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tec.News 17: HARTING Technology Group
Information provided by injection mold simulation
Process-related Product-related Cost factors
Fillability Porosity Machine size
Pressure effects Shrinkage and warpage Cycle time
Temperature distribution Location of weld seams Reduction in rework
Effectiveness of cooling Quality of weld seams Lower material consumption
Gate balancing
Clamping force
Fiber orientation
Sink marks
The goals and capabilities of simulation
The goal of simulation is to produce a meaningful, highquality
analysis of injection-molded parts as early as
possible in the design cycle. The capabilities range from
simple analysis of the filling process to simulation of the
entire injection molding process, including the gating
system and the mold that will be used later on. Key
parameters such as balanced melt flow, homogeneous
temperature and pressure distribution and the position of
critical weld seams are analyzed up front and optimized
on the virtual product. Besides optimizing part geometry,
engineers can simulate the injection mold process. They
can vary and analyze characteristic process parameters
such as the temperature of the tool and the melt, injection
speed and pressure, the holding pressure profile and
cooling time. Shorter correction loops and reduced cycle
times save time and money later on.
Case study
Snap fit joints are often used to assemble plastic parts. The
application discussed here (see fig. 1) is a detachable snap
fit joint on a T-feeder. Figure 2 shows a cross-section of the
cantilever. The results of the fiber distribution simulation
are visible on the illustration. The fibers in the red zones
Linking injection mold simulation with finite element
structural analysis for thermoplastics is another major
application area. Glass fiber is added to thermoplastics
to improve the mechanical properties. When the plastic
is melted and injected into the tool, the complex flow
characteristics create local variations in fiber orientation.
When the parts cool, their mechanical properties generally
tend to be heavily anisotropic rather than isotropic.
Injection mold simulation provides information about local
glass fiber distribution, which can then be used as an input
variable for subsequent structural analysis.
Fig.1: T-Infeeder with snap-fit joints
exhibit strong orientation. Distribution of the fibers is
random in the blue zones.
Elastic finite element structural analysis using an isotropic
material model and 35% fiber content produces the forcetravel
curve that is shown in red in figure 3. The black
curve shows the result when local fiber alignment from
52 harting tec.News 17 (2009)