A Brief Analysis of Common Technical Issues in the Use of Tissue Closure Clips (Ligation Clips)

Materials Used in Tissue Occlusion Clips (Ligation Clips)

1. POM material: This material exhibits excellent mechanical strength and rigidity, outstanding resistance to organic solvents, strong resistance to repeated impact, good wear resistance, and self-lubricating properties. However, it is prone to thermal degradation under prolonged exposure to high temperatures during processing, has poor acid resistance, and displays a significant molding shrinkage.

2. Polylactic acid material: This is a novel biodegradable material characterized by excellent biocompatibility, high gloss, good heat resistance, superior thermal stability, and outstanding resistance to solvents. It also exhibits favorable mechanical and physical properties. At present, its development in China is still in the early stages, and its performance and characteristics require ongoing experimentation and validation; please refer to the next issue for details.

Features of the Organizational Closure Clamp Mold

The design of closed-clamp assembly products places high demands on mold precision, and the corresponding materials are prone to thermal degradation, imposing stringent requirements on mold gating systems and runner designs. There are primarily two methods for mold opening:

1. Cold runner subgate: Layout configurations are 1x2 and 1x4.

2. Needle-valve hot-runner gating: Given that the molded parts have a low weight due to their closed-cell structure, this is a micro-injection molding process, and the material is prone to thermal degradation. Therefore, adopting this approach requires a systematic and rigorous analysis of the material properties, hot-runner system design, mold design, injection-molding machine selection, and molding-process optimization—placing high demands on all aspects. However, this method can significantly reduce material consumption while markedly improving production efficiency.

Analysis of Common Issues and Solutions for Organizational Closure Clips

1. Product dimension deviation:

Analysis: This is caused by defects in mold design, insufficient machining accuracy of the mold, inadequate mold base precision, and ineffective dimension control.

Plan:

1. In mold design, critical dimensions must be clearly dimensioned with appropriate tolerances, and rigorous measurement and control must be implemented at every stage—ranging from part machining to assembly and subassembly—for both critical dimensions and assembly dimensions.

2. The mold frame must also ensure both opening-frame accuracy and positioning accuracy;

3. Based on the material’s theoretical shrinkage rate and the product’s structural characteristics, determine an appropriate material shrinkage rate.

Dimensional variations can directly affect product accuracy during hot-press riveting assembly and the performance of the finished product after riveting; therefore, when designing and fabricating clamping-and-riveting tooling in a single setup, it is essential to take into account the tolerance requirements imposed on the equipment.

2. Product flash

Analysis: Flash primarily occurs at the fitting areas of inserts and along parting lines.

1. Mold design must be rational and rigorous, with a comprehensive assessment of the material’s corresponding properties;

2. Define the dimensional tolerance and assembly requirements for each workpiece;

3. Ensure the dimensional accuracy of all mold machining components;

4. Professional mold assembly techniques.

3. Residual at the entry point

Analysis: This is caused by an unreasonable design of the gating system and uneven ejection, among other factors.

1. The structural configuration of the access point must be designed to be reasonable and effective;

2. The layout of the product ejector pins must be optimized to ensure balanced ejection.

4. Insufficient strength at the crescent-shaped adjustment hole

Analysis: The structural strength of the product’s crescent-shaped section is insufficient, the final position of the forming line is suboptimal, and the molding process parameters are improperly set.

1. The structural strength at the product’s crescent-shaped section must be designed appropriately;

2. The layout of the entry point location must be reasonable;

3. Set reasonable process parameters;

4. The exhaust at the joint must be unobstructed.

5. Poor closure performance

Analysis:

1. The design issue of the interlocking characteristics of the tissue clamp itself;

2. The structural features related to the product lack sufficient strength;

3. Insufficient dimensional accuracy of features related to mold machining;

4. The forming process parameters are set improperly.

1. The occlusal characteristics related to the product must be designed reasonably and effectively;

2. The strength of product-related components must be designed appropriately;

3. Ensure mold machining accuracy;

4. Establish a reasonable forming process.