Reverse Engineering to Solve Legacy IM Tooling Issues

Introduction

With injection mould tools often achieving a lifespan of 30+ years, many of these pre-date modern CAD and data management systems, and often the longest-serving employees at a company! Without sound drawing office procedures for document management, exacerbated by personnel change and company mergers, it is easy documentation errors to slip through the cracks.

As mould tools approach the end of their operational life and require replacement challenges can arise. Accurately replicating these aging tools and producing suitable replacement parts without historical knowledge becomes a complex task.

The Brief

Round Peg was recently enlisted by a manufacturer grappling with this very challenge. Several injection mould tools for components of one of the company’s flagship products had reached the end of their serviceable life and new tools were developed using original engineering drawings. However, product failures emerged during verification testing, affecting up to 50% of the cavities on some of the new tools.

Due to the performance-critical nature of these components and the tight manufacturing tolerances, Round Peg were brought in to investigate the issue.

How We Tackled the Challenge

Initial work focussed on identifying the sources of error. The strategy Round Peg engineers adopted was to pull together as much data as possible to gain a holistic view of the problem. This included:

  • A thorough review of design and testing documentation.
  • Visual inspection of physical samples.
  • CT scanning of components for comparison with nominal CAD.

An example comparison between physical samples

For the scanning of components, CT scanning was chosen for its ability to offer non-destructive 3D imaging of both internal and external features. It can detect internal defects, provide precise dimensional measurements, and visualize complex structures.

The acquired scans were converted to solid CAD data and compared to existing CAD models. This serves three purposes:

  • To identify missing component features, due to changes made to tooling without updating drawings.
  • To quantify out-of-tolerance features based on drawing tolerances.
  • To observe internal component interactions in the device that might vary from design intent.

An example comparison of physical scan and CAD data,
using drawing tolerances to identify discrepancies .

 

Each discrepancy between the data sources was investigated. The team assessed how each component contributed to the overall functionality of the device and whether any observed changes would impact the device performance.

An initial functional tolerance analysis was then performed, which included:

  • Removing conflicting tolerances that exist on the current drawings, with decisions driven by the function of the component.
  • Removing dimensions and tolerances not related to device function and which could be captured under the general machining tolerance in the drawing border.
  • Noting where tolerances exist that may be unreasonably tight for the general manufacturing methods used – based on experience of good manufacturing practice, with reference to relevant ISO standards.

A report of recommendations was produced, including strategic suggestions like loosening manufacture tolerances where it did not compromise functionality to facilitate easier production and part inspection.

Based on the investigative work, a new set of robust 3D CAD models and clear drawings were created. These used a consistent design philosophy to assure data integrity and ease of future development.

Conclusion

The culmination of this project was delivery of a comprehensive data pack, allowing the client to implement necessary tool modifications and rectify the identified issues with confidence and precision.

An illustration of our reverse engineering process

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