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Plastic welding is used in the medical industry
Publisher: suzhou kailinneng automation equipment co., LTD Release time：2023-03-23 15:09:35 Click on the number of times：290 Shut down
For the medical industry in particular, it can be difficult to find adhesives that meet biocompatibility requirements and FDA approval. In addition, many commonly used polymers, such as PP, PE and PTFE, have Low surface energy, which makes bonding difficult with adhesives.
Adhesives are often used as a quick, temporary solution in prototyping. In subsequent mass production, however, plastic welding is a more cost-effective solution that provides a consistent, high-strength weld without additional consumables.
The risks and challenges of plastic welding are often caused by improper welding process selection, weld design and testing methods, as well as parts deformation and size deviation. These problems can be reduced or eliminated through step-by-step elimination analysis and improvement measures.
The development of the plastic welding process follows the following steps:
Step p1: Define the problem
Step2: Select the process
Step3: Joint design
Step4: Test and verify
1. Define the problem
In the selection of welding process, clear product material and performance requirements, the process selection is very important. By defining these early, you can avoid subsequent losses.
The following questions should be considered and answered before deciding on weld location or welding process
1.1 Strength
What is the direction of the load? What stretching or shearing force will be experienced?
If possible, the weld should be designed to operate under as much shear force as possible, since plastic welds bear the greatest load in the direction of shear force. Plastic welding can bear the second tensile load, can bear the weakest stripping force.
1.2 Sealing
Does this product need to be sealed? And if so, what is the pressure? Is it airtight or watertight? Is there a test temperature requirement?
Products with sealing requirements are usually designed with closed welding lines and corresponding grooves or narrow gap Spaces around the chamber to be sealed, and melted plastic is filled with slots or gaps to achieve sealing requirements. The size and shape of the product is different, the selection of plastic welding process will be different.
1.3 Appearance
Are there any appearance requirements? Where is the "A" side? Allow overflow visible?
Most welders have the potential for appearance defects. However, these problems can be limited by improving the fixture and optimizing the welding parameters, or by simplifying the surface of the part, or by hiding the welding surface. If it cannot be avoided, it may need to be prevented by adding a previous process (e.g. drying) or corrected by adding a later process (e.g. spill-removal), but these measures increase the cost
1.4 Particulate Pollutants
Are particles or loose spills allowed in the product?
For welding processes that rely on surface friction to generate heat, such as rotary welding and vibration friction welding, it is difficult to avoid the production of particle contaminants, as well as loose overflow.
1.5 Materials
The factors affecting the welding performance of materials include various additives, such as colorants, fillers, impact modifiers, lubricants, etc., in addition to the properties of the base resins in the materials. These components together affect the choice of welding process. For example, when the laser welding process is used, the upper parts are required to be colorless to allow the laser to pass through; Carbon black is added to the lower parts to fully absorb the laser energy.
In general, the filler content should be minimized to ensure that sufficient resin is available for welding to ensure welding strength. Therefore, it is recommended that the filler content be controlled below 33%.
In addition, the two parts must be material compatible, that is, have the same or similar melting point and viscosity, in order to allow intermolecular diffusion to complete the welding.