Rubber Injection and Transfer Molding Process

Rubber Injection Molding

根据旨在成型塑料的工艺，橡胶的注射成型始于1960年代中期。橡胶注塑成型成功通过加热橡胶并将其放置在模制中的每平方英寸的腔表面压力下，成功地改变了塑料过程。这与在较小的压力下冷却材料的塑料注射成型过程不同。通过各种创新，注射成型已成为创建最有效的方法之一molded rubberproducts in many cases.

The process of injection and injection-transfer molding starts with efficient material preparation. To begin, the material is mixed in bulk and then stripped immediately into continuous approx. 1.25" wide & .375" strips. These strips are then fed into a screw which, in turn, fills a barrel with the appropriate predetermined amount of rubber material.

Advantages of injection molding:

1. The complete elimination of pre-forms
   • The production and need for pre-forms is a labor intensive step that can potentially affect the finished product through variability in pre-form weight and shape.
2. Elimination of operator placement of pre-forms.
   • 由于pre-forms琳inated, the need for operators to place the pre-forms in a cavity (compression molding) or pot (transfer molding) is removed.
3. Injection screw pre-heats material before forcing it into cavities
   • 该过程降低了材料的粘度，使其更容易流入腔体。
   • This pre-heating provides the potential for decreased cure times through
     1. 由于粘度较低而导致更快的空腔填充
     2. Material already being in the curing process through the heat added during screw charging and shear created during injection
4. Reduced cycle time
5. Flashless tooling
6. Economical process for high volumes of medium to high precision components
7. Capable of producing overmolded components
8. Minimal material waste

转移成型

As with compression molding, transfer molding requires secondary raw material preparation into pre-forms. It differs, however, in the placement of these pre-forms into a "pot" located between the top plate and a plunger. When the pre-forms are placed into the pot, the mold is then closed and the material is compressed by the plunger and transferred through sprues into the cavity below.

Some possible advantages of transfer molding over compression molding can include:

1. High Cavity Count - In many cases, transfer molded rubber products require fewer and simpler pre-forms. One pre-form can fill hundreds of cavities
2. Cost effective tooling
3. Tighter control of dimensional tolerance - the mold is not held open by excess material spilling out of the cavity parting line; all the excess hold the plunger open from the pot
4. 中等至高精度组件的经济过程
5. 颜色模制橡胶零件的好处 - 可以手工从原材料手工切割预定件，从而减少了由压缩成型机械准备或注射成型中的注射螺钉和桶的机械准备所致的污染机会。
6. Capable of producing overmolded components

The primary disadvantage of transfer molding is found in the increase of waste or excess flash. This can be seen in the "flash pad" or the rubber left in the pot after the transfer is cured which can either be recycled or discarded.

Compression Molding

压缩成型是一个涉及服用的过程118bet.net金博宝app or mixed raw material and creating "pre-forms" in the basic shape of the end product. The pre-forms provide a surplus of material to be placed in the cavity, thus ensuring a total cavity fill. Once in place, the mold is then closed, applying both heat and pressure to the pre-form and allowing it to fill the cavity. When the cavity is filled, excess pre-form material spills out into overflow grooves. Following this step the rubber is then demolded, usually by hand, leaving us with themolded rubber product.

Compression molding is often chosen for medium hardness compounds in low volume production or in applications requiring particularly expensive materials. This process helps to minimize the amount of overflow, or flash created during the rubber molding process.

In creating compression molded rubber products, the pre-forms can be difficult to insert into more complex mold designs. Furthermore, the compression molding process does not lend itself well to the material flow requirement of harder rubber compounds.

Benefits of Compression Molding

• Cost effective tooling
• Maximized cavity count
• Economical process for medium precision

在以下情况下，压缩成型可能是一种经济有效的解决方案：

1. The tooling already exists
2. 零件的横截面非常大，需要长时间的治疗时间

Applications of compression molding range from simple o-ring drive belts to complex brake diaphragms with diameters of more than 10 inches. Timco can also offer a variety of other molded rubber products through compression molding.

偏转

Removal of the waste edge, or flash, from amolded rubber productcan be accomplished in a number of ways. Depending on the material, part size, tolerance and quantity deflashing methods commonly include:

• Manual tear trimming
• 低温处理
• Tumbling
• 精确研磨