Injection molding is a cyclic process, each cycle mainly includes: dosing - melting and plasticizing - pressure injection - mold cooling -Opening the mold to pick up the part. After removing the plastic part and then close the mold for the next cycle. [edit this paragraph] structure injection molding machine according to the plasticizing method is divided into plunger injection molding machine and screw injection molding machine, according to the machine transmission can be divided into hydraulic, mechanical and hydraulic - mechanical (linkage) type, according to the operation mode is divided into automatic, semi-automatic, manual injection molding machine.
(1) horizontal injection molding machine: this is the most common type. Its clamping part and injection part are on the same horizontal centerline, and the mold is opened along the horizontal direction. Its characteristics are: short body, easy to operate and maintain; low center of gravity of the machine, the installation of a smoother; products can be used after the ejection of gravity automatically fall, easy to realize fully automatic operation. At present, the injection molding machine on the market mostly adopts this type.
(2) Vertical injection molding machine: the part of the mold and the injection part of the same vertical center line, and the mold is open in the vertical direction. Therefore, its footprint is small, easy to place inserts, loading and unloading of the mold is more convenient, from the hopper into the material can be more uniform plasticization. But the products are not easy to fall automatically after ejection, must be removed by hand, not easy to realize automatic operation. Vertical injection molding machine should be used for small injection molding machine, generally in the 60 grams of the following injection molding machine is used more, large and medium-sized machine should not be used.
(3) corner injection molding machine: its injection direction and mold interface in the same surface, it is particularly suitable for processing the center part does not allow traces of the gate of the plane products. It covers an area smaller than the horizontal injection molding machine, but into the mold inserts are easy to tilt down. This type of injection molding machine is suitable for small machines.
(4) multi-mode rotary table type injection molding machine: it is a multi-station operation of the special injection molding machine, which is characterized by the closing device using a rotary table type structure, the mold rotates around the rotary axis. This type of injection molding machine gives full play to the plasticizing ability of the injection device, can shorten the production cycle, improve the production capacity of the machine, and thus is particularly suitable for the cooling and shaping time is long or because of the placement of inserts and the need for more auxiliary time for the production of large-volume products. However, due to the huge and complex mold closing system, the mold closing force of the mold closing device is often small, so this injection molding machine is more commonly used in the production of plastic shoe soles and other products.
The general injection molding machine includes injection device, mold closing device, hydraulic system and electrical control system and other parts.
The basic requirements of injection molding are plasticizing, injection and molding. Plasticization is to achieve and ensure the quality of molded products as a prerequisite, and in order to meet the requirements of molding, injection must ensure that there is sufficient pressure and speed. At the same time, due to the high injection pressure, the corresponding high pressure in the mold cavity (the average pressure in the mold cavity is generally between 20 to 45MPa), so there must be a large enough clamping force. It can be seen that the injection device and mold closing device are the key components of the injection molding machine. [edit]Operation 3.1 Action Procedure of Injection Molding Machine
Closing Mold→Pre-Molding→Reverse Shrinkage→Nozzle Advance→Injection→Pressure Holding→Nozzle Backward→Cooling→Opening Mold→Ejecting→Opening the Door→Taking the Workpiece→Close the Door→Closing the Mold.
3.2 Injection molding machine operation project
Injection molding machine operation project includes control keyboard operation, electrical control cabinet operation and hydraulic system operation in three aspects. Separately, the injection process action, feeding action, injection pressure, injection speed, ejection form selection, barrel temperature and current and voltage monitoring of each section, injection pressure and back pressure pressure adjustment.
3.2.1 Selection of injection process action
General injection molding machine can be operated manually, as well as semi-automatic and fully automatic operation.
Manual operation is in a production cycle, each action is realized by the operator toggle the operating switch. It is usually used when the machine is being tested and the mold is being adjusted.
Semi-automatic operation of the machine can automatically complete a cycle of action, but after the completion of each production cycle, the operator must pull open the safety gate, remove the workpiece, and then close the safety gate, the machine can continue the next cycle of production.
Fully automatic operation of the injection molding machine can automatically enter the next work cycle after completing the action of a work cycle. There is no need to stop the machine for control and adjustment during normal continuous operation. However, it should be noted that if fully automatic operation is required, (1) the safety door should not be opened in the middle of the process, otherwise the fully automatic operation will be interrupted; (2) the material should be refilled in time; (3) if the electric eye sensor is used, care should be taken not to cover up the electric eye.
In fact, in the fully automatic operation is also usually required in the middle of the temporary stop, such as to the machine mold spraying release agent.
Normal production, the general choice of semi-automatic or fully automatic operation. At the beginning of the operation, according to the production needs to choose the mode of operation (manual, semi-automatic or fully automatic), and accordingly dial manual, semi-automatic or fully automatic switch.
Semi-automatic and full-automatic work program has been determined by the line itself, the operator only needs to change the speed and pressure of the size of the electric cabinet, the length of time, the number of times the ejector pin, etc., will not be due to the operator to adjust the wrong buttons and make the work program confusion.
When a cycle of each action is not properly adjusted before, you should first select the manual operation, to confirm that each action is normal, and then select the semi-automatic or full-automatic operation.
3.2.2 Pre-molding action selection
Based on the pre-molding before and after the filling of the injection seat backward, that is, whether the nozzle left the mold, the injection molding machine is generally equipped with three options.
(1) Fixed charging: the nozzle is always pressed into the mold before and after pre-molding, and the seat does not move.
(2) Front filling: the nozzle is pressed against the mold for pre-molding filling, and when pre-molding is completed, the seat backs up and the nozzle leaves the mold. The purpose of choosing this way is: pre-molding the use of mold injection hole against the nozzle, to avoid the melt in the back pressure is higher out of the nozzle, pre-molding can be avoided after a long period of contact between the nozzle and the mold and heat transfer, affecting the relative stability of their respective temperatures.
(3) rear filling: after the injection is completed, the injection seat back, the nozzle leaves the mold and then pre-molding, pre-molding after the injection seat forward. This action is suitable for processing plastics with particularly narrow molding temperatures. Due to the short contact time between the nozzle and the mold, it avoids the loss of heat and the solidification of the melt in the nozzle hole.
After the injection is finished and the cooling timer has timed out, the pre-molding action begins. The screw rotates to squeeze the plastic melt to the front of the screw head. Due to the action of the check valve at the front of the screw, the molten plastic accumulates at the front of the barrel, forcing the screw backward. When the screw retreats to a predetermined position (this position is determined by the travel switch, which controls the distance that the screw retreats to achieve dosing), pre-molding stops and the screw stops rotating. Immediately after the inverted shrinkage action, inverted shrinkage that is, the screw to do a small amount of axial backward, this action can be gathered in the nozzle at the melt pressure can be lifted, to overcome due to the pressure imbalance between the inside and outside of the barrel caused by the phenomenon of "salivation". If there is no need to retract, the retraction should be stopped and the switch should be adjusted to the proper position to stop the pre-molding. At the same time when the switch is pressed on, the retraction stop switch is also pressed on. When the screw moves backward in a retracting motion until the stop switch is pressed, retraction stops. Then the seat starts to move backward. When the seat backs up to the press-up stop switch, the seat stops backing up. If the fixed filling method is used, the position of the travel switch should be adjusted.
Generally, the fixed feeding method is used to save the operation time of the injection seat and speed up the production cycle.