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plastic to metal joining methods Posted Aug 30, 2019

Understanding the Heat Staking Process

heat staking equipment

What do you do when you need to join two components made of two different materials that cannot be welded together? One solution is to use hardware to join the two together. However, this may not be necessary if one of the components is made of plastic. A more efficient way to join a plastic part to a component made of different material is with heat staking. Multiple types of manufacturing make use of heat staking services.

What Materials Are Suitable for Heat Staking?

Heat staking is used most often to join plastic and metal components together. However, it can also be used to connect plastic components to parts made of different materials, such as cardboard and textiles, as well.

When it comes to the types of plastics used in heat staking, some materials are better suited than others. The following produce particularly high-quality results:

  • Acrylonitrile butadiene styrene
  • Polycarbonate
  • Nylons
  • Polypropylene
  • Ultem
  • Polystyrene

However, most blended or native thermoplastics will produce a good result from heat staking.

How Does Heat Staking Work?

The plastic component features one or more bosses. A boss is a plastic protrusion that extends out from the surface. The non-plastic component, or base material, will have one or more holes of the correct size and position to accommodate the bosses on the plastic component. Then the two components are joined together so that the plastic bosses fit into the holes.

A heat staking machine then applies heat and pressure to the two components. Heat is applied directly to the bosses with a thermal tip so that they melt and can be molded into a new shape. Light pressure causes the bosses to conform to the holes in the other component.

A machine manufacturer produces thermal tips with different shapes. As a thermal tip heats the plastic boss, it will reshape the boss into a particular stake pattern. There are many options, but they can be classified broadly as high-profile stakes, which extend up from the surface, and low-profile stakes, which do not. Depending on the thermal tip used, the stake can be flush with the surface of the base component, which would obviously be considered a low-profile stake. The geometric relationship between the thermal tip and the boss determines the strength and integrity of the thermal staked assembly.

Once the stakes have formed, they are cooled to a point below the glass transition temperature. This causes the plastic to become firm once again. The stakes remain in the shape that the thermal tip formed them into, providing a solid connection between the two disparate components.

What Applications Are Appropriate for Heat Staking?

Heat staking is useful for manufacturing operations that deal with delicate materials that could become damaged due to exposure to heat applied broadly. For example, heat staking works well with glass-filled plastic because the heat is applied only where needed on the plastic boss. Examples of industries in which heat staking is useful include the manufacture of electronic, telecommunication, automotive, and medical equipment.

What Are the Advantages of Heat Staking?

Heat staking offers a number of advantages over hardware fasteners in addition to those already discussed. The latter are prone to quality control issues like breakages or defects over time. There is no need for extra hardware with heat staking, which makes it less labor-intensive and more cost-effective. Fastener-based methods may require individual operations for each fastener. Heat staking, on the other hand, requires only a single machine cycle to complete. As an added bonus, it also allows the base material to remain as is.

Heat staking also has advantages over ultrasonic assembly. This method produces the necessary heat to bond plastics via high-frequency vibrations. However, the vibrations can put mechanical stress on the components, which can damage sensitive components like those used in electronics.

When you need a heat staking machine manufacturer, think Kimastle Corp first. Use our convenient online form to contact us with inquiries.

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