Impact of Injection Molding Machine Production Parameters on Molded Parts
Last Updated on December 29, 2025
The quality of injection-molded parts depends on rational mold design, appropriate raw material selection, and rigorous quality control during production. Among these factors, the setting of injection molding machine production parameters significantly influences product quality. These parameters include: pressure settings, speed settings, temperature settings, and holding pressure/cooling parameters. The following sections detail how adjustments to these parameters affect various aspects of product quality.
I. Pressure Parameters
Pressure parameters are primarily categorized into three types: injection pressure parameters, holding pressure parameters, and backpressure parameters. Excessively high or low pressure settings can lead to various product quality issues:
Injection pressure refers to the force applied by the injection molding machine’s screw to push molten plastic through flow resistance and fill the mold cavity.
Excessive injection pressure: Excessive melt impact force can cause mold expansion, white marks, mold height increase, mold cracking, and other issues. It may also cause flash and product deformation due to increased internal stress.
Insufficient injection pressure: Inadequate injection pressure prevents the melt from filling the cavity as designed, leading to short shots, sink marks, dimensional inaccuracies, and weight deficiencies.
Hold pressure refers to the continuous pressure applied by the screw to the melt within the mold cavity after injection is complete. It primarily fills the space created by melt shrinkage, ensuring dimensional and structural stability.
Excessive holding pressure: Increases internal stress in the product, leading to deformation, cracking, and other quality issues after demolding.
Insufficient holding pressure: Causes product shrinkage, internal voids, and failure to meet design strength standards.
Back pressure refers to the pressure applied to the screw during the retraction and material intake phase, preventing quality issues caused by excessive retraction speed.
Excessive back pressure: Overheated melt shear causes product color changes, resulting in localized or overall color inconsistencies. It also facilitates material degradation and denaturation due to overheating, causing finished material properties to deviate from design requirements.
Back pressure too low: Leaves air bubbles and uneven plasticization in the product, ultimately affecting its strength and appearance.
II. Speed Parameters
Speed parameters primarily refer to the injection speed of the molten material suitable for injection molding.
Similar to injection pressure parameters, improper injection speed settings can also cause a series of product quality issues, though the manifestations may differ.
Excessively high injection speed: Rapid melt entry into the mold cavity exceeds the mold’s venting capacity per unit time, causing poor mold venting and bending of inserts, which may damage the mold. Simultaneously, excessive injection velocity creates surface defects like injection marks and gas lines, and may cause mold swelling.
Injection speed too low: The injection process may become interrupted, leaving distinct weld lines where broken melt segments reconnect, compromising both appearance and strength. It also increases the risk of insufficient filling, air bubbles, and short shots.
III. Temperature Parameters
The equipment’s temperature parameters primarily consist of three: barrel temperature, mold temperature, and injection temperature.
Barrel temperature primarily serves to heat granular solid raw materials, transforming them into a molten state suitable for injection.
Excessive barrel temperature: Incompatible high temperatures with the raw material may cause decomposition, discoloration, bubbles, or black spots.
Barrel Temperature Too Low: Raw material fails to reach the melt state, resulting in poor melt flow, insufficient filling, and rough surface finish.
Mold Temperature refers to the surface temperature of the mold cavity. It controls the cooling rate, crystallization process, and flow characteristics of molten plastic, directly impacting product dimensional accuracy, surface quality, and internal structure.
Mold Temperature Too High: Extends cooling time and increases shrinkage rate, affecting finished product dimensions.
Mold temperature too low: Melt cools too rapidly, increasing internal stress and causing pronounced weld lines.
From the barrel to the mold cavity, an appropriate nozzle temperature maintains optimal melt conditions during pressurized flow, ensuring consistent fluidity.
Nozzle temperature is too high, causing drooling and leading to gate blockage.
Nozzle temperature is too low, reducing melt flowability and causing gate blockage due to cold material issues.
IV. Time Parameters
The primary time parameters for equipment are holding pressure time and cooling time.
Holding pressure time, in conjunction with holding pressure, compensates for plastic cooling shrinkage during filling.
Excessive holding pressure time: Increases internal stress, making demolding more difficult.
Insufficient holding pressure time: Prevents effective compensation for space created by melt cooling, leading to sink marks, voids, and other defects. This results in undersized products with insufficient weight.
Cooling time constitutes the longest phase of the injection molding cycle. It primarily allows the melt to cool to solidify and reach a stage suitable for demolding.
Insufficient cooling time: Demolding before proper solidification causes product deformation.Excessive cooling time: Abnormal shrinkage rates occur, resulting in finished products that deviate from design specifications in appearance and weight.
Summary
In summary, injection molding machines influence product outcomes through pressure, speed, temperature, and time parameters. Honju-Optics strictly controls these parameters during production to ensure product quality and durability. Do you currently produce related plastic products? Contact us for a quote!
