Materials used for tissue closure clip (ligation clip)
1. POM material: the material has good mechanical strength and rigidity, good resistance to organic solvents, strong resistance to repeated impact, good wear resistance, and self-lubricating property, but it is easy to decompose under high temperature for a long time during processing, poor acid resistance, and large molding shrinkage.
2. Polylactic acid material: it is a new type of biodegradable material with good biocompatibility, glossiness, heat resistance, thermal stability, solvent resistance, mechanical properties and physical properties. At present, it is in the early stage of development in China, and the material properties and characteristics need to be continuously tested and verified. See the next issue for details.
Organize Closed Clamp Mold Features
The product itself of the tissue closed clamp has high requirements on the precision of the mold, and the corresponding materials are easy to decompose, so it has requirements on the inlet point of the mold, runner design, etc. There are two main mold opening methods:
1. Cold runner submerged rubber: 1 * 2 and 1 * 4 for alignment
2. Needle valve type hot runner feeding: because the weight of the tissue closed clamp is light, it belongs to micro injection molding, and the material is easy to decompose, this method requires systematic and rigorous analysis of the physical properties of the material, the design of the hot runner system, the design of the mold, the selection of the molding machine, and the design of the molding process. However, this method can greatly reduce the use of materials and significantly improve the production efficiency.
Analysis of common problems of tissue closure clamp and solutions
1. Product size out of tolerance:
Analysis: mold design defects, insufficient mold processing accuracy, insufficient mold base accuracy and inadequate size control.
Scheme:
1. In mold design, the key dimensions shall be clearly marked, and the tolerance shall be reasonably marked. For key dimensions and assembly dimensions, each process shall be strictly measured and controlled from part processing to assembly assembly;
2. The precision of mold base shall also ensure the precision of opening frame and positioning;
3. Grab reasonable material shrinkage based on the theoretical shrinkage rate of materials and product structure characteristics.
The size influence will directly lead to the product accuracy during hot press riveting assembly and the use effect of the finished products after riveting. Therefore, the requirements of the tolerance range on the machine must be taken into account when organizing the one-time production of clamping riveting tooling.
2. Product burr
Analysis: Burrs are mainly generated at the fitting and parting surfaces of inserts.
1. The mold design shall be reasonable and rigorous, and the corresponding characteristics of materials shall be comprehensively evaluated;
2. Define the dimensional tolerance assembly requirements of each workpiece;
3. Ensure the precision of all parts processed by the mold;
4. Professional mold assembly method.
3. Inlet residue
Analysis: unreasonable design of inlet structure and unbalanced ejection.
1. The inlet structure shall be designed reasonably and effectively;
2. The layout of the product ejector pin should be reasonable to ensure balanced ejection.
4. Insufficient strength at the crescent of the adjusting hole
Analysis: the structural strength design at the crescent of the product is insufficient, the final position of the bonding line is unreasonable, and the setting of the molding process is unreasonable.
1. The structural strength of the crescent of the product shall be designed reasonably;
2. The layout of entry points shall be reasonable;
3. Set reasonable process parameters;
4. The exhaust at the junction line shall be smooth.
5. Poor closing effect
analysis:
1. The design of the mutual occlusion feature of the tissue clip itself;
2. The strength of product related structural features is insufficient;
3. The characteristic precision related to mold processing is not enough;
4. The setting of forming process is unreasonable.
1. The relevant occlusal features of the product shall be designed reasonably and effectively;
2. The strength of relevant parts of the product shall be designed reasonably;
3. Ensure the mold processing accuracy;
4. Set reasonable molding process.