Principle of Vacuum Blister Machine | Basic Structure of Vacuum Blister Machine---Pan'an Vacuum Blister Machine

Principle of Vacuum Blister Machine | Basic Structure of Vacuum Blister Machine---Pan'an Vacuum Blister Machine

As we all know, the vacuum blister machine (also known as the thermoplastic forming machine) is a high-grade packaging box and frame that absorbs the thermally plasticized PVC, PE, PP, PET, HIPS and other thermoplastic coils into various shapes. And other products of the machine, widely used in various packaging industries. In this article, the editor of Xianji.com will take you to understand the principle and basic structure of the vacuum blister machine. If you want to know, come and see! ---Pan'an Vacuum Blister Machine

The principle of vacuum forming

Vacuum forming is also called thermoplastic forming. This forming process mainly uses the vacuum suction generated by a vacuum pump to heat and soften thermoplastic plastic sheets such as PVC, PET, PETG, APTT, PP, PE, PS[1]. The mold is blistered into various shapes of vacuum covers, blister trays, blister shells, etc.

The vacuum forming process is a thermoforming method. A method of making open shell articles using thermoplastic sheets. The plastic sheet is cut into a certain size, heated and softened. With the help of the air pressure difference or mechanical pressure on both sides of the sheet, it is deformed and then attached to a specific mold contour surface. After cooling, it is shaped and trimmed.

Vacuum forming is a forming method that relies on vacuum force to stretch and deform the sheet. Vacuum force is easy to realize, master and control, so simple vacuum forming is the earliest and most widely used thermoforming method.

The vacuum system is composed of vacuum pump, gas storage tank, valve, pipeline and vacuum gauge. In vacuum forming, a single type vacuum pump is often used. The vacuum degree of this pump should reach 0.07~0.09 Mpa (520mmHg) or more. The gas storage tank is generally a cylindrical box welded with thin steel plates, and the bottom is oval. The capacity of the gas storage tank should be at least half larger than the capacity of the largest forming chamber. The vacuum line must be fitted with appropriate valves to control the vacuum narrow volume. ---Pan'an Vacuum Blister Machine

The rotating power of the vacuum pump is determined by the size and molding speed of the molding equipment. The equipment with larger or faster molding speed is usually as large as 2~4KW. The size of the vacuum central system depends on the specific production and development requirements of the factory.

In addition to a large amount of compressed air for forming, a part of it is used for demoulding, external cooling of the initial product, and the power to manipulate the mold frame and the movement of the sheet and other parts. ---Pan'an Vacuum Blister Machine

In order to improve production efficiency, vacuum forming products often need to be cooled before demoulding. Ideally, both the inner and outer surfaces of the part in contact with the mold are cooled, and molds with built-in cooling coils are preferred. For non-metal molds, such as wood, gypsum, glass fiber reinforced plastic, epoxy resin and other molds, because they cannot be cooled by water, air cooling can be used instead, and water mist can be added to cool the outer surface of vacuum forming parts.

If natural cooling is used in production, annealed parts can be obtained, which is beneficial to improve the impact resistance of the parts. Although water cooling has high production efficiency, the internal stress of the parts is relatively large.

Demoulding is to move the product out of the mold. Usually, whether it is a concave mold or a punch, in most cases, the product is close to the mold due to the cooling and shrinkage of the product, so it is demolded through a vacuum suction hole or blowing in the opposite direction. ---Pan'an Vacuum Blister Machine

Especially for molds with small demoulding slope or with concave molds, use the demoulding mechanism to bump or oscillate demoulding at the same time.

The control system generally includes the control of various parameters and actions of instruments, meters, pipes and valves in the process of vacuum forming and finishing. Control methods include manual, electrical-mechanical automatic control, computer control, etc. The specific selection should be comprehensively considered based on factors such as initial investment labor costs, technical requirements, raw material costs, production and maintenance equipment costs.

When the plastic sheet is formed, the sheet is fixed on the clamping device. Clamping devices that are convenient for fixing sheets of various sizes are mostly used on general-purpose vacuum forming machines and composite thermoforming machines. In some cases, the entire molding machine is equipped with a set of clamping frames. ---Pan'an Vacuum Blister Machine

Clamping devices can be divided into two categories: one is frame type and the other is split type. The frame type clamping device consists of upper and lower frames. The sheet is sandwiched between the two frames. When the frame is open, the lower frame generally remains fixed. The lower part of the upper frame of various types of single-station forming machines is directly fixed on the forming chamber. Both manual and semi-automatic forming machines for hand loading of parisons and finished product removal are equipped with safety operating devices within the opening range of the frame when the frame size is large. For the parison with large sliding property, it is required that the clamping force can be adjusted in a relatively wide range. For this reason, two rubber-coated rollers are used, which are pressed against each other by springs, and equipped with a pressure adjusting device. The clamping of the continuous pull tab forming machine is the combined action of the two side zippers and the front and rear gates.

The clamping device is preferably controlled automatically, in order to move quickly, which can help improve the quality and efficiency of the workpiece.

In the vacuum forming process of thermoplastic sheets and films, one of the main processes is to heat the sheet to soften the sheet into plastic equipment. The duration and quality of electrical heating depends on the structure of the heater, the thermal inertia of the temperature heat transfer after the radiated surface, the distance between the sheet and the heater, the radiant energy absorption coefficient, the properties of the heater surface, and the thermophysical properties of the material. Commonly used heaters are electric heaters, crystal radiators and infrared heaters. ---Pan'an Vacuum Blister Machine