With the new BM 12 bolt-making machine, Amba increases the range of products covered by its All-in-One series of machines.

The first machine of the new series will be used to produce fastening elements between 160 and 1,500 mm (~ 6.3 “ and 59 “) long with diameters of up to 18 mm (~ 0.7 “) directly from the coiled wire. The forming of the large-volume bolt heads requires the application of very high forces. Therefore, Amba has for the first time integrated an inductive heating system for hot forming into one of its machines.

All-in-One principle

Like all Amba machines, the new machine operates according to the All-in-One principle. This means that all process steps from coiled wire feeding, straightening and cutting to length up to the upsetting of the bolt head and the rolling of the thread are performed step by step within one single plant – at production rates of 40 to 60 bolts per minute.

Amba has received the first order for a BM 12 machine from a customer in the USA. There, the machine will be producing square bolts as used in the millions in energy transmission applications. The new machine has already passed comprehensive tests and is scheduled to be shipped to the customer in early 2025. It will replace two existing machines arranged in series that require intermediate reloading of the workpieces. The new machine will be completely housed. This will significantly reduce noise emissions, enable the extraction of emulsion vapors and, last but not least, markedly enhance workplace safety.

The solution: hot-forming technology

The new design of the BM machine makes it possible to form wire gages of up to 12 mm (~ 0.47 “), as before, by cold upsetting and thicker gages of up to 18 mm (~ 0.7 “) by hot upsetting. Designing a machine that would be able to handle such a wide range of gages was a challenge even for the experienced engineers from Amba because the step from 10 mm to 12 mm (~ 0.40 “ to 0.47 “) wire gages requires forming forces about 40% higher than those for which the machine’s predecessor, BM 10, was built.

As a solution, Amba integrated hot-forming technology into the machine – an absolute novelty in the company’s more than 100 years of history. This presented the engineers with a number of challenges: Every single stage of the process – from the wire feeding system (WFS), the straightening process, the cutting of the blanks, the upsetting of the bolt heads and the rolling of the threads – had to be redesigned from scratch. Additionally, it became necessary to provide a cooling system for the forming tools and shield the components exposed to the intensive heat generated by the induction system. The bearing shells of the transport spindles had also to be cooled in order to minimize material expansion due to the heat transfer from the heated bolt blanks.

To ensure that the machine will be able to perform as required, comprehensive numerical simulations of the forming behavior were run and subsequently verified in real tests.

The technology in detail

A decoiling and straightening section provided by the customer feeds the rod wire via a pre-drawing system that reduces the wire to the target diameter, a rotary pre-straightener and cut-to-length device to the transport system. As an option, the machine can also be fed with cut-to-length wire directly from a storage system.

Ahead of the initial upsetting stage, the ends of the blanks are heated over a length of 450 (~ 17.8 “) mm from room temperature to more than 1,000 °C (~ 1,850 °F) in about 13 seconds by means of the inductive heating system integrated into the machine. The temperature of the pre-heated area of each individual workpiece is checked inline by means of a pyrometer. If the specified minimum temperature has not been reached, the machine stops the further transport to the first upsetting unit.

The forming of the bolt head is a two-stage process. In the first upsetting unit, the end of the blank is compressed into a preformed head, in the second one, the head obtains its final square shape. Both dies operate with upsetting forces of up to 100 t.

The thread rolling station is a completely new development. It uses more than 400 mm (~ 15.8 “) long threading dies (up to TR8 / Waterbury #60). The tooling concept has been adopted from the customer. It provides the possibility of rolling the thread and beveling the bolt tip in a simultaneous operation. The finished bolts are discharged from the machine via a belt conveyor.

As always, the new compact press drive is a customized drive solution specially designed for the system. In addition to the required drive power at maximum production speed, the design parameters also include the highest possible working capacity with good controllability and response behavior in set-up mode.

On top of that, Amba has integrated a mechanical overload clutch into the main shaft, which prevents damage to the system and drive unit in the event of blockages or breaking tools.

Amba supplies the machine complete with the process control systems and the option of remote maintenance service.

Complete functional testing at the Amba facilities in Alsdorf

To be sure - before the shipment of the new machine - that all steps from the coiled wire through to the ejection of the finished products at the end of the process will run smoothly and reliably, the US customer shipped the decoiling and feeding equipment intended to be linked with the new machine to Amba for testing. Amba set up the equipment and linked it with the machine’s process control system. In this way, it is guaranteed that the entire process will later run without a hitch.

Things to be observed in hot forming processes

In addition to mastering the forming process itself, the integration of hot forming into the manufacturing process called for a number of special engineering measures, such as the installation of several water circuits to cool the upsetting dies and the threading tool. Amba solved these tasks by equipping the new machine with innovative, precisely adjustable air/water heat exchanger systems designed for active cooling. A further challenge to be dealt with are the oil and grease vapors arising from the inductive heating of the bolt blanks. These vapors have to be extracted. Primarily for this reason, the machine will be completely housed after its installation at the customer’s site.

For Lars Henning, Managing Director of Amba, the new BM 12 machine marks a milestone in the company’s technological development:

“The new machine with its inductive heating capability is an example of our transition from a machinery supplier to a technology integrator. While our previous All-in-One machines were designed for cold-forming processes, we now also supply machines with integrated inductive heating, machining and welding systems. For our customers this means that they can produce a constantly growing range of ready-to-use products that, while having a more complex geometry, can still be produced with the same high efficiency. This gives our proven “All in One” principle a much broader meaning.”

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