mechanical gripper design calculations

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mechanical gripper design calculations

2022.07.31
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mechanical gripper design calculations

It is an important component of industrial robots because it interacts with the environment and objects, which are grasped for manipulative tasks. The thickness of the pulley is 3mm. It should be precisely controllable through computer operations or manually. The control string for each finger segment is threaded through the hollow spaces in each subsequent finger link and down through the palm itself. what kind of objects can be grasped and what kind of manipulations can be performed with a grasped object.

By application of pressure of two opposite pistons the jaws move synchronously towards each other. Figure 1(a): Fingers with single link , W: weight of object. 55 UNIT: 6 Prototype Development The finger segments and hand base were solid modelled in Rapid protyping. Therefore, x Normal reaction force = Load on each side or normal reaction force = 49.05/0.7 = 70.07 N This is the total reaction force on the thumb side as well as the finger side. 6. By attaching a tool to the robot flange (wrist), the robotic arm can then perform designated tasks. (i) (ii) The sine component of the tension force increases. When the liquid is supplied, the gripper jaws will close on an object and firmly hold the object while some operation is performed, and when the liquid is taken out, the gripper will release the object. The design of the gripper must be such that it can easily hold irregular bodies and the entire gripper and the body must be stable after the gripping is done. The control is performed by four microcontrollers, one for each finger, Finally the coordinated control of the hand is demanded to a supervision computer connected through a CAN bus link.

They are very compact by virtue of the fact that the drive is integrated into the housing and are low weight due to the use of high-strength material (e.g. They are controlled through a computer interface which takes TTL level inputs representing commands for finger contraction and extension, and converts them to drive signals for each motor. But as we increase the distance, decreases and hence the sine component of the force.

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4) The gripper cannot hold objects below 6 mm in dimension. The EH1 Milano series firmware routines allow to perform grasps automatically, by just sending a single byte from your application. After checking the value of k and Tsin for a variety of values of we see that for = 30, the clearance k is 10 mm for a pulley radius of 5 mm. Designed for applications requiring three points of contact and, due to its high durability, works particularly well in harsh environments (for example grinding and deburring). Hydraulic systems require fewer parts, making them more durable. The advantage of this design is that the jaw support is greatly increased. Acrylonitrile Butadiene Styrene (ABS) - This material is a terpolymer of acrylonitrile, butadiene and styrene. Due to the tension force on the string, the pulley will be subjected to 2 tension forces as shown in the figure. 27 5.2 - DETERMINATION OF DISTANCE BETWEEN THE SHAFT OF THE FINGER AND THE EDGE OF THE THUMB (X) As discussed earlier X is the distance between the shaft of each finger and the edge of the thumb facing the shaft i.e, the distance AB in figure 10 From equation (5), we have, X = L = 50 Hence X = 50mm Figure 10 28 5.3 - DETERMINATION OF DISTANCE BETWEEN THE SHAFTS OF THE THUMB (Y) As discussed earlier Y is the distance between the shaft of the two thumbs. 51 The components of the designed gripper are described below. 63 UNIT: 9 BIBLIOGRAPHY 1) IMAGE TABLE LINKS IMAGES Image1 Image 2 Image 3 Image 4 Image 5 Image 6 Image 7 Image 8 Image 9 Image 10 Image 11 Image 12 Image 13 Image 14 Image 15 http://www. With this, the thread gets wounded on side pulleys and relaxed on the other. Now as we increase the angle , two things take place. Typical uses are to change orientation or to move an object as in a pick-n-place operation. Pulley: Figure 24 Figure 24 shows the pulley used in the gripper. Their valuable guidance and advice has made it possible for us to complete this project on time. Therefore total length of the string = 3* L1 + 2* Lw1 + 2* L2 + 4* Lw2 + 2*L3 + Lw3 + L = 3*6 +2*39.35 + 2*6 + 4*1.855 + 2*30 +43.26 + 20 = 239.38mm Hence change in length of the string = 258.332mm 239.38mm = 18.952mm Hence the change in length of the string required for maximum movement of a finger = 18.952mm 48 5.11 - SHAPE DETERMINATION Based on the above calculations, the following few conceptual designs were put forward. 8. 45 Tearing stress on the link on each thumb: Tearing stress between link A and link B Force = 2T cos(60 - /2) Or Force = 700.7 cos(60 - /2) [since T= 350.35 on the finger side] Area = thickness x length of tear = 30 x 6 = 180 mm2 t = force/area = 700.7 cos(60 - /2) / 180 = 3.9cos(60 - /2) N/mm2 Where is the angle between link A and B. Tearing stress between link B and link C t = 3.9cos(60 - /2) N/mm2 Where is the angle between link B and C. Tearing stress between link C and the base t = 3.9cos(60 - /2) N/mm2 Where is the angle between link C and the base.

5. Hence 3 + 3 + 3 = 180 Since the two thumbs move symmetrically, 3 = 3 , 3 = 3 , 3 = 3 and also since each link moves equally, 3 + 3 + 3 = 3 + 3 + 3 = 180 or 3 = 3 , 3 = 3 , 3 = 3 = 60 putting in equation (6), we have, Lcos60 + Y + Lcos60= - Lcos(120) Lcos(180) Lcos(180) Lcos(120) Or Y = 2L Or Y = 100mm 29 Variation of X, Y and L with respect to the angles 1, 1, 1, 2, 2, 2 The above table shows the variation of X,Y and L with the variation of the angles 1, 1, 1, 2, 2, 2 for the gripper to be capable of holding a body of maximum dimension of 120mm and a minimum dimension nearly equal to zero. Now the distance k must be such that there is enough clearance between the circumference of the pulley and the point where the string is fixed. Good Flow 7.

It has a chemical formula of C6H5C2H3 and is liq, Fundamentals of Mechanical Design, engineeringFull description, Engineering Encyclopedia Saudi Aramco DeskTop Standards Similarly, Shear stress on the pulley between link B and link C: = 7.435 cos(60 - /2) N/mm2 where is the angle between link B and C. Shear stress on the pulley between link C and the base: = 7.435 cos(60 - /2) N/mm2 where is the angle between link C and the base. e6O*"5z9"Al.05!&If? B R`18mf${20M9/"300 X{ Since the string is has very little contact with the shafts of link B and link C, the shear in their case will be negligible. All rights reserved.

There are different types of gripper. As the design involves arrangement of pulleys and gears so it is easy and cheap to manufacture. The basic idea about grippers and type of gripper currently available is discussed in Unit 2. 41 Shear stress on the pulleys on each thumb Shear stress on the pulley between link A and link B: Force = 2T cos(60 - /2) or force = 2x 350.35 cos(60 - /2) [ since tension T for finger = 350.35N] or force = 700.7 cos(60 - /2) Area =2xxrx2 Since radius of the pulley is 5mm Therefore, Area = 62.832 mm2 = force/area = 700.7 cos(60 - /2)/62.832 N/mm2 = 11.152 cos(60 - /2) N/mm2 Where is the angle between link A and B.

Design of a gripper tool for robotic picking and plac, 1.0 INTRODUCTION

The four fingers are identical, and consist of two phalanges.

The distance k decreases. 30 5.4 - CALCULATION OF GRIPPING FORCE The load to be lifted by the gripper is 10kg. The study done on various type of hand gripper and its characteristic has been included in Unit 3. Figure 19 Hence from geometry we see that the radial component of each force is equal to T x cos(60 - /2) [for the pulley placed between link C and the base] Where T is the tension in the string. So less maintenance is required. Each of the four fingers has three links and three revolute joints to pitch the finger forward out of the plane of the palm. Each degree of freedom has the potential for ultra reliable noncontact absolute sensing and limit switches providing extra positioning redundancy for safety critical applications 4. The fingered gripper offers: Better flexibility in griping an object. One in the radial direction and another perpendicular to the radial direction. It can be used for gripping operation in robots which performs grabbing and releasing of hazardous materials from one place to another provided the gripper is installed with an arm. Rapid protyping is the automatic construction of physical objects using additive manufacturing technology. Also the Tsin component for = 30 is considerable. 55 0 obj <> endobj aluminium).High gripping force through wedge and hook principle is achieved. [5] Sarah Jane Wikman. INTER-FINGERCOORDINATED DC MOTOR DRIVEN GRASPING ROBOTIC HAND. The side on which it gets wounded becomes the inner side of the folding finger. Shear stress for the finger side Shear stress = = tension force/area Tension force for the finger side = 233.57 N Area = cross sectional area of the shaft Diameter of the shaft is taken as d = 4 mm. Some common type of gripper is illustrated below: 1. 132 0 obj <>stream

3) The gripper cannot be used for carrying loads exceeding 8kg. From the above figure we have, Lcos1 + Lcos(1+1) + Lcos(1+1+1) + X = D ..(1) For proper gripping without slipping, 1 + 1 + 1 = 90 Hence, from equation (1) we have, Lcos1 + Lcos(1+1) + Lcos(90) + X = D Or Lcos1 + Lcos(1+1) + X = 120 ..(2) Now since the gripper is symmetrical i.e. Evaluating Mechanical Design of Tank Structures And it must also be able to fine-manipulate a grasped object. 9.Dainichi Company, Ltd. Kani, Japan, Kawasaki & Mouri Lab Gifu hand form is approximate for the human hand to not only size but also motor function like geometrically in order to realize grasp and operation of the object by changing human. The strings controlling the finger are connected to a motor. reports/pptsc_lg.asp.htm http://www.shadowrobot.com/reports_es.htm http://www.megabots_reports/grippers.html http://mindtrans.narod.ru/hands/pictures/openarm_v2 http://www. These design characteristics can be achieved by considering specific end-effectors or grippers strength. EMG signals can be used to interface the robot hand non-invasively to a patient and electrical stimulation can be used as a substitute for tactile feedback. Hydraulic systems can be used over long distances or periods of time with little wear due to their comparatively fewer moving parts. The Elu2-Hand is a human-scale anthropomorphic robot hand able to approximate real hand movements at humanlike speeds. Usual compositions are about half styrene with the balance divided between butadiene and acrylonitrile. By rotating the motor, one side pulleys rotate in one direction and the other side pulleys in the other. Each finger has three DOFs and is actuated by four independent tendons driven by DC motors. The design requirement, its concept with working principle has been discussed in Unit 4. Each finger consists of 3 links. High Flow General Purpose, 6. 46 5.10 - CALCULATION OF THE CHANGE IN LENGTH OF THE STRING REQUIRED FOR MAXIMUM MOVEMENT OF A FINGER Figure 21 The configuration of the finger in its ideal state is shown in the figure. Basic features for a gripper depend strongly of the grasping mechanism. The use of additive manufacturing for rapid prototyping takes virtual designs from computer aided design (CAD) or animation software.