While the vast majority of fasteners bought at DIY-stores are made using traditional machining methods, a significant number of manufacturers prefer cold forging techniques because of the higher output quality, reduced material cost and the ability to produce more complex objects. Nedschroef Machinery in Herentals, near Antwerp, designs and builds cold forging machines for the global market. It’s a niche business, and a challenging one. “Building a 10,000 component machine within three months requires us to be perfectly organised in terms of engineering and logistics,” says Technical Director Peter Janssen.
A challenging niche business
Almost all the bolts, screws and furniture fixings one finds at DIY-stores all over the world are made using traditional metal-removing techniques such as turning and moulding. Due to labour and material costs, an increasing number of manufactures switch from traditional metal removing techniques to cold forging or a combination of the two techniques, especially when it comes to producing more complex fasteners such as those used in the automotive industry.
High-precision complex metal objects
“Cold forging means deforming a simple piece of metal until it has exactly the required shape,” explains Peter Janssen. “It’s a very versatile technique, enabling us to produce almost any object imaginable, including complex high-precision elements such as cogwheels and screw threads. Starting from a simple metal cylinder it requires four to six deformation stages to produce the fastener, depending on the complexity of the target object.”
An additional advantage of cold forging compared to traditional methods is speed. Peter Janssen: “These machines have an output speed ranging from 75 pieces/min to 300 pieces/min where conventional machining may take several minutes for one part. In addition, during the cold forging process the material gains in strength. And finally, cold forging produces no waste such as the metal chips coming from conventional machining. The forged part has exactly the same weight as the initial cylinder. In large quantities this means a substantial saving on material costs.”
The only drawback of cold deformation is the higher engineering and development cost. “Our machines are tailor-made,” says Janssen. “Manufacturers come to us with a prototype of what they want to produce. We then figure out how to manufacture that object using cold forging. It requires about 500 hours of engineering work to develop the entire production process. The end result is a machine measuring up to 20 by 4 metres, weighing 15 to 275 tonnes and containing 5,000 to 12,000 high-tech components. You can imagine that this represents a big investment. Customers need a production volume of at least 150,000 pieces/part to make it profitable.”
Twelve weeks lead time
Janssen remembers the days when Nedschroef could take about a year to produce such a machine. “That was how we did business fifteen years ago,” he says. “Those days are gone. Nowadays machines are ordered just in time, based on signed contracts for end product delivery in order to assure investment profitability. This gives us a lead time of at most twelve weeks, with penalties in the event of a delay. And the market has become more demanding in other respects too. For example, we’re expected to deliver fully operational production processes now, rather than bare machines. That means that at delivery we must demonstrate the machine’s productivity rather than its compliance to specifications.”
Nowadays, delivering means that we must demonstrate the machine’s productivity rather than its compliance to specifications.
Remaining a best performer
Nedschroef Machinery has gradually adapted its organisation in the past few years to meet these new demands. For example, they have set up a new Techno Centre where customers are invited for training and to carry out tests in the context of production process development. In addition, logistics have been completely reorganised and extra storage space has been built (see also ‘Caring for every detail’). Peter Janssen explains: “In contrast to several years ago, we now store a significant proportion of our components based on sales forecasts. We also purchase some of the components well in advance, because that allows us to negotiate a much lower price. These are the things that enable us to stay among the best performers in our market.”
Strong, leak-tight and perfectly flat
A seemingly trivial but essential element of the Nedschroef cold forging machines is their supporting base, which is a large rectangular shape beneath the machine. “The machine base actually serves three purposes,” explains Peter Janssen. “First of all it must carry the entire weight of the machine, which may reach up to 275 tonnes. Then it’s also a kind of basin which according to environmental regulations must collect lubricants that may leak in the course of a production cycle or during maintenance activities. Thirdly, the base must prevent the machine from slowly shifting as a result of production-related vibrations. For these reasons the bottom plate must be extremely strong, 100% leak-tight as well as perfectly flat, with a maximum tolerance of 1 or 2 millimetres. Now that’s very hard to achieve with lengths up to 20 metres, so we need top-class suppliers with great welding expertise. In addition, the supporting base is one of the critical elements in our manufacturing planning: it has to be made to order in a very short time frame. That’s why we rely on TCS to manufacture these bases for us.
Caring for every detail
TCS not only produces the machine bases for Nedschroef Machinery, it has also supplied most of the hoisting equipment in the Herentals workshop, as well as performing preventive and corrective crane maintenance. In addition, the long-standing professional relationship between Nedschroef Machinery and TCS recently entered new territory with the construction of the Techno Centre and the extension of the storage building. “They assumed the role of general contractor in this project,” says Peter Janssen. “And that was a blessing for us. While many construction companies have a rather easy-going attitude when preparing and planning a project, TCS is different. Their proposal was perfectly rounded out, leaving no uncertainties. And during the project they are just as well-organised as they are in their crane construction or steelwork activities, leaving nothing to chance and caring for every detail.”