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