Fig. 3. 3D solid modeling and wireframe modeling of the mould.

262    S.H. Tang et al. / Journal of Materials Processing Technology 171 (2006) 259–267

Fig. 4. Extra air vents to avoid short shot.
escape.  Meanwhile,  flashing  was  reduced  by  reducing  the
packing pressure of the machine. Warpage can be controlled
by controlling various parameters such as the injection time,
injection temperature and melting temperature.
After these modifications, the mould produced high qual-
ity  warpage  testing  specimen  with  low  cost  and  required
little finishing by de-gating. Fig. 4 shows modifications of
the  mould,  which  is  machining  of  extra  air  vents  that  can
eliminate short shot.

3.2.  Detail analysis of mould and product

After the mould and products were developed, the analysis
of mould and the product was carried out. In the plastic injec-
tion moulding process, molten ABS at 210 ◦C is injected into
the mould through the sprue bushing on the cavity plate and
directed  into  the  product  cavity.  After  cooling  takes  place,
the product is formed. One cycle of the product takes about
35 s including 20 s of cooling time.
The  material  used  for  producing  warpage  testing  speci-
men was ABS and the injection temperature, time and pres-
sure were 210 ◦C, 3 s and 60 MPa respectively. The material
selected for the mould was AISI 1050 carbon steel.
Properties of these materials were important in determin-
ing temperature distribution in the mould carried out using
finite element analysis. Table 2 shows the properties for ABS
and AISI 1050 carbon steel.
The critical part of analysis for mould is on the cavity and
core plate because these are the place where the product is
formed. Therefore, thermal analysis to study the temperature
 

Fig. 5. Model for thermal analysis.

distribution  and  temperature  at  through  different  times  are
performed using commercial finite element analysis software
called  LUSAS  Analyst,  Version  13.5.  A  two-dimensional
(2D)  thermal  analysis  is  carried  out  for  to  study  the  effect
of thermal residual stress on the mould at different regions.
Due to symmetry, the thermal analysis was performed by
modeling  only  the  top  half  of  the  vertical  cross  section  or
side view of both the cavity and core plate that were clamped
together during injection. Fig. 5 shows the model of thermal
analysis analyzed with irregular meshing.
Modeling for the model also involves assigning properties
and process or cycle time to the model. This allowed the finite
element solver to analyze the mould modeled and plot time
response graphs to show temperature variation over a certain
duration and at different regions.
For the product analysis, a two dimensional tensile stress
analysis  was  carried  using  LUSAS  Analyst,  Version  13.5.
Basically the product was loaded in tension on one end while
the other end is clamped. Load increments were applied until
the model reaches plasticity. Fig. 6 shows loaded model of
the analysis.

3.3.  Result and discussion for mould and product
analysis
For mould analysis, the thermal distribution at different
time  intervals  was  observed.  Fig.  7  shows  the  2D  analysis 注塑模具的设计与热分析英文文献和翻译(5):http://www.youerw.com/fanyi/lunwen_513.html