What are the specific steps to adjust the barrel temperature parameters of an injection molding machine?

Adjusting the temperature parameters of the injection molding machine barrel must follow the logic of "raw material characteristics as the basis, equipment type as the reference, and defect orientation as the basis for adjustment". The specific steps are as follows:
1. Preparation stage: clarify basic information
Confirm the raw material characteristics
Check the processing temperature range (melting point/glass transition temperature Tg, thermal decomposition temperature, recommended melt temperature) provided by the raw material supplier, for example:
ABS: melt temperature 220-260℃, thermal decomposition temperature about 270℃
PC: melt temperature 260-320℃, thermal decomposition temperature about 340℃
Record the fluidity of the raw material (higher temperature is required for poor fluidity) and hygroscopicity (hygroscopic materials need to be dried in advance, such as PA and PC).
Understand the equipment parameters
Confirm the number of barrel sections (such as three-section: feeding section, melting section, nozzle; five-section: feeding section, compression section 1/2, metering section, nozzle).
Differentiate equipment types:
Screw injection molding machine: Relying on screw shear heat, barrel temperature can be slightly lower (10-20℃ lower than plunger type).
Plunger injection molding machine: weak shearing effect, requiring higher temperature (relying on barrel heating).
Check equipment status: heating coils of old equipment may be aged (measure the temperature with an infrared temperature gun to ensure that the error between the set value and the actual value is less than 5℃).
2. Initial temperature setting: segmented gradient distribution
1. Segmented setting according to barrel function (taking five-segment type as an example)
Segment Function Temperature setting principle Example (ABS)
Feeding section (rear end) Convey solid raw materials to prevent premature softening The temperature is slightly higher than the softening point of the raw materials (to avoid raw materials sticking to the screw), 10-20℃ lower than the compression section 180-200℃ (softening point 105℃)
Compression section (middle section) Raw materials softening, compaction, initial melting The temperature gradually rises to close to the melting point, increasing by 5-10℃ each section Compression section 1: 210℃, compression section 2: 220℃
Metering section (front section) Fully melted to ensure uniform melt Set to the median of material processing temperature (or the middle value of recommended melt temperature) 240℃ (median of 220-260℃)
Nozzle Control melt flow to avoid drooling 5-10℃ higher than the metering section (to improve fluidity), or lower 5-10℃ (anti-drooling, such as PVC, heat-sensitive materials) 250℃ (10℃ higher than the metering section)
2. Adjustment for special situations
Thermosensitive materials (such as PVC, POM): The nozzle temperature can be 5-10℃ lower than the metering section to prevent high-temperature decomposition.
High-fluidity materials (such as PE, PP): The nozzle temperature is the same as or slightly lower than the metering section to avoid molten material dripping (drooling).
Screw parameter matching: When the screw speed/back pressure is high, the shear heat increases, and the barrel temperature can be reduced by 5-10℃; the temperature needs to be increased at low speed.
III. Mold trial observation: verify the initial parameters
1. Empty shot test (manual injection without installing the mold)
Observe the melt state:
Ideal: The melt is smooth, without bubbles, and the color is uniform (such as ABS is transparent and slightly yellow, without burnt particles).
Abnormal handling:
The melt is wire-drawing and has particles → the temperature is insufficient, increase the metering section/nozzle by 5-10℃.
The melt is yellow and has scorch marks → the temperature is too high or the retention time is long, reduce the temperature of the corresponding section by 10℃, and clean the screw material.
2. First piece production and defect analysis
Insufficient filling/lack of material: It may be that the temperature of the metering section or nozzle is low, the fluidity is poor, and the temperature is increased by 5-10℃.
Burst/flash: The melt viscosity is too low (the temperature is too high), cool down by 10-15℃, or reduce the injection pressure.
Bubbles/silver streaks: The raw material contains water (needs to be dried) or the melting is uneven, increase the temperature of the feeding section/metering section to ensure the evaporation of water.
Surface flow marks/welding marks: The melt temperature is uneven, and fine-tune the temperature difference between the compression section and the metering section (control it within a gradient of 5-10℃).
IV. Dynamic fine-tuning: gradually optimize parameters
Adjustment amplitude and frequency
Adjust 5-10℃ for each single section to avoid excessive temperature fluctuations, and wait for 10-15 minutes after adjustment (wait for the heating coil to stabilize).
Prioritize adjustment of the nozzle and metering section (directly affecting mold filling), and then optimize the middle section and feed section.
Defect-oriented adjustment strategy
Product defects Temperature-related reasons Adjustment steps
Burning, black spots Local overheating (nozzle/screw dead corner) Reduce the temperature of the corresponding section by 10℃, check the cleanliness of the screw
Cold material spots (feed port) Low nozzle temperature, melt front cooling Nozzle temperature increase by 5-10℃, or increase nozzle heating power
Poor transparency (PC) Insufficient temperature leads to insufficient melting Metering section temperature increase by 5-10℃ to ensure uniform melt
Dimensional instability Large melt temperature fluctuation Reduce the temperature difference between sections (control the gradient within 10℃), check the accuracy of the temperature control system
Precautions for cross-material switching
When changing raw materials, it is necessary to clean the barrel (to avoid high-temperature decomposition of residual materials) and reset the temperature according to the characteristics of the new material (such as changing from ABS to PA, the temperature needs to be increased from 240℃ to 260-290℃).
5. Curing parameters: Form standardized records
Record key parameters
Establish a "Barrel Temperature Parameter Table", including:
Raw material model, equipment model, segmented temperature (feeding section/compression section/metering section/nozzle)
Screw speed, back pressure (affects shear heat and indirectly affects temperature)
Adjustment process (such as "drooling disappears after the nozzle drops from 250℃ to 245℃")
Final product effect (no defects, qualified size)
Long-term optimization
For the same material and the same product, accumulate historical data to form a "standard temperature curve" to reduce subsequent mold trial time.
Calibrate the temperature sensor regularly (once a year) to ensure that the set value is consistent with the actual value.
6. Precautions
Safe operation: Wear heat-insulating gloves when adjusting to avoid direct contact with the high-temperature barrel; perform hardware inspection (such as replacing the heating ring) after power off or shutdown.
Adaptation to equipment differences: Small diameter screws (Φ＜30mm) have less shear heat and need to be 5-10℃ higher than large screws (Φ＞60mm); after measuring the temperature of the old equipment, correct the set value according to the temperature difference (such as 10℃ lower, increase the set value by 10℃).
Summary steps
Preparation: clarify the characteristics of raw materials, equipment segmentation, and reference supplier parameters.
Initial design: segment according to barrel function, set temperature in a gradient (feeding section < compression section < metering section, nozzle adaptation).
Trial mold: empty shot to see the melt, check defects in the first piece, and locate temperature problems.
Fine-tuning: small adjustments (5-10℃), give priority to nozzles/metering sections, and gradually optimize until defects are eliminated.
Curing: record effective parameters, form standards, and adapt to equipment differences and material switching.
Through the above steps, the barrel temperature can be systematically adjusted to balance melt fluidity and thermal stability to ensure stable quality of injection molded products.