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Abstract Cooling system of an injection mold is important for the promotion of production rate and the quality of injection plastic components. Conformal cooling channels are newly developed temperature-adjusting method to promote the efficiency of cooling system. They can be made in the injection mold inserts via the method of indirect selective laser sintering combined with traditional powder metallurgy. This work discussed some processes such as thermal transmission, powders removing, and metal melt infiltration during the manufacturing of the mold inserts in detail. The result showed that redundant powders outside of laser-scanned areas might be sintered together with the sintered parts owing to the accumulation of laser energy during sintering process. This was solved by switching the temperature to initial level after one layer had been sintered.A limit length corresponding to some certain power vacuum system was found when the removal of unsintered powders in the cooling channels was carried out. Therefore, some subsidiary channels leading the cooling channels outside were made to help the removal of powders within the cooling channels. Dripping method was adopted during metal melt 22872
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infiltration process, which was proven to be relevant for
maintaining of the final shape of infiltrated inserts.
Keywords Selective laser sintering . Injection mold .
Conformal cooling channels .Manufacturing detail
1 Introduction
The production rate and the quality are much of a concern
currently when more and more plastic components with
complex structures are demanded. The adjusting of cooling
rate and thermal arrangement through conformal cooling
channels (CCC) provide an effective way to satisfy these two
requirements. Nowadays, rapid manufacturing methods
offer the opportunity to create CCC in the core/cavity inserts
of injection mold. Among these methods, selective laser
sintering (SLS) is the appropriate one. Metal powders
blended with polymer material are heated by laser beam
layer by layer to generate a green shape with CCC firstly.
Then, the polymer material is burnt out when the green shape
is heated up to degradation point of the polymer material,
and it is presintered with the increasing of temperature from
the degradation point. Finally, the presintered shape with
metal material (infiltration metal) of low melting point is
heated at a higher temperature than the melting point of the
infiltration metal to finish the infiltration densification.
Although several previous works have discussed the
manufacturing of injection mold insert with CCC by using
indirect SLS, they focused only on the surface treatment
method of SLS green insert [1], the thermal properties of
SLS hybrid materials and the optimization of cycle time
of the mold [2], and the CCC arrangement for the purpose
of achieving the temperature homogeneity within the insert
[3]. However, the manufacture cycles of CCC inserts werenot mentioned in these investigations. Lakshminarayan et al.
[4] indicated in 1995 that iron–copper composite part can be
produced via indirect SLS combined with traditional powder
metallurgy method employed in injection tooling. But they
only discussed the mechanical properties of the copper
infiltrated iron parts and their application performance.
Ikonen and his coworkers in 1997 studied the manufacturing
of injection mold through indirect SLS, but they also briefly
presented the several cycles such as sintering, debinding,
and infiltration processes [5]. Similar with Lakshminarayan,
they employed polymer-coated metal powders as forming
materials and did not discuss the key points of these
processing cycles. For an example, the thermal transmission
between the powders, air, and scanning layers during laser
sintering, and its controlling were not found in their works.