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How does the injection molding machine work?

2020-12-17

Injection molding machine is also known as injection molding machine or injection machine. It is the main molding equipment that uses plastic molding dies to make thermoplastic or thermoset plastics into various shapes of plastic products. Divided into vertical, horizontal and all-electric. The injection molding machine can heat the plastic and apply high pressure to the molten plastic to make it eject and fill the mold cavity.


The working principle of the injection molding machine is similar to the syringe used for injection. It uses the thrust of the screw (or plunger) to inject the plasticized plastic in the molten state (that is, the viscous fluid state) into the closed mold cavity. The process of obtaining products after curing and shaping.


Injection molding is a cyclic process, each cycle mainly includes: quantitative feeding-melting plasticization-pressure injection-mold filling and cooling-mold opening and taking parts. After taking out the plastic part, the mold is closed again for the next cycle.


How to use the injection molding machine? How to set the parameters? Knowledge sharing of vertical injection molding machine adjustment parameters:


1. Confirm and prepare the parameters before setting the parameters of the vertical injection molding machine


⑴ Confirm whether the material drying, mold temperature and heating cylinder temperature of the vertical injection molding machine are correctly set and reach a processable state.


⑵Check the vertical injection molding machine opening and closing molds and ejection action and distance settings.


⑶ Vertical injection molding machine injection pressure (P1) is set at 60% of the maximum value.


⑷Keep the vertical injection molding machine pressure (PH) set at 30% of the maximum value.


⑸ Vertical injection molding machine injection speed (V1) is set at 40% of the maximum value.


⑹The screw speed (VS) of the vertical injection molding machine is set at about 60RPM.


⑺The back pressure (PB) of the vertical injection molding machine is set at about 10kg/cm2.


⑻Vertical injection molding machine loose retraction is set at 3mm.


⑼The position of the holding pressure switch of the vertical injection molding machine is set at 30% of the screw diameter. For example, for a screw with φ100mm, set 30mm. ⑽The measuring stroke is set slightly shorter than the calculated value. ⑾The total injection time is slightly shorter, and the cooling time is slightly longer.

2. Manual operation of vertical injection molding machine parameter correction


⑴The vertical injection molding machine locks the pet preform mold (confirms the rise of the high pressure), and the injection seat moves forward.


⑵Inject manually until the screw stops completely, and pay attention to the stop position.


⑶The screw of the vertical injection molding machine revolves and feeds.


⑷After the vertical injection molding machine cools, open the injection mold and take out the molded product.


⑸ Repeat the steps ⑴~⑷, the screw finally stops at the position of 10%~20% of the screw diameter, and the molded product has no short shot, burr, whitening, or cracking.


3. Correction of semi-automatic operating parameters of vertical injection molding machine


(1) The correction of the metering stroke of the vertical injection molding machine [metering end point] Increase the injection pressure to 99%, temporarily adjust the holding pressure to 0, adjust the metering end point S0 forward until short shot occurs, and then adjust backward until flash occurs. Take the middle point as the selected position.

(2) Correction of the output speed of the vertical injection molding machine to restore the PH to the original level, adjust the injection speed up and down, find out the individual speeds where short shots and burrs occur, and use the middle point as the appropriate speed. [This stage can also be entered at multiple speeds Parameter setting for appearance problems.

(3) Maintain the vertical injection molding machine pressure correction up and down to adjust the holding pressure, find out the individual pressure of surface depression and burrs, and choose the middle point as the pressure holding.

(4) Plasticization parameter correction of vertical injection molding machine

①Confirm whether the back pressure of the vertical injection molding machine needs to be adjusted; 

②Adjust the screw speed to make the metering time shorter than the cooling time; 

③Confirm whether the metering time is stable, try to adjust the temperature gradient of the heating ring. 

④Confirm whether there is dripping in the nozzle, whether pig tails or sticky molds occur in the main runner, and whether the finished product has air marks, etc., and adjust the nozzle temperature or loosening distance appropriately.

(5) stage holding pressure and multi-stage firing rate


①Generally speaking, without affecting the appearance, the vertical injection molding machine injection should be based on the principle of high speed, but it should be carried out at a lower speed before passing through the gate and switching between the holding pressure; 

②The holding pressure should be gradually reduced. In order to avoid too high residual stress in the molded product, the molded product is easily deformed.


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