1. Functional description of the liquid silicone strap
Liquid silicone straps (hereinafter referred to as straps) are new favorites on wearable devices such as watches, and are widely used. It is soft and comfortable, easy to clean and not easy to scratch.
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Second, the structural characteristics and difficulties of liquid silicone straps
The product structure is complex, there are many holes, and there are many sealing positions. The combination of the second-shot silica gel and the first-shot hard glue is complicated, and the appearance requirements are high.
3. Mold characteristics of liquid silicone strap
The product structure is complex, there are many holes, and there are many sealing positions. The requirements for the overall dimensional accuracy of the mold and the overall assembly requirements for the mold are very high. Our mold mainly adopts the cold runner dispensing method, and the number of holes is reasonably set according to the actual consumption demand.
4. Analysis and solutions of common problems of liquid silicone straps
1. The product size is out of tolerance:
Analysis: Mold design defects, insufficient mold machining accuracy, insufficient mold base accuracy, and inadequate size control.
plan:
(1) In the mold design, the key dimensions should be clearly marked and the tolerances should be reasonable. Each process should be strictly measured and controlled in place for key dimensions and assembly dimensions, from parts processing to assembly;
(2) The accuracy of the mold base should also ensure the frame opening accuracy and positioning accuracy;
(3) Grab the standard shrinkage rate according to the physical property table of the selected silicone material.
2. Product burrs
Analysis: The structure of the silicone strap is complex, and there are many parting surfaces. The liquid silicone itself has good fluidity and small overflow value. It is easy to produce burrs on the parting surface and the entrance, etc. The overall processing accuracy of the mold and the coordination of the sealing position High precision is required.
plan:
(1) The mold design needs to be reasonable and rigorous, comprehensively evaluate the properties of the liquid silicone material, and define the dimensional tolerance assembly requirements of each workpiece;
(2) The matching dimensional accuracy of each insert and mold core needs to be processed and controlled in place;
(3) It is necessary to design a reasonable tearing groove structure;
(4) Reasonable preload value for one shot of hard glue with molds.
3. Poor exhaust problem
Analysis: The design of the mold exhaust method is unreasonable, and the molding parameters are unreasonable.
plan:
(1) When the mold structure allows, a vacuum pumping mechanism must be designed;
(2) The mold flow analysis needs to predict the position of the gas trapped in the bonding line in advance, and design a reasonable and effective exhaust;
(3) The smoothness of the parting surface and the mold clamping must meet the requirements;
(4) The injection speed, pressure and mold forming temperature should be set reasonably;
(5) The mixing of A/B rubber is uneven, resulting in a large gas content in the material itself.
4. Not easy to tear the edge
Analysis: The design of the tearing groove is unreasonable, and the tearing edge is worn.
plan:
(1) Reasonably designed tearing groove;
(2) Regularly perform mold maintenance to prevent knife edge damage.
5. The appearance is easy to get dirty
Analysis: The surface of the silicone strap is prone to static electricity, and it is easy to absorb dirt and dust.
plan:
(1) The production operation needs to control the pollution caused by environmental factors in the process;
(2) The production needs to wear dust-free gloves for operation;
(3) Prevent the product from electrostatically adsorbing dust.
