QMT Features: April 2012
Red Bull cuts it
Red Bull Technology improves machining accuracies to meet ever-stringent design specifications using Heidenhain compensation routines.

Red Bull Technology – the manufacturing power behind the all-conquering Red Bull Racing Formula One team - has become the first UK company to harness the power of a relatively low-cost yet highly innovative piece of Heidenhain software that has not only saved the team a significant investment in capital equipment, but is also ensuring that its pattern-making machine accuracy is as true as possible to original design specification.

Red Bull Racing’s highly successful F1 campaigns haven’t made too much difference to the team’s relentless quest for superlative performance in what is unquestionably the world’s most glamorous and exciting sport.
Indeed, the technicians at Milton Keynes are continually hard at work on car design and manufacture.  “Manufacturing every component within microns helps to shave split seconds off lap times,” comments Red Bull Technology production engineer, Mike Hughes.

“So, if we can improve machining accuracies to meet ever-stringent design specifications – and achieve reduced production times in the bargain - then it can only mean more accurate and streamlined manufacturing, delivering a car that can potentially be even more effective on the track.

“That strategy,” he emphasises, “applies to every component produced by the team - including the carbon fibre chassis that is produced from moulds taken from male patterns that are machined on multi-axis CNC routers.
“Because the accuracy of the finished form ultimately depends on the accuracy of the machines, we need to ensure the geometric accuracy of the machines is as true as possible to original design specification.

“We knew there were inherent inaccuracies with the machine tools, as with any large complex mechanism. We therefore decided to determine – and correct – any axis positioning, straightness (in two directions perpendicular to the axes) and angular error, including roll, pitch and yaw, as well as any rotary error and axis misalignment.
“Our capex guidelines are constrained and, although we did initially consider buying a new five-axis machine for pattern making (even though one of the required capacity would have required a very significant investment), we decided to take an alternative innovative approach, making full use of what we already have.

The machines feature Heidenhain control systems, as do all our milling machines. Not only are the Heidenhain systems world renowned for their milling and five-axis machining capabilities, but standardisation of our CNC systems also allows unrestricted working. When HEIDENHAIN (GB) – an important and proactive supplier to the team – learnt of our concerns, we discovered the company’s KinematicsComp routines.”

Developed in conjunction with KinematicsOpt – which is based around the use of a touch probe system in conjunction with a precision sphere to determine the required compensation parameters – Heidenhain’s KinematicsComp innovation enables the compensation of known component and location errors of linear and rotary machine axes.

KinematicsComp can accommodate any combination of rotary head and table axes; the kinematic description of the machine is extended to include the axes errors, so different tool lengths and rotary axis positions are automatically taken into account. And so, up to 43 parameters (on a five-axis machine) can be subjected to body error modelling.

For Red Bull Technology, the first UK company to adopt Heidenhain’s KinematicsComp routines - 21 errors of the machine’s linear axes were measured (using an Etalon LaserTracer tracking laser interferometer) and compensated.

The tracer was set up on the machine table and the reflector mounted in the toolholder, and the machine was then moved to multiple points throughout its working volume and the distance between tracer and reflector measured. This was repeated with multiple set ups, aided by the use of a simulation strategy that illustrates the effect of measurement uncertainties.

Each set up took 30 minutes measurement time and, using an optimisation algorithm, the compensation parameters were calculated then transferred to KinematicsComp within the machine’s high-specification iTNC 530 control system. The Heidenhain CNC then incorporated the enhanced kinematic model to, uniquely, enable the volumetric errors to be compensated for in the linear and rotary axes as well as with consideration for tool length.

The time for the actual measurement depends on the machine size and the strategy; in this application, measurement and set-up times accumulated to 3.5-4 hours.

“Once we appreciated what KinematicsComp could do, and in relation to investing a significant amount in a new machine, the Heidenhain software was a no-brainer,” adds Mike Hughes.
Domed test pieces were used initially to ‘test’ the corrections – these featured axial and radial quadrants, plus bores and slots, for example – before any components were machined.

“The result,” says Mike Hughes, “was that the KinematicsComp routines provided accuracy improvements in the order of 2.5-5 times!”

Two machines, in fact, underwent the Heidenhain treatment; one having its iTNC 530 CNC upgraded (slight updating to its hardware/RAM), and another having a new iTNC 530 retrofitted. Heidenhain specialists from Germany flew over to install and commission the routines, in conjunction with colleagues from Heidenhain GB).
A further major advantage is that the routines will now simply be used annually to calibrate the machines.
“We did look at another (linear only) compensation software option but, unlike the Heidenhain progam, this could not accommodate all degrees of freedom,” concludes Mike Hughes.

“The close collaboration between Red Bull Technology and Heidenhain (GB) is,” he adds, “just one example of the F1 team’s ‘culture of collaboration’ with chosen technology suppliers; a way in which the team can fully embrace world-class innovation and technology from these partners – as part of the team effort to stay at the forefront of the grid.”l
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