Ultrasonic welding of plastic
suitability guide,

Ultrasonic welding of plastic - suitability guide

The process of ultrasonic welding of plastic 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 plastic 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