Introduction to Injection Mold

2021/04/20


1.1. Practical scope:
Injection molds are actually used for thermoplastics such as ABS, PP, PC, POM, etc., while thermosetting plastics such as phenolic plastics, epoxy plastics, etc. use rubber molds; 
1.2. Classification of injection molds:
 According to the structure: two-plate mold, three-plate mold according to the nozzle: large nozzle, point nozzle, hot water nozzle
1.3. Injection mold structure:
A. Molded parts: it is what we usually call the front and back mold CORE, which is also the most closely related part of the product;
B. Pouring system:
The flow channel that the molten plastic leads from the nozzle to the cavity can be divided into: main flow channel, branch runner, gate, cold slug well, etc.
C. Guiding system:
Determine the relative position of the front and rear molds when closing the mold. Generally, there are guide posts and guide sleeves. If necessary, the ejection part also needs to be positioned by guide posts and guide sleeves;
D. Demoulding structure:
It is the device that ejects the rubber part from the mold. Commonly used are: thimble, top plate, tube, etc.;
E. Temperature regulation system:
In order to meet the mold temperature requirements of the injection molding process, cooling water channels added to the front and rear molds;
F. Lateral parting and lateral core pulling:
When the plastic part has a structure that is inconsistent with the demolding direction, it must use the row position. Common forms: slider, inclined top, core pulling, etc.;
G. Exhaust structure:
There are two common forms of exhaust: exhaust grooves and gaps between formed parts.
In order to remove the air in the cavity and the gas generated during the molding process during the injection molding process, an exhaust groove is often set on the parting surface. The principle of setting up the exhaust slot is that the exhaust slot should be as large as possible without affecting the overflow and the front. The inserts, thimbles, and inserts are exhausted from the gap of the formed parts.
Two, mold repair
During the normal use of the mold, due to normal or accidental wear and tear, as well as various abnormal phenomena during the plastic molding process, it needs to be repaired.
2.1. The preparation work of the mold mechanic after receiving the task
A. Find out the degree of mold damage;
B. Refer to the repair model to analyze the repair plan;
C. Degree: We repair the mold, to a large extent, under the condition of no drawings, and our maintenance principle is "not affect the structure and size of the plastic part", which requires our mold repair technicians to design When the size changes, you should take the number first before doing the next step.
2.2 Precautions for assembly and disassembly
A. Marking: When the mold repair technician removes the guide post, the cylinder, the thimble, the insert, the pressing block, etc., especially if there is a direction requirement, be sure to see the corresponding mark on the mold base so that it can be seated when the mold is installed .
In this process, two points must be noted:
1. The identifier must be unique and must not be repeated;
2. Unmarked mold inserts must be marked with marked characters;
B. Foolproof: Do the foolproof work for the parts that are prone to wrong installation and ensure that they cannot be installed in the case of reverse installation;
C. Placement: The disassembled parts must be placed neatly, screws, springs, rubber rings, etc. should be packed in plastic boxes;
D. Protection: Take protective measures for precision parts such as cores and cavities to prevent accidental injury by others.
2.3 Matters needing attention when repairing the textured surface
A. Mold saving on the machine: When the plastic parts have mold sticking, dragging, etc., which need to be saved, the parts with the grained surface should be protected before maintenance. Do not save the texture of the machine when saving molds. If you are not sure, you should require mold maintenance;
B. Welding: If welding the textured surface, you must pay attention to:
1. The welding rod must be the same as the mold CORE material;
2. Tempering should be done after welding;
3 Pattern repair: When the mold is repaired and needs to be repaired at the factory, the repairer needs to protect the pattern with paper, and mark the position of the pattern, with a pattern template. When the etched pattern is returned to the factory, the quality of the etched surface should be checked carefully, and the mold can be installed after confirming OK. If you are not sure about the repair effect, you should try the mold first and confirm OK before leaving the factory to repair the pattern.
Three, mold maintenance
Mold maintenance is more important than mold maintenance. The more the mold is repaired, the shorter its lifespan. The better the mold is maintained, the longer its lifespan.

3.1. The necessity of mold maintenance
A. Maintain the normal movement of the mold and reduce unnecessary wear and tear of moving parts;
B. Make the mold reach the normal service life;
C. Reduce oil pollution in production.
3.2 Mold maintenance classification
A. Daily maintenance of molds;
B. Regular maintenance of the mold;
C. The appearance and maintenance of the mold.
3.3, the content of mold maintenance
A. Daily maintenance:
1. Refuel various moving parts such as thimble, row position, guide post and guide sleeve;
2. Clean the mold surface;
3. Discharge of water transportation;
b. Regular maintenance:
1, 2, 3, same as above;
4. Clean up the exhaust slot, add exhaust when the trapped air burns the black level;
5. Correction of damaged and worn parts;
C. Appearance maintenance:
1. Paint the outside of the mold base to avoid rust;
2. When dropping the mold, the cavity should be coated with anti-rust oil;
3. It should be closed tightly during storage to prevent dust from entering the mold CORE.
3.4 Precautions for mold maintenance
A. For sports parts, daily maintenance must be refueled;
B. The mold surface must be clean: do not stick label paper on the P/L surface. The product will continue to be delivered without the mold being removed before the product is stuck, and the P/L position glue wire is serious;
C. If abnormalities are found, such as abnormal ejection, loud mold opening and closing, etc., it must be repaired in time;
Fourth, the safety issues in mold repair and maintenance
When doing anything, safety must be the first priority. Mold repair and maintenance are dealing with molds and equipment (steel). This issue must be taken seriously;
1. When using the lifting ring, you must first check to ensure that it is intact;
2. When using equipment, especially when flying debris is generated, be sure to wear glasses for operation;
3. Wear protective clothing and protective glasses when welding;
4. It is strictly forbidden to work under the mold;
5. When working on the machine, ensure that the injection molding machine is in a stopped state and hang up the sign.