How to do reasonably in the molding of injection molding medical devices in Dalian?

In the molding of injection molding medical devices in Dalian, the injection stroke must be determined first. In theory, the injection stroke can be calculated according to the following formula:

S1=4（CVp+Va）/ ρ Ds2

In the formula: injection stroke Vp – product volume ρ– Resin density C – number of cavities Va – gate volume Ds – screw diameter

In actual production, if the total weight of "product+gate" is known, the injection stroke S1=(M/Mmax) · Smax+(5-10) mm can be calculated by the following formula

In the formula, S1: injection stroke, mm M - total weight of "product+gate", g Mmax - large injection volume of injection molding machine, g/Smax - large injection stroke of injection molding machine

Due to the different geometric shapes of the runner system and various parts of the mold, in order to meet the product quality requirements, different parts have different requirements for the flow state of the mold-filling melt (mainly refers to the pressure and speed when flowing). In an injection process, when the screw pushes the melt into the mold, it is required to achieve different pressure and speed at different positions, which is called multi-stage injection molding.

Generally, it is more scientific to set at least three or more injection sections for plastic parts during molding, that is, the first section is at the main runner, the second section is from the runner to the gate, the third section is about 90% of the cavity filled with the product, and the rest is the fourth section. The switching position of each section can be determined by the weight calculation method;

In actual production, the multi-stage injection process parameters should be scientifically analyzed and reasonably set according to product quality requirements, runner structure, mold exhaust conditions, etc. Usually, the adjustment and observation method can be used to set the pressure/speed of the switching position point needed for injection to 0, observe the melt direction and the product defect condition, and gradually adjust until a reasonable position point is found. However, in the process of debugging and observation, attention must be paid to the demoulding condition of under-injected products to avoid mold sticking due to under-injection at some concave parts of the mold.