How to set the injection molding material temperature -dgmf mold clamps co., ltd

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How to set the injection molding material temperature?
Written By Jasmine HL
In injection molding, temperature is one of the five major factors in injection molding, which
affects the plasticizing effect of the material, the flow rate of the solution, the crystallization rate,
and the cooling rate of the mold. Reasonable use of temperature control can reduce a lot of
detours when debugging process parameters. Let's explore the influence of temperature in the
forming process together.
One: In injection molding, how is the barrel and nozzle heated and temperature detected?
The heating device of the injection molding machine is usually fastened to the outside of the
barrel and nozzle using a resistance heating coil. When the thermocouple detection temperature
does not reach the set value, the relay and contactor are energized and closed, and the heating
circle will generate thermal energy, which will slowly transfer the heat to the barrel and nozzle for
heating. The thermocouple is sandwiched between the barrel and the heating circle to detect the
temperature. ; When the thermocouple detection temperature reaches the set value and
allowable error value, the relay and contactor are powered off and normally open, the heating
ring stops working, and the barrel and nozzle are not heated, but there will be residual heat,
keeping the barrel and nozzle at constant temperature.
Two: In injection molding, which sections are the barrel temperature and nozzle temperature?
Material is transferred from the discharge port through the screw rotation to the final section
area--conveying section
The final temperature setting should be higher than the softening temperature of the material.
The final temperature is the lowest temperature of the entire barrel.
The function of the last stage is to prevent the screw from clogging at the feed opening.
If the temperature at the end of the barrel is set too high, or incorrect injection process
parameters are likely to induce melt backflow, the cooling water circuit will be added to prevent
this from happening in the last half of the barrel.

In the process parameters, the end temperature should be set reasonably. If the temperature is
set too low, the screw torque will increase, making the screw rotation speed slower, and the
shear heat will increase. After the shutdown, the screw may not turn and plasticize, and the
screw time The accumulated wear shortens the service life; if the end position is set too high, the
solution countercurrent material will condense.
The melt is transferred from the end region to the middle section by the rotation of the
screw--the plasticizing section
It is usually the section with the highest temperature setting, set between viscous flow
temperature and thermal decomposition temperature.
The role of the middle section is to uniformly plasticize the materials, color masterbatches,
additives, etc.
In terms of process parameters, if the middle temperature is set too high, it will cause thermal
decomposition of the material, destroy the polymer structure, cause defects and unpleasant
odors; if the temperature is low, it will cause the material to be uneven and homogeneous, and it
will also affect the quality and strength of the product. .
The melt is transferred from the interruption zone to the front section by the rotation of the
screw-the metering section
The front temperature setting should be slightly lower than the middle temperature by 15 ℃
-25 ℃.
The role of the front section is to prevent the middle section solution from drooling forward, and
the plasticized material can be prepared for use in the die again.
In terms of process parameters, if the material temperature is too high, the surface appearance
brightness increases, the impact strength increases, and the product has good fluidity, but it is
easy to induce the solution's delayed thermal decomposition; if the temperature is too low, the
mold filling rate becomes slower, the pressure increases, and the orientation Increasing force and
internal stress will affect the quality of refill molding.
The solution is transferred from the front section to the nozzle through the rotation of the screw
Nozzle mold--the nozzle temperature setting should be higher than the front section temperature
and slightly lower than the middle section temperature (different nozzles have been developed
according to different products). The hot runner mold-nozzle temperature setting does not have
too many requirements and mainly plays the role of the runner. .
The function of the nozzle is to effectively control the solidification of the melt or the injection of
the melt into the mold, causing product defects.
In terms of process parameters, setting the nozzle temperature too high will cause melt drooling
and thermal decomposition of the material, which will affect the product quality. If the nozzle
temperature is set too low, the melt will solidify and produce cold materials, which will block the
flow channel and prevent normal production. Therefore, the setting of the nozzle temperature is
important for injection molding.
Three: In injection molding, how to set the barrel temperature and nozzle temperature?
The temperature setting of the barrel and nozzle is determined according to the type of plastic,

the shape of the product and the type of screw. The injection temperature of different materials
is different. For materials with a narrow range of softening temperature and melting point, the
temperature should be set lower; For a wider range of materials, the temperature can be
increased appropriately.
Usually it is divided into four sections: conveying section-plasticizing section-metering
section-nozzle, temperature: low-high-medium-high.
The following are the planned temperatures for the commonly used materials in the barrel and
nozzle in the injection molding production.
Material name: Polypropylene (PP)
Softening temperature (℃): 165
Thermal decomposition temperature (℃): 330
Temperature of conveying section (℃): 150-180
Temperature of plasticizing section (℃): 200-260
Measuring section temperature (℃): 200-220
Nozzle temperature (℃): 180-220
Material name: Polyoxymethylene (POM)
Material name: Polycarbonate (PC)
Material name: Polyamide (PA6)
Material name: Double 6 nylon (PA66)

Material name: ABS
Material name: Polystyrene (PS)
Four: Precautions for temperature control in injection molding
1. The residence time of the melt in the barrel and the nozzle is also required. If the shutdown
time or the cycle time is too long, the residence time of the material in the barrel will cause the
material to thermally decompose and the melt to solidify the nozzle. And the dwell time is too
short, which will lead to the inability to make the material uniform and homogeneous, which will
cause product quality problems.
2. The use position of the screw should be reasonably controlled, and the measurement of
product use should account for 50% -75% of the total measurement of the screw. Over- and
under-screw metering is not suitable for injection molding. Shooting out and shooting out should
be prohibited, and screw metering should be selected reasonably.
3. It is not recommended to adjust the temperature by a large amount. The flow rate of the
product changes particularly. The temperature change is a gradual process. The buffering process
takes 10 minutes to 20 minutes. Inattention will cause serious consequences, which will seriously
affect the product quality and Use intensity.
4. During the injection of the melt, from the last stage to the middle stage to the front stage, the
nozzle, the diameter of the melt is changed from large to small, which is affected by pressure and
speed during injection, and the melt temperature passes. Shear heat will be increased at the
nozzle of the mold, so the actual temperature of the nozzle during injection is about 30 °C higher,
so the nozzle temperature should be adjusted reasonably to prevent thermal decomposition.
5. When the screw temperature rotates, the friction of the screw will generate frictional heat, so
the materials matched by the manufacturer will differ by 10--25 ° C in the actual temperature
setting, and when the screw stops rotating, it will generate heat of accumulation. The deviation
of the screw temperature from 3 to 15 ° C (different screw models and equipment wear

conditions) is a normal parameter.

How to set the injection molding material temperature -dgmf mold clamps co., ltd

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