Braiding is a process where 16 wires are woven around the base-coat. These wires have a thickness range from 0.05 to 0.07 mm and generally are round shaped, although flat wires can be applied as well.
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Basic extruded layer. |
Braiding layer, braiding pattern of metal wires.
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| Surface extrusion layer covers the braiding, gives extra strength, enlarges the torque and ensures a smooth surface. |
Two carousels, placed in the braiding machine, rotate in opposite directions and apply the braiding layer on the base coat that is let through the center of the apparatus in vertical direction. On each carousel eight braiding wire spools are placed. These spools are automatically unwinded due to the movement of the carousels, while applying the braiding onto the base coat.
The ratio between rotation speed of the spools rotating around the base coat, the feeding speed with which the base coat is led through the braider and the gear ratio determine the pitch. The braiding wire consists of stainless steel wire which is braided 2 on 2 on the base-coat.
The application of a braided layer between two extrusion layers hugely enlarges the strength and stiffness of the extrudate. In addition, the kink resistance of the extrudate is significantly improved. In balloon catheters, used for dottering calcified blood vessels, braiding can be applied in order to be able to use a much higher fluid pressure, and thereby making the treatment more effective. When the physician rotates the proximal end of a catheter, it is important that the distal tip at the other end, inside the patient, accurately follows this rotation. When a catheter follows the rotation accurately and promptly, it has a good torque. The torque value of extruded material with a braiding layer is considerably higher than the torque of a product with the same dimensions without braiding.
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