Some advice on ultrasonic welding plastics - suitability guide |
The process of ultrasonic welding 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 some advice on ultrasonic welding 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 | ||
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. 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. 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 & speed, no stress build up & 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 & tight assemblies. For more advice on plastics for your application (costs, properties etc), please view our material selection guide |