Design Considerations for Inserting Copper Nuts in Plastic Parts

Data push the 121st day

First, there are three ways to design copper nuts in the design.

Hot melt nut

Hot-melt embedding is the most common and common method of embedding. It is usually embedded in a hot melt machine and a manual electric iron.

Injection nut

Injection molding is generally required to have a strict hole diameter for the nut, and the aperture control is within 0.05 mm. Since the product is fixed by Molding Pin and placed in the injection molding die, the nut diameter is controlled by the size of the PIN pin of the injection molding machine.

Ultrasonic nut

Ultrasonic embedding is a kind of ultrasonic vibration that causes the friction between the nut and the workpiece surface and the intrinsic molecules to increase the temperature of the transmission to the interface. When the temperature reaches the softening temperature of the workpiece itself, the nut is embedded in the rubber piece. In the middle, when the vibration stops, the workpiece is cooled and shaped at a certain pressure.

Second, the nut material:

1: standard brass C3604

2: Bottom lead copper, in line with ROHS environmental requirements

3: stainless steel

Note: In general, the surface of the nut does not need surface treatment, special requirements can be used to plate the surface.

Note: D: nut outer diameter L: nut length d: nut base C: plastic aperture W: plastic hole wall thickness Y: plastic hole depth

1. The d size is the nut base, also called the guide positioning part. It is matched with the plastic C part before being embedded. Therefore, the bottom part d of the nut is smaller than the inner diameter C of the plastic BOSS to facilitate positioning;

2, D size is the outer diameter of the nut, which matches the size of the inner diameter C of the plastic BOSS. Generally, the inner diameter of the plastic nut of the mobile phone is smaller than the outer diameter of the nut by about 0.25-0.3 mm;

3. The L dimension is the length of the nut. It is matched with the depth of the plastic BOSS hole Y. Generally, the depth of the plastic hole is greater than the height of the nut (length) by 0.5-1.0mm for the storage of glue;

4, W is the thickness of the plastic hole wall, the general plastic BOSS hole thickness is 0.8-1.0mm or more, the larger the nut size specification, the greater the meat thickness.

Remarks: All of the above are suggested data. If you have other required sizes, you can make them separately!

Fifth, the impact of plastic BOSS hole size opening size

If there is no problem in the choice of plastic and nut, the standard state of the nut after embedding the plastic is shown in Figure (1).

If the nut size is too small, the plastic BOSS hole is too large, and the nut can not be eaten after the plastic is buried in the plastic, which will cause insufficient twisting force as shown in Figure (2).

If: the nut size is too large, the BOSS hole is too small, it will produce overflow or burst phenomenon as shown in Figure (3)

If there is no problem with the size of the nut and the size of the plastic, and there is an abnormal phenomenon, then we usually consider improving by some optimized design;

Example 1. The plastic BOSS has a shallow hole depth, which will result in insufficient torsion tension.

Because the BOSS hole depth is shallow, such as the choice of double-twill nuts, in the proportion of the various sizes of the nut, especially on the embossing, the embossing step is shorter, such a nut is buried in the plastic, the embossed plastic surface is too Less, there will be insufficient tension and pull, so it is generally recommended to set the BOSS hole depth to 2.5mm or more. The nut size is generally recommended to be 2.0mm or more. Improvement plan: Similar to this situation, in the case of inconvenient customer modification, it is recommended to change the nut shape to the single oblique BS1, as shown in the right figure, so that the embossing step is increased, and the embossed plastic surface is increased. Large, thus increasing the twisting force.

Because the left-hand style nut is selected, after embedding the plastic, A1 and A2 expand, and B shrinks sharply, which makes the plastic extrusion difficult. The upper and lower ends of the nut are prone to overflow phenomenon, which seriously affects the product view;

Improvement plan: Positioning with “C” part, the nut can be placed safely into the plastic hole position, which improves the efficiency and yield. Due to the addition of the C-end guide part, A2 is also reserved after a certain amount of rubber is squeezed. Sufficient rubber is applied to the A1 part. At the same time, the A1 and A2 parts are twill with a 90° angle of intersection of 45°, and the high-strength nodes can be formed at the intersection angle. The torsional power on the impedance circumference greatly increases the torsional pulling force!

Nut burying common problems

Six, the advantages and disadvantages of nut implants

Seven, nut implant test tensile force and torque

The tensile force and torsion torque that can be withstood by the hot-pressed nut on the plastic part are as shown in the table, and the tensile torque torque specification table of the hot-pressed nut

Model Tensile force (kg) Torque torque (kgf.cm)

Hot pressing nut temperature

Plastic softening is not a melt. But it is about 15~25 degrees lower than the melting temperature.

Ultrasonic: Since ultrasonic implantation will release energy instantaneously, it will easily damage the nut structure, especially the screw part. Therefore, it is recommended that the nut below M1.6 should not be implanted with ultrasonic waves.