SMC Lightweight Tray For Surgical Instrument Sterilization Drives Mold Innovation

I. Mold Material Selection: Balancing Precision Retention and Medical Compatibility

Medical sterilization trays need to withstand high-temperature and high-pressure sterilization (e.g., 134℃ steam sterilization) and corrosion from chemical disinfectants (e.g., chlorine-containing disinfectants). Additionally, mold surfaces must not release harmful substances. Therefore, material selection must balance mechanical properties and medical safety:

 

1. Core Mold Steel Selection

Mold steel is chosen in grades based on the precision requirements of the tray. Common types and their applicable scenarios are as follows:

P20 Steel: Suitable for general-precision sterilization trays (dimensional tolerance ±0.2mm). It has good machinability and polishability, with low cost. Its wear resistance can be improved through chrome plating, and its service life is approximately 100,000 molding cycles.

718 Steel: Designed for high-precision trays (dimensional tolerance ±0.1mm), such as complex trays with compartments and snap-fit structures. It achieves a balanced hardness (HRC 30-35) and toughness. After nitriding treatment, its surface hardness can reach over HV 800, enabling long-term retention of mold precision, with a service life extended to more than 150,000 molding cycles.

H13 Steel: Used in scenarios requiring frequent high-temperature molding (molding temperature >160℃). It exhibits excellent hot strength and thermal fatigue resistance, preventing mold cracking caused by repeated thermal shock. It is suitable for molds of sterilization trays produced in large batches (daily output >500 pieces).

2. Surface Treatment Technology

Surface treatment is essential to achieve three core functions: "antibacterial performance, corrosion resistance, and easy demolding". Mainstream solutions include:

Hard Chrome Plating (thickness 5-10μm): The surface finish can reach Ra ≤0.02μm, improving wear resistance by 3 times. It also reduces the risk of adhesion between SMC material and the mold. Moreover, the chrome plating layer has high chemical stability and can withstand long-term erosion by medical disinfectants.

Gas Nitriding Treatment: Forms a nitrided layer with a depth of 0.1-0.3mm, with surface hardness reaching over HV 1000. It eliminates the risk of coating peeling (avoiding migration of metal ions to the tray) and meets the biocompatibility requirements of medical-grade materials (e.g., ISO 10993-5 cytotoxicity testing).

https://www.jiutaimould.net/sanitary-ware-mould/bathroom-tray-mould/smc-tray-mould.html

II. Core Mold Design Essentials: Adapting to Tray Functions and Production Efficiency

The structural characteristics of sterilization trays (e.g., compartments, drainage holes, stacking snaps) and their usage scenarios (repeated sterilization, load-bearing >5kg) determine that mold design must focus on overcoming three key technical challenges:

 

1. Precision Structural Design

Parting Surface and Demolding System: A "curved parting surface + angled ejector mechanism" is adopted to avoid molding defects (e.g., flash, scratches) on complex structures of the tray such as compartments and snaps. The draft angle is controlled between 1.5° and 3° to ensure smooth demolding while preventing tray deformation.

Exhaust System Optimization: Since SMC material releases trace gases during molding, 0.03-0.05mm wide exhaust grooves are set at the edge of the mold cavity to prevent bubbles on the tray surface (bubble diameter must be <0.1mm to avoid bacterial hiding).

 

2. Thermal Management System

A multi-zone temperature control design is adopted. Through heating tubes (power 500W per set) and cooling channels embedded in the mold, the uniformity of mold temperature is controlled within ±2℃:

The molding temperature is usually set at 150-170℃ to match the curing characteristics of SMC material.

The distance between cooling channels and the mold cavity is maintained at 15-20mm to ensure rapid cooling of the tray after molding (cooling time <30s), thereby improving production efficiency.

 

3. Digital Simulation Optimization

CAD/CAE technology is used to avoid design defects in advance:

Flow field simulation is conducted to analyze the filling process of SMC material in the cavity, optimizing the gate position (side gates are usually used to avoid fiber agglomeration caused by uneven material flow).

Structural simulation is used to verify mold strength. For example, the mold cavity corresponding to the load-bearing part of the tray must undergo finite element analysis to ensure deformation <0.01mm, preventing the tray from sagging after long-term use.

III. Manufacturing Process: Driven by Both Intelligence and Compliance

Medical-grade molds must meet strict quality control standards (e.g., ISO 13485 Medical Device Quality Management System). The manufacturing process needs to integrate precision machining and intelligent testing technologies:

1. Precision Machining Process

Cavity Machining: Five-axis CNC machine tools are used, with a positioning accuracy of ±0.005mm, ensuring the molding precision of detailed structures such as compartments and snap grooves.

Polishing Process: Conducted in three stages (rough polishing → fine polishing → mirror polishing), with the final surface finish reaching Ra ≤0.01μm to reduce the risk of SMC material residue on the cavity surface.

 

2. Intelligent Quality Control

During the molding process, sensors collect temperature and pressure data in real time (sampling frequency 100 times per second). Combined with AI algorithms, process parameters are adjusted to control the product defect rate below 1%.

Machine vision is used to detect surface defects of the mold (e.g., scratches, dents) with a detection accuracy of 0.01mm, preventing defects from being transferred to tray products.

IV. Industry Development Trends: Upgrading Toward Lightweight and Intelligence

With the advancement of localization of medical consumables and technological breakthroughs in SMC materials, the mold industry is showing two major upgrade directions:

 

1. Lightweight Trays Driving Mold Innovation

The application of bio-based SMC materials (e.g., castor oil-based resin matrix) reduces the tray weight by 30%, requiring molds to adapt to the fluidity characteristics of new materials:

Optimize gate size (diameter increased to 8-10mm) to improve the filling efficiency of bio-based SMC.

Adopt modular mold design to realize rapid switching of "one mold compatible with trays of different thicknesses (2-5mm)", meeting the personalized needs of hospitals.

 

2. Integration of Intelligent Production

Application of Digital Twin Technology: Build a virtual mold model to map the temperature and wear status of the physical mold in real time, and provide early warnings for maintenance needs (e.g., automatically reminding repair when the chrome plating layer is worn down to 3μm).

Automation Integration: Molds are linked with robotic loading and unloading systems to realize full-process automation of "SMC sheet feeding → molding → tray removal → inspection", increasing the daily output of a single production line to over 1,000 pieces.