Design and Dynamic Analysis of an Automatic Tool Changing Mechanism used in VMC

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ISSN (Print): 2321-5747, Volume-1, Issue-1, 2013

129

Design and Dynamic Analysis of an Automatic Tool Changing Mechanism used in VMC

M. B. Vaghela, V. J. Savsani & S. B. Jadeja

B. H. Gardi College of Engineering & Technology, Rajkot, Pandit Deendayal Petroleum University, Gandhinagar,

E-mail : [email protected], [email protected], [email protected]

Abstract - Design analysis of high speed automatic tool changing mechanism for high speed machines like VMC, and minimize tool changing cycle time as compare with current used ATC. To get the result of displacement, velocity, acceleration at every connecting point for tool changing cycle time 2s by using mechanism module in Creo Parametric 1.0 software. By dynamic analysis get the results for acceleration at every connecting point in tool changing mechanism. Main goal of this paper is find out total force applied at every connecting points with consider total mass of component and also consider relative force applied at point from getting acceleration result from the dynamic analysis of tool changing mechanism in Creo parametric 1.0 software. With getting this total applied force, do the FEA for critical component of tool changing mechanism and as per that result if possible than redesign the component ant try to reduce the tool changing cycle time.

Keywords - ATC: Automatic Tool Changer, Creo Parametric 1.0, Dynacam 10, Dynamic Analysis, FEA: Finite Element Analysis, Motion Analysis, Tool Changing Mechanism, and VMC: Vertical Machining Centre.

I. INTRODUCTION

Today’s fast growing automatic manufacturing process; to develop high speed automatic machine is a very challenging task for that required to develop high speed tool changing mechanism with minimum tool changing cycle time for VMC type of machine.

Tool changing mechanism of ATC for VMC type of machine having simultaneously two types of motion which is occurred at shaft, downward and upward motion and rotary motion of shaft. For downward and upward motion of shaft used radial cam and for rotary motion of shaft used globoidal cam. To design and analysis of radial cam used graph [8] of arm downward and upward movement versus cam rotation angle and

for globoidal cam used graph [8] of arm rotating chart versus cam shaft rotation angle with the help of Dynacam 10 software [10]. To design and develop high speed tool changing mechanism, do the design and analysis of some critical components like radial cam, globoidal cam [1] and take existing design of shaft and linkage mechanism from the company [9] and also design the other components which is required for make a complete assembly of tool changing mechanism of ATC [1]-[2].

ATC with using Creo Parametric 1.0 software and to get the results of displacement by position analysis, velocity by kinematic analysis and acceleration by dynamic analysis for each defined connecting points with using mechanism module of Creo parametric 1.0 software. Compare result of displacement of shaft with actual required movement and from the result of dynamic analysis got the result for acceleration, with using acceleration result find the total applied force at each define connecting point.

II. DESIGNANDANALYSISOFCAMS In tool changing mechanism of ATC two motions which is occurred at shaft, downward and upward motion of shaft and rotary motion of shaft. For downward and upward motion of shaft used radial cam and for rotary motion of shaft used globoidal cam.

A. Design and Analysis of Radial Cam

To design and analysis of radial cam used Dynacam 10 software [10] and graph of arm downward and upward movement versus cam rotation angle[8].Radial cam design for maximum displacement 115 mm. From Dynacam 10 software getting results of displacement, velocity, acceleration and jerk for each degree 0° to 360° and also get cam profile of radial cam. Based on

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130 this cam profile prepare solid model of radial cam [4]

using Creo Parametric 1.0 software as shown in “Fig.

1”.

Fig. 1 : Radial cam B. Design and Analysis of Globoidal Cam

To design and analysis of globoidal cam used Dynacam 10 software [10] and graph of arm rotation angle versus cam rotation angle [8]. From Dynacam 10 software getting results of displacement, velocity, acceleration and jerk for each degree 0° to 360°. Prepare solid model of globoidal cam using Creo Parametric 1.0 software as shown in “Fig. 2”.

Fig. 2: Globoidal cam

III. DESIGN OF TOOL CHANGING

MECHANISMOFATC

To design final tool changing mechanism assembly [3] of ATC make a design of radial and globoidal cam [5] and take existing design of shaft, linkage from company [9] and also design other components required to make an assembly using Creo Parametric 1.0 software. Prepare design of final tool changing mechanism assembly of ATC in Creo Parametric 1.0 software as shown in “Fig. 3”.

Fig. 3 : Tool changing mechanism of ATC IV. MOTIONANALYSIS

In Creo Parametric 1.0 software powerful mechanism module is given for motion analysis. There can be prepare mechanism assembly [3] as per connecting joint and motion; also do the analysis for position, kinematic, dynamic, static and force balance and measure definition for position, velocity, acceleration, connection reaction, net load and may more in mechanism module. Do the motion analysis [6]

of tool changing mechanism of ATC for position, kinematic and dynamic analysis for tool changing cycle time 2 s.

A. Position Analysis

For position analysis using Creo Parametric 1.0 software, after completion of final assembly of tool changing mechanism select analysis definition type position in mechanism module and run the analysis for tool changing cycle time 2 s. To measure the position of each connecting point, select measure results graph type measure versus time and measure definition type position in mechanism module and get the results of displacement for each connecting point as shown in

“Fig. 4”.

Fig. 4 : Displacement chart of Tool Changing Mechanism

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131 Get the result of displacement at shaft 114.95 mm which is very much nearest value as per required displacement 115 mm for upward and downward movement of shaft.

B. Kinematic Analysis

For kinematic analysis using Creo Parametric 1.0 software, select analysis definition type kinematic in mechanism module and run the analysis for tool changing cycle time 2 s. To measure the velocity of each connecting point, select measure results graph type measure versus time and measure definition type velocity in mechanism module and get the results of velocity for each connecting point as shown in “Fig. 5”.

Fig. 5: Velocity chart of Tool Changing Mechanism From the kinematic analysis of tool changing mechanism of ATC for tool changing cycle time 2 s, maximum velocity obtain 1638.76 mm/s at both the end point of arm.

V. DYNAMICANALYSIS

For dynamic analysis using Creo Parametric 1.0 software, add the En24 material [7] to each component of tool changing mechanism assembly and define gravity, direction and magnitude to simulate the gravitational force and select analysis definition type dynamic in mechanism module and run the analysis for tool changing cycle time 2 s. To measure the acceleration of each connecting point, select measure results graph type measure versus time and measure definition type acceleration in mechanism module and get the results of acceleration for each connecting point.

By dynamic analysis using Creo Parametric 1.0 software get the acceleration at following points.

A. Acceleration at Arm-1

Point arm-1 is a connecting point of yellow color arm and green color tool as shown in “Fig. 3”. From dynamic analysis of tool changing mechanism for tool changing cycle time 2 s, result of acceleration at arm-1 get as shown in “Fig. 6”.

Fig. 6 : Acceleration at Arm-1 B. Acceleration at Arm-2

Point arm-2 is a connecting point of yellow color arm and red color tool as shown in “Fig. 3”. From dynamic analysis of tool changing mechanism for tool changing cycle time 2 s, result of acceleration at arm-2 get as shown in “Fig. 7”.

Fig. 7 : Acceleration at Arm-2 C. Acceleration at Shaft

Shaft point is a connecting point of arm and shaft as shown in “Fig. 3”. From dynamic analysis of tool changing mechanism for tool changing cycle time 2 s, result of acceleration at shaft get as shown in “Fig. 8”.

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132 Fig. 8 : Acceleration at Shaft

D. Acceleration at Link1-1

Link1-1 point is a connecting point of pink color link2 and yellow color link1 as shown in “Fig. 3”. From dynamic analysis of tool changing mechanism for tool changing cycle time 2 s, result of acceleration at link1-1 get as shown in “Fig. 9”.

Fig. 9 : Acceleration at Link1-1 E. Acceleration at Link1-2

Link1-2 point is a connecting point of shaft and yellow color link1 as shown in “Fig. 3”. From dynamic analysis of tool changing mechanism for tool changing

cycle time 2 s, result of acceleration at link1-2 get as shown in “Fig. 10”.

Fig. 10 : Acceleration at Link1-2 F. Acceleration at Link2-1

Link2-1 point is a connecting point of pink color link2 and green color link3 as shown in “Fig. 3”. From dynamic analysis of tool changing mechanism for tool changing cycle time 2 s, result of acceleration at link2-1 get as shown in “Fig. 11”.

Fig. 11 : Acceleration at Link2-1 G. Acceleration at Link2-2

Link2-2 point is a connecting point of pink color link2 and yellow color link1 as shown in “Fig. 3”. From

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133 dynamic analysis of tool changing mechanism for tool changing cycle time 2 s, result of acceleration at link2-2 get as shown in “Fig. 12”.

Fig. 12 : Acceleration at Link2-2 H. Acceleration at Link3-1

Link3-1 point is a connecting point of radial cam and green color link3 as shown in “Fig. 3”. From dynamic analysis of tool changing mechanism for tool changing cycle time 2 s, result of acceleration at link3-1 get as shown in “Fig. 13”.

Fig. 13 : Acceleration at Link3-1

I. Acceleration at Link3-2

Link3-2 point is a connecting point of pink color link2 and green color link3 as shown in “Fig. 3”. From dynamic analysis of tool changing mechanism for tool changing cycle time 2 s, result of acceleration at link3-2 get as shown in “Fig. 14”.

Fig. 14 : Acceleration at Link3-2 VI. RESULTDISCUSSION

From dynamic analysis do in Creo Parametric 1.0 software gets the result of acceleration at each connecting point of tool changing mechanism of ATC for tool changing cycle time 2 s, as shown in “Fig. 15”.

Fig. 15: Maximum Acceleration at each point of Tool Changing Mechanism

From the dynamic analysis of tool changing mechanism of ATC for tool changing cycle time 2 s, maximum acceleration obtain 59068.7 mm/s² at link1-2 and link2-1.

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134 VII. CONCLUSION

Due to lengthy analytical calculation used Creo Parametric 1.0 powerful software for position, kinematic and dynamic analysis. By position analysis obtain very close displacement at shaft of tool changing mechanism, actual displacement is 115 mm and by position analysis obtain 114.95 mm displacement at shaft. So deign of tool changing mechanism proper.

Obtain the maximum acceleration at each connecting point of tool changing mechanism of ATC by dynamic analysis in Creo Parametric 1.0 software.

With this acceleration result get the total force at each connecting point and with this total force and define proper constraint do the finite element analysis. After concluding the FEA result can be optimize the design of

component and tool changing mechanism.

VIII. REFERENCES

[1] “Cam Design and Manufacturing handbook”, Robert L. Norton, Pearson Education.

[2] “Theory of Machine and Mechanisms”, Joseph E.

Shighley, Oxford Uni. Press.

[3] Wen-Tung Chang and Long-Iong Wu, “Tolerance analysis and synthesis of cam-modulated linkages”, Elsevier Science Ltd, Mathematical and Computer Modeling, Vol. 57, 2013, pp.641- 660.

[4] Sun Jianping and Tang Zhaoping, “The Parametric Design and Motion Analysis about Line Translating Tip Follower Cam Mechanism Based on Model Datum Graph”, Elsevier Science Ltd, Procedia Engineering 23, 2011, pp.439 – 444.

[5] Zongyu Chang, Changmi Xu, Tongqing Pan, Lei Wang and Xichao Zhang, “A general framework for geometry design of indexing cam mechanism”, Elsevier Science Ltd, Mechanism and Machine Theory, Vol. 44, 2009, pp. 2079–

2084.

[6] Owen Butler, Buddhi Paranamana, William Powers and Arvind Srinivasan, “Project report on Design of a servo driven, adjustable pick and place mechanism”, Worcester Polytechnic Institute, 2011.

[7] “Machine Tool Design Handbook”, Cmti, The McGraw-Hill.

[8] Manual of “Pragati Automatic Tool Changer 4020 V”, http://www.pragati-automation.com.

[9] Jyoti CNC Automation Pvt. Ltd., Rajkot, http://www.jyoti.co,in.

[10] Dynacam 10,

http://www.designofmachinery.com.

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