Definition: Temperature required to dry polymer in advance to ensure molding quality
Function: 1. Remove moisture from raw materials. 2. Ensure quality of finished products
Setting principles: 1. Polymer will not decompose or agglomerate (polymerize). 2. Drying time should be as short as possible, and drying temperature should be as low as possible without affecting drying effect. 3. Drying temperature and time vary with different raw materials.
Note: 1, A means using a hot air dryer.
2, D means using a dehumidification dryer.

Definition: Temperature set on material tube to ensure smooth progress of molding.
Function: Ensure good plasticization (melting) of polymer, smooth mold filling, and molding.
Setting principles: (1) It will not cause plastic to decompose and carbonize. (2) It rises sequentially from feeding cutoff to nozzle. (3) Nozzle temperature should be slightly lower than front cutoff temperature of barrel. (4) Required temperature depends on type of material. Different. (5) It will not have a bad impact on quality of product.

Definition: Temperature of mold cavity surface that product contacts
Function: Controls cooling rate of product in mold cavity and apparent quality of product.
Setting principles: (1) Consider properties of polymer. (2) Consider size and shape of product. (3) Consider structure and runner system of mold.

Definition: Speed at which melt is injected from nozzle into mold under a certain pressure.
Function: (1) Increasing injection speed will increase filling pressure. (2) Increasing injection speed can increase flow length and uniform product quality. (3) High viscosity and fast cooling speed during high-speed injection are suitable for long-process products. (4) Flow is smooth at low speed and product size is stable.
Setting principles: (1) Prevent mold support and avoid overflow. (2) Prevent scorching caused by excessive speed. (3) Try to choose high-speed filling while ensuring product quality to shorten molding cycle.

Definition: Speed of screw when melting during plasticizing process.
Function: An important parameter that affects plasticizing ability and plasticizing quality. The higher speed, the higher melt temperature, and the stronger plasticizing ability.
Setting principles: (1) When adjusting melt speed, it is generally adjusted gradually from low to high. (2) Speed of machine with a screw diameter greater than 50MM should be controlled below 50RPM, speed of machine with a screw diameter smaller than 50MM should be controlled below 100RPM.

 

Definition: Maximum pressure generated at injection outlet at the tip of screw is closely related to oil pressure generated in injection cylinder.
Function: Used to overcome pressure loss of melt from nozzle - runner - gate - cavity to ensure that cavity is filled and required product is obtained.
Setting principles: (1) It must be within rated pressure range of injection molding machine. (2) Try to use low pressure when setting. (3) Try to avoid using high pressure at high speed to avoid abnormal situations.

Definition: Pressure established in melt cavity during plasticization process of plastic.
Function: (1) Increase specific gravity of the melt. (2) Make melt plasticized evenly. (3) Reduce gas content in melt and improve plasticizing quality.
Setting principles: (1) Adjustment of back pressure should consider properties of plastic raw materials. (2) Adjustment of back pressure should refer to apparent quality and dimensional accuracy of product.

Definition: Closing force exerted by mold clamping system on mold to overcome expansion force that separates mold during injection and holding stages.
Function: (1) Ensure that mold will not expand during injection and pressure holding process (2) Ensure apparent quality of product. (3) Ensure dimensional accuracy of product.
Setting principles: (1) Size of mold clamping force depends on size of product and size of machine. (2) Generally speaking, in order to ensure that product does not produce hair, the smaller mold clamping force requirement, the better. (3) Setting of mold clamping force should not exceed rated pressure of machine.

Definition: Period of time from when mold cavity is filled with plastic, and injection pressure continues to be applied to mold cavity plastic, until gate is completely cooled and closed, requires a very high pressure support technology. This pressure is called holding pressure.
Function: (1) Supplement amount of material close to gate, prevent unhardened plastic in mold cavity from flowing back under residual pressure before gate is cooled and closed, preventing shrinkage of part, avoiding shrinkage, and reducing vacuum bubbles. (2) Reduce tendency of parts to crack or bend due to excessive injection pressure.
Setting principles: (1) Holding pressure and speed are usually set to 50~60% of maximum pressure and speed when plastic fills mold cavity (2) Length of holding pressure time is related to material temperature. Gates with high temperatures have a long closing time and a long holding time. (3) Holding pressure is related to projected area and wall thickness of product. Thick and large ones require a longer time. (4) Holding pressure is related to shape and size of gate.

Definition: After plasticization starts, during rotation process, screw starts to retreat from injection end position under force of plastic melt until it reaches retreat limit switch. This process is called metering stroke.
Function: Ensure that enough plastic fills mold cavity to obtain desired appearance and size of product.
Setting principles: (1) Metering stroke should be set according to size of product and size of machine. (2) Metering stroke should not be too large to avoid excessive injection of plastic staying in material tube for too long and causing carbonization. ( 3) Metering stroke should not be too small to ensure sufficient metering for filling and to avoid mechanical damage to screw and nozzle. There should be a buffer amount of 3~5mm.

Definition: Position change of screw during injection process
Function: Combining speed and pressure to control flow state of plastics
Setting principles: (1) Measuring end position is determined by filling amount of finished product. Usually, a 3~5mm impulse is added to this value to determine final setting. (2) Switching point to second speed is usually switched to position of filling hot runner and material head. (3) Switching point to third speed is set at 90% of filling level of molded product. (4) Pressure holding switching point is generally set at position of 90% of filling level of finished product. (Note: Above is based on four stages as an example)

Definition: After screw is pre-molded (measured) in place, it recedes linearly for a certain distance. This retreating action is called back-retraction, and distance of retraction is called amount of retraction or amount of anti-delay.
Function: Function of back loosening is to increase specific volume of melt in metering chamber, decrease internal pressure, and prevent melt from flowing out from metering chamber.
Setting principles: (1) Setting can be made based on viscosity and relative density of plastic raw material and actual situation of product. A larger loosening amount will mix bubbles in melt and affect quality of product. (2) Setting of loosening amount should be compatible with screw speed and back pressure. (3) For raw materials with higher viscosity, such as PC materials, there is no need to set loosening amount.

 

Definition: After screw is injection molded, we do not want to inject all molten material in the head of screw, but also want to leave some to form a sacrificial material amount, which is buffer amount.
Function: (1) Prevent mechanical damage from contact between screw head and nozzle. (2) Control repeatability of injection amount.
Setting principles: (1) Buffer amount should not be too large, nor should it be too small. If it is too large, there will be too much residual material, causing pressure loss and degradation of raw materials. If it is too small, purpose of buffering will not be achieved. (2) To determine buffering amount, 3~5mm is generally appropriate.

Definition: Time from the end of mold opening to the end of mold opening after next injection has been cooled.
Function: Ensure that product is formed, completely cooled and finalized
Setting principles: (1) Cycle should be as short as possible. (2) Cycle must be shortened while ensuring product quality.

Definition: Time required for product to cool and solidify without deformation after demoulding.
Function: (1) Let product solidify (2) Prevent product from deforming
Setting principles: (1) Cooling time is an important component of cycle time, and should be kept as short as possible while ensuring product quality. (2) Cooling time depends on melt temperature, mold temperature, product size and thickness .

Definition: In order to prevent plastic from flowing back, cooling and shrinking after injection, pressure continues to be applied after injection molding.
Function: (1) Prevent melt backflow after injection molding. (2) Feeding effect of cooling shrinkage.
Setting principles: (1) Holding time will vary depending on thickness of product. (2) Holding time will vary depending on temperature of melt. The higher temperature, the longer time will be, and the lower time will be shorter. (3) In order to improve production efficiency, holding time should be as short as possible while ensuring product quality.

Definition: Time it takes for melt to fill the entire cavity.
Function: Injection time is determined by factors such as injection pressure, injection speed, and product size.
Setting principles: (1) Keep injection time as short as possible while ensuring molding of product. (2) Injection time is affected by factors such as material temperature and mold temperature.
18. Melting time
Definition: After injection is terminated, time required for screw to reach metering end position
Function: Ensure adequate melting of glue
Setting principles: (1) Screw speed and back pressure are mutually controlled. (2) Do not let molten plastic stay in screw for too long, so as not to cause plastic to decompose and carbonize under long-term high temperature conditions.

 

Definition: Time required to dry raw materials in advance using drying equipment
Function: (1) Improve surface gloss, improve bending and tensile strength, avoid internal cracks and bubbles. (2) Improve plasticizing ability and shorten molding cycle. (3) Reduce water and moisture in raw materials.
Setting principles: (1) Drying time varies depending on raw materials. (2) Drying time must be set appropriately. If it is too long, drying efficiency will be reduced and raw materials may even agglomerate. If it is too short, drying effect will be poor.