Stronger than glue! Repairing plastic parts by melting and embedding the core [Cowl Repair].

How to
4.25/5 (4)

Plastic parts can crack or chip not only due to accidents and falls, but also due to deterioration over time.
Welding with a soldering iron is effective for strong repairs in places where strength is required, but the repair part You can expect even higher strength by adding reinforcement to the
If repaired well, you can use a plastic repair kit that won't show any traces.

Repairing plastic parts that need to be strong is a pain

When the slit on the resin part is fixed to the hook on the frame, the slit will deteriorate over time. The part may crack. Due to the small size of the cracked part and the force applied to it, it will come off again with a simple adhesive.

The plastic parts used for the exterior of the bike are ABS, PP, acrylic, FRP and carbon. Various materials are used in different ways. Of these, ABS is the most frequently used material for scooter exteriors and motorcycle side covers.

To repair plastic parts that have been damaged by external impacts, such as cracks and dropouts, you can use Adhesives are commonly used. Adhesives are chemicals that act chemically, physically or mechanically on the adhesive surface of a resin material to bond it together. Depending on the resin material to be glued on, there are products that can be used and products that cannot be used.

Moreover, unlike a plastic model that is mainly for display, the force is applied to the parts for motorcycles even after adhesion. In some cases, not only do they look like they're there, but they also need mechanical strength.

This is where Sunday mechanics with a lot of repair experience often use a repair technique using heat It is the same logic as welding metal materials. In the same logic as welding metal materials, the damaged part is heated with a soldering iron used in electrical work, and then melted while melting it. It's all about integration. In addition to heating the damaged part against each other, the same plastic material as the welded part can be used to make the missing part It can also be filled in or raised.

However, since the repair material itself will melt, it may be deformed or carbonized if heated excessively. A certain level of experience and know-how is required. In the case of butt welding, which has a small area of welded parts, the weld strength is not as high as expected and the welded parts may be damaged again. It is important to note that there are some cases.


  • Effective welding for repairing plastic parts that require strength
  • Tips on how to use the familiar soldering iron

Melt stainless steel pins heated by electricity

This is a straightforward repair kit from a toolmaker. The stainless steel pins are heated by running electricity through them and then melted into a resin to repair them. It is similar to a nichrome wire heater in that it uses electrical energy into heat.

Among the repair methods that use the same heat, there is a method that can ensure strength while localizing the area of influence of the heat. There is. That is a plastic repair kit that embeds a metal pin in the repair area. There are several products available from several manufacturers, but all of them are designed to be used to repair the switch in the handle. When pressed and energized, the stainless steel pins are heated by the current flowing through them, which melts the resin and embeds it in the resin. The plastic repair kit minimizes the heat effect on the repaired part by heating only the thin pins, while the soldering iron risks deforming the part by heating the welded part widely.

With a soldering iron, the part itself may be deformed by heating the welded part widely, but with a plastic repair kit, only the thin pins are heated, minimizing the heat effect on the repaired part.

Also, if a soldering iron is used to heat a thick material to the center, the part to be repaired will need to be reworked, but if the pin is pressed down, it will go into the material in its original shape, so the repair can be done without overly expanding the area affected by the heating.

In addition, because metal pins remain in the welded area, repairs can be made to thin surfaces such as side covers and cowls. Compared to gluing or simple welding, the physical strength is improved when performing a repair. The pin is corrugated to prevent it from biting into the repaired part and coming off. It's also flexible enough to bend to fit.

Different thicknesses and shapes of pins are used depending on the area to be repaired. A thicker pin is more advantageous from the standpoint of strength alone, but it should be selected according to the thickness and size of the material to be repaired.


  • Stainless steel pins are heated and welded to the resin.
  • Strengthen the joint with the pin effect

It can't be used for FRP or carbon, but its high versatility is attractive.

The cracks are butted together and pins are embedded as if sewing the cracks. The heat is added to the resin around the welded area by firmly inserting the corrugated pin, which increases its strength. Do not get too greedy, as the closer you get to the surface of the part, the more the corrugated pattern comes out.

In the case of the products introduced here, the heating temperature of the pins can be adjusted in three stages according to the thickness and volume of the repair material. It is. Relatively thin materials such as cowl need to be strong at low temperatures, like the cowl's fixing pins, and the volume Large areas can be heated to a high temperature for a durable repair without affecting the appearance.

It's very simple to use, just bridge the pins over the area to be repaired and press the switch to heat it up. Only. Unlike the soldering iron, the heat is only applied to the pin while the switch is being pressed, and yet the temperature rise is not as pronounced as with the soldering iron. The response is so fast that it buries itself into the repaired part before the heat is transferred to the area around the pin.

Instead of pressing down hard on the handle, the heated pin dives into the plastic part with its own weight. It can be repaired successfully if you treat it by feel. It is better to embed the resin around the pin to some extent than to have the pin stick to the surface of the crack area. Melting it down increases its strength.

Another feature of welded pins is that by embedding the pins from the back side in the damaged area where the cross-sections fit together perfectly when cracks are butted together, it is possible to create a finish that does not affect the painted surface on the front side and does not reveal any repair marks.

However, if the force pressing down on the pin is too strong or the temperature is too high for the thickness of the material, it may penetrate to the opposite side, and the pin may be damaged. It is also important to note that the corrugations of the pins may stand out on the surface. In addition, since the pins are not melted into thermosetting resin such as FRP and carbon, it is important to use the following methods to prevent them from being melted into the resin parts. It cannot be used.

Nevertheless, its adaptability, ease of use and high finish strength for plastic parts in general are very attractive. It is. The side of an out-of-print car with a wobbly cowl that has cracked at the joints and a broken pin that sticks in the grommet. A great ally for reusing damaged parts such as covers and other parts that are a shame to throw away but cannot be used as is. There is no doubt that this is the case.


  • It cannot be used for thermosetting resins such as FRP and carbon.
  • It is possible to repair materials that are difficult to adhere to with adhesives

Please rate our translation!

Copied title and URL