Plastic Repair Kit that Uses Heat to Bond Plastic Parts that are Difficult to Strengthen with Adhesives Alone

Resin parts such as ABS and PP, which are mainly used for exterior parts, have various advantages, but they also have drawbacks that make them difficult to repair when damaged. Welding-type repair items are a strong ally in cases where repair is possible, except in cases where replacement is required without any questions asked. In addition to embedding a metal pin, a welding rod can also be used to heap and repair a base material that has become thin due to heating.

The cordless type allows the repair of plastic parts without the need to secure a power source.

This plastic repair kit is now on sale at Straight, a nationwide tool store. The kit includes a cordless body with two different trowels and welding rods for ABS, PP (polypropylene), PE (polyethylene), and PS (polystyrene). The color of the welding rods is all black, but the key to successful welding is to use the same material as the part to be repaired. If the motorcycle is from the late 1990s onward, the type of material is often indicated on the back of the part.

When repairing the base of a cracked side cover boss, it is difficult to weld if the welding area is dirty, so clean the area with neutral detergent and wipe the affected area with acetone. Since acetone can be used as an adhesive for ABS materials, adhesion may begin simply by applying it with a cotton swab. Care must be taken when handling acetone, as it can damage the paint if it adheres to the surface.

Heat and weld the cracked area with a trowel while correcting it to the original shape. If the thicknesses of the materials on the joining surfaces are obviously different, the trick is to heat the thicker side first, as the thinner side will melt first. Also, at first, fix multiple points by dotting, and then weld the entire piece after the shape has been restored. The resin is so soft immediately after heating that it may be deformed if you release your finger from holding it down, so release your hand after the temperature drops and hardens.

When the repaired part is missing or has melted down due to heating, it is recommended to use a welding rod to repair the wall. In this case, if only the welding rod is heated and heaped on the repaired part, it will easily peel off.
While melting the base metal, the welding rod is further melted into the base metal to ensure overall strength. At this time, be sure to shape the area to be heated by the welding rod so that it does not interfere with other parts.

Plastic, which can be molded into complex shapes and is lightweight, is an essential material for motorcycle exterior parts. In particular, the design of scooters and Supersports models, in which the entire body is covered by a cover, would not be possible without plastic parts.

However, once damaged due to a fall or mishandling, repairing the damage is not easy. It is important to follow the procedure for removing the exterior of a scooter, where the panels overlap each other in a complex manner.

The advantage of resin is that it can be designed into complex shapes during the molding process, but its structure is complex and delicate, and it is often difficult to maintain the original strength even if the damage is slight. If the damage is so severe that it is obvious that the product is no good, the only solution is to replace it, but if the damage is only a broken boss, chipped pin, or crack, there are cases where the product can be repaired and reused.

In such cases, plastic repair kits come in handy. There are adhesives that can bond resins such as ABS and PP, and ABS can be bonded even with acetone, but depending on the damage, the bonding area may be too small to ensure sufficient strength. In particular, chipped claws and broken bosses are subjected to a large amount of force in contrast to the small size of the joint, so it is not uncommon for them to break again even after being glued once.

The plastic repair kits introduced here are welder-type repair items that join resins by melting them with heat. The kit shown in the image, which is sold at the tool store Straight, can work cordlessly thanks to lithium-ion batteries and is set with welding rods of different materials according to the resin material to be repaired.

In the process of melting and attaching, it is also common to use a soldering iron for electrical work. Compared to a normal soldering iron, the soldering iron has a larger tip area and can heat a wider area, and by changing the tip, it is possible to join and heap while feeding the melted welding rod.

Convenient not only for repairs but also for one-off parts production and partial processing

Welding with plastic repair kits is also useful for repairing plastic parts and attaching parts that have been separated in crafting. The joint surfaces are melted together to form a single piece, but the cross-sectional shape should be molded to fit as closely as possible.

The metal pin is melted using the welding pinhead, which is an option in the Straight repair kit. If the wall thickness of the repaired part is thin, the corrugated shape of the pin may appear on the surface, and even if it does not penetrate, the surface will sag, so work carefully. Since the thick air cleaner case is being processed here, the pins are driven in deep to ensure strength, and then the gap is filled with welding.

Plastic repair, which utilizes the same principle as metal welding in terms of joining the base material while melting it, has a slightly different finish than the repair method in which heated metal pins are melted into the cracked area.

When metal pins are fused in, the cracks between the pins remain intact, exposing the cracks when force is applied. Even if you repair the cracked cowl with a pin from the back side and repair the surface with putty, the putty may crack if you twist it.

In contrast, welded repairs can continuously repair damaged areas by melting and integrating the resin in the joint area, resulting in a stable finish in terms of strength. If the joint area is small, there is a concern that the base material may meltdown due to heating.

However, as with soldering and metal welding, resin welding will not be strong unless the welding rod is melted into the base metal, so it is important to melt the welding rod into the base metal after the base metal is melted to make it one piece. If too much heat is applied at this time, the base material itself may melt significantly, causing deformation and damage. When repairing from the backside, work while checking for temperature and deformation by supporting the front side of the repaired part with a finger.

In addition, this kit also includes an optional bifurcated head for welding pins, which allows heated metal pins to be fused into the repaired area. The metal pins can be used in combination when there is concern about the strength of the weld repair alone.

Even outside of obvious accidents such as contact or falls, welding repairs are effective for repairing indicator lenses, tail lenses, and plastic headlight housings that have cracked due to the over-tightening of the mounting screws. Plastic repair kits that can be repaired with heat are sure to be useful items for owners of older motorcycles, not to mention current motorcycles.