The most common quick return ratio of the time of the cutting. Existing mechanism the current crank driven toggle quick. This makes the slotted lever oscillate about the pivoted point a. The total machining time decreases and the rate of production increases. Shaper machine is a production machine in which the single point cutting tools are attached and the workpiece is fixed and while moving forward the tool cuts the workpiece and in return, there is no cut on the workpiece and used for producing flat and angular surfaces. Shaper consists of a hollow machine bed made of cast iron which rests on the ground. Specialized mechanisms whitworth quick return mechanism. A usual shaper machine operates by a principle of whit worth quick return mechanism where materials are processed at one end and other end remains idle. Explain with the diagram working of crank and slotted. Electric motor runs the driving pinion at a uniform speed. Quick return ratio qrr ratio of forward stroke to the cutting stroke qrr forward stroke return stroke since, forward stroke return stroke so, qrr 1 for single slider mechanism without any offset, forward stroke return stroke theref.
This mechanism is called slotted lever quick return mechanism and it drives a horizontal ram which reciprocates in the guide ways provided on the top surface of the machine frame. Sep 3, 2017 types of quick return mechanism there are three types of quick return mechanism 1. Design and construction of a quick return device for use. In the crank and slotted link mechanism, the power is transmitted to the bull gear through pinion. As can be seen in the animation opposite, the red linking pin has to travel a much greater distance around the top of the crank circle than the bottom during. Therefore, w ww 21 7 otherwise, w ww 12 8 in addition, w wzw r2p 9 by definition, the time ratio. This mechanism is made of a driving crank and of a driven slider crank. The quick return mechanism of a machine can e obtained by the following methods.
Quick return schematic the kinematic length of the coupler goes to zero. The whitworth quick return mechanism, mbm2, is a mechanism able to transform circular movement into reciprocating movement. It is a four bar mechanism comprised of fixed link, crank, pin sliding in the slot and a sliding pair. Build a cardboard model and determine the toggle positions and the minimum transmission angle. Pdf quickreturn mechanism design and analysis projects. Quickreturn qr mechanisms feature different input durations for their working and return strokes. Sandor and erdman 9 gave an example of its use in connection with a flow metering pump. Is your new mechanism an improvement on the crank and slider mechanism. Utilizing these two loops, the following sections will go through the kinematic analysis of the crank and slotted lever quick return mechanism. A thesis in mechanical engineering the requirements.
The working of the slotter machine is similar to the shaper machine do but the main difference between them is the shaper machine works horizontally whereas slotter machines work vertically. One known as the whitworth quick return, is used to drive the cutting tool of a shaper which cuts a flat surface off a block of steel as it is advanced perpendicular to the motion of the tool. Its cut is analogous to that of a lathe, except that it is archetypally linear instead of helical a wood shaper is a similar woodworking tool, typically with a powered rotating cutting head and manually fed workpiece, usually known simply. The shaper machine involves two theoretical concepts of machine designing i. Feb 17, 2016 the output gives a slow forward linear motion followed by a quick return to the start position along the same path. Hydraulic type i mentioned the working principle of hydraulic shaper machine below in this article. Design a fourbar grashof crank rocker for 90 deg of output rocker motion with no quick return. The quick return and its motion trajectory are shown schematically in figure 1. The final fabrication model will be represented as shown below. Cutting stroke is slower than the idle return stroke. Mechanism synthesis in achieving thelps his goal in fewer steps. Whitworths quick return mechanism from wolfram library. 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. For example, ham, crane and rogers 8 described its use as a crank shaper.
What is the purpose of quick return mechanism in a shaper. Quick return mechanism explore mechanical expressions. This mechanism is sensitive to small changes in the lengths of the links and the distance between the two rocker points. When one of the links of a kinematics chain is fixed, the chain is known as mechanisms.
Apr 30, 2018 in the forward stroke, cutting action takes place. Explain with the diagram working of crank and slotted lever. For the model to be considered a quick return the desired time ratio should determine the radius of the crank and the length of the slider. Oct 24, 2015 this video covers the working of a quick return mechanism using a 3d animation. Quick return mechanism to download and make rob ives. Crank and slotted lever quick return mechanism mechanics. There are a number of variations of the quick return mechanism. Draw an alternative mechanism or combination of mechanisms that will produce the same forwards and backwards motion. Seminar on shaping machine pdf report free download. Crank and slotted lever quick return motion mechanism. A quick return mechanism is an apparatus to produce a reciprocating motion in which the time taken for travel in one direction is less than in the other. A quick return mechanism is a mechanical assembly to create a reciprocating motion which is so designed to reduce ideal time required for return stroke.
The whitworth quick return mechanism changes rotary to oscillating motion but, unlike the crank and slider, the forward reciprocating motion is at a different rate to the backward stroke. The link 3 corresponds to the connecting rod of a reciprocating steam engine. The time ratio tr of a qr mechanism is the ratio of the change in input displacement during. The depth of the cut increments by moving the workpiece, and the workpiece is fed by a pawl and ratchet mechanism.
Therefore, in order to reduce total machining time, the shaper mechanisms should be designed. 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 quick return is a common feature of tools in which the action is performed in only one. The shaper mechanism should be so designed that it can allow the ram to move at a slower speed during the forward cutting stroke. Add a comment or brief description of this mechanism. The reciprocating movement of the ram and the quick return mechanism of the machine are generally obtained by anyone of the following methods. Design, fabrication and analysis of crank and slotted.
Design and construction of a quick return device for use as a. The high performance and highly powerful, pneumatic operated shaping machine is efficient machine which works by pneumatic power, instered of crank and shaping link mechanism here pneumatic power is employed with quick return mechanism, this system consist of ram, pneumatic cylinder, solenoid valve, timer circuit, when air from compressor is. But in a dual side shaper machine, materials are processed at both ends which become advantageous when compared to usual shaper. A novel design for quick return mechanisms, where the new mechanism is composed by a generalized oldham coupling and a slider crank mechanism is proposed in 6. Abstract quickreturn qr mechanisms feature different input durations for their working and return. A slider attached to the crank pin at b slides along the slotted lever ap.
An offset slider crank mechanism the radius of the crank and length of the slider are important factors to consider when designing a quick return mechanism. Here, the connecting rod is the frame, which is fixed. Apr 27, 2015 introductionthe whitworth quick return mechanism converts rotary motion into reciprocating motion, but unlike the crank and slider, the forward reciprocating motion is slower rate than the return stroke. Quick return qr mechanisms feature different input durations for their working and return strokes. Angle covered by the crank is more in cutting stroke. An electrical motor runs the driving pinions at a uniform speed. The quick return mechanism was modeled after the crank and slider arm, and this is present in its appearance and function. These mechanisms are widely used on machine tools to give a slow cutting stroke followed by a fast return stroke with a constantangularvelocity drive crank. The speed of the bull gear is changed by the different. Our machine is a crank shaper quick return mechanism designed to run at low speed, to highlight the differences between front and back strokes. Design of a crankdriven toggle quickreturn mechanism.
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. Crank and slotted lever mechanism engineering essay. The quick return is a mechanism with numerous industrial applications, such as the shaper mechanism shown in. Draw a diagram of the shaping machine and explain how the quick return mechanism. The crank cb in the fig below revolves about the fixed center c. Mar 23, 2020 it is a reciprocating member of the shaper which holds the tool and the reciprocates on the guideways on the top of the column by means of quick return motion mechanism.
Design, fabrication and analysis of crank and slotted lever quick return mechanism 1. Introductionthe whitworth quick return mechanism converts rotary motion into reciprocating motion, but unlike the crank and slider, the forward reciprocating motion is slower rate than the return stroke. This mechanism is mostly used in shaping machines, slotting machines and in rotary internal combustion engines. Inside its shellcasing is a crank and slider mechanism that pushes the cutting tool forward and returns it to its original position. The output gives a slow forward linear motion followed by a quick return to the start position along the same path. The whitworth quick return mechanism converts rotary motion into reciprocating motion, but unlike the crank and slider, the forward reciprocating motion is slower rate than the return stroke.
By reclamping the material, multiple sides can be cut to any desired shape. Draw a diagram of the shaping machine and explain how the quick return mechanism works. As the ram moves at a faster rate during return stroke, the time taken becomes less. Elliptical trammel is a device used to draw the ellipses. Additionally, the device allows for easy changing of the time ratio. It houses the screwed shaft for altering the position of the ram with respect to the work. Whitworth quick return mechanism linkedin slideshare. The reciprocating movement of the ram and the quick return mechanism of the machine. Design and construction of a 6 bar kinematic quick return. In a standard shaper, cutting of material takes place during the forward stroke of the ram and the return stroke remains idle.
It finds application in shaping machine, slotting machine, rotary internal combustion engine. This mechanism is known as the quick return mechanism. In this project you are asked to analyze an existing mechanism and to redesign it for a different timeratio. Moreover, let w w and w r denote the angular displacement of the link 2 for the working and the return strokes, respectively. Dec 01, 2012 shaper quick return mechanism devesh ranjan loading, animation of quick return mechanism,shaping machine, 247 online lecture 24 hydraulic circuit design and. The most common quick return ratio of the time of the cutting stroke to the time of the return stroke is about 3. The mechanism analyzed here is a quick return one which has numerous industrial applications. The rotation of the crank op in clockwise direction through the angle p 1 rp 2 refers to the forward cutting stroke. Feb 27, 2019 a quick return mechanism is an apparatus to produce a reciprocating motion in which the time taken for travel in one direction is less than in the other. Quick return mechanisms are used in shapers, powerdriven saws, and many other applications where a slower working stroke in comparison to return stroke is desired. The return is governed by a quick return mechanism. The slider on the rocker arm which is also connected to the frame is the piston.
Certain time is spent in cutting operation depending upon strength of material, speed, feed, depth of cut etc. This video covers the working of a quick return mechanism using a 3d animation. Several procedures were devised for selected mechanisms to help designers in the synthesis process, this includes the slider crank, fourbar, crank shaper, point and threetwo point mechanism which will be discussed in this chapter. With the help of above design of different components it has been combined together to form a crank and slotted lever mechanism which is seen mainly in shaper machines. Quickreturn mechanism design and analysis projects ron.
Based on the type of driving mechanism types of shaper machines. Inside the hollow portion the machine drive mechanism is housed. This pinion receives its power from the individual motor. For a quick return mechanism, w w is greater than w r. Quick return mechanism, shaper machine mechanism figure. Quick return mechanism as shown in the diagram, ka indicates the starting point of the forward cutting stroke and kb the end of the cutting stroke. This is an application of the oscillating cylinder mechanism.
The whitworth quick return mechanism changes rotary to oscillating motion but, unlike the crank and slider, the forward reciprocating motion is at a different rate to the backward stroke as can be seen in the animation opposite, the red linking pin has to travel a much greater distance around the top of the crank circle than the bottom during a full right to left stroke cycle. Torque required to accelerate a mass at e is output in this inverse dynamic app. The cutting speed depending upon the type of material and machining condition whereas during the return idle return time. Feb 10, 2019 quick return ratio qrr ratio of forward stroke to the cutting stroke qrr forward stroke return stroke since, forward stroke return stroke so, qrr 1 for single slider mechanism without any offset, forward stroke return stroke theref. The advantages of the new design are easier to be balanced dynamically and more compact in volume as discussed in sec.
Complete the diagram below by adding the missing parts that make up the crank and slider mechanism. The following mechanisms are used for quick return of the ram. 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. Quickreturn mechanism design and analysis projects ron p. These are usually obtained by following the four types of shaper machine mechanisms. Now the ram is connected to the crank and crank connected to the gears. Two of the most common which are found in shaping, planning and slotting machines for metal cutting are the scotch yoke mechanism and the whitworth quick return motion. In a shaper, the metal is removed during forward cutting stroke, while in return stroke no metal is removed. The crank and slotted lever quick return motion mechanism is shown in the length of links o 1 o 2, o 1 c and o 2 a are 10 cm, 20 cm and 5 cm respectively.
145 159 1314 1085 1460 1504 450 1609 42 1599 1572 534 914 863 1332 1085 1468 7 439 1151 21 1477 1311 461 705 1178 657 1399 1449 1021 855 872