Bakelite (thermosetting plastic) injection molding, application process of injection bakelite powder.

Basic introduction

The application process of injection bakelite powder, if it can be controlled according to its performance characteristics, will be of great help to improve the rate of finished products; reduce the workload of the injection machine; reduce the wear of the screw barrel; shorten the molding cycle; and improve the appearance of the product. Reasonable use of injection bakelite powder can extend the service life of general nitrided steel screws to 8-12 months and improve the damage to the mold.

1. Concept: The material must be fully melted and plasticized in the barrel through the screw under appropriate temperature conditions, so that it presents a good molten state and fluidity, so that it has the best injection molding process. Injection bakelite powder has good barrel thermal stability. It can be kept in the barrel for more than 10 minutes at 120¡æ, and presents the best molten flow state at 85-100¡æ. The barrel retention time can reach 20 minutes.

2. Recommended barrel temperature setting conditions:

1. 1. Two-stage temperature control barrel: front 90-95¡æ, rear 75-85¡æ; 2. Three-stage temperature control barrel: front 90-100¡æ, middle 80-90¡æ, rear 70-80¡æ; 3. The fluidity of the material can be adjusted by appropriately increasing or decreasing the temperature of the front barrel according to the process requirements. 4. Relationship of back pressure: Injection bakelite powder is basically granular. In addition to the temperature coordination to make it melt, the back pressure must be adjusted to complete and improve the pre-plasticization of the material, so that the fluidity is good during injection and the amount added is uniform and stable.

Back pressure adjustment can generally control the nozzle to have appropriate material outflow when the feeding is loose, and adjust the feeding stability during the injection process, which is about 3-5 kg/cm2 depending on different machines

Fourth, pressure and injection (shot) speed: Since the material is fully molten and has good fluidity, it does not require very high injection pressure to fill the cavity, which can greatly reduce and lighten the load of the machine tool. Generally, about 60 kg can meet the requirements of injection molding. The rapid friction between the shot and the nozzle, runner, gate, and mold will produce excessively high temperatures and aggravate the wear of the screw and barrel. Especially for injection machines controlled by a single proportional valve, high pressure and high speed will cause more serious damage to the screw mold, so the shot speed should not be too fast. Too slow will affect efficiency and is not desirable. Generally, depending on the size of the part and the form of the gate, it is controlled at 10-25 grams per second. It is better not to produce hard bubbles in the part and gas to support it and not be injected into the head.

5. Mold temperature and mold holding time: Injection bakelite powder has a faster molding speed, and its molding requirements can be met at 170¡æ. The mold holding time is 14 seconds per millimeter and decreases with the increase of thickness. The mold cycle of general parts is 60-80 seconds.

The above conditions need to be adjusted according to the machine tool, mold, runner gate, part shape, thickness and other conditions. The continuous stability of injection bakelite powder between batches and large quantities can make it more convenient for users to use.

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