Hot-pressed nuts and embedded nuts for plastic parts Installation and technical requirements Installation methods:
In order to standardize the processing technology of hot-stamped nuts and embedded nuts for plastic parts, it is easy to control the processing technology and quality of processing plants and ensure the quality of subsequent processing of plastic parts.
2 Scope of application
This technical requirement applies to the subsequent processing of plastic parts at the company's product development and production stages for reference by processing plants, mechanical designers, SQA, and inspectors. The technical requirements not specified in the drawings refer to this article.
3 hot pressing nut, embedded nut processing technology
3.1 Hot-pressed nuts
3.1.1 Hot-pressed nut specifications
The plastic hole may not be chamfered; the size and size of the hot-pressed nut may be the following:
3.1.2 Pulling force and torque of the hot-pressed nut
The tensile and torsion moments that hot-pressed nuts on plastic components can withstand are recommended in the following table:
3.1.3 hot pressing temperature
For different materials, the hot-pressing temperature of the nut is different. The hot-pressing temperature is regulated by the following table:
3.1.4 hot nut process requirements
The hot-press nut operates as follows:
Simple parts use general-purpose tooling with heat-insulating material positioned in the height direction; special parts are made with special hot-pressing tooling;
Before hot pressing, the diameter and depth of the cartridge hole shall be sampled and must meet the dimensional requirements specified in Table 1.
It is recommended to use a 50W adjustable temperature heating rod. The heating rod is heated with the recommended temperature and contact copper nut in Table 3, the heating time is 7-10s;
When the inner hole of the plastic column is softened, the top surface and outer surface of the plastic column shall not be softened, and the nut shall be slowly pressed vertically into the column to prevent the plastic flow from being insufficient. After the nut is pressed into the nut, the heating rod shall be lifted vertically;
The Cooling time of parts at room temperature is 8 hours;
The nut is flush with the top surface of the glue column, not exceeding 0.3mm; the verticality tolerance of the nut in the glue column is φ0.2mm;
No significant swelling or cracking of the column.
3.1.5 recommended tooling, under a hot pressure tooling schematic
The material of the heating rod can be H62, and the material of the gasket can be glass fiber board;
The heating rod, hot press head and copper rod are fixed, and the copper rod is fixed on the work bench;
Put the work piece on the workbench, put the copper nut into the pre-press hole of the work piece, align, can't have the inclination;
Put the insulating gasket on the plane of the nut supporting column of the workpiece and pass through the copper nut;
Gaskets need to be cooled for a period of time due to higher heating temperatures, so multiple gaskets need to be prepared to ensure high efficiency.
3.1.6 hot head design recommendations
The front end of the copper bar of the above hot-pressing tooling is mainly used for heat conduction and pressure to the part of the nut called hot head. The material can be H62. Its design is recommended in the figure below (taking M3 nut as an example)
3.2 embedded nuts
3.2.1 Specifications of Embedded Nuts
The specifications of the embedded nuts are based on the specifications of the hot-pressed nuts. Refer to the table above.
3.2.2 Pulling force and twisting moment of embedded nut
The following table is recommended for the tension and torsion moment value of the nuts pre-embedded on the plastic parts.
3.2.3 embedded nut technology requirements
The process requirements for embedded nuts are as follows:
The embedded nut shall be positioned with the mandrel, and the coaxiality of the mandrel and the nut shall be ensured to be φ0.03mm; the fitting tolerance between the cylindrical bore of the mold and the mandrel shaft segment shall be H9/f9;
The nut must be reliably positioned in the mold, not loosened during the mold clamping movement of the moving mold, and it should not be displaced, leaked or dropped under the impact of the high pressure melt.
For PC, PC + ABS and other sensitive materials, the nuts need to be pre-heated, or follow-up insulation treatment, in order to reduce the generation of thermal stress (PC material is not recommended to use embedded nuts process, because PC will have residual stress after injection molding It is fearful that the embedded nut and the plastic junction are easily cracked or cracked after a certain period of time, so that it is impossible to improve the process, increase the mold temperature, reduce the pressure holding time, reduce the holding pressure and injection pressure, increase the barrel temperature, etc. It is also possible to heat the product at 90-100 degrees to release the stress in advance.)
After pre-embedded nuts, the nut should be flush with the top surface of the glue column, and the top surface of the glue column should not exceed 0.2mm.