Heated tool welding

FIGURE 12.1 Heated tool welding of same or similar polymer, (a) Heating stage, (b) platen removal, and (c) welding pressure. 

FIGURE 12.2 Heated tool welding of different polymers (a) Heating stage, 

---

Welding - A method used for joining thermoplastic parts without an adhesive. Heat, pressure, and time are variables used to weld together plastic parts. A simple method consists of clamping the parts together and heating the joint with a heater band. Also see Heated Tool Welding. 

Welding by Distance - A form of heated tool welding in which mechanical stops on the hot tool and holding fixtures are used to control the dimensions of the welded parts. See also Welding by Pressure, Heated Tool Welding. 

Resistance wire welding can be used on any plastic that can be joined effectively by heated tool welding. The process is typically applied to relatively large structures. Contacting the plastic resin manufacturer for details concerning the specific parameters of this process is recommended. 

Ultrasonic welding is the most common thermal assembly process used with polybuty-lene terephthalate parts. However, heated tool welding and other welding methods have proven satisfactory joints when bonding PET and PBT to itself and to dissimilar materials. Solvent cementing is generally not used to assemble PET or PBT parts because of their solvent resistance. 

Polystyrene can be joined by either thermal or solvent welding techniques. Preference is generally given to ultrasonic methods because of its speed and simplicity. However, heated tool welding and spin welding are also commonly used. 

Heated-tool welding is suitable for almost any thermoplastic but is most often used for softer, semicrystalline thermoplastics. Common plastic substrates that are suitable for heated-tool welding include polyethylene, polypropylene, polystyrene, acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), and acetals. It is usually not suitable for nylon or other materials that have long molecular chains. Dissimilar yet chemically compatible materials that have different melting temperatures can be welded in heated-tool welding by using two heated platens, each heated to the melting temperature of the part to be welded. 

See also heated tool welding hot-gas welding resistance wire welding laser... 

Infrared welding is at least 30 percent faster than heated-tool welding. High reproducibility and bond quality can be obtained. Infrared welding can be easily automated, and it can be used for continuous joining. Often, heated-tool welding equipment can be modified to accept infrared heating elements. 

The alternative methods next to sewing include adhesive bonding, conventional thermal (e.g., hot air and heated tool) welding, and advanced thermal (e.g., ultrasonic or laser) welding. These joining methods are the focus of this chapter. A general description of these processes, along with applicable substrates and applications, is provided in Table 13.1. 

---