The design and manufacture of an injection mould tool can arguably be the most critical stage when producing your plastic component. It is here when you may incur potential costly mistakes and delays to your project – or indeed avoid them; the dependant factor is down to the manufacturer and tool maker that you work with on your project.
It is also at this stage where there are significant cost, weight and production time savings that can be gained when working with a proactive and knowledgeable supplier. To get the most out of your tooling, it is important to work with a supplier that is experienced in optimising every aspect of the tool design phase.
In this article we discuss the main processes that a reputable supplier will take you through, along with some real case study examples, to optimise your tool design and manufacture.
Early considerations for injection mould tooling
The first consideration a supplier will assess, on receipt of an RFQ or enquiry, is whether the component design is suitable for injection mould tooling. The component design also defines the need for tool actions such as feed positions, hot runner systems and cavity finish. If you have the dimension tolerances and specifications at this stage, it is good to share them with your supplier. Essentially, the more information they have at the early stage, the more accuracy and thought can be put into their initial judgement of the tool design.
Component material selection has an impact on the tool design
Building on that, component material selection plays a big role in terms of the impact on tool design. For example, if the material has high glass content which affects tool wear or if requires a high temperature tool, both might affect the tool steel material selection and design. Therefore, material selection is an important consideration and should be discussed with your supplier in the early stages. At ENL Group, we advise and guide our customers on material selection.
You might wish to read our article on the subject of polymer selection: How to gain major advantages for your plastic parts
Part volumes will influence your tool design
It’s important to build a picture of the proposed annual and batch quantities, as well as the expected lifetime total for the product. Try to think as long term as possible. We work with customers who require new tools because the volume demand has increased and therefore their current tool needs to be made larger, in order to produce higher batch quantities.
Share with your supplier what the immediate volume requirements are, and if you have the insight, what the potential requirements could be. This all defines the tool layout, such as number of cavities that are required, or what material for the tool is required for manufacture.
Be open about your budget at the start of the tool design phase
Customer budget constraints are a really important consideration for tool specifications and materials. At ENL, this can affect whether the tool is quoted for in-house manufacture or sourced offshore. Offshore is an alternative solution we offer for customers who have tighter budget constraints. All offshore supplied tooling is specified, designed and managed by the ENL tool designers and engineers, so the level and quality of service remains very high, but we’re able to adapt the tooling process to meet customers’ budget when they’re more restricted. It’s an alternative that isn’t suitable for every customer, but this all needs to be discussed upfront at the start of the process, to optimise the tool design process.
The tool manufacturing process should always begin with a feasibility review
When a tool is ready to be manufactured, the first and most important task that is required is to perform a full detailed feasibility review on the component. This is to ensure its design is completely suitable for manufacture. It is at this stage that the supplier should really engage with the customer on a technical level, sharing their knowledge and experience with the customer in order to get the design right before the tooling manufacture even begins.
What does a feasibility review look like?
At ENL Group we use several tools in the feasibility process, namely DFM (design for manufacture) studies and flow analysis. These tools allow us to identify areas of the component design that will be unsuitable or problematic for tooling manufacture and processing. Such design issues can have a dramatic effect on cost, quality and time throughout the project lifecycle, so it’s vital at this early stage that the supplier works closely with the customer to eliminate these issues, using their expertise to recommend design changes and improvements to ensure all the customers’ requirements are fulfilled or, better still, improved upon.
An example of feasibility testing – case study
Image 1: original part design
This is a part that a customer asked ENL Group to produce for them. One of their specifications was that the surface finish on the outside of the part had to be smooth and blemish-free. In the first picture, you can see that the ribs on the inside of the part was going to cause a problem for this specification. The ribs were too thick where they joined the top surface and would cause sink marks on the outside face, which would not meet the specification of a blemish-free part.
By recommending a simple design change to the rib thickness, so that the thickness where it meets the top face was reduced, it completely eliminated the sink marks. This design then gave the customer the surface finish they needed. The process remained optimised as we didn’t have to extend it in order to improve on the sink marks and, as an added bonus, the part weight was also reduced.
Image 2: The amended design
The feasibility testing delivered the customer the tool they required, along with additional savings. We used less materials, which is a saving we were able to pass on. It also reduced the cycle time, which was another saving we were able to pass on.
Not only did it provide the customer with cost savings, without a doubt, it avoided costly mistakes. We were able to deliver the part the customer wanted, at first samples. If the design was left as it was, there would have been problems and a lot of time and money consumed before the tool was fit for purpose.
It’s absolutely necessary to do feasibility testing
High quality tooling is an absolute must at ENL Group, in order to ensure we meet the needs of our customers time and time again. Some of the sectors that we work within, automotive for example, are very demanding with high quality and high-volume requirements, so the tooling must be capable of meeting these demands. For that reason, we only partner with high end suppliers of tooling ancillaries; these are partners who can really provide technical expertise, innovation and quality.
Hot runner feasibility testing
A technical moulder like, ENL Group, will frequently manufacture tooling for high end polymers, which can be quite demanding for both the tooling and processing. This is why, at ENL Group, we work with Synventive , a trusted partner who we’ve been working with for a long time. When we require hot runner systems in these instances, working with Synventive ensures we get the right design and quality of hot runner system specified to meet the tooling needs. Synventive will measure feasibility using methods from simple pressure drop calculations, cross referencing their database for past jobs, right up to full cool and warp analysis.
ENL Group has a customer base that expands across Europe, which is served from its two plants in the UK and Slovakia. Therefore, it’s essential to work with a supplier, in this case Synventive, who is able to support all of our tooling feasibility and production needs – across the continent as well as for our off-shore tooling, which goes further afield. This is something to bear in mind and to ask your supplier the question, ‘Who are your technical tooling partners and how do they support you in other countries?”.
Hot runner case study
Here is a recent project, which involved two four-impression tools – a pre-mould and an over-mould. Both tools had Synventive hot runner systems. The tools were running side by side in a fully-automated cell, with a robot transfer between the pre-mould and the over-mould tool. Our customer was awarded a new contract, which meant the volumes would ramp up significantly. Therefore, we had to create new 12 impression tools, in order to meet the new volume demands. The one and only constraint was that the tools had to run in the same fully-automated cell as the current four-impression tools. This presented a big challenge because hot runner systems for 12 impression tools are not easily balanced. To achieve the balance, it would add a lot of complexity on the systems, which in turn would increase the tools’ overall size. This was a problem as we had strict height restrictions for the tools.
Initially the request was for a five and ten drop hot runner, which proved tricky as we couldn’t keep the hot runner systems compact enough for the tool design. Synventive proposed a solution for a six and twelve drop, which gave ENL more flexibility for the tool design and Synventive an optimal layout to balance the system. With this workable solution, we then had to make sure it would work cohesively with the two selected materials. This involved ensuring that the system delivered the melt into the cavity, with minimal pressure lost, whilst following material guidelines for residence time within the heated channel.
With the support from Synventive, we were able to manufacture the new tools within the existing cell. This allowed us to achieve an increase in production by 200% and a reduction in part cost of 30%.
- Work with a tool manufacturer and injection moulder who clearly demonstrates they can provide a robust tool based on good component and tool design, using a component material selection to ensure function, consistency and reliability.
- A good partner will provide a cost-effective tool selection to meet customer production needs based on the expected tool lifetime.
- Hot runner systems help to save materials, reduce plastic waste and improve process optimisation with the added benefit of quicker cycle times.
- The benefit of a supplier who does both the tool design, manufacture and production ensures greater ownership and invested interest in optimising the tool’s longevity, cost and production optimisation.
- Work with a tool manufacturer and moulder who is aligned with credible technical partners, and who they involve early on in the technical discussions.