Test & measurement Tweaking
a tool Tips for quick fixes
Updating or repairing an injection mould tool can be complex. Yet, it is something that Broanmain’s tool manager Kamil Stec does daily to help extend the lifespan and maintain the quality of precision mould tools. Here, Stec runs through a couple of the basic rules that make these modifications more straightforward and addresses several misconceptions.
product engineers has to be the operational lifespan of the tooling. Rather than investing in a full tool replacement, modification options can range from cutting a new hole, to increasing the part size or expanding the wall thickness. The process usually begins with a drawing. However, Stec says most proficient toolmakers can eyeball a tool and present viable modification options and cost breakdowns. In the four years Stec has worked in
T
Broanmain’s toolroom, he proudly reports that they have not scrapped a single tool. “Generally
he cost of creating an injection moulding tool can run into thousands of pounds. One of the key considerations for
speaking if something breaks within the tool, there is always a way around it. Obviously the more involved the repair is, the more it is likely to cost. Yet, it’s incomparable to a full tool build.” The main instance where a new commission might be warranted is when changing the moulding material or when making multiple changes to the tool dimension, which requires adding rather than removing metal.
Expanding part gEomEtriES It is always easier to cut more material, rather than add material in a tool. Removal is often done in small increments. If the size of the tool cavity allows it, metal can be added. But this can
be highly complex and isn’t usually advisable for high-speed moulding. Making a moulded polymer part thicker is
relatively straight forward. By making the initially geometries in the tooling thin, the thickness can be expanded by making cuts into the tool. Likewise, it is advisable to make the outside diameter and shape of the part with the tool as small as possible. This then enables the tool to be altered instead of replacing it.
adding fEatUrES Imagine carving into stone. Once the features are etched in, they are virtually impossible to remove. Until the features of the part are fully determined, leave them out. Ribbing, raised text, texture etc. can be added once the tool is near completion. In some instances it is possible to replace the core of the tool. This is more commonplace in today’s modern moulding tools, which rather than being a solid hardened steel tool comprises 200+ individual components assembled together. Also consider future features and the
different iterations that might potentially be needed. If these are factored into the development phase of the tool, future modifications are more straightforward. Stec highlights that the most common
adaptation is changing the size of holes within the tool. “Because holes are typically formed using easily replaceable core pins, it’s never that much of an issue,” he notes.
48 February 2021 Instrumentation Monthly
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