Thermoforming of Wuhan HanDern Plastic
日期：2020/12/4 9:16:16 / 阅读： / 来源：本站
Thermoforming of Wuhan HanDern Plastic
Thermoforming is a method of manufacturing materials using thermoplastic sheets as raw materials. During manufacturing, the sheet material with a certain size and a fixed shape is first clamped on the frame to heat it to a thermoelastic state, and then the pressure is applied to bring it close to the mold surface to obtain a shape similar to the mold surface. After cooling, the last piece is taken out of the mold, and finally becomes a product after proper modification.
The characteristics of thermoforming products are: ①The wall thickness is thin, the thickness of the sheet used as the raw material is only 1~2mm, or even thinner, and the thickness of the product is smaller than this value; ②The surface area of the thermoformed product can be large. Small products such as cups, saucers and other daily utensils, medical utensils, electronic instrument accessories, radios and TV sets, toys, helmets, and large products include auto parts, building components, chemical equipment, radomes and aircraft cabin covers, etc. Wait. handern.com Spunbond Non-woven Fabric machinery
Another feature of the thermoforming method is its high production efficiency. If a multi-slot mold is used for production, the output can be as high as hundreds of pieces per minute. The equipment is simpler and less investment. However, since the raw material used is sheet material, the processing cost is high and there are many post-processing procedures. Because it can manufacture products with a large area and the equipment investment is small, this method has developed rapidly in recent years. handern.com non-woven machinery
Second, the basic method of thermoforming
1. Differential pressure forming
Differential pressure forming is the simplest one of the thermoforming methods and also the simplest vacuum forming. The characteristics of the products made by this method are: (1) The structure is relatively clear, the fine part is the side that is attached to the mold surface, and the finish is higher; (2) When the sheet is formed, where the sheet and the mold surface are attached The thickness of the part that becomes longer in time becomes smaller.
The method of implementing differential pressure molding is: first clamp the sheet to the mold with a clamping frame and heat it with a heater. When the sheet has been heated to a sufficient temperature, remove the heater and take appropriate measures to make The two sides of the sheet have different air pressures, so that the sheet will bend down and fit the mold surface. When it is sufficiently cooled, compressed air is used to blow out the formed sheet from the bottom of the mold through the vent hole, and it becomes a product after modification. handern.com Spunbond Non-woven Fabric machinery
2. Cover molding
The characteristics of the products made by overmolding are: (1) Like differential pressure molding, the surface quality of the surface that is attached to the mold surface is higher, and the structure is clear and detailed; (2) The largest part of the wall thickness is The top of the mold, and the thinnest part is at the junction of the side and bottom of the mold; (3) Drafting and cooling stripes often appear on the side of the product. The reason for the streaks is that each part of the sheet is attached to the mold surface in order of time. The part that first contacts the mold surface is cooled by the mold first, so in the subsequent buckling process, its pulling behavior is not as good as the part without cooling. Strong, this kind of streak is usually the most at the side near the top of the die surface.
The covering method has been effectively applied in every application field of plastic sheet thermoforming. The general product design is that the ratio of depth to diameter is 1:1. However, for some newer, deep-stretchable sheets, such as calendered polyvinyl chloride, the ratio can be increased to 1.5:1. handern.com Spunbond Non-woven Fabric machinery
An important aspect of this method is the manufacture of household appliances, such as refrigerator doors and internal components. For example, a modified polystyrene sheet with a thickness of 1.5~4.75mm is used to form the refrigerator door and its internal parts on a water-cooled covering mold. It is estimated that 75%
The modified polystyrene sheet is used for sheet forming.
3. Plug-assisted vacuum forming
The plug-assisted vacuum forming system uses a female mold. Before vacuum suction, the plunger extends into the mold cavity to push the sheet to the bottom, and then vacuums to pull the sheet away from the plunger to make the shape of the sheet consistent with the mold . In this case, the plunger is usually not heated, and the thickness of the final product has a better distribution, because the plunger grips the sheet tightly, leaving more material at the bottom of the product. Since the vacuum forming only moves the sheet a short distance, the mold itself can work at a lower temperature, which reduces the cooling time. Of course, this kind of product is thicker at the bottom and thinner on the sidewalls, and the surface is not necessarily good for deep suction products.
For deeper products, in order to make the thickness distribution more uniform, the plunger must be heated to a sufficient temperature, so when the plunger enters the sheet, the sheet can slide along the plunger to move the thicker bottom material to both sides. In this case, the column observation temperature must be higher than the sheet temperature.
In order to obtain a more ideal result, the plunger enters the sheet very fast, up to 750mm/s, the thickness of the selected sheet
Evenly, heating needs to be even. The plug-assisted vacuum forming method is widely used in processing cold storage door linings, fruit containers, etc.