ultrasound welding | What is Ultrasonic Welding Process | How Ultrasonic Welding process works
The basicS of ultrasonic welding.
Step 1 , Parts in fixture.
The two thermoplastic parts that need to be assembled are placed together, one on the top of the other, in a supportive
nest called a fixture.
Ultrasonic welding parts in fixture.
Step 2 , Horn contact.
A titanium or aluminum component called a horn is brought into contact with the upper plastic part.
Ultrasonic welding horn contact.
Step 3 , Pressure applied.
A controlled pressure is applied to the parts, clamping them together against the fixture.
Ultrasonic welding pressure applied.
Step 4 , Weld time.
The horn is vibrated vertically 20,000 (20 kHz) or 40,000 (40 kHz) times per second for a precise amount of time - also
called the weld time. The various parts parts are precisely engineered so that the energy is directed to specific points of
contact between the two parts.
The mechanical vibrations are transmitted through the thermoplastic materials to the joint interface to create frictional
heat. When the temperature at the joint interface reaches the melting point, plastic melts and flows, and the vibration is
stopped. This allows the melted plastic to begin cooling.
Ultrasonic welding weld time.
Step 5 , Hold time.
The clamping force is maintained for a predetermined amount of time to allow the parts to fuse as the melted plastic cools
and solidifies. This is known as hold time. Improved joint strength and hermetical sealing may be achieved by applying a
higher force during the hold time. This is accomplished using dual pressure at various points in the hold time.
Ultrasonic welding hold time.
Step 6 , Horn retracts.
Once the melted plastic has solidified, the clamp is removed and the horn is retracted. The two plastic parts are now
joined as if molded together and are removed from the fixture as one part.
Ultrasonic welding horn retracts.
Ultrasonic welding for plastic assembly is a fast, clean, efficient, and repeatable process that consumes very little
energy. No solvents, adhesives, mechanical fasteners, or other consumables are required, and finished assemblies are strong
and clean.
important factors of ultrasonic plastic welding
The welding time and the welding head pressure can be adjusted with the amplitude determined by configuration of the
converters and rods. Generally, the main variables are
Amplitude rods and converters
Welding head pressure
Welding time
Hold time.
The adjustment must be precise. If the frequency is too high or the amount of time the signal is applied is too long, the
plastics can easily deform outside of the boundaries of the connection points. If the applied energy is too weak, then a
poor connection forms.
Advantages and disadvantages:
Advantages of Ultrasonic Plastic Welding
The ultrasonic welding technology sets itself apart with fast welding speeds, high welding strength and good sealing
performance. This is a suitable replacement for traditional welding/bonding processes. The process is clean because it
doesn't use harmful solvents or glues while also not damaging the product. This technology is also easy to implement in a
production process and has a low fault rate. As a bonus, all of these advantages help lower production costs.
Disadvantages of Ultrasonic Plastic Welding
When the thickness and hardness of the plastic parts are increased, the power required for welding increases exponentially
related to the parameters of the plastics. This increases the manufacturing cost of the ultrasonic welding machine. If the
power requirement is too large, the design and manufacturing of the acoustic system and the process effects will produce a
series of problems that are difficult to solve. Therefore, the technology is more generally limited to thin parts such as
wires, foils, and sheets. The state of this technology limits the joint form of the ultrasonic welding system to lap joints
and is limited by the tool head. The parts can only protrude within the allowable size range of the welding system. The
welded joint form and the size range are limited.
These limitations mean that the parts that are to be welded need to be precisely designed to take the most advantage of
this process.
Application areas
Ultrasonic plastic welding is suitable for virtually all thermoplastics. When planning welds between semi-crystalline
plastic pieces of work, it is important to remember that the welding behaviour of these plastics differs considerably from
that of amorphous plastics.
Ultrasonic plastic welding can be used to a limited extent for joining together two different thermoplastics (amorphous
plastics). Ultrasonic welding is not suitable for use with thermosetting plastics. Today ultrasonic welding is used in
every industry that processes plastics. The most common uses are in the Automotive, Medical, Textile, Food, Plastics, and
Packaging industries.
35 kHz ultrasound technology to bond technical textiles. This application is called ultrasonic