashof’s law?
1. What is the condition involved in Grashof’s law? Explanation: According to Grashof’s law, in a four bar mechanism, the sum of the lengths of the shortest and the longest link should be less than or equal to the sum of the lengths of two remaining links for continuous relative motion between them. Therefore, s+l≤p+q.
For what purpose are the quick return mechanism used?
A quick return mechanism is an apparatus to produce a reciprocating motion in which the time taken for travel in return stroke is less than in the forward stroke. It is driven by a circular motion source (typically a motor of some sort) and uses a system of links with three turning pairs and a sliding pair.
What are the types of quick return mechanism?
TYPES OF QUICK RETURN MECHANISM
- Hydraulic drive.
- Crank and slotted link mechanism.
- Whitworth mechanism.
How do you make a quick return mechanism?
Quick-return mechanisms Quick-return (QR) mechanisms feature different input durations for their working and return strokes. The time ratio (TR) of a QR mechanism is the ratio of the change in input displacement during the working stroke to its change during the return stroke.
How does a Whitworth quick return mechanism work?
The Whitworth quick return mechanism converts rotary motion into reciprocating motion, but unlike the crank and slider, the forward reciprocating motion is at a different rate than the backward stroke. This mechanism is most commonly seen as the drive for a shaping machine.
Which link is fixed in Whitworth quick return mechanism?
The crank OC is fixed and OQ rotates about O. Whitworth quick return motion mechanism: Third inversion is obtained by fixing the crank i.e. link 2. Whitworth quick return mechanism is an application of third inversion.
What is quick return ratio?
Quick return ratio (QRR) = Ratio of forward stroke to the cutting stroke. QRR = forward stroke/return stroke. since, forward stroke > return stroke.
Which mechanism is used in shaper?
In construction, the crank shaper employs a crank mechanism to change the circular motion of a large gear called “bull gear” incorporated in the machine to reciprocation motion of the ram. It uses a crank mechanism to convert the circular motion of the bull gear into reciprocating motion of the ram.
What is the function of shaper?
A shaper is a type of machine tool that uses linear relative motion between the workpiece and a single-point cutting tool to machine a linear toolpath. Its cut is analogous to that of a lathe, except that it is (archetypally) linear instead of helical.
Why clapper box is used in shaper?
Clapper Box: The clapper box is needed because the cutter drags over the work on the return stroke. The clapper box is hinged so that the cutting too] will not dig in. Often this clapper box is automatically raised by mechanical, air, or hydraulic action.
How is stroke length adjusted?
Initial, the stroke length has to be adjusted. It is ready by turning stroke adjusting shaft or stroke selector. The majority of shapers contain a scale on ram by a pointer to point out the length of stroke. Stroke length is adjusted while the ram is in its excessive return place.
What is stroke length?
The stroke length is how far the piston travels in the cylinder, which is determined by the cranks on the crankshaft. Engine displacement is calculated by multiplying the cross-section area of the cylinder (determined by the bore) by the stroke length.
What are functions of the clapper box?
Clapper box: The main function of clapper box is to provide clearance for tool in return stock. It prevents the cutting edge dragging the work piece while return stock and prevent tool wear.
What is the function of RAM in shaper machine?
Ram is the main part of the shaper machine. Ram is made with cast iron and slide left and right in the guideway of the column. It holds the tool and provides reciprocating motion to it. In the crank driven machine, Ram is connected with the rocker arm which provide motion to the Ram.