Services OverviewUltrasonic Welding
The process of ultrasonic welding of plastics is achieved by applying a vibrating metal tool, usually refered to as a horn, at 90° to the stationery plastic parts which then vibrate. When combined with pressure, friction produces heat and melts the parts at the horn contact point. Once cooled down a solid homogeneous weld between the 2 parts is created.
To assist, this guide lists the most common unfilled grades of plastic available and their suitability for each style of ultrasonic welding. As a rule, stiffer materials are easier to weld and those with higher melt temperatures need more energy. To weld different materials, they need similar molecular structures - crystalline ones are only weldable to themselves.
| Material Types, Abbreviations & Structures | Close Welding |
Distant Welding |
Inserting | Spot Welding |
Staking | ||
| Acetyl Co/Homopolymer | POM | C | 3 | 2 | 3 | 2 | 2 |
| Acrylic | PMMA | A | 3 | 2 | 3 | 3 | 2 |
| Acrylic - Impact Modified | PMMA | A | 2 | 1 | 1 | 2 | 2 |
| Acrylonitrile Butadiene Styrene | ABS | A | 4 | 3 | 4 | 4 | 4 |
| Cellulose Acetate | CA/B/P | A | 1 | NS | 4 | 1 | 3 |
| Polyamide 6 & 66 (Nylon) | PA6 & 66 | C | 3 | 2 | 3 | 2 | 2 |
| Polycarbonate | PC | A | 3 | 2 | 3 | 3 | 2 |
| Polycarbonate/Abs | PC/ABS | A | 3 | 2 | 3 | 3 | 3 |
| Polyester - Thermoplastic | PBT/PET | C | 3 | 2 | 3 | 2 | 2 |
| Polyethylene - Low/High Density | LD/HDPE | C | 1 | 1 | 3 | 3 | 2 |
| Polyphenylene Oxide | PPO | A | 4 | 3 | 4 | 4 | 4 |
| Polyphenylene Sulphide | PPS | C | 3 | 2 | 3 | 2 | 1 |
| Polypropylene | PP | C | 2-1 | 1 | 3 | 4 | 4 |
| Polystyrene - General Purpose | GPPS | A | 4 | 4 | 3 | 2 | 2 |
| Polystyrene - High Impact | HIPS | A | 3 | 1 | 3 | 2 | 2 |
| Polyvinyl Chloride - Flexible | PVC | A | 1 | NS | NS | 1 | NS |
| Styrene Acrylonitrile | SAN/ASA | A | 4 | 4 | 3 | 2 | 2 |
1 - Poor 2 - Fair 3 - Good 4 - V. Good
A (Amorphous) - polymers with a random molecular chain structure. This and their wide softening temperature range enables them to soften gradually without solidifying quickly, thus making ultrasonic welding them easy.
C (Crystalline) - polymers with an orderly molecular chain structure. This and their sharp melting and solidification points makes them absorb vibrations when solid, thus making ultrasonic welding them more difficult.
Close Welding - ultrasonic welding where the horn is applied close to (<6.35mm) the assembly joint - good for welding materials whose low modulus of rigidity dampens vibrations a short distance away from the horn.
Distant Welding - ultrasonic welding where the horn is applied away from (>6.35mm) the assembly joint - good for welding materials whose high modulus of elasticity propagates vibrations without dampening them.
Inserting - ultrasonic embedding of metal components like inserts into preformed holes in the moulding - provides high strength and speed, no stress build up and reduced moulding cycles.
Spot Welding - ultrasonic assembly of parts without premade holes or energy directors - good for large parts.
Staking - melting and reforming a post on the moulding to mechanically lock dissimilar materials in place - provides short cycles, good appearance and tight assemblies.
