First, according to plastic parts structure and use requirements, determine position of feed port. As long as structure of plastic parts allows, nozzle and nozzle head in fixed mold insert do not interfere with molding structure, and inlet of hot runner system can be placed at any position of plastic part. Position of feed opening for conventional plastic injection molding is usually selected based on experience. For large and complex shaped plastic parts, position of injection port of injection molding can be simulated by computer aided analysis (CAE) in cavity of molten plastic, and cooling effect of each part of mold is analyzed to determine ideal position of inlet.
Second, determine nozzle form of hot runner system. Use characteristics of plastic parts materials and products are key factors in selecting nozzle head form. Production batch of plastic parts and manufacturing cost of mold are also important factors in selecting nozzle head form.
Third, according to production batch of plastic parts and tonnage size of injection equipment, determine number of cavities per mold.
Fourth, number of nozzles is determined by determined inlet position and number of cavities per mold. If a certain product is formed, one cavity and one feed port are selected, then only one nozzle is used and a single-head hot runner system is selected; if a certain product is formed, one mold and multiple cavities or one mold and one cavity, two or more feed ports is required, and multiple nozzles are required, that is, a multi-head hot runner system is selected, except for mold structures with cross runners.
Five, according to weight of plastic parts and number of nozzles, determine size of radial dimension of nozzle. At present, nozzles of same form have multiple size series, which respectively meet requirements for forming plastic parts in different weight ranges.
Six, determine mold structure size according to plastic part structure, then select standard length series size of nozzle according to thickness of fixed mold insert and fixed mold plate, and finally modify thickness of fixed mold plate and other dimensions related to hot runner system.
Seven, determine shape of hot runner fixing plate according to shape of hot runner plate, layout power cable lead grooves on the board, design sufficient cooling water loops near hot runner plate, nozzles, and nozzle heads.
Eight, complete design drawing of plastic mold of hot runner system.
Injection mold design often uses hot runner to feed material, so what should be paid attention to when designing hot runner?

1. It is necessary to add a guide post to protect hot nozzle. Height must be higher than hot nozzle. Two lock wires must be used. It cannot be locked from panel to the end for easy assembly and disassembly.

 

2. Ground side needs to be added with a drainage groove, 3-5MM deep, and a pressurized wire board is required. Cavity can be reduced by cut-off body sent by hot nozzle company, but there must not be any sharp angles inside the frame, so as to avoid scratch hot nozzle or hot nozzle line.

 

3. Open-type hot nozzle, only 3MM is required at sealant. Top surface of hot nozzle is 0.2-0.5MM lower than runner or PL. It is used to release thermal expansion of hot nozzle. Cavity in mold core is cut by drawing file provided by hot nozzle company, and no changes can be made.
4. EWIKON hot nozzle point feed material, keep 0.3MM straight position at sharp point, so as to avoid wear of nozzle multiple times, steel is damaged.
5.MOLDMASTER open-type hot nozzle feeding, need to avoid 0.2MM according to drawing of hot nozzle company, used to release thermal expansion of hot nozzle, and cut cavity elsewhere according to drawing given by hot nozzle company.

 

6. MOLDMASTER needle valve type hot nozzle is used to feed material, leaving 0.7MM to match position sealing material. In other places, cavity was cut according to drawing given by nozzle company.

 

7. GUNTHER hot nozzle point feed material, need to leave 0.3MM straight, so as to avoid multiple wear of nozzle multiple times, steel is damaged.