Design of Automated Moving Fixture for Conveyorised Special Purpose Machine

Design of Automated Moving Fixture for Conveyorised Special Purpose Machine

M. Y. Dakhole Department of Mechanical Engineering, KDK College of Engineering, Nagpur.

Prof. P. G. Mehar

Asst. Professor, Department of Mechanical Engineering KDK college of Engineering, Nagpur.

Prof. V. N. Mujbaile

Asst. Professor, Department of Mechanical Engineering KDK college of Engineering, Nagpur.

Abstract

It is required to fix typical shape engine components on conveyor while performing cleaning operation. In conveyorised multistage washing machine, to fix these typical shape components is very difficult. Hence these components need dedicated fixturing with poke-yoke to avoid accidents inside the zone on conveyor. This project gives feasible solution on conventional roller chain conveyorised arrangement with dedicated moving fixture with conveyor for the tractor components like rear axle career, bull gear and shaft of a tractor model. This arrangement will be widely used for numerous cleaning purposes owing to its effectiveness for high production volume, reliable and durable performance.

1. Introduction

   1. Project background

      For an automobile industry its very difficult job to clean the engine component in the assembly line before assembly of the engine to obtain the required Millipore value. Hence in automotive, aviation, auto ancillaries and other industries automated washing machines are highly demanded to save the time, man power and to improve washing and drying quality.

      The conventionally using conveyor in production line is worldwide known, but in special purpose machine conveyors are needed with special design and parameter for its operational feasibility. In this automated moving fixture arrangement fixturing

      parameters like V pads, vertical rods, mounting pads, etc. moves along with chain roller conveyor and reach at multiple station with stop and go operation with given speed by gear box.

   2. Problem statement

      In an industry, it is required to clean engine component rear axle career, bull gear, and shaft of tractor engine in assembly line. It is very difficult to fix and clean these components on conveyor. Hence automated washing machine with fixture on conveyor is highly needed. Hence dedicated fixture for these components and chain conveyor to reach these components at various workstations is designed.

   3. System legends

      The travelling of components from one station to another should be operation oriented. Following important legends are considered to design planning the system as objectives.

      1. To design fixture for auto moving components (Rear axle career, Bull gear and shaft).

      2. To design chain and sprocket arrangement with proper guiding rollers.

      3. To design driving and driven shaft.

      4. To calculate required torque, pulling load, speed

      5. To mount fixture on conveyor by considering movability on forward and return side of conveyor.

      6. To select the sensors.

      7. To select the material

   4. Scope of the project

      1. The fixture to fix the typical shape components will be designed.

      2. Chain conveyor to move automotive components will be designed.

      3. Design feasibility will be based on theories of chain drive and fixture design fundamentals

2. Literature Review

   1. Conveyor

      Different types of conveyors are available viz., slat type conveyor, powerised roller belt type conveyor, etc., as shown in figure.

      Slat type Conveyor

      Powerised roller belt type conveyor

      All these type of conveyor are not feasible for the require purpose because of no scope for Fixture arrangement, no scope for return arrangement, since the return of pallets is must.

      A SPM Manufacturer has designed the same purpose machine by return roller conveyor. But it needs lifter and pusher arrangement which was pneumatically operated. Fixture on pallets was not fixed on the conveyor, it needs the manually separation.

      Procedures for Selecting Roller Chain

      The following factors must be considered when selecting roller chain.

      1. Source of power

      2. Driven machine

      3. Horsepower to be transmitted

      4. RPM of driving and driven shafts

      5. Diameter of driving and driven shafts

      6. Canter distance of the shafts

   2. Fixture

      Fixtures are important in both traditional manufacturing and modern flexible manufacturing system (FMS), which directly affect machining quality, productivity and cost of products. The time spent on designing and fabrication fixtures significally contributes to the production cycle in improving current product and developing new products.

      Therefore, great attention has been paid to study of fixturing in manufacturing (Thomas and Ghadhi, 1986). A fixture design used in machining, assembly, welding and other manufacturing operation to locate and hold a work piece firmly in position so that the required manufacturing process can be carried out corresponding to design specifications (Nee and Senthil kumar,1991).

      Fixtures were develop for job, batch and mass productions, which are widely used in manufacturing operations locate and hold a part firmly in position so that the required manufacturing process can be carried out according to design specifications (Hoftman,1991) In machining processes geometry accuracy of manufactured part mainly depend on the relative position of work piece (silicon chip) to the machining tool (Rong, 1988).Fixture are needed to locate the workpiece relative to the machining tool in order to ensure the manufacturing quality. It is clear that the primarily requirement s for a fixture are located and secured the workpiece in a given position and orientation on a worktable of a machining tool. To secure the workpiece on a fixture, clamps are often utilized to keep a stable location against the machining force. Clamping method can be classified into top and side clamping, which may provide normal and friction force, but in this case polishing due on top surfaces and top clamping is not encouraged. The fixture must be rigid enough to resist the harmful deformation and vibrating during machining. Clamping method and clamping position should be carefully selected to firmly hold the workpice. In addition to the primary requirements in fixture design, many other demands also found, such as ensuring productivity like easy load and unload of the workpiece, utilization of automated or clamping semi automated devices. Special design for reducing formation of weak rigidly parts, simple and safe operation and effective cost reduction. Hence the fixture design is complicated process. The application of these fundamental principles to individual fixture design depends on primarily designers experience in manual fixture design.

      1. Dedicated Fixture

         Since dedicated fixtures are commonly used in mass production, dedicated fixtures design are usually applied the fixture construction is perfectly designed for specific operation. As part of machining tooling, the application of dedicated fixture has greatly contributed to the development of automated manufacturing system. Therefore dedicated fixture designs are specially designed for each specific operation, with special consideration of fixture structure, auxiliary support, and other operational properties. Moreover, the operations can be conducted quickly and the tolerance requirement can easily assured n the operation. The problem involving in dedicated fixture application includes the flexibility and long lead time required to designed and fabricate the fixture. When product design change like the shape and the size changes he dedicated fixture are usually not longer useful and scrapped. Today a flexible fixture is desired to a certain extent in order to design variations of the products.

      2. Fixture design principle

      Fixtures are one of operational equipment in manufacturing which are used to ensure the product quality and operational efficiency. Fixture design is desired to be rapid or on time, effective and economic.

3. Design of Fixture

   1. Fixture Design Fundamentals

      Fixture design consists of a number of distinct activities: fixture planning, fixture layout design, fixture element design, tool body design, etc. They are listed in Figure 3.1 in their natural sequence, although they may be developed in parallel and not necessarily as a series of isolated activities in actual execution. Fixture design deals with the establishment of the basic fixture concepts: Fixture layout is an embodiment of the concepts in the form of a spatial configuration of the fixture, Fixture element design is concerned with the concrete details of the locators, clamps and supports, Tool body design produces a structure combining the fixture elements in the desired spatial relationship with the machine tool.

      3.1.1 Fixture Design

      Fixture planning is to conceptualize a basic fixture configuration through analyzing all the available information regarding the material and geometry of the workpiece, operations required, processing equipment for the operations, and the operator. The following outputs are included in the fixture plan:

      Fixture type and

      complexity Number of workpieces per fixture

      Orientation of workpiece within fixture Locating datum faces

      Clamping surfaces Support surfaces, if any

      Fig. 3.1 Various aspects of fixture design

4. Design and Selection of Chain and Sprocket

   1. Selection of chain

      ISO Roller Chain no. 64B Pitch = 4 = 101.6mm

      Minimum bearing load = 67000 N Weight of chain = 6.5 Kg/m

      Table 4.1 Weight of the components

      S N	Name of Comp.	Wt./ Component (kg)	No. of Component	Total Wt. of Component (kg)
      1	Rear Axle Career	26.4	2	52.8
      2	Shaft	22.6	2	45.2
      3	Bull Gear	7.8	2	15.6
      	TOTAL		6	113.6

      Weight of components on one fixture tray = 113.6 kg Maximum number of fixture tray on conveyor at a time

      = 06

      Total weight of component at a time on conveyor = 113.6 x 6 = 681.6 kg ~ 700 kg.

      Chain Sprocket Parameters

      Chain pitch (P) = 101.6 mm

      Chain speed (v) = 4 m/min

      Number of teeth on sprocket (z) = 13

      Total pulling weight = Weight of chain + Weight of components

      Fig. 4.1 ISO Chain 64B

      Pitch circle diameter of sprocket

      = 150 + 700

      = 850 kg

      Maximum pulling weight = Total pulling weight × Coefficient of friction

      In general, for rolling application, the coefficient of friction is considered to be 0.2.

      Hence,

      Maximum pulling weight = 850 × 0.2

      = 170 kg.

      PCD = 424.5 m

      ~ 425 mm

      PCD of sprocket (Dp) = 425 mm = 0.425 m. Sprocket outside diameter (Do) = Dp + 0.8 d Where, d = Roller diameter

      = = 63.5 mm Do = 425 + (0.8 × 63.5) = 475.8 mm

      Inner width i.e. minimum distance between roller link plate = = = 63.5 mm

      Let, g = 10 m/s2 Hence,

      Maximum pulling weight = 1700 N.

      Pulling Torque

      = 361.25 Nm

      Final output torque = Required torque × Service factor Let, Service factor = 1.5

      Hence,

      Final output torque (T) = 361.25 × 1.5

      = 541.9 Nm

      ~ 550 Nm

      = 31.75 mm

      Thickness of link plate = = 12.7 mm Centre distance 80 × pitch

      Hence,

      Maximum centre distance = 80 × 101.6

      = 8128 mm

      = 8.128 m

      But due to the space availability, let us consider centre distance (C) = 5000 mm = 5 m.

      Length of chain

      Where,

      C = Centre distance = 5000 mm

      N1 = Number of teeth on driven sprocket = 13 N2 = Number of teeth on driving sprocket = 13 Hence,

      Length of chain = 23 m.

      Weight of the chain

      For the selected chain number C100, weight of the chain is 6.5 kg/m

      Hence, Weight of the chain = 6.5 × 23

      = 149.5 kg

      ~ 150 kg.

      Hence,

      Pulling Torque = 550 Nm.

      mm

      Time to travel pitch Pc = 13 sec.

      Where, z = number of teeth = 13 Hence,

      Require RPM = 2.97 rpm

      ~ 3 RPM

      kW

      Hence,

      Final output Torque (T) = 550 Nm Final output RPM (n) = 3 rpm

      Final output Horsepower (hp) = 0.22 HP

      Required kilowatt (kW) = 0.17 kW.

      Sprocket parameter

      Pitch circle diameter of sprocket

      PCD = 424.5 m

      ~ 425 mm

      PCD of sprocket (Dp) = 425 mm = 0.425 m.

      Top diameter, (Do)max = D + 1.25p d1

      = 488.5 mm

      (Do)min = D + p(1-1.6/z)- d1

      = 450.59 mm

      Hence, let us take top Diameter = 475 mm Root diameter, Df = D 2ri

      Where, ri = roller seating arrangement (ri)max = 0.505d1 + 0.069(d1)1/3

      = 32.34 mm

      (ri)min = 0.505d1

      = 32.06 mm

      Take ri = 32.3 mm

      Hence root diameter = 410.8 mm Tooth flank radius

      (re)max = 0.008d1 (z2+180) = 117.3 mm

      (re)min = 0.12d1 + (z+2) = 114.3 mm Take tooth flank radius = 115 mm

      Roller seating angle ()

      ()max = [120 (900/z)] = 113.080 ()min = [140 (900/z)] = 133.080

      Hence take

      = 1250

      Tooth height above the pitch polygon (ha)max = 0.625p 0.5d1 + (0.8p/z) = 38 mm (ha)min = 0.5(p d1) = 19.05 mm

      Hence

      Fig. 5.1 Fixture arrangement on fixture tray

      Fig. 5.2 Mounting of rear axle career on fixture

      Fig. 5.3 Mounting of shaft on fixture

      ha = 25.4mm

      Tooth width, (bf)max = 0.95b1 = 60.325

      ~ 60.5mm

      Where, b1 = 63.5mm

5. View of Dedicated Fixture Arrangement

   Fig. 5.4 View after mounting all components on fixture

6. Working Process of the System

As shown in fig.2.1, system will be of six stations where from one end component will get loaded and after going through the various stations it will get unloaded at last station.

Fig. 6.1: Process Layout

1. On loading station, operator will load the multiple components on dedicated fixture with full proofing.

2. Operator will press the Cycle start Button. Proximity sensors will sense the existence of component on fixture then only conveyor will start moving otherwise it will show error.

3. Fixture will having the unique sensing Dogs for receiving the presence of proximity fixed at every station to stop at that station for processing on components. Station wise respected operation will be done one by one like washing, Degreasing, cold air blowing, hot air blowing. All operations separated zone wise.

4. Another operator exist at unload station will unload the components manually .here also if proximity get sense of availability of comonents on unload station it will not allow to move the conveyor unless and until the components are not unloaded from the fixture.

Fig. 6.2 Working view of the system

1. Result and conclusion

   As discussed above, the dedicated fixtures are designed for the components rear axle career, bull gear and shaft. To carry these components to various workstations, a chain conveyor is designed by selecting ISO chain no. 64B.

   The parameters of chain conveyor are as follows.

   Chain No. : ISO Chain 64B Pitch (p) = 101.6 mm Roller Diameter = 63.5 mm

   Width between inner plates = 63.5 mm Pin diameter = 31.75 mm

   Pin length = 130.00mm

   Inner plate height = 90.17mm Plate thickness = 15.00 mm

   Sprocket parameters are as follows.

   Pitch circle diameter = 425 mm Top diameter = 475.8 mm Root diameter = 410.8 mm

   Roller seating radius = 32.2 mm Tooth flank radius = 115 mm Roller seating angle = 125o

   Tooth height above the pitch polygon = 25.4 mm Tooth width = 60.5mm

   This project gives the suitable solution on the other conveyors to carry the components like Rear Axle Carrier, Bull Gear, shafts of tractor before going to assembly line. Also this project suggests the dedicated fixturing arrangement for these components.

2. References

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2. Asada, H. and A.B. By. Kinematic Analysis of Work part Fixturing for Flexible Assembly with Automatically Reconfigurable Fixture. IEEE Journal of Robotics and Automation, 1(2), pp. 86- 94. 1985.

3. Chou, Y.C. Geometric Reasoning for Layout Design of Machining Fixtures. Int. J. Computer Integrated Manufacturing Vo1.7, No.3, pp175-185. 1994.

4. Cogun, C. The Importance of the Application Sequence of Clamping Forces. ASME Journal of Engineering for Industry, Vol. 114, pp. 539-543. 1992.

5. DeMeter, E.C. Restraint Analysis of Fixtures which Rely on Surface Contact. Journal of Engineering for Industry, 116(2), pp. 207-215. 1994a.

6. DeMeter, E.C. The Min-Max Load Criteria as a Measure of Machining Fixture Performance. Journal of Engineering for Industry, 116(1 I), pp.500-507. 1994b.

7. Fuh, J.Y.H. and A.Y.C. Nee. Verification and Optimization of Work holding Schemes for Fixture Design. Journal of Design and Manufacturing, 4, pp.307-318. 1994.

8. Aron S. Wallack, John R. Canny, Modular fixture design for generalized polyhedra, University of California, Bekeley.

9. Diana M. Pelinescu, Micheal Yu Wang, Multi- objective optional fixture layout design

   Robotics and computer aided Manufacturing, 18 (2002), 365-372.

10. Iain M. Boyle, Kevin Rong, David C. Brown, and CAFIXD: A case based reasoning fixture design method, framework and indexing mechanism, DETC04, ASME 2004, Design engineering technical conference.

International Journal of Engineering Research & Technology (IJERT)

ISSN: 2278-0181

Vol. 1 Issue 5, July – 2012