Spotlight on Form, Fit and Function Prototypes

In this article, we take a closer look at form, fit and function prototypes and take you through the benefits of the processes involved and how they can help you to create your desired physical product, without the need to make expensive design changes further down the line.

What are form, fit and function prototypes?

Form, fit and function prototypes validate a design by providing the opportunity to physically examine specific parts and features, test functionality or test the fit of a part against other components, such as electronics, in the same assembly. The lines and features can also be examined through form models.

What type of industry, if any, would predominantly require this?

Form, fit and function prototypes provide a valuable framework for use by all industries. Irrespective of the quality of the on-screen CAD or renders, there is no substitute for a physical model. Being able to see, touch and feel a part or prototype allows for meticulous checks to take place and any necessary changes to be made. This could prove very costly if left to be identified at the later tooling stage. Being able to test components at an early stage can spark ideas on how your design can be optimised to improve the experience of users.

What are the key processes employed for this and what materials are available?

Most of the processes available here at Ogle will be used in some form or another. However, because each process and material will have individual properties to support the testing phase or match as close to individual production and testing requirements, the specific processes and the associated materials chosen will be entirely dependent on each product. For example, we know that stereolithography (SLA) 3D printing provides greater accuracy (perfect for testing fit) but possesses a lower material strength and SLS will give a more robust part, more suited to functional testing. For larger models, CNC machining is usually more appropriate because of its cost effectiveness on this scale, but also gives the opportunity to test in the actual production material if desired. Lines and form of the model can also be assessed in greater detail by utilising model board with a higher density as opposed to materials such as polystyrene where details may be lost or difficult to see.

Here at Ogle, both SLA and SLS have been successfully used in the production of wind tunnel models to verify and validate the aerodynamics of buildings, parts and components. Its adaptability facilitated the printing of scale models in short timescales, of aircraft, vehicle and buildings for wind tunnel testing.

Exploring the serviceability of a product or component, through the use of form, fit and function prototypes helps avoid prolonged assembly and lengthy repair times. Engineers and technicians involved in the production line can use the prototype to look carefully at how the product as a whole is assembled and disassembled as well as examining how it interacts with the components around it. Examining the details at this early stage avoids future costs associated with prolonged and complicated assembly and repairs.

How would Ogle approach this type of project?

In order to achieve the best results for our clients we ask a few simple questions:

1. What’s the end use?
2. What are your core objectives from this prototype?
3. What environment will this be used in?
4. Do you have a specific material you’d like us to use or properties to imitate?
5. Is surface finish important at this stage.

Using the answers provided we set to work to prepare a proposal providing details of the materials, processes and lead time.

What are the common misconceptions about this type of model?

Despite not being a regular occurrence here at Ogle, sometimes, due to the perceived costs, start-up businesses can overlook this vital stage in the design process. In our experience, it’s worth spending the time and money at this stage to iron-out issues which can prove more costly further down the design process.

The use of desktop 3D printers is great for very early stage fit and form prototypes. However, as the design progresses, for greater accuracy, reliability and a quality closest to your end use, it is strongly advised that industrial machines and an experienced team are used.

What kind of finishes are available?

Plenty of finishes are available, from ‘straight off the machine’, to fully finished and painted. A good tip: Sometimes, if you have fine details, lines and features on an SLA print, it may be better to bead blast the surface because you get less reflection on the parts to further highlight the lines and features. This is especially used for a large part or vehicle (such as a yacht) that has been scaled down for the purposes of a form model.

What key examples would help bring this to life?

We produced the early development steering wheels for the Bloodhound Supersonic Car in SLS to test the form and fit around the driver’s hand. The core purpose of creating a form, fit and function prototype was to enable testing and amends prior to moving to metal 3D printing for the production wheel, thus saving costs.

We were also approached to support a project assessing car parking sensor calibration and test fits. CNC was used to produce front and rear bumpers from a mid-density model board with the SLA process being utilised for adding inserts for the finer, more complex details to keep costs down.

When we were tasked with producing an aircraft seating mock-up we used production composite materials to check whether the wiring harnesses could be physically routed through and around the parts and also to make the wiring as efficient and as short as possible, therefore saving weight and associated fuel costs once in production on the aircraft.