Common screw problems of injection parts and countermeasures
Injection molding is a manufacturing process for producing parts from thermoplastic or thermosetting plastic materials. Screws are an essential part of injection molding, and when they malfunction, they can cause big problems for the entire production line.
In the assembly of electronic products, the wrong screw selection or improper screw hole column design is a time bomb in production. In addition, the selection of screw heads on the production line is also very important.
This blog post will discuss some of the most common screw problems and how to fix them.
Screw head slippery wire
This problem is caused by the poor quality of the screw head. The wire is not properly annealed and hardens during injection, causing it to slip off the screw head. This can be solved by using a high-quality screw head with proper annealing.
It is also possible that the electric torque is too large, the wrong electric driver head (BIT), or the electric driver head has been crooked.
Please first make sure that the electric driver head is correct and then try to reduce the bottom electric torque; The working bear often sees the grooves of the screw head, and the electric driver head does not match in the production line, which causes the screw head to slip. Most of them are caused by the flat head groove screw but the sharp head of the electric driver head to lock.
In addition, if the electric driver head is carelessly maintained, it is easy to bend. The method of checking can make the electric driver idling to observe whether the driver’s head is a straight line. If it turns crooked, the driver’s head should be replaced, which is generally a management problem.
Suppose the above steps are confirmed correct but still can not solve the problem of screw head sliding teeth. In that case, it is necessary to try screw hardening treatment; it generally can solve the problem of sliding teeth, but the price will be higher, so it is recommended to change the design of the screw hole, or choose a more appropriate screw to solve.
The inner wall of the screw hole of injection parts is damaged
This is a common problem in injection molding, and it is also a fatal problem. Once the inner wall of the screw hole is damaged, it will cause the entire product to be scrapped. The main reason for this problem is that the screw hole diameter of injection parts is too small, and the clearance between the screw and the inner wall of the screw hole is too small. In addition, the injection speed is too fast, or the injection pressure is too high, which will also damage the inner wall of the screw hole.
To solve this problem, you need to check whether the inner aperture of the screw hole is too large, and pay attention to whether the draft Angle of the screw hole affects the screw aperture.
Check whether the pitch of the screw is too small. The screw with a small pitch is not conducive to repeated lock removal. If the situation permits, the screw with a larger pitch can be considered.
If you find this injection molding problem, please increase the diameter of the screw hole or increase the clearance between the screw and the inner wall of the screw hole. In addition, you need to slow down the injection speed and reduce the injection pressure.
The screw hole of injection parts is a Crack
This is another common injection molding problem. Once the screw hole is cracked, it will cause the entire product to be scrapped. The main reason for this problem is that the injection speed is too fast or the injection pressure is too high.
If the injection speed and injection pressure are no problem before and no related design changes, but the screw hole is broken suddenly, please check whether there is secondary material doped in plastic injection molding. Or plastic injection molding when plastic particles are not completely dry?
To check whether the screw selection is correct if it is in trial or mass production? Is there enough space under the screw hole to hold plastic debris? Is the screw hole wall thickness design too thin? Is there too much torque in the screw?
The screws of the injection parts are not tight
Please check whether the screw torque is too small, and whether the screw hole design is too small to lock the screw to the end? Is the number of screws eating teeth too small? The number of teeth to eat the general screw had better have 3 teeth above.
In addition, if there is stress inside the product or if there is a jacking design on the two locking pieces, you should be especially careful about the possibility of loose locking.
The screws of injection parts become loose after locking:
This is a troublesome problem, usually in the internal stress of the design, or the need for vibration above the product, such as dot matrix printers, and automotive electronics. Sometimes some of the especially sensitive to thermal expansion and contraction of the plastic also easy to cause the problem of loose screws.
The solution is usually to glue fixed screws or add gaskets.
The screw is stuck in injection parts
This is a very common injection molding problem. This problem will cause the material to be pushed into the screw hole, resulting in the screw being stuck. If there is no problem in the inner wall of the screw hole of the injection parts, the reasons for this injection problem are as follows:
- The screw hole is not cleaned, and there is debris blocking the screw hole;
- Screw diameter is too small, and the screw hole size does not match;
- The screw is too short to be locked;
- If the injection speed is too high or the injection pressure is too high, the inner wall of the screw hole will be damaged.
To solve this problem, it is necessary to check whether the inner aperture of the screw hole is too large and pay attention to whether the draft Angle of the screw hole affects the aperture of the screw hole.
Improperly installed screws:
Improperly installed screws cause this problem. Make sure that the screws are installed correctly and that they are tightened properly.
If you are unsure of how to install the screws, consult with a professional or the manufacturer of your injection molding machine.
These are some of the most common injection molding problems and their solutions. Aria Manufacturing Limited is a professional injection molding company; if you have any injection molding problems, please get in touch with us immediately. Thank you for reading!
Gavin Leo is a technical writer at Aria with 8 years of experience in Engineering, He proficient in machining characteristics and surface finish process of various materials. and participated in the development of more than 100complex injection molding and CNC machining projects. He is passionate about sharing his knowledge and experience.