Automation in one batch
| By: Ralf Högel
Robot-assisted automation in the manufacture of small quantities: This challenge has been accomplished by Darne Sport Composites S.L. in Spain. The company manufactures high-value CFRP components for motor racing and employs an ultra-flexible Stäubli six-axis robot for the milling and drilling of molds, models and CFRP components.
Every automotive plant and major OEM supplier uses robots in large amounts. This is due to the ideal conditions for fully automated systems, such as large batch sizes, robot appropriate work processes and the recurring, complex assembly steps.
Stäubli TX200 robots have given a good account of themselves in this type of work for a long time now. They score excellent marks in terms of high precision and repeat accuracy and meet a very high level of availability under heavy load – for example, in continuous use in the three-shift manufacture of vehicle engines.
Milling robot replaces machining center
There are, of course, also quite different requirement profiles and batch size specifications in the automotive environment, but a TX200 six-axis machine is able to cope with these, as Darne Sport Composites S.L. at Sabadell near Barcelona in Spain demonstrates. The company designs and manufactures composite parts, predominantly for motor racing, which means smaller quantities, including batches of one. The product portfolio includes lightweight doors and spoilers. A car maker looking to increase the top speed of a vehicle by reducing its weight and optimizing its aerodynamics will find high quality parts that meet their requirements.
The company works with a high level of vertical integration. Not only the parts themselves but also the molds and models required for production are manufactured in-house. A Stäubli TX200 is used – in the same industry as high-volume manufacturers with short cycle times, but under completely different conditions and with a completely different requirement profile. Here a single robot has to perform a versatile range of tasks.
Three requirements for automated processing
The decision to purchase the robot arose from growing dissatisfaction with the existing solution for the production of molds and the machining of CFRP components. Jaume Darné commented: “We had a three-axis machining center, but we were unable to use it for making multiple products to precise customer specification.”
The company was looking for a system with additional axes that had to fulfill three basic requirements: 1) the machining of molds and models for CFRP parts demands a very high degree of precision, i.e. the parts that are produced in the mold must fit 100%, and 2) because of the small quantities, processing has to be very flexible which 3) calls for user-friendly programming.
Milling in batch sizes of one – flexible and precise
Darne Sports brought in the system integrator eProject4, and together they concluded that these requirements were best served by the large Stäubli six-axis TX200. Darné: “We are able to use the robot to first mill the molds and then machine the finished CFRP parts, we benefit from the very high precision of the TX200. The mold forming process produces perfect surfaces, and in CFRP machining, delamination and irregular edges are avoided, for example on any holes that are drilled. The rapid tool change also contributes to high flexibility: on average, we change the tool four to five times per part. It’s quickly done and precision is not compromised.”
Good experiences with robot assisted CFRP machining
With programming for small batch sizes being significantly more time-consuming, the availability of offline programming soon pays dividends. “While the robot is still machining one part, we can already get on with programming the next job. We use the SprutCAM software package which offers us versatile automated processing options.”
During the project planning stage, it proved to be an advantage that the eProject4 integrators already had extensive experience gained from other CFRP machining projects with Stäubli robots. The fully-enclosed design of the TX200 turned out to be a plus point as well: it prevents the abrasive CFRP dust from getting inside the robot where it could cause mechanical failure.
In conclusion: an extraordinarily versatile robot
This case study shows that the TX200 is a true all-rounder among six-axis robots. It is proving itself worldwide in highly precise and reliable repetitive work at cycle times of around one second. At Darne Sport, it machines one-offs and small series with the same unvarying precision. The powerful six-axis model with its impressive range of 2,194 millimeters further demonstrates the advantages conferred by flexibility and simple (offline) programming.
Darne Sport Composites are able to produce a wide range of CFRP parts and the requisite molds at speed and with cost efficiency. Jaume Darné: “Furthermore, the six axes of the robot give us completely new design freedom, the use of the robot has also enabled us to further enhance the quality of our high-quality racing components.”