2016 International Conference on Applied Mechanics, Mechanical and Materials Engineering (AMMME 2016) ISBN: 978-1-60595-409-7 Development of Resin Vacuum Potting Equipment Bin HONG 1,*, Hong-mei WANG 2, Ju HU 2, Qing LIU 2 and Jing HOU 2 1 Internal Combustion Engine Research Institute of Tianjin University, China 2 Tianjin Tianbo Science & Technology Co., Ltd., China *Corresponding author Keywords: Potting machine, Potting process, Final-tank mixed type, On-line mixing type. Abstract. In order to resolve the problem of bubble defect after encapsulation, from the vacuum casting process requirements, the equipments were developed for the needs of production and scientific research. The development of the equipment adopts two schemes: final-mixed type and on-line mixing type. The equipment adopts compact design, automatic control, and easy to operate. The system functions of the prototype were tested and their technical indexes meet the design requirements. And the encapsulation parts encapsulated by the prototypes are tested to solve the bubble defect of the high-pressure module. Potting products have been detected, and it shows the two equipments effectively improved the bubble defects. Introduction Vacuum potting technology is the key technology to encapsulate the electrical components under the vacuum condition and curing at a certain temperature and pressure conditions. This technology can be achieved on the insulation protection of electrical components and improve the product's pressure rating and moisture-proof shock [1,2]. This technology, originated in the 1960s, has been widely used in aerospace, automotive, electronics and power industries. And it achieved good economic and social benefits. Vacuum potting products have many advantages, such as high reliability, low leakage coefficient, the small partial discharge, and high dielectric strength. Therefore, the vacuum potting technology is an important means to reduce the risk of electrical component insulation and improve the reliability of electrical systems [3,4]. The reasonable vacuum potting process is the key of product quality of the electrical insulation products [5-7]. Discussion of the bubble defects has been a sensitive issue in the industry. Since the bubble defects after vacuum potting are usually found in the tiny gap of the complex cavity of the electrical components, and it is difficult to find the bubble defect by the conventional detection means. When the bubble defects lead to the quality of the entire electrical system accidents in the field operation, the engineer was aware of the hazards of bubble defects. The technology to solve bubble defects by vacuum casting mainly depends on the traditional or personal experience of the formation. In order to solve the problem of bubble defect in the potting products, two kinds of vacuum potting equipment, which are suitable for the experimental research and mass production, are developed. Firstly, the overall design scheme of vacuum encapsulation equipment is expounded to determine the key technical parameters and equipment compositions. Then, the equipment is developed through the design and research of the key technologies, such as mixing technology, degassing technology and control technology, Development of Vacuum Potting Equipment. Process Analysis The vacuum potting process comprises the following steps: Vacuum degassing of potting material, dry the workpiece, vacuum degassing of vacuum potting chamber to drain the gas inside the device and finally potting. It infiltrate into the electrical components depend on the flowability and permeability of the resin. And finally cure in a certain temperature conditions [8].
Vacuum pouring process has two types, final-mixed type and on-line mixed type [9,10]. First, the resin and the hardener are haled into the degassing tank according to a certain percentage. Under vacuum conditions, the stirrer under the motor drive stirs them. The time cannot exceed 1 hour. At last, the products are potting in chamber. This process separates mixing and metering. On-line mixed type is a more advanced vacuum potting technology [11,12]. First, the resin and the hardener are respectively metered according to the pre-set amount. Then, they are mixed under vacuum conditions. The potting materials are metered and mixed according to the actual needs. Mixed materials have the advantages of low viscosity, good Infiltration. Process Analysis In order to solve the problem of bubble defect in the potting products, two kinds of vacuum potting equipment, which are suitable for the experimental research and mass production, are developed. The equipment of final-mixed type is suitable for a variety of potting materials and preliminary scientific research. The equipment of on-line mixed type is suitable for mass production. The device uses a compact design, automatic control, easy to operate. The main function includes: (a) Storage tanks with the functions of stirring, degassing and heating. (b) High-precision volumetric metering device (c) Pressurized device with overvoltage protection switch uses dry air or nitrogen to pressurize the potting chamber. (d) Simple cleaning device can prevent potting material curing in pipeline. And to ensure that the equipment in the long-term shutdown state without residual mixed material. (e) Safe and effective vacuum device. (f) Heating device for potting materials and the pipeline, and temperature drift is less than 2. (g) The electrical system carries on the overall control to the equipment, and guarantees each system automatic and coordinated work. Solution Design The Final-Mixed Type The potting equipment of the final-mixed type mixed and degassed the potting material in a final-mixed tank. The layout of the device is the upper and lower structure. The degassing tank is perpendicular to the potting chamber. The temperature system adopts intelligent PID control and its accuracy is high. The equipment is operated manually and automatically. The schematic diagram of this potting equipment is shown in Figure 1. 1.0 Vacuum-Pressure Potting chamber 2.0 Potting valve 3.0 final-mixed Tank 4.0 Spare Tank 5.0 Vacuum controlling system 6.0 Heating system 7.0 Pneumatic system 8.0 Framework 9.0 Cleaning system Figure 1. The Process schematic of the final-mixed type.
Potting chamber, with programmed thermal control function, has 4-points temperature measurement and 1 point temperature control. Temperature sensor is easy to disassemble. The pallet can be rotated manually. The vacuum and pressure of the potting chamber should be sampled in the final-mixed tank nearest test. The observation window is used to observe degassing conditions to determine the optimum process parameters. The potting chamber has a pressurized function, and the pressurized gas is dry compressed air or nitrogen. Potting chamber with pressure relief valve to ensure the safety of the operator, and the pressure value can be remote control operation. Cleaning device consists of cleaning tank, storage tank and pipeline valve composition, through controlling the pneumatic to clean the final-mixed tank and potting pipeline valve cleaning. The cleaning work is done automatically under the fully closed state. The On-Line Mixed Type The schematic diagram of the on-line potting equipment is shown in Figure 2. The equipment is composed of resin tank, harder tank, metering pump, mixer, potting chamber and control unit. The use of visual human-machine interface is suitable for the actual mass production. A vacuum nozzle is equipped for small batch continuous production. Process the potting material under fully enclosed state to avoid contact with the human body. The metering pump and the quantitative pump are integrated together to improve the accuracy. On-line mixed mode improves the mixing efficiency and does not need waiting time. Modular design enhances system operability. 1.0 Vacuum-Pressure Potting chamber 2.0 Metering and Mixing System 3.0 Resin Tank A 4.0 Hardener Tank B 5.0 Vacuum control system 6.0 Heating system 7.0 Pneumatic system 8.0 Framework 9.0 Cleaning system Figure 2. The Process schematic of the on-line mixed type. Prototypes (a) 3D design (b) prototype Figure 3. 3D design and the prototype of the final-mixed type.
The 3D design and the prototype of the final-mixed type is shown as Figure 3. The final-mixed tank has a thermal control function, low pressure degassing function, automatic mixing function and the formation of film degassing function. The minimum potting amount is 50ml, and the maximum potting amount is 500ml. The final-mixed tank, with a windows to observe the inside situation, is made of stainless steel. It adopts high-grade vacuum valve and standard air-tight connection. And the inner wall is smooth to facilitate cleaning. The 3D design and the prototype of the on-line mixed type is shown as Figure 4. First, resin and harder will be respectively inhaled into the storage tank, and it start stirring and degassing. Secondly, the potting amount is pre-set through the MCGS interface. Then, potting under vacuum condition, and curing according a certain temperature curve. Finally, reset and clean the device. (a)3d design (b) prototype Figure 4. 3D design and the prototype of the on-line mixed type. Summary In order to resolve the problem of bubble defect after encapsulation, from the vacuum casting process requirements, the equipments were developed for the needs of production and scientific research. The development of the equipment adopts two schemes: final-mixed type and on-line mixing type. The equipment adopts compact design, automatic control, and easy to operate. The system functions of the prototype were tested and their technical indexes meet the design requirements. And the encapsulation parts encapsulated by the prototypes are tested to solve the bubble defect of the high-pressure module. Potting products have been detected, and it shows the two equipments effectively improved the bubble defects. Acknowledgement Sponsored by the Science and Technology Planning Project of Tianjin, China (14ZXCXGX003). References [1] James V Crivello, Zhibiao Mao, Synthesis of novel multifunctional siloxane oligomers using sol-gel techniques and their photoinitiated cationic polymerization[j], Chem Mater, 1997, 9: 1554~1564. [2] T Agag, T Takeichi, Synthesis and characterization of Resin film cured with reactive polyimide [J], Polymer, 1999, 40(23): 6557~6563. [3] Rath S K, Chavan J G, Sasane S, et a1, Two component silicone modified Resin foul release coatings: Effect of modulus, surface energy and surface restructuring on pseudobanacle and macrofouling behavior[j], Applied Surface Science, 2010, 256: 2440~2446.
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