How to Choose the Right Piston Rod for Medical Devices? Precision Requirements and Application Analysis

Piston rods in medical devices are key components of hydraulic systems, injection devices, and other critical functional parts. When choosing the right piston rod for medical equipment, in addition to requiring high precision, it must also meet stringent quality standards to ensure the safety and reliability of the medical device. Below are the precision requirements and application analysis for selecting a piston rod suitable for medical devices:

1. Material Selection

   • Stainless Steel: Piston rods in medical devices are commonly made from 304 or 316 stainless steel. 316 stainless steel is especially suitable for applications requiring high corrosion resistance, as it resists chlorides effectively, making it ideal for various liquid and drug delivery systems.

   • Titanium Alloy: Titanium alloys, known for their excellent biocompatibility, are suitable for medical devices, especially for implants. Titanium alloy piston rods not only prevent corrosion but also provide good mechanical properties, adapting to high-pressure and high-frequency usage demands.

   • Aluminum Alloy: In some medical devices, aluminum alloy can also be used for piston rods, especially in equipment that requires lightweight materials. Aluminum alloys have good strength and corrosion resistance, and are commonly used in non-implantable devices.

2. Precision Requirements

   • Dimensional Tolerance and Straightness: Piston rods in medical devices require extremely high dimensional tolerance and straightness, typically with tolerances within ±0.01mm. Accurate dimensional tolerance and straightness help reduce friction during operation, ensuring stable device performance.

   • Surface Roughness: To reduce friction and ensure sealing, the surface roughness of piston rods is usually required to be below Ra0.4. Fine surface treatment not only improves mechanical performance but also ensures that the piston rod does not experience excessive wear during high-frequency motion.

3. Corrosion Resistance and Biocompatibility

   • Chemical Corrosion Resistance: Piston rods in medical devices often come into contact with drugs, liquids, or bodily fluids, so they must possess strong chemical corrosion resistance. In applications such as drug injection or implants, piston rods must resist erosion from drugs, disinfectants, and other substances.

   • Biocompatibility: For medical devices implanted in the body, the piston rod needs to have good biocompatibility to prevent adverse reactions with human tissue. Titanium alloys and certain stainless steel materials typically meet this requirement.

4. High Pressure and High Temperature Resistance

   • High Pressure Resistance: Piston rods in medical devices need to withstand high pressure, especially in devices like injectors and infusion pumps. When selecting materials, the strength and stability of the piston rod under high pressure should be considered.

   • High Temperature Resistance: Some medical devices need to operate in high-temperature environments, particularly during high-temperature sterilization processes. In such cases, the piston rod material must have good high-temperature resistance and should not deform easily.

5. Durability and Reliability

   • Fatigue Resistance: Piston rods in medical devices must operate stably over long periods, avoiding fatigue fractures caused by repeated motion. The fatigue resistance of the piston rod is critical to ensuring the long-term stable operation of the medical device.

   • Long-Term Stability: Medical devices often require the piston rod to maintain good performance over many years or even decades, particularly in long-term implanted devices. The long-term stability of the piston rod is crucial in these applications.