The assembly of plastic parts is a design consideration in all applications in all markets. Despite the trend of "ease of disassembly" for recycling purposes the industry still firmly believes in welding polymers as the most efficient and reliable technique for mass assembly. It has been accepted that when joining two parts together a point of weakness has been introduced into the final part, in addition a weld joint can only be as strong as the unreinforced material being welded, as structural reinforcements such as glass fibers do not contribute to the strength of the resultant weld joint. Considering these factors the correct placement and design of a weld joint in a component is a determining factor influencing final part performance and selection of the ideal welding technique.
In its basic form, welding polymers involves raising the temperature of the materials to beyond their melting point and allowing them to cool while holding them together under pressure. Different ways in which to heat the polymers exist:
- External Heating – Hot Plate
- Mechanical Friction – Vibration, Ultrasonics, Rotation and more recently Orbital.
- Electromagnetic – Laser, Infra Red.
There are many other imaginative techniques but the greater part of the industry use, or are familiar with, those listed above. Along with a few mechanical assembly techniques like:
Selecting the correct technology is determined by a number of factors:
- Material type – amorphous, semi-crystalline, additives, compatibility.
- Joint expectations – fully sealed, strength requirements,
- Part design – size, wall thickness, stiffness.
- Production rate – parts per hour.
The expertise in place at the DuPont Technical Centres is a result of over 40 years experience in joining materials, close contacts to institutes, welding machine manufacturers and successful development projects with our customers.
Knowledge of our materials and their welding performance in different techniques is a core competence and is fundamental to a development's successful commercialization. Reducing application development time and costs can be greatly enhanced by considering the assembly issues early in the design phase, and by engaging DuPont's assembly technology expertise will ensure this is achieved.
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