reference, etc. of the runner). Therefore, ASU composes 1-
cavity mold; the GSU of combination and transfer of basic
attributes of the ASU composes 2-cavity and 3-cavity mold;
similarly, CSU composes multi-cavity molds, which are the
combination of GSUs, namely, 2-cavity and 3-cavity molds.
III.   KNOWLEDGE DRIVEN MECHANISM OF HOT-RUNNER
STRUCTURE DESIGN
As a special component of a hot-runner plastic injection
mold, hot-runner system is used to deliver thermoplastic melt
to a mold or into the cavity. A hot-runner system consists of
hot-runner components (including gate, hot-runner plate and
nozzle), heating system, temperature control system and
auxiliary parts. During design process of a plastic injection
mold hot-runner, these parameters must be considered,
namely, technical parameters of product raw material, weight
of the plastic piece, wall thickness of the product, number of
cavities, preset gate number and position, plastic injection
machine type (mechanical, hydraulic, or manufacturer), preset
clamping force (ton), preset injection pressure (kg/cm3
), preset injection velocity(cm3
/sec), preset injection period,
temperature (including molten plastic temperature, injection
nozzle temperature, and mold cavity temperature), pressure
(including plastication pressure, injection pressure, and mold
cavity pressure), and corresponding operation time (including
injection time, dwell time, and cooling time) etc..
Applying rheology law, hot-runner should be able to
keep balance naturally. Mechanical equilibrium spreader plate
is usually applied to design hot-runner for multi-cavity mold.
In other words, the runner length of each gate between nozzle
and cavity of the plastic injection machine is the same, so is
the diameter. No matter how the cavities are laid out in a
multi-cavity mold, only continuous melt can guarantee
product quality.
The volumetric velocity of melt flow Q is calculated as:
3
/(/sec) QQ s cm pm ρ =  
Where, Qp is the weight of plastic piece (g); s is the injection
time (sec); m is the melt density, and
23
()/[10'()](/) m P RT P g cm ρπ ωπ −IF plastic flowability = [poor],
THEN gate dimension = [more than the estimation]
For runner design of a hot-runner plate, less heat loss,
less injection pressure loss, and less runner volume are main
requirements, by which the corresponding rules are organized
for section shape selection and hot-runner plate structure
design. For example, the difficulty of manufacturing and the
heat loss can partially determine the design rules of the section
shape selection of a runner.
Rule5. IF heat loss = [small],  
THEN runner section shape = [round] or [regular hexagon] or
[combination of semicircle & trapezoid]
Rule6. IF processability = [good],  
THEN runner section shape = [round]
Nozzle is at the end of a hot-runner system. As a key
part, a nozzle connects to the cavity directly. A nozzle consists
of a body equipped with heating system, and an insert at the
end. Nozzle design must meet these requirements: constant
melt temperature during flowing to avoid solidification when
under-heating at the end, or, to avoid degradation at internal
over-heating; even temperature distribution; heat insulation
between nozzle and mold to reduce cavity cooling time, and to
reduce internal stress between molds caused by temperature
rising; leak-free nozzle insert, which is a precise component in
the runner system; leak-free between nozzle and runner plate;
and maneuverability. Moreover, the nozzle and the runner
plate fixing, plastic material, shape and height of the gate
should be considered as well. 塑料注射模热流道设计英文文献和中文翻译(3):http://www.youerw.com/fanyi/lunwen_6870.html