design to manufacture, intricate plastic injection mouldingWe were approached by a company that sold table top wargame miniature figurines, as they wanted to look at a plastic solution rather than their current solution of manufacturing their range of military wargame figurines and battle vehicles in steel.

Producing these products in steel would have been more expensive, but gave a high quality and intricate appearance. The aim of this project was to minimise costs, create a higher volume method of production but keep the quality and intricacy of the figurines. 

Not only would this be a difficult task, as steel is a much more sturdy and strong material, able to be moulded into highly intricate shapes, but we were provided with very limited data and were required to produce this project using a very brittle, poor-flowing material, not generally suited to the injection moulding process.

However, this was the material that fit with their industry standards and so, we quite simply just needed to make it work!

Complexity and complications

The intricate design of the figurines along with the complexity associated with using the required material, the development of the range was a very complicated task. As such, a number of uncertainties were present from the outset which we had to consider before and during the design and manufacture. Some of these were:

  • As mentioned, we were given a limited amount of data; therefore, we needed to digitise the figurines successfully to provide a mould dataset accurate enough to produce the small and intricate figurines. Would this be achievable?
  • If not, could an alternative mould design be found and created?
  • Due to the required material being poor-flowing, could the figurines be successfully produced?
  • Would there be a loss of detail to the figurines due to the material not flowing to all of the arms in the mould?
  • This project requires a number of different parts on one plastic sprue in each mould, with different sizes and shapes, therefore with different reaction profiles to the moulding process. Would this be possible?
  • Would it be possible to maintain the desired level of detail and density to the parts whilst enabling a breakage free de-gating mechanism?

Back to the drawing board

We really had to go take this project back to the drawing board. Due to the lack of available data, we needed to reverse engineer the figurines in order to design and develop the new injection moulding tools. We basically needed to essentially design and develop both the tooling for the moulds, and the injection moulding process itself, from scratch.

Our design team redesigned the figurines, using his expert knowledge of plastic injection moulding. During this stage, it was identified that it would not be possible to produce the figurines in one solid mould. And that instead, the figurines would need to be moulded piecemeal and assembled separately to create the relevant piece.

During the moulding stage, Dudley Associates were aware of two main issues needed to be overcome.

Firstly, the material required is a brittle and poor flowing material. In order to ensure that this filled every detail of the cavity, the molten styrene would have to be packed into the mould at a very high pressure to avoid sinks, hollows and air gaps. 

Secondly, if we were to pack the material into the mould at a very high pressure, a large amount of breakages would probably our due to the de-gating process.

What we did…

Dudley Associates are equipped and have expertise in all areas of the plastic injection moulding process. Because of this, we were able to provide a complete service and were able to create prototypes for pre-production trials. Through this, we were able to establish the optimum mould design to prevent breakage.

The key factors that influence the design were the number and locations of the gates, thr thickness of the sprues and the injection pressure. These conditions were systematically adjusted until the optimum design was discovered. 

As a result, Dudley Associates initially successfully completed the design, development and production of two whole armies, later followed by a further two armies.