Added value16 November 2017 | Mike Farish
Although additive manufacturing is not new, the latest techniques are offering OEMs more options for its use
The use of additively manufactured parts in vehicles is now unexceptional, if not yet pervasive, at least at the high end of the market characterised by low volume and high purchase price. But there are other uses for additive techniques besides final part production and their original application area of rapid prototyping. One that has quietly been making headway for some time is the manufacture of production tooling, both handheld devices for shopfloor workers and attachments for equipment such as robots.
Alissa Wild, engineering manager of manufacturing tooling for additive manufacturing system supplier Stratasys, headquartered in Minneapolis, Minnesota, says this application area is “underappreciated”, but this is beginning to change. Wild identifies a number of reasons why additive materials and techniques lend themselves to the manufacture of production tooling. One is that devices made by such means are likely to be less expensive than those made by the conventional method of computer numerical control (CNC) machining. But other benefits, she explains, are more qualitative – and arguably more valuable in their contribution to manufacturing effectiveness.
The layer-by-layer additive process in itself is quite slow, but time advantages can be gained in other ways, for example through the use of in-house additive equipment that can be left unattended to make parts overnight. Another benefit is the ease of customisation to specific requirements, most obviously if the parts are then assembled into a manual device for component handling on the shopfloor. As Wild points out, such devices can be made to suit the physical characteristics of individuals, including hand size.
“The use of FDM provides us with greater design freedom regardless of part complexity, allows us to perfect designs early and has a significant impact on our turnaround time. In the case of the greasing nozzle, we have reduced our lead time by 70%” – Carlo Cavallini, GKN Driveline
Moreover, if an additive polymer is used instead of machined metal there may also be opportunities for significant weight saving in the final device – as much as 90%, according to Wild. A handheld device that might otherwise weigh perhaps 20lbs could be only 2-3lbs if made by an additive technique, leading to considerable improvements in ergonomic efficiency, procedural effectiveness, and health and safety. A further quality, seemingly trivial but in fact quite useful, is that printed devices can be made in different colours, helping an assembly worker to select the right tool first time.
GKN sees beautiful results in Florence
One company exploiting the potential of additive manufacturing is GKN Driveline, which uses the technology at its plant in Florence, Italy, where it produces sideshaft components for constant velocity joints for the Italian operations of Fiat Chrysler Automobiles as well as assembling the full sideshaft. Until recently, the plant produced tools for itself either from its own in-house CNC machining resources or from external suppliers, but this way of working increasingly came to be perceived as inefficient and costly.
According to Carlo Cavallini, additive manufacturing specialist and team leader in Florence, “a two- to three-week turnaround time” could be required when tool manufacture was outsourced. “This would delay our ability to undertake feasibility analysis of a new production tool, which is essential to the operation of our assembly line,” he says. The implications were not confined to the plant itself. “Should iterations to the tool be required, this would further escalate our lead times and have a knock-on effect throughout the supply chain,” he states.
The company therefore opted for additive manufacturing as an-house solution and purchased a Fortus 450mc fused deposition modelling (FDM) 3D printer from Stratasys. The results have been very positive, and in some cases quantifiable. For example, a grease dispenser had previously been just a simple flexible tube through which oil would be forced into a single point inside a drive axle joint, a procedure that was prone to spillages that necessitated time-consuming manual cleaning and could cause costly interruptions to production. The solution involved printing a dispenser with multiple internal valves in Stratasys’ Ultem 9085 thermoplastic material, which improved grease distribution and eradicated spillages.
“The use of FDM provides us with greater design freedom regardless of part complexity, allows us to perfect designs early and has a significant impact on our turnaround time,” explains Cavallini. “In the case of the greasing nozzle, we have reduced our lead time by 70%. This has been crucial to streamlining the production cycle of the half-shaft, enabling us to provide these parts to customers faster than before.”
The printing machine also proved useful when it was noticed that a cable bracket was missing from a newly delivered robot. “The brackets prevent the cables from interfering with the movement of the robot and, without this bracket, machine functionality cannot be guaranteed,” says Cavallini. So the additive machine was used to print a replacement, and what was intended as a temporary solution proved surprisingly effective. “The 3D-printed bracket exceeded our expectations in terms of performance and practicality,” Cavallini confirms. “We saved at least one week compared to waiting to receive the part from the supplier.” The service the 3D printer provided in this case was not simply a spare part but business continuity.
Now the company is in the testing stage for further additive solutions to manufacturing problems where ease of customisation is crucial. This includes robust robotic attachments to handle components on the production line. Previous end-effectors were not only unwieldy but, due to the limitations of CNC machining, could even prove unfit for purpose. The additive techniques enable the production of customised end-of-arm tools to fit various individual parts.
Beyond the substantial time savings, Cavallini says the core value of FDM 3D printing is its ability to dramatically improve business performance. He concludes: “3D printing enables us to overcome barriers traditionally associated with CNC machining, offering us the ability to realise our most complex designs, as well as print bespoke tools on demand. These capabilities allow us to improve our workbench flexibility, optimise our workflow and eliminate costly downtimes of the production line.”
BMW believes in additive technology
Illustrating the fact that additive technologies have been used for some time in the automotive industry, two years ago BMW celebrated the 25th anniversary of its first foray into the technology. Now, as then, the focus of the OEM’s activities is in Munich, where it operates an additive manufacturing centre; a facility devoted to application development, prototyping and direct manufacturing as well as support for relevant activities elsewhere within the group.
The head of the centre is Jens Ertel, who confirms that these activities involve several different types of additive techniques, including FDM and selective laser melting of metal powder. The latter has already been used to make a component for an on-road production vehicle: an aluminium water pump wheel for use in the German Touring Car Masters event and also in custom racing vehicles. Production of these parts started in 2010 and the 500th unit was made in 2015.
Otherwise, the only regular use of additive parts in on-road vehicles anywhere within the Group occurs in the Rolls-Royce brand. Since 2012, Phantom II vehicles have made use of several small additively manufactured parts, including holders for central locking buttons and hazard warning lights; over 10,000 such parts had been made by the middle of 2016. Mounting brackets for fibre-optic cables in the Rolls-Royce Dawn were added to this list the same year. These two vehicles were chosen as pioneers, Ertel explains, largely because their small production volumes made the use of additive manufacturing economically feasible.
Nevertheless, the output of additively manufactured parts from the Munich centre, which employs about 50 individuals, is quite considerable: around 100,000 parts per year. Ertel says they are used predominantly for the traditional additive application of rapid prototyping but also for the production of other items to support manufacturing operations, including jigs and fixtures, plus devices for use by shopfloor personnel.
One BMW Group location that has a significant installation of additive equipment, primarily FDM, is Regensburg in Germany, where the emphasis is on the production of jigs and fixtures for use both at the plant and elsewhere. Another is the factory at Spartanburg, South Carolina. Both facilities are networked to the Munich centre so that they can act as supplementary manufacturing resources if the equipment in Munich is at capacity.
BMW’s use of additively manufactured aids for shopfloor personnel is now quite widespread, according to Ertel. One of the earliest examples was a thumb protector manufactured precisely to fit each assembly worker, whose physical details had been recorded by a 3D scanner. The devices support an assembly operation in which rubber plugs are manually pressed into place, for example to seal drain holes for painting. The material used is a thermoplastic polyurethane powder, which is selectively fused by a CO2 laser.
Heading for a higher plane
Ertel indicates that further expansion of additive applications in cars is likely to depend on the introduction of faster techniques that will make higher production rates practicable. Such techniques are, he adds, already being explored; BMW is investigating the potential for a new generation of ‘planar’ technologies, which are characterised by their ability to cure the complete surface of a layer of powder or resin simultaneously rather than sequentially by the tracking of a single laser beam.
For this planar approach, BMW has worked with two technology suppliers, though in quite different ways. One is technology giant Hewlett-Packard (HP) and the other a much smaller, US-based newcomer called Carbon. In HP’s Multi-Jet Fusion process, polyamide powder materials are sprayed with fusing and detailing agents from above before they are subjected to infrared radiation. The Carbon technique, known as CLIP (continuous liquid interface production), inverts that approach by exposing the complete underside of a tank of liquid polyurethane material to a beam so that successive layers are cured.
Ertel says BMW has been investigating these new techniques for the past few years and that the Carbon technology has already been deployed in a short-run, cosmetic application. Last year, it was used to produce individualised side indicators for 100 BMW Minis in a German car hire fleet after a nationwide social media campaign in which people suggested names for them.
At BMW, the longer-term potential of the planar approach is regarded as considerable. Ertel says that, depending on part size and geometrical complexity, a suitable technique could increase productivity by a factor of five to ten compared with today’s examples as well as decreasing the cost, though he declines to give an estimate.
He confirms that BMW is now “in the qualification phase”, checking factors such as the “quality and reproducibility” that the method can achieve. Ertel says that, as with more established additive techniques, “we would want to bring them into our prototyping activities first”. He will not suggest a timescale for the introduction of the technology to BMW’s manufacturing processes other than to say that for a significant production volume it will “not be before the next decade”.
Meanwhile, Ertel says that another type of new additive technology now in BMW’s sights is ‘desktop metal’, in which a binder is applied to a metal powder and the resultant part is cured in a microwave oven. A cooperation with the US-based company from which the technology takes its name, Desktop Metal, is already underway. In short, BMW’s attitude to additive technologies is broad-minded. “We have believed in additive manufacturing right from the beginning and we remain committed to bringing the benefits into customer applications,” states Ertel.