Some help with ultrasonic welding of plastics - suitability guide |
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The process of ultrasonic welding of plastics is achieved by applying a vibrating metal tool (horn) at 90° to the stationery plastic parts which then vibrate. When combined with pressure, friction produces heat & melts the parts at the horn contact point. Once cooled down a solid homogeneous weld between the 2 parts is created. To give you help with ultrasonic welding of plastics for your application, this ultrasonic welding guide lists the most common unfilled grades of plastic available & their suitability for each style of ultrasonic welding As a rule, stiffer materials are easier to weld & 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 |
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| Acetal
Co/Homopolymer |
POM |
C |
Good |
Fair |
Good |
Fair |
Fair |
| Acrylic |
PMMA |
A |
Good |
Fair |
Good |
Good |
Fair |
| Acrylic - Impact Modified |
PMMA |
A |
Fair |
Poor |
Poor |
Fair |
Fair |
| Acrylonitrile
Butadiene Styrene |
ABS |
A |
V.Good |
Good |
V.Good |
V.Good |
V.Good |
| Cellulose
Acetate... |
CA/B/P |
A |
Poor |
NS |
V.Good |
Poor |
Good |
| Polyamide
6 & 66 (Nylon) |
PA6 &
66 |
C |
Good |
Fair |
Good |
Fair |
Fair |
| Polycarbonate |
PC |
A |
Good |
Fair |
Good |
Good |
Fair |
| Polycarbonate/Abs |
PC/ABS |
A |
Good |
Fair |
Good |
Good |
Good |
| Polyester
- Thermoplastic |
PBT/PET |
C |
Good |
Fair |
Good |
Fair |
Fair |
| Polyethylene - Low/High Density |
LD/HDPE |
C |
Poor |
Poor |
Good |
Good |
Fair |
| Polyphenylene
Oxide |
PPO |
A |
V.Good |
Good |
V.Good |
V.Good |
V.Good |
| Polyphenylene
Sulphide |
PPS |
C |
Good |
Fair |
Good |
Fair |
Poor |
| Polypropylene |
PP |
C |
Fair-Poor |
Poor |
Good |
V.Good |
V.Good |
| Polystyrene - General Purpose |
GPPS |
A |
V.Good |
V.Good |
Good |
Fair |
Fair |
| Polystyrene - High Impact |
HIPS |
A |
Good |
Poor |
Good |
Fair |
Fair |
| Polyvinyl Chloride - Flexible |
PVC |
A |
Poor |
NS |
NS |
Poor |
NS |
| Styrene
Acrylonitrile... |
SAN/ASA |
A |
V.Good |
V.Good |
Good |
Fair |
Fair |
A (Amorphous) = polymers with a random molecular chain structure. This & their wide softening temperature range enables them to soften gradually without solidifying quickly, thus making ultrasonic welding them easy. |
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C
(Crystalline) = polymers with an orderly molecular chain structure. This & their sharp melting & solidification points makes them absorb vibrations when solid, thus making ultrasonic welding them more difficult. |
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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. |
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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. |
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Inserting = ultrasonic embedding of metal components like inserts into preformed holes in the moulding - provides high strength & speed, no stress build up & reduced moulding cycles. |
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Spot Welding = ultrasonic assembly of parts without premade holes or energy directors - good for large parts |
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Staking = melting and reforming a post on the moulding to mechanically lock dissimilar materials in place - provides short cycles, good appearance & tight assemblies |
For more help with plastics for your application view our ultrasonic welding diagrams or material selection guides

