When Thomas Bartels wants to convince a visitor of the advantages of 3D printing, he presses an aluminum bottle opener into their hand. It feels ultralight and flexible. “Try to break it”, urges Bartels. But no amount of bending, pressing, or pulling helps: The opener remains intact. A filigree support structure sees to that. “It’s bionic, based on nature”, he explains, insisting that “this can only be achieved by using 3D printing”. Bartels is a calm and calculating businessman, but it’s easy to detect his enthusiasm for the new technology, which first took root at Rheinmetall Automotive in 2012. That was when the first plastic 3D printers began to appear in big box electronics stores, which were good at best for making keychains and other tchotchkes at home. However, some experts in the Rheinmetall prototype department were quick to grasp the true potential: In the meantime, it was possible to print metal objects that were just as strong as conventionally produced models. Moreover, parts produced in the metal printer featured another major advantage. Until then, engineers had to wait several weeks before they could test their design. That’s how much time it took for a mold maker – based on the design data – to fabricate the tool necessary for casting the part. The time saved here not only shortens the total development period, but also enables changes to be made and secured at short notice.
A company in its own right since 2017
3D printing has revolutionized the production of proto-types at Rheinmetall Automotive. In the meantime, 99 percent of all sample parts are fabricated additively, to use the proper technical term.
. As tends to be the case in revolutions, no one has foreseen the results produced. In 2015, after the first three machines from SLM Solutions had been installed in Neuss, a number of employees suggested setting up a company that would also offer 3D printing services to external customers. Within two years, the idea had become reality. Solidteq GmbH functions as an autonomous company, generating around half its sales from customers other than Rheinmetall Automotive. The startup does not operate completely outside its parent company’s structures. “Of course, in some domains we can draw on our parent company’s expertise”, notes Benedikt Szukala, who’s in charge of corporate development at Solidteq. “For instance, this is relevant when we need to advise customers regarding their designs,” he explains. While it’s true that 3D printing is Solidteq’s raison d’être, it actually constitutes only one part of a five-stage value-added chain that extends from initial consultation with the customer to design optimization, preparation of construction data, printing and postprocessing.
Solidteq generates roughly half its sales outside Rheinmetall Automotive
When it comes to metallic 3D printing for professional applications, just sending the part specifications to the printer and pressing the start button clearly isn’t enough. “Before we start, we try to find out what the customer wants to achieve”, explains Szukala.
This is important, because if the part produced by the printer isn’t supposed to serve as a prototype but instead is intended to go directly into a machine or system as a small production run component, the design can be modified to take advantage of the possibilities offered by additive production techniques. To cite just one example, recently Solidteq cast a matrix mixer for a major industrial plant for the company RSC Engineering. The channels in the mixer measure just two-tenths of a millimeter in diameter. “There’s no way you can use casting to make something like that”, declares Szukala.
Each layer is just 50 micrometers thick
Once the design has been finalized, the data first have to be prepared for printing. The technique employed by Solidteq, selective laser melting, works by using one or more lasers to fuse powder applied to a base plate, which subsequently solidifies. Of course, this results only in an extremely thin layer of solid material, which, depending on the machine setting, is around 50 micrometers thick or perhaps a bit more. Then comes the next layer, equally thin. This is why the part is sliced into a corresponding number of layers in a computer simulation – and the travel distances of up to four lasers operating in parallel are controlled by the program in a way that they do not interfere with each other. In addition, supports have to be designed that grow in height with the workpiece. Without them, the part would easily warp due to its own weight and the ambient heat of the process. Intended for subsequent removal, the supports themselves are as delicate as possible, assuring that only minimal material is wasted.
Complete preparation of the design data is supported by software. “A lot of know-how goes into this part of the process”, says Szukala. The speed with which the data can be processed is decisive in determining the competitiveness of the entire technique.
Which machine is to be used afterwards depends not just on general availability, but also on the material the component will be made of. Currently, the company processes steel, aluminum, and an especially corrosion-resistant nickel-based alloy. “If possible, we always use the same machine for each material”, declares Szukala. This is because even miniscule amounts of foreign powder could result – for example – in corrosion or in lack of stability in subsequent operation.
Medium-sized companies in particular are eager to obtain a finished part that can be used immediately
Once the printing process starts, the first thing you have to do is wait. How long largely depends on the height of the workpiece, since the powder is applied layer after layer and fused by the laser. The machines currently on hand enable a maximum height of 330 millimeters, a length of 500 millimeters, and a width of 280 millimeters. In practice, however, fabrication of such large components is rare. Instead, several parts grow on the base plate together, an approach which saves time and money. On average, it takes around two days to complete the process. But this doesn’t mean that Solidteq’s job is done. First, the workpieces have to be lifted from the plate and the supports removed – a process that isn’t automated and requires a high degree of manual dexterity. The result is a blank, which, much like a cast part, still requires post processing. As a rule, the first step involves sandblasting in order to achieve an even surface structure. It is then milled and turned, just as in conventional fabrication, e.g. to produce the threading that will enable the component to be subsequently screwed into place.
“Here, we draw on the entire scope of supply and services and the existing expertise of the Rheinmetall Group”, notes Szukala, adding that “being able to use a part immediately is especially important for medium-sized customers”.
When every hour counts
But prototype construction isn’t the only area where fast access to parts can be crucial. Particularly in the field of machine and plant engineering, a defect can result in an urgent need for a spare part. If none are in stock and the tool is no longer available, 3D printing offers a viable alternative to conventional manufacturing methods. Since every hour counts – when a rolling mill threatens to grind to a halt, for example – Solidteq uses a new Internet-based service. This way, potential customers anywhere in the world can upload the design data of a part. In response, they immediately receive a price quotation and can also confirm the order online. But automation of the commercial process is only one side of Solidteq’s expansion. The other consists of better consultation. This is particularly important when construction data for an urgently needed part is lacking because the supplier no longer exists. “Thanks to our reverse engineering skills, based on a physically existing component we’re able to generate the data needed for 3D printing”, promises Szukala.
Given its many advantages, the question arises as to whether 3D printing will ever completely supplant conventional casting. “This is extremely unlikely”, says Szukala. “We see this method as a supplementary technology.” Given the high production numbers typical of the automobile industry, cycle times on machines are measured in minutes, not days. It’s not easy to say exactly where the boundary lies, because a lot depends on how complex a part’s geometry is. For example, 3D printing can be used to produce a single part, whereas a conventional method might churn out two or three. In turn, this saves time during assembly. “We always re-commend taking the full array of costs into account”, insists Szukala. By taking this tack, Solidteq is already in contact with other Rheinmetall units and at present excitedly waiting for the validation results of a new 3D-printed camera housing, delivered as a pre--production model to the defence branch of the Group.
“Extremely stable lightweight designs”
Mr. Bartels, the Internet is full of service companies offering metallic 3D printing. What makes Solidteq a good choice in this market?
For one thing we’re a startup, with the flexibility that comes with being a young company. But we’re also an integral part of the Rheinmetall Group. For our customers, this means they can count on getting individual advice even when they come to us with extremely recondite inquiries. But they also know that we’re able to draw on the full mechanical engineering expertise of Rheinmetall. This is a pretty unique combination in the market.
What’s so important about consultation?
Some people think that all you have to do is feed in the design data and print out the part, like printing a Word document in the office. But this isn’t the case. To get a good result, you need decent data preparation. In addition, you can make parts with 3D printing that would be impossible to produce otherwise. If you want to exploit the full potential of additive production, you need to know a lot about engineering.
Who exactly are you offering your services to?
While it’s true that Solidteq continues to produce prototypes for Rheinmetall Automotive, we also operate in the market as an independent service provider, primarily for medium-sized mechanical and plant engineering companies. We supply customers in practically every sector, with two exceptions: on account of the special certification rules, we don’t work for the aviation industry or for the medical technology sector.
We definitely get orders from China and Japan which we process here in Neuss. But they’re still the exception to the rule.
How does Rheinmetall benefit from its new subsidiary?
In the long term, we see our expertise in metallic 3D printing as a competitive advantage. In the defense industry in particular, production runs are often quite small. In addition, 3D printing enables lightweight designs that offer extreme dimensional stability. Thanks to this combination, we’re able to give our own design engineers new degrees of freedom.
With your hand on your heart, do you really believe that additive production techniques will ever supersede traditional casting methods? eines Tages klassische Gussverfahren ersetzen können?
When it comes to producing prototypes, this is already the case. But as far as large-scale production runs are concerned, additive techniques today aren’t even close to being competitive. The two will be existing side by side for a long time to come. But you should never say never when you’re talking about technology. Twenty years ago, who would have thought that we’d all be running around with smartphones in our pockets.