Thermoforming 热成形 真空成型 压力成形 机械成形

2010-10-13 17:06:30 作者:机知网 来源:机知网 浏览次数:0

Thermoforming describes the process of heating a thermoplastic sheet to its softening point, stretching it over or into a single-sided mold, and holding it in place while it cools and solidifies into the desired shape. The thermoplastic sheet is clamped into a holding device and heated by an oven using either convection or radiant heat until it is softened. The sheet is then held horizontally over a mold and pressed into or stretched over the mold using vacuum pressure, air pressure, or mechanical force. The softened sheet conforms to the shape of the mold and is held in place until it cools. The excess material is then trimmed away and the formed part is released. Excess material can be reground, mixed with unused plastic, and reformed into thermoplastic sheets. 

Thermoforming is commonly used for food packaging, but has many applications from plastic toys to aircraft windscreens to cafeteria trays. Thin-gauge (less than 0.060 inches) sheets are mostly used for rigid or disposable packaging, while thick-gauge (greater than 0.120 inches) sheets are typically used for cosmetic permanent surfaces on automobiles, shower enclosures, and electronic equipment. A variety of thermoplastic materials can be used in this process, including the following:


  • Acrylic (PMMA)
  • Acrylonitrile Butadiene Styrene (ABS)
  • Cellulose Acetate
  • Low Density Polyethylene (LDPE)
  • High Density Polyethylene (HDPE)
  • Polypropylene (PP)
  • Polystyrene (PS)
  • Polyvinyl Chloride (PVC)

As mentioned above, there are different methods of forcing the thermoplastic sheet to conform to the mold. These types of thermoforming include the following:
 

热成型过程中描述的形状塑料片材加热到接近软化点,单面拉过来或成模具,并持有它的地方,而在它冷却并凝固成所需。 对塑料片材夹成控股和软化的加热装置是用烤箱或对流或辐射热,直到它。 该表是横握,然后在一个模具压入或武力伸过来机械模具用真空压力,空气压力,或。 软化表符合形状的模具,是地方举行,直到它冷却。 多余的材料,然后削去形成的部分被释放。 多余的材料可修磨,混有未使用的塑料和热塑性塑料成片改造。 

热成型通常用于食品包装,塑料玩具,但有许多应用,从飞机挡风玻璃到食堂托盘。 薄规格(小于0.060英寸)表大多用于刚性或一次性包装,而厚规(大于0.120英寸)设备,电子表是通常用于化妆品永久表面上汽车,淋浴房,和。 阿各种热塑性材料,可用于在这个过程中,包括以下内容:


  • 压克力(有机玻璃)
  • 丙烯腈丁二烯苯乙烯(ABS)
  • 醋酸纤维素
  • 低密度聚乙烯(LDPE)
  • 高密度聚乙烯(HDPE)
  • 聚丙烯(PP)
  • 聚苯乙烯(PS)
  • 聚氯乙烯(PVC)

如上所述,有不同的方法对模具的塑料片材,迫使以符合。 热成型这些类型包括以下内容:


  • 真空成型 -真空是模腔之间形成的塑料片材的形状。真空压力(通常是14磅)的部队工作表,以符合模具,形成的一部分。 
     

  • Vacuum forming - A vacuum is formed between the mold cavity and the thermoplastic sheet. The vacuum pressure (typically 14 psi) forces the sheet to conform to the mold and form the part shape. 

     
    Vacuum Forming

  • Pressure forming - In addition to utilizing a vacuum underneath the sheet, air pressure (typically 50 psi, but up to 100 psi) is applied on the back side of the sheet to help force it onto the mold. This additional force allows the forming of thicker sheets and creating finer details, textures, undercuts, and sharp corners. 

     
    Pressure Forming

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