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Key facts

  • Proto Labs has helped to rapidly create injection-moulded aircraft parts
  • Injection moulding has also been used to make six-spoke wheel rims
  • In addition, this process aided the production of the Gocycle electric bike
  • Protomold is said to help companies keep costs down to affordable levels

Rapid prototyping has come of age, and in many cases is now more rapid manufacturing than prototyping. Examples of this trend can be seen with injection-moulding specialist Protomold, whose rapid service is in demand for a wide range of applications.

Oxfordshire-based Airline Components International (ACI) designs and manufactures aircraft interiors, which is a demanding business, according to director James Deans. Typically, airlines ground aircraft for the annual overhaul — a process that takes about two weeks. But during this time, everything must be completed, including any changes to the cabin interior.

’They send us their statement of requirements of aircraft interior parts and we design, reverse engineer or remake before the aircraft returns to operational service. The window for doing so may be a matter of days,’ he said.

Some of ACI’s work consists of fixing problems with components arising from design compromises when the aircraft was first built. As the cabin interior is, largely, made from non-safety-critical components, compromises can be made to cut down on weight and cost; for example, seat trim parts might be made from thinner plastic than was originally specified. However, these components tend to be weaker, fail more often and need to be replaced with sturdier versions.

ACI had previously used an in-house fused deposit modelling machine to build design prototypes before contracting out the production of steel tooling and the final injection-moulded parts. However, Protomold subsidiary Proto Labs provided an alternative.

’Initially, we were looking for a company that could produce larger prototype models than we could in house,’ said Deans. ’We were delighted when we discovered that, as well as making prototype injection-moulded parts, Proto Labs could also deliver short production runs that are so much more time effective than traditional injection-moulding suppliers.’

The key moment was a project to make large injection-moulded parts for the Royal Air Force. ’The steel tooling for this one small project was going to cost more than £200,000 and the finished parts were going to take 12-16 weeks,’ said Deans. ’Proto Labs told us we could have a finished, injection-moulded part in the same production-intent material without compromising performance in one, three or five of 15 business days.’

Proto Labs has added its expertise in reverse engineering, finite element analysis and stress, strain, cyclic loading and fatigue testing to ACI’s design and testing facilities to make seat parts, carpet joiners, galley products, overhead bin components and seatback video surrounds, to name a few. ’When an ACI part is ready to go into production, it’s considerably better than the original,’ said design manager Will Matthews.

Moving into the leisure sphere, Protomold is also helping German industrial engineer and entrepreneur Albert Müller to tap into a new extreme sports trend: off-road boards, the offspring of skateboards and snowboards.

The suspension components of Gocycle are made from a special nylon with a very high glass content

Resembling a snowboard with axles bearing large wheels at the front and back, off-road boards are gaining popularity in the Alps during the summer, where adrenaline junkies are using them to tackle rugged trails down hills. Prices for professionally manufactured boards are currently around €2,000 (£1,740), which is prohibitive for many riders wanting to give the sport a try. Müller’s company, Flame Offroadboards, is trying to produce a budget board to retail at €450 to €1,000.

One key component for an off-road board that was causing problems was the wheel rim, Müller explained. His board features a bespoke axle, combining the simplicity of a standard skate axle with the superior stability of a channel axle, and this has necessitated a wheel rim with a non-standard distance from bearing to bearing. ’There is nothing like it on the market, so we didn’t approach the established wheel rim manufacturers,’ he said.

The rims have to be able to accommodate two different tyre diameters, as riders prefer 8in (20cm) tyres for freestyle and downhill racing and 9in tyres for pathless terrain and softer ground. ’Good riders use high tyre pressures up to 4 bar, so the wheel rim has been conceived as a six-spoke design featuring six bolts to achieve the greatest possible rigidity,’ said Müller.

Discussions with Protomold led to Müller opting to use a rapid injection-moulding technique to make the rims. The original material, which was very hard and rigid, produced disappointing results, with breakages occurring in extreme situations, so the team chose a new glass-fibre-reinforced, stabilised material with greater elasticity that had previously been used for rims on BMX bikes.

If everything goes smoothly, Protomold will make 5,000 wheel rim halves from this material. Müller believes that using conventional mould tools from another supplier would have cost four to five times as much.

Wheels and their operation were also key to another project: an electric bicycle called Gocycle, made by UK company Karbon Kinetics. The bike’s main suspension components are made from a special glass-filled nylon with an extraordinarily high glass content — 60 per cent — and that uses long fibres. Protomold’s engineers had never worked with a resin containing so much glass before and were concerned that the components might warp, as tends to happen with glass-filled resins.

The Protomold team modelled the injection process, testing the points where the resin enters the mould and analysing the temperature and pressure conditions needed for successful moulding. This included developing tools to identify potential weak spots if the moulding process was not uniform and determining the precise injection velocity needed to produce components with a consistent, shiny black finish.

’On parts where aesthetics are very important, it’s easy to end up with deviations in colour or texture as a consequence of abrupt material acceleration,’ said managing director John Tumelty. ’If you get the process wrong when moulding material with very high glass content, the fibres can rise to the surface and you end up looking at black plastic through glass fibre; it’s a strange silvering effect that’s very unattractive.’

Karbon Kinetics founder and Gocycle designer Richard Thorpe credits Protomold with keeping the cost of the product down to affordable levels. ’This meant we could compete with big-name cycle manufacturers with substantially bigger budgets.’

Model behaviour: rapid injection-moulding techniques take to the road

Key facts

  • Proto Labs has helped to rapidly create injection-moulded aircraft parts
  • Injection moulding has also been used to make six-spoke wheel rims
  • In addition, this process aided the production of the Gocycle electric bike
  • Protomold is said to help companies keep costs down to affordable levels

Rapid prototyping has come of age, and in many cases is now more rapid manufacturing than prototyping. Examples of this trend can be seen with injection-moulding specialist Protomold, whose rapid service is in demand for a wide range of applications.

Oxfordshire-based Airline Components International (ACI) designs and manufactures aircraft interiors, which is a demanding business, according to director James Deans. Typically, airlines ground aircraft for the annual overhaul — a process that takes about two weeks. But during this time, everything must be completed, including any changes to the cabin interior.

’They send us their statement of requirements of aircraft interior parts and we design, reverse engineer or remake before the aircraft returns to operational service. The window for doing so may be a matter of days,’ he said.

Some of ACI’s work consists of fixing problems with components arising from design compromises when the aircraft was first built. As the cabin interior is, largely, made from non-safety-critical components, compromises can be made to cut down on weight and cost; for example, seat trim parts might be made from thinner plastic than was originally specified. However, these components tend to be weaker, fail more often and need to be replaced with sturdier versions.

ACI had previously used an in-house fused deposit modelling machine to build design prototypes before contracting out the production of steel tooling and the final injection-moulded parts. However, Protomold subsidiary Proto Labs provided an alternative.

’Initially, we were looking for a company that could produce larger prototype models than we could in house,’ said Deans. ’We were delighted when we discovered that, as well as making prototype injection-moulded parts, Proto Labs could also deliver short production runs that are so much more time effective than traditional injection-moulding suppliers.’

The key moment was a project to make large injection-moulded parts for the Royal Air Force. ’The steel tooling for this one small project was going to cost more than £200,000 and the finished parts were going to take 12-16 weeks,’ said Deans. ’Proto Labs told us we could have a finished, injection-moulded part in the same production-intent material without compromising performance in one, three or five of 15 business days.’

Proto Labs has added its expertise in reverse engineering, finite element analysis and stress, strain, cyclic loading and fatigue testing to ACI’s design and testing facilities to make seat parts, carpet joiners, galley products, overhead bin components and seatback video surrounds, to name a few. ’When an ACI part is ready to go into production, it’s considerably better than the original,’ said design manager Will Matthews.

Moving into the leisure sphere, Protomold is also helping German industrial engineer and entrepreneur Albert Müller to tap into a new extreme sports trend: off-road boards, the offspring of skateboards and snowboards.

The suspension components of Gocycle are made from a special nylon with a very high glass content

Resembling a snowboard with axles bearing large wheels at the front and back, off-road boards are gaining popularity in the Alps during the summer, where adrenaline junkies are using them to tackle rugged trails down hills. Prices for professionally manufactured boards are currently around €2,000 (£1,740), which is prohibitive for many riders wanting to give the sport a try. Müller’s company, Flame Offroadboards, is trying to produce a budget board to retail at €450 to €1,000.

One key component for an off-road board that was causing problems was the wheel rim, Müller explained. His board features a bespoke axle, combining the simplicity of a standard skate axle with the superior stability of a channel axle, and this has necessitated a wheel rim with a non-standard distance from bearing to bearing. ’There is nothing like it on the market, so we didn’t approach the established wheel rim manufacturers,’ he said.

The rims have to be able to accommodate two different tyre diameters, as riders prefer 8in (20cm) tyres for freestyle and downhill racing and 9in tyres for pathless terrain and softer ground. ’Good riders use high tyre pressures up to 4 bar, so the wheel rim has been conceived as a six-spoke design featuring six bolts to achieve the greatest possible rigidity,’ said Müller.

Discussions with Protomold led to Müller opting to use a rapid injection-moulding technique to make the rims. The original material, which was very hard and rigid, produced disappointing results, with breakages occurring in extreme situations, so the team chose a new glass-fibre-reinforced, stabilised material with greater elasticity that had previously been used for rims on BMX bikes.

If everything goes smoothly, Protomold will make 5,000 wheel rim halves from this material. Müller believes that using conventional mould tools from another supplier would have cost four to five times as much.

Wheels and their operation were also key to another project: an electric bicycle called Gocycle, made by UK company Karbon Kinetics. The bike’s main suspension components are made from a special glass-filled nylon with an extraordinarily high glass content — 60 per cent — and that uses long fibres. Protomold’s engineers had never worked with a resin containing so much glass before and were concerned that the components might warp, as tends to happen with glass-filled resins.

The Protomold team modelled the injection process, testing the points where the resin enters the mould and analysing the temperature and pressure conditions needed for successful moulding. This included developing tools to identify potential weak spots if the moulding process was not uniform and determining the precise injection velocity needed to produce components with a consistent, shiny black finish.

’On parts where aesthetics are very important, it’s easy to end up with deviations in colour or texture as a consequence of abrupt material acceleration,’ said managing director John Tumelty. ’If you get the process wrong when moulding material with very high glass content, the fibres can rise to the surface and you end up looking at black plastic through glass fibre; it’s a strange silvering effect that’s very unattractive.’

Karbon Kinetics founder and Gocycle designer Richard Thorpe credits Protomold with keeping the cost of the product down to affordable levels. ’This meant we could compete with big-name cycle manufacturers with substantially bigger budgets.’

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