Product Specification

Product details

1. Material Selection

The material selection of stainless steel for medical needles is crucial to ensure that the needles meet stringent medical standards for safety, performance, and biocompatibility. Our AVF needles are usually made of stainless steel 304 and 316L. These grades are chosen because they offer high resistance to corrosion from bodily fluids and sterilization processes.

304 Stainless Steel is widely used for general-purpose medical needles. On the other hand, 316L Stainless Steel provides superior corrosion resistance, especially against chlorides and bodily fluids, due to its lower carbon content, which enhances its resistance to intergranular corrosion. This makes it preferred for needles exposed to more aggressive environments or requiring higher corrosion resistance.

Our medical-grade stainless steels come with material certifications and traceability documentation to ensure compliance with medical device regulations. Additionally, these stainless steels meet biocompatibility standards, such as ISO 10993, which evaluates the biological response to the material.

2. Grinding

The grinding process for AVF needles, used in dialysis, is a precision machining method that shapes and finishes the needle tips to achieve the desired sharpness, geometry, and surface finish. This involves removing material using abrasive grinding wheels through methods like centerless grinding, cylindrical grinding, and surface grinding.

Centerless grinding offers high production efficiency and consistency, making it suitable for producing large quantities of needles. Cylindrical grinding is used for both rough and fine grinding to achieve the desired sharpness and geometry. Surface grinding creates specific features and finishes flat surfaces on the needle, providing a smooth surface finish for final polishing.

For AVF needles, the focus is on achieving a very sharp tip with minimal burrs and a smooth surface to ensure patient comfort and minimize tissue trauma. These needles may have a slightly higher penetration force due to their larger size and thicker walls, typically around 50-100 grams (0.5-1.0 N).

We perform regular testing during production to ensure each batch of needles meets required specifications, adhering to standards like ISO 7864 and ASTM F3014-14 for sterile hypodermic needles. These standards outline the requirements and test methods for needle penetration, ensuring high quality and safety.

3. Custom design

A standard Arteriovenous Fistula (AVF) needle typically has one hole at the tip. This hole is designed to allow the efficient flow of blood during dialysis procedures.

However, there are variations in needle designs that might include additional side holes to optimize blood flow and reduce the risk of clogging. Manners is currently making custom AVF needles with additional side holes for some of our customers to help with their product research and development.

4. Laser grooving

The small holes in AVF needles are made using the 5-axis laser cutting technique, which includes a process called laser grooving. Laser grooving is a precise method that uses a focused laser beam to create narrow, exact grooves or channels on the surface of the needle. This technique is commonly used in needle manufacturing to enhance fluid flow or add structural features.

Using 5-axis laser cutting to create small holes in AVF needles offers significant advantages in terms of precision, flexibility, efficiency, and quality. First, the precision of 5-axis laser cutting results in smooth, burr-free edges, which reduces tissue trauma during needle insertion and withdrawal.

Second, it can create intricate grooves on medical needles for better fluid dynamics or structural features that would be difficult or impossible with traditional 2D laser cutting. The additional axes provide greater control and precision, allowing for the creation of very fine and intricate grooves with tight tolerances.

The general tolerance for 5-axis laser cutting typically ranges from ±0.05 mm to ±0.1 mm (±0.002 inches to ±0.004 inches). For applications requiring extreme precision, such as medical devices or aerospace components, tolerances can be as tight as ±0.01 mm (±0.0004 inches).

5. Electropolishing and Ultrasonic Cleaning

After the laser slotting process for AVF needles is complete, the needles move on to the cleaning stage. At this point, we use both electropolishing and ultrasonic cleaning to ensure the highest quality.

Electropolishing is an electrochemical process that removes a thin layer from the needle’s surface, eliminating burrs, sharp edges, and embedded particles. This step is crucial for medical applications, as it ensures a smooth and safe surface.

Next, ultrasonic cleaning uses high-frequency sound waves to agitate a cleaning solution, effectively removing contaminants like machining oils, debris, and particles from the needle’s surface. This thorough cleaning process ensures that each needle meets stringent medical cleanliness standards, making them safe and ready for use.