Nowadays, plastic parts are used in all aspects of our life, we need plastic parts in all fields, and its use is very wide. When we use plastic parts, when the plastic parts need to be removed and assembled for many times, the best way to tighten is to choose metal nuts embedded in the plastic parts. So, what are the methods of plastic nut insertion? Metal nut inserts are available in four ways: thermal inserts, ultrasonic inserts, nut injection molding, and cold press inserts. Next, let's get to know it in detail!
1. Hot pressing process of nut insert
Applicable to thermoplastics
High overall performance, low process cost
Both hot pressing and ultrasonic inlaying processes require a hole to be preformed in the plastic part. The hole diameter is specified by the manufacturer of the nut insert and is slightly smaller than the outer diameter of the nut. The holes may be straight or conical. The front diameter of the nut is slightly smaller than the aperture, which helps to position the insert.
During hot pressing, the nut is heated to a certain temperature by a hot die. When the nut is inserted into the plastic part, the nut will melt a small part of the plastic around the hole. The softened resin flows into the knurled tooth and then solidifies and hardens to form a firm bond with the nut. Because the process is easy to control, relatively low cost, and easy to automate (multiple nuts can be pressed at once), hot pressing is a common nut inlaying process for thermoplastics.
2. Ultrasonic inlay process
Applicable thermoplastic with high overall performance
Fast production beat
Ultrasonic inlay is also a part of the plastic around the melting hole, and the melting area is larger than that of the hot pressing process. By ultrasonic high-frequency vibration (15-30Khz), the plastic in contact with the nut produces high-frequency strain and stress, thereby generating heat to melt the plastic. The ultrasonic inlay process is faster than the hot pressing process. The disadvantage is that it may cause the nut end abrasion problem.
3. Injection molding process of nut insert
Suitable for thermoplastic and thermosetting plastics, with the best pulling force and maximum torque.
The processing of the pin and the correct insertion of the mold are the core of the process. In each injection molding process, the nut should be properly placed on the pin and placed into the mold. In this way, the resin completely fills the outer surface of the nut and is able to form the best bond strength. However, nut injection molding greatly increases the complexity and development cost of the mold, and the need to insert pins and nuts each time increases the process cycle. The nut insert may be a through-hole nut. This means that the nut needs to be in close contact with the pin and cavity surface at both ends to prevent resin from flowing into the nut. The inserted nut can also be a "blind hole nut", that is, the nut is closed at one end and does not need to be in contact with the cavity surface. When the wall is thick, or there is a requirement for internal sealing, the "blind hole nut" can be used.
4. Cold pressing process
Suitable for thermosetting plastics, simple installation, minimal cost, only need a simple indenter or press.
Although the cold-pressing process may not perform as well as the above types, it is a very economical option. Because they are easy to install, they usually do not require special equipment. Sometimes referred to as an "expandable insert," this insert is characterized by slots on the side that allow it to elastically deform upon insertion. When the screw is screwed in, the side wall of the "expansion insert" is forced to open outward-creating an "occlusive" contact with the inner wall of the hole. The principle is similar to that of household expansion screws. Higher performance inserts do not have slots and require some pressure to be inserted. Although it does not achieve the bonding strength of other processes, it can still provide a very cost-effective insertion process.
The above is the introduction of the plastic nut insertion method, I hope to help you!
ZIBO HUIWEN Plastics offers a full range of plastic molding capabilities to efficiently mass-produce parts specializing in injection molding and have served customers in variety of industries such as medical, automotive, packaging, construction, home appliances , and agriculture. The company has two factories which occupy a total area of more than 18,000 square meters, and a total of 102 sets of injection molding machines .
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