Rapid prototyping technology keeps race team on track

After each race, Joe Gibbs Racing (JGR) engineers have just three days to diagnose a problem, find a solution and implement it before the car ships to the next race.

Engineers perform this feat by creating concept models, functional prototypes, manufacturing tools and end-use parts in a matter of hours.
It’s JGR’s ability to speed from concept model to production part that has led it to three championships and positioned it as one of the most competitive teams on the NASCAR circuit.

In a recent race, a tyre blew out on a JGR car, forcing it to crash and leave the race. It was determined that extreme heat from a brake rotor overheated the tyre, causing the blowout. A duct outlet supplying air to the tyre was not doing its job.

In the past, it would have taken at least several weeks to develop a concept design, build a prototype using CNC machines, evaluate the prototype’s performance, update the design, build a new prototype, build a mould via CNC to make a composite part, make the part and finally install it on the car. By this time, the team would have run the risk of losing several races.

It’s JGR’s ability to speed from concept model to production that has led it to three championships

’Our 37 engineers generate great ideas,’ said JGR engineering director Nelson Cosgrove. ’Our challenge is getting those ideas onto the cars fast enough to win next Sunday’s race.’

On Monday morning following the race, after determining the problem, JGR mechanical engineer Scott Temple designed a new duct outlet that followed the contour of the wheel.

He designed it to deliver air over the tyre bead exactly as needed to keep it cool. Then, using a 3D production system from Stratasys, Temple built a concept model from ABS-M30 plastic in four hours.

’It’s impossible to evaluate fitment in a CAD [computer-aided design] program because the CAD geometry does not always exactly match the geometry of the car,’ he said.

Temple chose red ABS-M30 as JGR uses red to indicate concept models and other colours for the various other stages in the component’s development.

After completing a couple of iterations of the concept on Monday, Temple was ready to move on to a functional prototype. He chose PC-ABS to create one with good impact strength and used the machine to build the prototype overnight.

On Tuesday morning, Temple performed bench testing on it and determined that the airflow could be improved with minor changes to the design.

After evaluating the prototype’s fitment on the car, he discovered that it interfered with the brake calliper, so he created another iteration in CAD, making a number of small but significant changes to the geometry.

“It’s important to us to have a system that is versatile enough to handle both design and production stages”

NELSON COSGROVE, JOE GIBBS RACING

Temple then utilised the machine to create the new part late on Tuesday morning.

’More iterations equal better designs,’ said Cosgrove. ’Having the ability to make multiple versions allows our engineers to optimise the part for functionality, fitment and manufacturability.’

On Tuesday afternoon, Temple confirmed the fourth design iteration’s prototype fitted perfectly, and the airflow was now optimised over the tyre bead to keep it at the proper temperature.

Using the 3D production system, he then produced the part again this time using high-temperature PPSF plastic to be used as a tooling buck to create a fibreglass mould.

On Wednesday, the mould was used to create the final duct outlet part from carbon fibre. JGR often creates a fused deposition modelling (FDM) part from PPSF for this application as the material can handle either the 100°F+ (38°C+) temperatures of the wet lay-up process or the 350°F+ (177°C+) temperatures of the ’pre-prep’ lay-up process. The carbon-fibre part cured over the morning and early afternoon. Late in the afternoon on Wednesday, the part was bolted on the car before being loaded to the hauler and transported to the next race.

’We designed, validated and manufactured a problem-solving duct outlet in only 56 hours with the help of FDM technology,’ said Cosgrove. ’Conventional manufacturing methods would have taken several weeks.’

An analysis of time to perform concept modelling, functional prototyping and core-core production via CNC milling and other conventional methods showed it would have taken JGR 33 days without FDM.

’Back when we evaluated the leading additive fabrication systems, we selected Fortus as it produces thermoplastic parts durable enough for functional testing and sometimes even use on the race car,’ said Cosgrove. ’Having access to a range of materials on one system lets us pick the best material for the application. It’s important to us to have a system that is versatile enough to handle both design and production stages.

’We’re making similar FDM parts on a weekly basis that gain us seconds on the track the difference between winning the race and finishing last.’

Stratasys’s FDM additive fabrication technology is available in the UK from Laser Lines.