Business News Agency January 17th In today's widespread use of plastic materials in the field of medical devices, new types of plastics production and processing technology emerge in an endless stream. Laser welding is one of them and has attracted widespread attention from the industry. This article describes the principle, process and application of plastic laser welding in the medical device industry.

Plastic welding principle

During the welding of thermoplastics, the two plastic parts to be welded are clamped together with a clamping fixture. One of the plastic parts allows the laser to penetrate and the other plastic part absorbs the laser energy. The laser beam reaches the welding plane through the upper transparent material and is then absorbed by the underlying material. The laser energy is absorbed so that the temperature of the underlying material is increased, the upper and lower layers of plastic are melted, and finally solidified into a strong weld.

Welding schematic

The advantage of plastic laser welding is that it is a non-contact welding method. The laser energy only acts on a very small welding area, which greatly reduces the thermal stress and vibration of the workpiece on the workpiece.

Plastic laser welding methods include: contour welding, synchronous welding, quasi-simultaneous welding, radial welding and Globol welding.

Contour welding

As the name implies, contour welding is to move the laser along the welding line of the workpiece and melt and bond the plastic layers to be welded together. Sometimes, the position of the laser can be fixed and the workpiece can be moved or rotated to achieve the welding purpose.

Synchronous welding

Synchronous welding first customizes the corresponding laser head according to the shape of the welding area. It is required that the shape of the welding area is generally symmetrical, such as a circle. Synchronously-welded laser beams originate from a plurality of diode laser beams, which simultaneously act on the contour lines of the welding area to melt the welding area to achieve the welding effect. The disadvantage of synchronous welding is that its lens must be customized according to the shape of the welding area of ​​the workpiece.

Mask welding

Mask welding requires the creation of a template that reflects or absorbs laser light. The template is used to locate the welding area, and the laser can melt the welding area through the template to achieve the welding effect. The advantage of mask welding lies in its flexibility. The template can be changed according to the shape of the welding area. At the same time, this welding method is also suitable for high-precision welding, and its precision can reach micrometers.

Globo welding

The patented welding process of Leister, Switzerland. Globo welding is welded along the outline of the product. The laser beam is air-cushioned and can be spot-free focused on the welding interface in a friction-free, arbitrarily rolling glass sphere that not only performs focusing but also acts as a mechanical clamping fixture. When the ball rolls on the surface, continuous pressure is applied to the joint surface. This ensures pressure clamping while the material is heated by the laser. The glass ball replaces the mechanical fixture and expands the application of laser welding in continuous three-dimensional welding.

Application of Plastic Welding on Medical Devices

In the field of medical devices, plastic laser welding is mainly used in injection systems, medical electronic equipment, various artificial graft and stoma products, and so on.

An interesting application is the use of a laser-welded Phonak Cerumio Protector. The entire Cerumen Protector is only a few millimeters in size. We need to weld a diaphragm to a washer about 3 mm in size. The diaphragm is transparent to laser radiation, and the gasket is made of a thermoplastic material that absorbs laser radiation. To achieve such a small workpiece, we use a mask welding method that is suitable for high-precision welding.

The plastic laser welding process is also widely used in some other high-end medical products, such as artificial care products and tip protection caps. In artificial beryllium care products, we use the Globo welding process. In the welding of the tip protection cap, we use the simultaneous welding process.

Plastic laser welding is also widely used in biomedical analytical instruments. Biomedical analytical instruments usually require sterility, without any chemical contamination, and so on. However, the traditional way of adopting glue adhesion may bring chemical substances into the analytical instrument, which will affect the accuracy. Other methods, such as friction welding, generate dust or spillage during processing, which can also contaminate the instrument. Laser welding as a non-contact welding method is particularly suitable for the production of such products. The range of heat influence in plastic laser welding is small, so it is also suitable for the welding of heat-sensitive materials, such as the welding of biochip with protein coating on the surface.

The best example of a biomedical analytical instrument is a liquid analysis chip that contains a microfluidic system for collecting and analyzing liquid substances. Usually the flow path is only a few centimeters long, may be tens of micrometers to several hundred micrometers wide, and its aspect ratio is less than one. The flow path is usually pressured by several psi. These microchannels typically consist of very thin plastic sheets, which may vary in thickness from a few millimeters to 20 micrometers. To weld such a delicate product, mask welding is the best method. After welding with a mask, welding can be completed by using a relatively low-quality diode laser, which saves a lot of investment. In addition, the use of mask welding can also greatly increase production efficiency.

The use of plastic laser welding technology in medical devices is far more than the above applications. The plastic laser welding process is being adopted by more and more medical device manufacturers, and its application prospects will be very bright.