ULTRASONIC TECHNOLOGY
If your business involves the sealing packaging, welding plastic moulded parts, punching out components or cutting textiles or food products, then ultrasound could be the perfect addition to your production process. Ultrasonic technology is fast, very energy-efficient and economical with materials, guaranteeing speed, precision and efficiency.
We will explain how ultrasonic technology works, how our machines are designed and what you can do with them – all in a way that’s easy to understand. We may just have the solution you need to optimise your production processes.
What is ultrasound?
Ultrasound is mechanical oscillation with a frequency between 20 kHz and 10 GHz. This means that it is inaudible to humans, as we can only hear sounds between 16 Hz and 20 kHz.
Ultrasound is generated using high-frequency electrical energy, which is then converted to mechanical energy. As a form of mechanical oscillation, the sound travels through the air and other media at a defined speed as a wave of pressure. Frequency is a measure used to express how often the cycles of a periodic process – like the contracting and deforming motions of our ultrasonic tools – recur. One hertz is equivalent to one oscillation per second.
How does the ultrasonic welding and cutting process work?
To weld and cut with ultrasound, we use energy and convert it to sound waves to melt the plastic. The operating frequency varies depending on the application. As Rinco covers a full spectrum of frequencies between 20 and 70 kHz, we can provide perfectly tailored ultrasonic solutions for any welding or cutting application.
How does mains power/energy get converted into ultrasound?
To convert electrical energy (electricity) into mechanical oscillations (ultrasound), you need a generator and a converter. The generator first converts the 200/230 V mains voltage and 50/60 Hz (socket) energy into a HF voltage with a defined frequency of at least 20 kHz. Depending on the application, the frequency can be anywhere between 20 and 70 kHz.
The downstream converter turns the high-frequency electrical energy into mechanical oscillation. Inside the converter, there are a number of piezo discs, which respond to the electrical energy by alternately contracting and deforming. This movement causes the converter to oscillate. The resulting ultrasound is emitted at an amplitude and frequency set by the generator, which are transmitted by the converter to the downstream booster and the sonotrode/work horn.
The sonotrode/work horn is the actual welding or cutting tool that makes contact with the workpiece. Often, the converter, booster and sonotrode are collectively referred to as the oscillation system or vibratory stack. These components must be acoustically fine-tuned to work together efficiently.
Which plastics can be welded with ultrasound and which materials can be combined ?
Ultrasound can be used to create reliable, sealed joins in moulded parts and to weld or seal films and technical textiles. The components to be joined should be made primarily of thermoplastics, which may be semi-crystalline or amorphous. Semi-crystalline thermoplastics include POM, CA, LCP, PEEK, PA, PBT, PE, PPS, PP and PTFE. Amorphous plastics include ABS, MABS, PMMA, PC, PET, PS and PVC. The best results are achieved when welding two components made from the same material, but you can also weld compatible pairings of different materials.
A list of compatible plastics can be found here.
Moulded parts must be designed for ultrasound compatibility – moulded part design
In order to weld two moulded parts together quickly and achieve a reproducible, high-strength result, one of the two components must be designed with integrated pointed elements.
These pointed elements, also known as energy directors or pinch seams, direct the ultrasonic oscillation into the second moulded part. This ensures that both moulded parts melt simultaneously along the seam to create a permanent join.
If there is no energy director or pinch seam, the surfaces will be welded together instead of a seam being formed. This type of welded join is not as strong; it also takes significantly longer to achieve and there is a risk of damage to the components.
Let’s take a closer look at the two most common join zone geometries:
Energy directors
Energy directors direct the energy into the material with a high degree of precision. They are usually triangular or have a V-shaped profile and they are primarily used with amorphous thermoplastics. When the ultrasound source is applied, the energy directors melt and excess material is forced out of the sides of the join. The design of the moulded part determines where the material flows out.
Pinch seam (Shear joint)
Due to their design, pinch seams are also known as stepped seams. This type of seam is ideal for seal welding and semi-crystalline plastics. This join zone geometry can also be used to create very attractive seams.
In addition to the two aforementioned join zone geometries, there are a number of other, less common forms of weld seam. Stud welding is one of the options.
Stud welding
If you need to permanently join two moulded parts but there is no need for the join to be sealed, stud welding is another option. This type of welding is suitable for hard amorphous and semi-crystalline plastics.
The design of the moulded parts has an enormous impact on the seal, strength and look of the welding result. This is why it is very important to consult with RINCO ULTRASONICS right from the start of your project. We will be happy to advise you.
Benefits of ultrasonic welding
Economical
Ultrasonic welding is a very economical technology. Compared to thermal welding, ultrasonic welding requires
- No warm-up time
- No cooling phase for the application
- Less material
Efficient
The welding cycle usually takes just a few tenths of a second. The weld seam also hardens in a fraction of a second.
And because the seams can be very narrow, you can also reduce material consumption.
Perfect weld seams
The weld seams can be designed to meet your exact requirements. Whether your goal is hermetically sealed seams or perfect visual results, your weld seams will always be strong and precise.
No additional materials
Ultrasonic welding is highly economical, as no additional materials are required to join the components. This also makes the materials easy to separate for recycling.
Welding without additional materials such as screws or adhesives also helps to make products safer – ideal if you manufacture children’s toys, for example.
Three-dimensional weld seams
The sonotrode – the actual welding tool – is designed and manufactured specifically to suit the customer’s requirements. As this design process is tailored to your needs, you can also opt for three-dimensional weld seams.
