Technical requirements for the installation and processing of hot-pressed nuts and embedded nuts of plastic parts Installation method

1 Purpose

In order to standardize the processing technology of hot-pressed nuts and embedded nuts of plastic parts, it is easy to control the processing technology and quality of the processing plant, and ensure the subsequent processing quality of plastic parts.

2 Scope of Application

This technical requirement applies to the subsequent processing process of plastic parts in the product development and production stage of the company, for reference by processing plants, mechanical designers, SQA and inspectors. Refer to this article for technical requirements not specified in the drawing.

3 Processing technology of hot pressed nuts and embedded nuts

3.1 Hot pressed nuts

3.1.1 Specifications of Hot-pressed nuts

Plastic hole can not be designed chamfer; The size specifications of hot pressed nuts and corresponding rubber column sizes are as follows:

3.1.2 Tension and torque of hot pressed nuts

The tensile force and torque that the hot compression nut on the plastic part can withstand are recommended as follows:

3.1.3 Hot pressing temperature

For different materials, the hot pressing temperature of the nut is different, and the hot pressing temperature is specified in the following table:

3.1.4 Process requirements for hot pressed nuts

The operation process of the hot pressed nut is as follows:

Simple parts use general tooling with insulation material positioning in the height direction; Special parts to make corresponding special hot pressing tooling;

The diameter and depth of the hole of the rubber column should be checked before hot pressing, and must meet the size requirements specified in Table 1;

It is recommended to use a 50W temperature-adjustable heating rod that is heated by touching the copper nut with the temperature recommended in Table 3 for 7-10s.

When the inner hole of the rubber column is softened, the top plane and outer surface of the rubber column shall not be softened, and the nut shall be slowly pressed vertically into the rubber column to prevent insufficient plastic flow. After pressing into the nut, the heating rod shall be lifted vertically quickly;

The cooling time of parts is 8 hours.

The nut is flush with the top plane of the rubber column, and the protruding does not exceed 0.3mm; The verticality tolerance of the nut in the rubber column is φ0.2mm;

The glue column should not have obvious swelling or cracking.

3.1.5 Recommended Tooling. The following is the schematic diagram of hot pressing tooling

Production method:

The material of heating rod can be H62, and the material of gasket can be glass fiber board;

The heating rod, hot indenter and copper rod are fixed, and then the copper rod is fixed on the work table;

Put the workpiece on the work table, put the copper nut into the prepressure hole of the workpiece, align it, and do not tilt it;

Place the heat insulation gasket on the plane of the nut support column of the workpiece and pass through the copper nut;

The gasket is heated at a higher temperature and needs to be cooled for a period of time, so multiple sets of gaskets need to be prepared to ensure high efficiency.

3.1.6 Recommended Design of Hot head

The copper rod front end of the hot pressing tool is mainly used for heat conduction and pressure to the nut part, which is called the hot pressing head. The material can be H62, and its design is recommended in the following figure (taking M3 nut as an example).

3.2 Embedded Nuts

3.2.1 Specifications of the embedded nut

The specifications of the embedded nuts use the specifications of the hot-pressed nuts. Please refer to the table above.

3.2.2 Tension and torque of the embedded nut

The following table recommends the values of tension and torque that the nuts embedded on the plastic parts can withstand

3.2.3 Process requirements for embedded nuts

The process requirements for embedded nuts are as follows:

The embedded nut shall be positioned with a mandrel, and the coaxiality between the mandrel and the nut shall be φ0.03mm; The matching tolerance between the cylindrical hole on the die and the mandrel shaft segment is H9/f9;

The nut must be reliably positioned in the mold, not loose in the mold closing movement of the moving mold, not offset, not leaking, not falling off under the impact of high pressure melt;

For sensitive materials such as PC and PC+ABS, it is necessary to pre-heat the nut or carry out subsequent thermal insulation treatment to reduce the generation of thermal stress (It is not recommended to use the embedded nut process for PC materials, because PC will have residual stress after injection molding, and the joint of the embedded nut and plastic is easy to crack or crack after a period of time, which is a terror. To avoid can be improved from the process, improve the mold temperature, reduce the pressure holding time, reduce the pressure holding pressure and injection pressure, improve the barrel temperature, etc., can also be done at 90-100 degrees heating products, release the stress in advance.)

After the nut is embedded, the nut should be flush with the top plane of the rubber column and fall into the top plane of the rubber column no more than 0.2mm.