Hemodialysis membrane spinnerent 128-hole

6. Application: Hemodialysis membrane (used to manufacture the core component of artificial kidneys—hemodialysis membranes.  The membrane must efficiently retain uremic toxins such as urea and creatinine while allowing rapid water transport, and ensure hemocompatibility to avoid hemolysis, coagulation, and other adverse reactions.)

7. Specification: 0.5/0.28/0.15 (unit: mm, corresponding to the outer annulus diameter, middle dope channel diameter, and inner bore-fluid channel diameter, respectively.  The three-layer structure must strictly match the three-phase flow coordination of "coagulation bath–dope–bore fluid.")

8. Manufacturing capability: 0.500±0.002 mm, 0.280±0.002 mm, 0.150±0.004 mm;  assembly concentricity 0.003 mm (medical-grade precision far exceeding standard industrial spinnerets, ensuring uniform wall thickness and pore-size distribution for every fiber.)

9. Spinneret material: Stainless steel (316L medical-grade stainless steel; surface roughness Ra ≤ 0.8 μm to prevent dope residue-induced fouling and to meet biocompatibility requirements.)

10. Applying material: PES (Polyethersulfone), PSF/PSU (Polysulfone) (both are medical-grade high-performance polymers with excellent resistance to moist-heat sterilization at 121°C, strong chemical stability, and good hemocompatibility; however, they have high viscosity and a narrow spinning window, imposing very high demands on channel smoothness and thermal stability.)

11. Additional notes: As a high-end product within the hollow fiber spinneret industry, hemodialysis spinnerets require overcoming three major technical barriers:

(i) high-precision synchronization across a large number of orifices (hundreds) to ensure per-orifice parameter consistency;

(ii) specialized channel architecture tailored to the NIPS process to balance dope coagulation rate and bore-fluid diffusion efficiency;

(iii) medical-grade materials and surface finishing to meet biosafety and long-term stability requirements.  This product not only embodies our core R&D capability but also represents the highest technical level of hollow fiber spinnerets in the industry.

12. Detailed collaboration process and customer assurance

(1) Customer background and core requirements

Before the 2017 purchase, Lengthen faced a critical bottleneck in scaling hemodialysis membrane capacity: incumbent spinneret production lead times were 6–12 months, severely affecting throughput.  Some older spinnerets also caused large fiber diameter deviations and uneven pore-size distributions, making it difficult to consistently meet the NMPA Technical Review Guidance for Hemodialysis and Related Medical Devices (urea clearance ≥ 180 mL/min with deviation ≤ 5%).  Their hemodialysis membrane production lines required a long-term stable supply of spinnerets (including maintenance and parameter-optimization support).  Accordingly, Lengthen set four core requirements for Trustech's spinnerets:

● 128-hole consistency: per-orifice diameter deviation ≤ 0.003 mm;  inter-orifice dope flow-rate deviation ≤ 3% to avoid performance fluctuations among fibers.

● Process compatibility: ultra-smooth inner channel surfaces (Ra ≤ 0.8 μm) to reduce PES/PSF dope flow resistance and prevent "bubble defects" caused by dope retention.

● Long-term stability: no corrosion or channel wear under 180–200°C spinning temperatures and prolonged exposure to dope (including DMAC solvent);  service life ≥ 12 months.

● Service package: provide necessary cleaning and maintenance training, and technical support to optimize spinneret parameters based on membrane performance feedback.

(2) Technical solution and pain-point resolution

In response to Lengthen's needs, Trustech implemented a customized solution:

● Multi-orifice uniformity control: a 5-axis precision machining center (positioning accuracy ±0.0002 mm) was used for synchronous machining of 128 orifices.  Post-machining, each orifice's diameter and roundness were verified by laser interferometry to ensure per-orifice deviation ≤ 0.002 mm.  Software simulation of flow distribution across the 128 channels and optimization of the inlet angle (12° taper) limited inter-orifice dope flow deviation to ≤ 2%, surpassing the 3% requirement.

● Surface finishing: the 316L spinneret underwent combined electropolishing and passivation, achieving surface roughness Ra = 0.08 μm, which reduces dope friction and prevents DMAC-induced corrosion.

● Lifetime assurance design: critical regions (orifice inlets, inner bore channels) received hardening treatment.  Accelerated aging tests (simulating 18 months of service) showed channel wear ≤ 0.002 mm;  in actual use, Lengthen's first batch exceeded lifetime expectations.

● Full lifecycle service: a dedicated technical service team completed on-site installation and commissioning within 72 hours of delivery.

(3) Application results and deepened collaboration

After delivery of Trustech's spinnerets, Lengthen achieved three major improvements:

● Stable membrane performance: fibers produced by the 128-hole spinneret had diameter deviation within 0.003 mm;  urea clearance stabilized at 185–190 mL/min, successfully passing NMPA on-site inspection.

● Improved production efficiency: minimal spinneret-related faults increased effective line runtime, boosting capacity by 10%.

● Cost optimization: longer spinneret service life and shorter production lead times reduced procurement costs.

Based on these positive results, Lengthen signed a three-year long-term cooperation agreement with Trustech in October 2017, with a framework purchase covering hollow fiber spinnerets totaling 12,000 holes.