2011 International
Conference on Computational Material Science
Design and Development of a New Automated and High Speed Cap Sealing System Zheng (Jeremy) Li University of Bridgeport, 221 University Ave., Bridgeport, CT 06825, USA
[email protected] Keywords: Ultrasonic welding, Automated sealing, Cost-effective manufacturing Abstract. Plastic welding is a technical process of welding plastic component together and it is one of the primary processes of joining plastics. There are several types of techniques in the plastic welding including hot gas welding, extrusion welding, contact welding, hot plate welding, injection welding, and friction welding, To increase the plastic welding speed and sealing capacity, this research introduces a new automated and high speed cap sealing system applied to cartridge filled with gas product. The computeraided modeling analysis and prototype testing show that this automated and high speed welding system has high production rate, good sealing quality, reliable function, and cost-effective manufacturing process.
Introduction One plastic welding process is using hot resource from outside to heat up the joining parts for sealing purpose
[1], [2]
. The hot air or hot metal tips were placed closed to the part surface or directly touch the
surfaces to be bond the work pieces
[3], [4]
. The high temperature softens the plastic parts and makes them
sticky so that the multiple surfaces can be bonded together
[5]
. Sometimes, a welding rod could be used in
the welding for filling the vacant or a bind material. The applications of this technology include hot gas welding, extrusion welding, contact welding and hot plate welding. Some welding methods make use of vibration between joining surface. One typical technique of this method is friction welding. In this way, they make two parts to be bonded together at a typically 100 - 300 kHz frequency and 1 - 2 mm amplitude. The ultrasonic welding technology will be used in this new plastic welding system. New Automated and High Speed Welding System Description Ultrasonic welding involves the use of high frequency sound energy to soften or melt the thermoplastic at the welding surface. The joining parts are being bonded together under welding force and subjected to ultrasonic vibration with a frequency of 20 – 40kHz. When ultrasonic vibrations stop, the molten material solidifies and weld is achieved.
2011 International
Conference on Computational Material Science
This new automated sealing system includes conveyor, gripping unit, placing mechanism, ultrasonic welding machine, cap and cartridge feeding mechanisms. The prototype of this automated and high speed welding system is shown in figure 1 and 2.
Fig.1 Automated and High Speed Cap Sealing System Layout Vertical Slider Horizontal Slider
Ultrasonic Welding Machine
Cap Gripper Cap Bowl Feeder
Gripper
Fig.2. Cap Feeding and Welding Mechanism When empty cartridge stops vertically under the welding machine horn, the gripper clamps to hold cartridge. The cap gripper with the double “V” shape clamps a cap from cap feeding system and moves upward by a vertical slider. The horizontal slider drives cap gripper and vertical slider toward the ultrasonic welding machine. Meanwhile the motor rotates cap gripper 180 degree angles. As cap being delivered to the position above cartridge, the gas is being filled in the cartridge, and the horizontal slider in the gripping
2011 International
Conference on Computational Material Science
system derives the gripper to insert cap into cartridge simultaneously. The caps will be separated and pushed out by a rotating wheel which can control the rotate degree and speed, shown in figure 3.
Fig.3. Sealing Cap Delivery System When cap is inserted into cartridge, the gripper releases cap and moves back to the initial location. The ultrasonic welding machine moves down by a slider and horn of ultrasonic welding machine touches cap to bond the parts. Technological merit The ultrasonic welding is the quickest welding method even with less than 1 second and can also avoid the damage in traditional cartridge cap sealing method. The traditional cap sealing methods use the mechanical principle using tight clearance between the bonded parts. Since the process of assembling parts needs punching cap into cartridge, it can bring a large swing load and vibration that could change the plug position due to manufacturing tolerance. This problem can be avoided in this new high speed ultrasonic sealing mechanism since the vibration occur in this new welding system is 60 – 100 µm. This new automated and high speed sealing system can be used to many other industrial applications including precision welding with high production rates. Computer-Aided Modeling and Simulation The computer-aided simulation of gas leaking rate Q can be determined as follow: Q = M * B * (Tb / Pb) * D2.5 * E * [(P12 - P22) / (L * g * Ta * Za * F)] 0.5 Here, B-constant
(1)
2011 International
Conference on Computational Material Science
D-cartridge diameter E-cartridge efficiency F-Darcy-Weisbach friction factor g-air specific gravity L-cartridge length Pb-pressure base P1-inlet pressure P2-outlet pressure M-air flow rate Ta-average temperature Tb-temperature base Za-compressibility factor The calculation from equation (1) indicates that the air leakage in this automated and high speed sealing mechanism is related to the air flow rate M and pressure drop (P1 - P2). This new automated and high speed welding system has good sealing capability that is verified and analyzed through the computer aided modeling and simulation. The simulation result, shown in Figure 4, indicated that the air leakage in this high speed sealing process can be ignored.
Figure 4.Gas leakage vs. cap linear speed
2011 International
Conference on Computational Material Science
Prototype Testing The prototype of this new automated and high speed sealing mechanism has been tested with results shown in Table 1. Table1. Gas leakage vs. cap linear speed Cap Linear Speed [Ft/Min]
Estimated Gas Leakage [SCFM]
Cap Linear Speed [Ft/Min]
Estimated Gas Leakage [SCFM]
10
0.0004
70
0.00091
20
0.00055
80
0.00093
30
0.00065
90
0.00096
40
0.00071
100
0.00098
50
0.00083
110
0.00101
60
0.00088
120
0.00106
Both prototype testing and computational simulation show the similar results that verifies the creditability and feasibility of this new automated and high speed cap sealing system with its good sealing functionality. Conclusion The application of automated and high speed manufacturing technologies brings revolution to the industrial productions with flexible, reliable, and cost-effective manufacturing control methodologies. Automated and high speed manufacturing is to use computer aided control system to reduce human interference, and prevent work forces from dangerous and hazard environment during manufacturing processes. It plays critical role and adds significant impact in modern industries. This technology is not only increasing the production quantity but also improving manufacturing quality. The study and analysis of this new automated and high speed cap sealing system can help to understand and develop more efficient high speed plastic welding systems to keep consistent welding quality, reduce production lead time, speed material handling process, improve work flow, and satisfy customer on their welding product demand with flexibility and convertibility in future manufacturing process and mass production.
References
2011 International
Conference on Computational Material Science
[1]. Pijush.K. Kundu and Ira. M. Cohen: Fluid Mechanics, 4th edition, Academic Press, (2008), ISBN 978-0-123-73735-9 [2] S. A. Isaev, P. A. Baranov, N. A. Kudryavtsev, D.A. and Lysenkoand A.E.Usachov: Comparative analysis of the calculation data on an unsteady flow around a circular cylinder obtained using the VP2/3 and Fluent packages and the Spalart-Allmaras and Menter turbulence models, Journal of Engineering Physics and Thermophysics, Vol. 78, No.6, (2005), pp 1199-2013. [3] C. Norberg: Fluctuating lift on a circular cylinder: Review and new measurements, Journal of Fluids and Structures Vol. 17, No. 1, (2003), pp. 57-61. [4] M.M. Zdravkovich: Flow Around Circular Cylinders, Applications of Physics, Vol. 2, No. 1, Oxford University Press, (2003). [5] J. Chakraborty, N. Verma and R.P. Chhabra: Wall effects in the flow past a circular cylinder in a plane channel: a numerical study, Journal of Chemical Engineering, Vol. 43, pp 1520 - 1537.
