Design of Fixture for the purpose of Piston Topping in Multicylinder

Transcription

1 Design of Fixture for the purpose of Piston Topping in Multicylinder Engines G.Natarajan 1, P.Naveen 2, S.S.Parthipan Raj 3 1 Department of Mechanical Engineering, Easwari Engineering College, Chennai, INDIA, 2 Department of Mechanical Engineering, Easwari Engineering College, Chennai, INDIA, 3 Department of Mechanical Engineering, Easwari Engineering College, Chennai, INDIA, Abstract With the advancements and developments in the technologies like CNC and CMM, the modern era has witnessed the application of those technologies in various Engineering field. It ultimately lead to the drastic improvements in various industries by increasing the productivity, decreasing the time consumption, thereby increasing the customer satisfaction. They also have good ergonomic considerations. Our project aims at developing a device which can be employed for the process of piston topping with the reduction in human errors and time consumption. The process of measuring the displacement of a piston moving inside the cylinder in excess or restrain with respect to Top Dead Centre (TDC) of the cylinder block. In conventional methods, piston topping was done by the means of a depth gauge which is prone to deviations. The major disadvantage of this manual method is that it involves more worker fatigue and lesser accuracy. Hence, an alternative approach to the measurement is found. In this method, a fixture is designed according to the dimensions of the engine gasket and the protrusions in the engine block. A fixture is a work-holding or supporting device used in the manufacturing industry which is used to securely locate (position in a specific location or orientation) and support the work, thereby allowing a smooth operation to take place. A Digitalized Display is placed on the fixture which is supported with the help of the clamp and the readings are taken. Then, the values are made to zero with the help of reset button so that the value will not vanish while readings are taken. I INTRODUCTION Piston topping refers to the measurement of displacement of the piston in excess or restrain with respect to the top dead centre of the cylinder block. Displacement of piston is subjected to a tolerance limit since its position at the top dead centre is not achieved every time practically. The limits used in Simpsons Pvt Ltd are-10 to +10 thou for Non Pre-Topped piston and -5 to +5 thou for Pre-Topped Piston. Where, 1 Thou = 1/1000 inches. Natarajan, Naveen, Parthipan Raj Page 103

2 A. Method currently used The conventional method of piston topping is by means of a depth gauge as shown in the figure. As discussed earlier, the piston topping is measured during the assembly of the cylinder block is as reference for measurement and the corresponding deviation in the position on the piston is measured. Added this measurement is considered effective when measured at the two extreme positions of the piston head along the axis of the gudgeon pin as the inclination factor of the pin is to be considered. Fig. 1 : Piston Topping II LITERATURE SURVEY A measuring device is a device used to make measurements or in order to display certain information, like time. A wide variety of tools exist which serve such functions, ranging from simple pieces of material against which sizes can be measured to complex pieces of machinery. Depending on usage, a measuring device can be described as "a device for measuring a physical quantity", for example "to determine thickness, gap in space, diameter of materials, or pressure of flow", or "a device that displays the measurement of a monitored system by the use of a needle or pointer that moves along a calibrated scale". A. Bore Measuring Gauges A bore gauge is a convenient term for the measuring or transfer tools that are used in the process of accurately measuring holes. A typical bore measuring gauge is shown in the figure. Fig. 2 : Bore Measuring Gauges Natarajan, Naveen, Parthipan Raj Page 104

3 B. Dial Bore Gauges A dial or vernier bore gauge measures a bore directly. The gauge has three symmetrical anvils that protrude from the gauge body that are connected to the dial or micrometer mechanism. As the knob is rotated it moves the anvils in or out with respect to the measurements. The knob usually has a slipping mechanism to take the feel out of the device and increase reliability between measurements. is the mean diameter of the three anvils, and is usually good. C. Piston Topping With Eddy current Sensors It is a mechatronic approach in which the piston topping is carried out with the help of eddy current sensors. Eddy current sensors from Micro-Epsilon are designed for non-contact measurement of displacement, distance, position, oscillation and vibrations. They are particularly suitable when high precision is required in harsh industrial environments (pressure, dirt, temperature). Eddy current sensors from Micro-Epsilon offer extremely precise measurements where sub-micron accuracy is required. They are robust sensors. Eddy current sensors do not recognize non-conductive materials. For this reason, dust, dirt and oil do not affect the measurement. This fact, combined with the sensor s robust, temperature-compensated design, enable measurements in harsh, industrial environments. The Eddy current sensor based piston topping, shown in the figure, measures in the range of 2-4mm. Fig. 3 : Eddy current sensor D. Piston Topping With Depth Gauges A depth gauge is a pressure gauge that displays the equivalent depth in water. Older types used a mechanical mechanism and analog display. The piston topping is measured during the assembly of the cylinder block is as reference for measurement and the corresponding deviation in the position on the piston is measured. Added this measurement is considered effective when measured at the two extreme positions of the piston head along the axis of the gudgeon pin as the inclination factor of the pin is to be considered. Moreover for multi-cylinder engines, this process needs to be followed for individual pistons which are more timeconsuming. It is also prone to many errors in the measurement including the man-made ones. Natarajan, Naveen, Parthipan Raj Page 105

4 III DESIGN AND ANALYSIS The construction of digitalized display is given below. The design is proposed in such a way that the gasket of the engine block is taken into consideration and it is traced for identifying the suitable dimensions of the set up. Also, the protrusions are considered so that the total display setup can be mounted easily on the engine block. The major components used in the design are explained below. A. Major Components of the Design There are various components used in the design which ensures the easy handling and high accuracy rate in piston topping. The components are designed separately and then they are assembled to form the required design for the inline engines. The components are denoted separately as shown in the figure. Fig. 4 : Design Components 1) Holding Plate The holding plates are those components which are used for the movement of the digital display in a horizontal direction. They are provided with a groove along which the display can be moved. The no of grooves or the guide ways can be provided depending upon the requirement. If the height between the tip of the probe and the piston head is high, then the display can be placed in some other suitable groove. Mild Steel is suitable material for the holding plate shown in the figure. Fig. 5 : Detailing of Holding plate 2) Sliding Block Natarajan, Naveen, Parthipan Raj Page 106

5 The sliding block is one of the major components of the design. It is attached to the holding plate along with the digital display. This sliding block also moves horizontally along the groove provided in the holding plate. It acts as the guide ways which is present in some machining devices like radial drilling machine along which the height between the tip of the probe and the piston head can be easily varied. It is provided with the lock nuts which holds the sliding block firmly along with the holding plate. Mild Steel is the recommended material for the sliding block. The sliding block views are shown in the figure. Fig. 6 : Detailing of sliding block - Front View Fig. 7 : Detailing of sliding block - Side View 3) Clamp A clamp is a fastening device to hold or secure objects tightly together to prevent movement or separation through the application of inward pressure. In the United Kingdom and Australia, the term cramp is often used instead when the tool is for temporary use for positioning components during construction and woodworking; thus a G cramp or a sash cramp but a wheel clamp or a surgical clamp. The design of the clamp is shown in the figure. Fig. 8 : Detailing of Clamp Natarajan, Naveen, Parthipan Raj Page 107

6 4) Groove In manufacturing or mechanical engineering a groove is a long and narrow indentation built into a material, generally for the purpose of allowing another material or part to move within the groove and be guided by it. Examples include: A canal cut in a hard material, usually metal. Mild Steel is the suitable material for the groove. This is shown in the figure. Fig. 9 : Detailing of Groove - Front View Fig. 10 : Detailing of Groove - Side View 5) Slider Slider is a device which is provided to the dial shaft which enables the sliding block and the display to slide horizontally along the holding plate. Mild Steel is the suitable material for the slider. The slider is shown in the figure. Fig. 11 : Detailing of Slider Natarajan, Naveen, Parthipan Raj Page 108

7 6) Dial Shaft The Dial shaft is the shaft in which the digital display slides horizontally so that it can be fixed and positioned after moving them to the desired place. Stainless Steel is suitable material for the dial shafts. The dial shaft is shown in the figure. Fig. 12 : Detailing of Dial shaft 7) Lock Nuts A locknut, also known as a lock nut, locking nut, prevailing torque nut, stiff nut or elastic stop nut, is a nut that resists loosening under vibrations and torque. Elastic stop nuts and prevailing torque nuts are of the particular type where some portion of the nut deforms elastically to provide a locking action. The first type used fibre instead of nylon and was invented in 1931.Locknuts, jam nuts, lock washers, and thread-locking fluid are ways to prevent vibration from loosening a bolted joint. Mild Steel is the suitable material for the Lock nuts which is shown in the figure. Fig. 13 : Detailing of Lock Nuts B. Proposed Design The Design is done based on the dimensions of the engine block with the help of engine gasket. The design for two cylinder, three cylinder and four cylinder engines are explained below. 1) Two Cylinder Engines The design suitable for two cylinder engine is shown in the figure. It consists of two pistons on which the probe of the digital display is going to be placed. The display moves horizontally along the groove provided in the holding plate which are placed beside the display. The vertical guide ways are provided in which the display can be adjusted and moved in the vertical direction. Displays slides along the dial shafts for positioning and after the positioning is done, the knobs which are provided in the dial shafts are used to hold the display Natarajan, Naveen, Parthipan Raj Page 109

8 tightly and hence it make sure that the display will not move away from the point where it is positioned. The lock nuts provide an extra support for fixing the display. Fig. 14 : Proposed Design for two cylinder engines 2) Three Cylinder Engines The experimental setup and the working process is same as in two cylinder engines. But the difference is three dials are placed for three pistons. The digital dials are positioned according to the cavity provided in the piston and then the readings are taken. The proposed design for the three cylinder engines is shown in the figure. Fig. 15 : Proposed Design for three cylinder engines 3) Four Cylinder Engines In four cylinder engines, four digital display is placed on the sliding dial shaft and then the dials are made to slide according to the requirements. The major difference between the design is the dimension of the engine block, no of pistons and the length of the dial shafts. Likewise, the dial shaft can be changed and used according to the dimensions of the engine block. Fig. 16 : Proposed Design for four cylinder engines Natarajan, Naveen, Parthipan Raj Page 110

9 C. Importance of the Proposed Design The design is done by considering the effect of cost and easiness in handling the device. The major advantage of this design is, it is very easy to use and possess less weight when it is fabricated with the help of mild steel rod. The fabrication based on the proposed design can be done with the help of casting and moulding. It is very effective and accurate. But the problem is the weight of the experimental set up and the cost. The weight is lot more higher and the cost is very high. One kg of casting costs Rs and weighs about 10kgs. It cannot be placed over an engine block which is held by a conveyor. An experimental set up of such weight cannot be carried easily by the operators. But, this experimental set up can be manufactured by mild steel sheet of 2mm thickness which can be welded together after the machining process and then it can be sent to surface grinding for the final finish. Thus it can be very much easier to use and handle. D. Analysis of Dial Shafts The Dial shaft is the one which bares the weight of the Digitalized Dial Gauge. So, in order to prove that the shaft is unbreakable to the given load, analysis of dial shaft is done. 1) Analysis of Dial Shaft for 2-Cylinder Engines The design of the shaft was analysed. The Dial gauge is placed after which the shaft undergoes deformation. This deformation depends upon the distances at which the Gauges are placed. Based on the overall result of this analysis, we can conclude that the design of dial shaft for 2,3, and 4 cylinder engines are safe. Fig. 17 : Analysis of Dial shaft for 2 Cylinder Engines Natarajan, Naveen, Parthipan Raj Page 111

10 Fig. 18 : Analysis of Dial shaft for 3 Cylinder Engines Fig. 19 : Analysis of Dial shaft for 4 Cylinder Engines IV RESULTS AND DISCUSSIONS From the above design and selection of the materials, it is clear that the piston topping method has become a lot more easier than the conventional method. These design can be implemented for various engines, especially the inline engines. The fixture design is done according to the dimensions of various engines. It can also be used in V engines. In the case of V engines, two fixtures can be used. The difference between the present method and proposed method was analysed and then the variations in error percentage, process ratio and takt time etc. The variations are tabulated and then displayed as follows. A. Present Method The various time for the present methods are calculated as follows: 1) Uptime Uptime % = (Actual time Value added time/availability time) x 100 Natarajan, Naveen, Parthipan Raj Page 112

11 Actual time for a month = 30 days * 24 hrs * 60 min = Value added time = 15 min. Uptime % = (( ) / 43200) Uptime = 99.96% 2) Takt Time T = T a / D where, T = Takt time, e.g. [work time between two consecutive units] T a = Net time available to work, e.g. [work time per period] D = Demand (customer demand), e.g. [units required per period] Takt Time = (Available time for labors / Total daily quantity sent for piston topping) 3) Process Ratio Takt Time = (480 / 120) ; Takt Time = 4 min. Value added time = 15 min. Process lead time = Actual time for labours - Allowance time Lunch break = 1 hr Miscellaneous time allowance = 20 min Process Lead time = Actual time for labours - (Lunch break + Miscellaneous time allowance) Process Lead Time = = 400 min. Process ratio = (Value Added Time / Process Lead Time) * 100 Process ratio = (15 / 400)*100 = 3.75% 4) Error Error = ((True value - measured value) / True value )*100 True value = +5 thou = 0.127mm Measured value = +3 thou = 0.077mm Error = ( / 0.127)*100 = 39.37% B. Case Study for Present Method Natarajan, Naveen, Parthipan Raj Page 113

12 TABLE I : CASE STUDY FOR PRESENT METHOD Description Cycle Time 15 min Operator 1 Uptime % % Available Time 480 Process Ratio 3.75 % Error % Piston Topping C. Proposed Method The values for the proposed method can be given as follows: 1) Uptime The uptime value for the proposed method is calculated as Uptime % = (Actual time Value added time/ Availability time) x 100 Actual time for a month = 30 days * 24 hrs * 60 min = Value added time = 11 min.(measured) Uptime % = (( ) / 43200) Uptime = 99.97% 2) Process Ratio Value added time = 11 min. Process lead time = Actual time for labours - Allowance time Lunch break = 1 hr Miscellaneous time allowance = 20 min Process Lead time = Actual time for labours - (Lunch break + Miscellaneous time allowance) Process Lead Time = = 400 min. Process ratio = (Value Added Time / Process Lead Time) * 100 Process ratio = (11 / 400)*100 = 2.75% 3) Error Error = ((True value - measured value) / True value )*100 Natarajan, Naveen, Parthipan Raj Page 114

13 True value = +5 thou = 0.127mm Measured value = +4 thou = mm Error = ( / 0.127)*100 = 20% 4) Takt Time Takt Time = (Available time for labors / Total daily quantity sent for piston topping) Takt Time = (480 / 120) Takt Time = 4 min. D. Case Study for Proposed Method The proposed method for piston topping is lot more efficient and good when compared to the preset method for the piton topping. The percentage of error is reduced. TABLE II : CASE STUDY FOR PROPOSED METHOD Description Cycle Time 11 min Operator 1 Uptime % % Process Ratio 2.75 % Error 20 % Piston Topping E. Importance of Method The major importance for implementation in this method is that it improves the quality of a product by decreasing the error factor. Here are some important aspects of proposed method for piston topping. It improves the process by decreasing the process lead time through proper utilization of man and equipment. It increases the accuracy in the measurement. Worker fatigue is completely reduced and human errors are eliminated. Time consumption is reduced by changing the analog display to digital display where the zero value can be brought easily with the help of reset button but in analog method, it is not that easy as it is in the digital display. Natarajan, Naveen, Parthipan Raj Page 115

14 V CONCLUSION This method is implemented according to the environmental conditions in the workplace. In the case of V Engines, two fixtures can be used separately by changing the dimensions of the dial shaft based on the requirement of the engine. Every parts that are employed in this design is the same and its working process remains the same. The dial shaft must be selected properly. The protrusions in the engine plays a major role in designing and the implementation. ACKNOWLEDGEMENT This satisfaction that accompanies the successful completion of a task would be incomplete without a mention of all people who have helped us to make it a reality. First and foremost, we would like to thank Dr.K.Srinivasan M.E.,Ph.D, our principal and our Dean Dr.K.Kathiravan M.Tech., Ph.D. for providing us support and all necessary facilities for the completion of the project. We would like to thank Dr.V.Elango M.E., Ph.D, Head of the Mechanical Department and all other faculty members of the Department of Mechanical Engineering, especially our project committee members, Mr.S.Anand M.E., Mr.G.K.Sathish Kumar M.E., Mr.K.G.Ashok M.E., Mr.B.Gopinath M.E.,M.B.A., Mr.S.Dheepak M.E., and Mr.K.Senthilnathan M.E., for their support. We are deeply indebted to Mr.J.Hariprasad M.E., our project guide for his valuable insight and unwavering support over the course of our project. Our sincere and heartfelt thanks to him for helping us develop our idea into a working model. We sincerely thank Mr.G.Mugundhakrishnan, Senior Engineer, Engine Assembly, Simpsons Pvt Ltd for his role as External Guide who gave us all instructions in the company and helped us as and when required which led to the successful completion of the project. Most importantly, we would like to remember our parents for standing by us through thick and thin, and for providing the monetary and emotional support that was necessary for the completion of our project. REFERENCES [1] Amir Sadrzadeh (2012) A genetic algorithm with the heuristic procedure to solve the multi-line layout problem, Journal of Computers and Industrial Engineering, vol. 62(4), pp [2] De Silva, G. M. S. (2002), Basic metrology for ISO 9000 certification, Butterworth-Heinemann, p. 28, ISBN [3] J. G. Landels, Engineering in the Ancient World, ISBN Natarajan, Naveen, Parthipan Raj Page 116

15 [4] Hatice E. Sanli, Fahrettin Eldemir Spiral facility layout generation and improvement algorithm. [5] Natarajan, Naveen, Parthipan Raj Page 117