Ultrasonic Welding
Injection Moulding | Vaccum Forming | Stereolithography | Selective Laser Sintering
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.
