Vibration welding of thermoplastics

Linear vibration welding is more common due to simpler and relatively cheaper machinery required.

Vibration welding is often used for larger applications where the parts to be joined have relatively flat seams, although the process can accommodate some out of plane curvature.

Since the heat is created at an interface, the molten polymers are not exposed to open air, preventing oxidation and contamination of the weld during the process.

[1] Vibration welding produces virtually no smoke or fume, requires little surface preparation, and works well for a multitude of applications, making it well suited to mass production environments.

The process does not lend itself well to low modulus thermoplastics or to joints between plastics with relatively high differences in melting temperatures.

[citation needed] In this first stage, vibration is commenced between two cold parts pressed together at a constant pressure.

In the electromagnetic version, the heart of this assembly is a tuned spring-mass system powered by electrical coils acting on oppositely charged lamination stacks.

The lifting table brings the workpieces together, and applies pressure between the moving and stationary portions of the tooling.

[3] Tooling refers to the fixtures which are attached to the vibrating assembly and lifting table that hold the work pieces in place.

The vibration welding process has five main variables: frequency, amplitude, pressure, time, and depth.

Higher amplitudes increase heat input at the cost of cleanliness and dimensional tolerances, making them more useful for larger parts.

Pressure is the primary controller of melt layer thickness, and must be kept within an optimal range in order to produce quality joints.

Although pressure can vary between 0.5 to 20 MPa (73 to 2,900 psi) across different materials and geometries, the tolerances for a given application are quite tight.

In general depth should be kept close to or above the thickness of the melt layer at the beginning of the steady state stage.