Generally, precision injection moulding machine has two indexes:
the repeated error of product size and the repeated weight error of
product.
The former is difficult to compare because of the size and
thickness of the product, while the latter represents the
comprehensive level of the injection machine manufacturer. The
weight repetition error of ordinary injection moulding machine is
about 1%, the better machine can reach O.8%, the precision machine
is less than 0.5%, the ultra-precision machine is less than 0.3%,
and the international highest level is less than O.15%.
Precision injection machines require the dimensional accuracy of
products to be within 0.01-0.001 mm, and many precision injection
moulding machines require high injection pressure and injection
speed;
the clamping system is required to have sufficient rigidity and
clamping precision; the pressure, flow rate, temperature,
measurement and other parameters are required to be controlled
accurately to the corresponding accuracy; multi-stage or stepless
injection is used to ensure the moulding process;
The reproduction conditions and the repetition accuracy of the
products are also discussed. The repetitive precision of injection
moulding weight is stable, which includes three aspects: repetitive
precision of plasticizing quantity, repetitive precision of
injection quantity and temperature control performance of moulds.
There are many factors affecting these accuracy, the most important
is the accuracy of the whole machine manufacturing and assembly, as
well as the configuration of screw, electrical appliances,
hydraulic and other parts of the injection machine, and the quality
of the mold.
