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What are the influencing factors of the blow molding process of the blow molding machine?
What are the influencing factors of the blow molding process?
1. Blowing pressure
The compressed air in blow molding has two functions, inflation and cooling. Low viscosity, low volume or thick wall parts should use low air pressure; high viscosity, large volume or thin wall parts should use higher pressure.
2. Blowing speed
In order to shorten the blowing time, in order to facilitate the product to obtain a more uniform thickness and a better surface, the inflation speed should be as large as possible, but the speed is too fast to easily produce the following phenomena: ① cause a vacuum at the air, causing this part of the parison to sink in However, when the parison is completely inflated, the diaphragm part will form a diaphragm; ② The parison of the die part may be pulled off by the fast air flow.
3. Blow-up ratio
is usually controlled at 2-4 times, if the inflation ratio is too large, the shape stability of the product is poor, and if it is too small, it will cause uneven wall thickness.
4. Mold temperature and cooling time
If the mold temperature is too low, the plasticity of the plastic at the jaws will be reduced, it is not easy to swell, and the part will be thickened, which is difficult to form; the mold temperature is too high, the cooling time will be extended, and the production cycle will be long. If the cooling time is too short, the cooling will not It is easy to cause deformation of the product, shrinkage increases, and the surface is dull.
5. Molding cycle
Including the process of extruding the parison, intercepting the parison, closing the mold, blowing, cooling, deflating, opening the mold, taking out the product and other processes. The principle of the selection of the molding cycle is to shorten as much as possible on the premise of ensuring that the product can be shaped.
Plastic blow molding machine should pay attention to processing control temperature in operation
PET stretch blow molding machine should pay attention to the processing control temperature during operation
1. Melting temperature TM: For crystalline polymers, it refers to the temperature at which the three-dimensional remote ordered state of the macromolecular chain structure changes into disordered viscous flow state, also known as melting point. It is the lower limit of crystalline polymer molding processing temperature.
Second, the glass transition temperature TG: refers to the transition temperature of the amorphous polymer (including the non-crystalline part of the crystalline polymer) from the glass state to the highly elastic state or from the latter to the former. It is the low temperature of the free movement of the macromolecular segment of the amorphous polymer, and also the upper limit of the working temperature of the product.
3. No-flow temperature: the high temperature at which no flow occurs under pressure. Full-automatic bottle blowing machine is to add the amount of plastic into the barrel at the upper end of the die of the capillary rheometer and heat it to a certain temperature. After the new 10MIN is known, apply a constant pressure of 50MPA. If the material does not flow out of the die, release the pressure Then increase the temperature of the material by 10 degrees. After holding it for 10 min, apply a constant pressure of the same size. Continue until the melt flows out of the die. Decrease the temperature by 10 degrees. This is the non-flow temperature of the material.
4. Flow temperature TF: refers to the temperature at which an amorphous polymer changes from a highly elastic state to a viscous state. It is the lower limit of the processing temperature of amorphous plastics.
V. Decomposition temperature TD: When the temperature of the polymer in the viscous flow state is further increased, the degradation of the molecular chain will increase, and the temperature when the polymer molecular chain is significantly degraded is the decomposition temperature.
