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required tolerances. In addition, proper materials are selected based on the function-
ality of the moulded part. Inexpensive materials such as medium carbon steel are
used for parts with a high wear rate, and chromium steel is used for the cavities
and the core. In addition, overall dimensions have been set small in order to
reduce the material cost.
6. Conclusions
A two-cavity plastic injection mould is developed to mould an UPVC pipe fitting
elbow with a 3608 internal undercut. The design is done using Pro/Engineer software
with its added feature, Plastic Advisor. Solid models are constructed in the Pro/ Engineer environment, based on which a set of concerns regarding the manufactur-
ability of the mould are discussed.
Moulding design involves quite a few inpidual parts. Direct gating is used in
the design. Based on the mould-filling analysis using Plastic Advisor, the location
and size of the gate and runners are determined. The software is also used to identify
possible places of air traps and weld lines to be present in the moulded part. Cavity
design is carried out after the gating system is established and cooling channels are
arranged to cool the cavity. Accordingly, a number of ejector pins, guide pins,
tapered interlocks and screws are positioned. A simple basic ejector system is also
developed. In the design, springs are used as the return system.
A side core is developed, in which a slide and a cam block are introduced as the
actuating mechanism. The moving distance of the side core is determined in accord-
ance with dimensions of the moulded part. The cooling system is designed in a
compact way for the side core.
To mould the groove feature, a three-stage, Ø50 mm, collapsible core is devel-
oped. An additional stage of translation is introduced, which clears more space for
collapse, thus facilitating the demoulding process. A few variables affecting the
release of the groove undercut are identified and studied in detail. The interference
among the segments of the collapsible core and the moulded part are checked using
Pro/Engineer software. An interactive, trial and error method is adopted to determine
the collapse angles for two different sets of segments.
The CAD models developed in the project provide an interactive mechanism for
dealing with trade-offs in order to develop a more complete solution for injection
moulding of pipe fittings. Future work is geared towards the automation of generat-
ing moulding tools for undercut moulds using advanced computational methods and
programming tools. The collapsible core for other sizes below Ø100 mm may be pro-
jects worth consideration. Besides collapsible cores, other moulding tools such as
curved side cores, rotational cores for unscrewing and sliding side cores can also
be considered for further study. In addition, established collapsible core designs
together with expert systems can be incorporated with the Internet applications to
enable real-time online customized injection moulding design for UPVC pipe fittings. 硬质聚氯乙烯管件在公共和工厂的自来水供给以及污水输送管道系统中得到广泛的应用。由于管件外形的独特性以及存在凹槽所以设计硬质聚氯乙烯管件的注塑模具通常都是一项困难的任务。一个360°的沟槽内表面需要一个特殊的模具结构，叫做伸缩型芯。对于较小尺寸的深沟槽来说，伸缩型芯必须是专门设计的而且要和特殊尺寸规格相一致。这篇文章详细的介绍了带有考虑对沟槽使用伸缩型芯的硬质聚氯乙烯管件注塑模具的设计。采用了Pro/Engineer的计算机辅助设计模具技术来解决各种各样涉及了模具设计的交换问题，此外，也用来分析模具的可制造性。模具注塑性的分析也同时进行，用以验证模具的注塑性能。三段式的伸缩型芯的制造为管材类塑料注塑模具提供了一个更加完美的解决方案。论文网