Lead Design Engineer, Jack, shares insight into how HD developed 2 novel devices from concept to manufacturing transfer in just 10 months with his 6 tips for lean device development:

Recently, we developed 2 devices concurrently from concept through to production in a short timeframe in order to meet our customers contractual and regulatory deadlines. Therefore, we had to take a lean approach to product development to ensure we didn’t cause unnecessary project delays.

Typically, as a project progresses, the cost of making changes increases and options for change become more limited. By affording time for upfront for planning and understanding a project, both time and money can be saved.

Our Approach to the project

Immersion:

When a customer presents an exciting new project, it can be tempting to jump straight into problem solving mode and start designing solutions. As part of our development process at Haughton Design, we always start with an Immersion Phase. This phase allows us to learn about our customer, the product/problem and the best way to approach the project.

With this particular project, there were reference devices that acted as a starting point. So, we started by creating interaction matrices for both devices as well as device characterisation documents which together, gave us an excellent insight into the devices we were tasked with developing. Presenting this work generated feedback from the client such as “you guys really get this project”. From this, we were able to identify that although there were 2 different devices, they functioned in a similar way and so could share common design features which would eliminate the need to refine parts of the design twice. We also identified that we could design the 2 devices with a slight stagger in the plan which meant that as the project progressed and designs were iterated, any learning could be applied to the other device which significantly reduced iterations and development time.

Concept:

Once we had produced a device development plan and a clear understanding of the requirements, we moved into our Concept Phase. For every project we hold brainstorming sessions with our team of experienced engineers, product and human factors designers where everyone can pitch ideas, no matter how conservative or blue sky they are. Often, we focus brainstorming sessions on specific parts of a device – we also welcome clients and other stakeholders to join these sessions throughout various stages of the project to ensure all perspectives and insights are considered.

For this project, once we had a good range of ideas, we broke the devices into separate sub-systems which could function independently. For each sub-system, we created weighted idea judgement matrices for the ideas which were relevant. As a result, we were able to bring the leading ideas from each sub-system together to create optimal concepts for both of the devices. This again reduced development time and number of prototypes produced.

 

Feasibility:

Once we had an agreed concept signed off with our customer, the next phase of the project was to review the Feasibility of the design(s) both commercially and technically. To do this, we typically gather quotations from suppliers to understand the final production cost as well as identify any technical risks associated with the proposed design. For this project, our customer requested prototypes to review the device’s function and technical feasibility. To do, this we provided prototypes which were manufactured via a process of vacuum casting and 3D printing. It’s very important to understand the limitations of low volume processes compared to what will be used for production to avoid wasting time over refining a design for a non-production process. For example, a common material used for technically complicated components is Acetal. Currently, neither vacuum casting nor 3D printing can produce a component with comparable properties. For one of the most critical components in the device, acetal was required to take the specified stress’s during operation and storage life too. Therefore, we also decided to manufacture a small number of prototype injection mould tool to produce parts which were fully representative of the design intent.

Detailed Development:

After our customer had reviewed the feasibility of the project, confirmed that there was a commercial benefit and that the technical risk was acceptable, we moved into Detailed Development. This is the phase where we fully develop the design so that it is robust and can be reliably manufactured. Before too much refinement work is done, it is important to understand how each component is going to be manufactured for example, whether its injection moulded, machined, fabricated, or even purchased in. Not understanding this before refinement work is done can result in significant waste, rework, and increased development costs. It’s advisable to speak to manufacturing partners as early as possible in the development process. Although the rules of manufacture largely translate from one company to the next, cost can be saved, and reliability increased if you work within your chosen manufacturers’ normal operational capabilities.

Creating a robust design consists of understanding how variables effect the function of the device and avoiding inflection points. Not doing this will lead to reliability issues in production and could lead to a design that functions “on a knife edge”.

In this project, to ensure our designs were robust, we went through an exercise of generating parameter diagrams (P-Diagrams) which were used to determine how an input would affect an intended output including what factors you have control over and what factors you don’t have control over (for example, noise). From this, each parameter could be analysed to identify the effect and sensitivity to change. For example, in the case of a snap fit, varying the thickness will have a cubic effect on its stiffness whereas the width is a linear relationship, therefore a small variation in thickness will have a much greater affect than varying the width. This information can be used to inform tolerance selection and defining critical dimensions. Analysis of each parameter can be done through a combination physical testing, CAD reviews, hand calculation, and FEA.

Manufacturing Data:

As discussed, at an early stage of the project we were able to identify that both devices could share a common mechanism. As a result, we were able to save a significant amount of time in the detailed development phase as we didn’t have to go through the process of refining and understanding 2 completely different devices.

The next phase in our development process is Manufacturing Data. This is where we generate the information that a manufacturer will use to ensure components and products meet the design intent. By ensuring that DFM was considered in the detailed design phase, there were no surprises after having detailed tooling conversations with manufacturers. This eliminated the need for extensive redesign to add draft or to rework large parts of the design because of features such as undercuts which couldn’t be formed. Where critical dimensions had been identified in the previous phase, we decided to make those parts of the tool steel safe. Although this can mean that parts are likely to be slightly undersized, it gives a lot more scope for refining the design. It’s a lot easier to machine more steel off the tool than weld up a brand-new tool or worse, remanufacture the tool which can add weeks if not months onto the project plan.

As with the design of the components themselves, the further you are through the process, the harder it is to accommodate change for the tooling design without full redesign. Gates and split lines must be carefully reviewed early on to ensure that material flow into the components won’t compromise the strength of critical elements and that potential flash doesn’t interfere with running surfaces. Because of our approach to sharing features across the 2 devices, this simplified the tool design and although the cavities and cores were different, the general design of the tool was common (i.e. hydraulic side pulls, multiple cavity systems, ejection sequence etc).

Verification:

Once the tool design was complete and the first off moulded components were manufactured, we began the exercise of Verification. Initially, the design required some refinement based on the first off moulded components to tune fits and forces. Due to the work undertaken in the design development phase, we already understood which variables to tweak in order to achieve the outputs to meet various specification requirements (typically, this could be cap pull off, firing or trigger forces). After the design had been tuned, we undertook a validation exercise to ensure the devices met the design intent and design input requirements. Testing included drop testing both individual devices (and their packaging), activation force testing, cap removal force testing, as well as geometric measurements such as weight, size and colour. Because we had taken the time early in the project to understand the design input requirements and undertaken design robustness studies as part of our development process, we were confident that the final product would pass all required tests. The devices have also undergone, and successfully passed, a range of human factors trials, ensuring they are easy and safe for use in the intended environments. We are pleased to say that the devices have been hard tooled for volume manufacture whilst the project was completed within the lean timeframes and budgets requested.

Tips for Lean Device Development

1. Less haste more speed:

Things take longer to change the further you are through the process. So, a day longer spent at the beginning of a project can save months of time later down the line not to mention the associated costs and associated stress of a delayed project!

2. Research:

Ensure that you fully understand the user needs and design input requirements prior to jumping into the design and having to make big changes further down the line.

3. Plan:

A good project plan will help you stay on track and stop you getting lost in the day-to-day noise of design. It will also help make decisions on the impact of change no matter where you are the project.

Having a clear plan allows everyone in the project to see where they are and need to be.

4. Aim to eliminate unnecessary waste:

The aim should be to limit the amount of redesign and rework to a minimum, however, as with any design project there is likely to be design iteration therefore, manufacturing prototypes early to learn and fail fast can significantly improve your understanding of the design. So, although waste is generated, value is added by reducing the time to fully understand the design.

5. Communication:

Ensuring that communication is clear and concise with customers, suppliers and other key stakeholders can reduce time spent having to re-explain details as well as reduce the need for additional meetings.

Making sure everyone is comfortable to raise potential issues with the project will catch problems before they escalate and cause project delays.

6. Monitor Risk:

Maintaining a specific design risk log throughout the project which is set up to easily capture risks and potential issues will help identify, monitor and manage design/engineering related issues. This log ensures risks are dealt with quickly and allows you to address them earlier. Dealing with high risks early and quickly will reduce the time required to resolve them, ensuring projects are completed swiftly.

From the complete development of  autoinjectors to optimising specific inhalation device mechanisms, here at Haughton Design, we have worked on a wide variety of medical and drug delivery device projects for pharmaceutical companies globally. Please don’t hesitate to get in touch if you have any questions or would like to discuss a project.

Jack Dunkley CEng - Medical Device Engineering Director at Haughton Design Jack Dunkley CEng 21 October 2022

Share

Get in Touch with Jack Dunkley CEng

Engineering Director

Jack is a chartered engineer who holds a Master’s degree in Mechanical Engineering from Cardiff University. He has experience working with design for injection moulding, machining and sheet metal as well as design for assembly and serviceability. Prior to HD, he worked at metrology company Renishaw for 6 years where he led several complex mechanical projects from initial concepts through to production. He has also worked at electrosurgical medical device manufacturer Olympus Surgical Technologies Europe (Gyrus ACMI).

Get In Touch

Our latest insights

Latest Posts

How Can Collaborating with the NHS Improve Medical Device Innovation?

Read More...

Digital Devices & Trust: Why Do We Trust Them More Than Their Non-Digital Counterparts?

Read More...

Share