All-in-One Screw Machine Thicker Material Now Also Formed Warm

Related Vendors

Aachener Maschinenbau GmbH

FAULHABER Drive Systems

Taiwan Machine Tool & Accessory Builders' Association (TMBA)

Wuxi InfiMotion Technology Co., Ltd.

All-in-one machines combine wire feeding from the coil, straightening and cutting, upsetting the head and rolling the thread in a single system and in a continuous process. Amba has now introduced a machine with wire diameters of up to 18 mm (0.7 inches) that integrates inductive heating.

For the first time, inductive heating is being used in the area of screw head forming, which Aachener Maschinenbau (Amba) is integrating into its machines. The first machine in the new series will produce fasteners between 160 and 1,500 millimetres long (~6 to 59 inches)  with a diameter of up to 18 millimetres (~0.7 inches) directly from the wire. As very high forces have to be applied when forming the large-volume heads, Amba is switching from cold to hot forming for the first time and integrating a system for inductive heating.

This machine is used to produce square-headed bolts, which are used in the field of energy transmission and are produced in millions of units. This development has enabled a customer to replace two old machines connected in series. By avoiding the manual reloading and moving of parts, it was possible to increase productivity in production. A complete enclosure for the machine significantly reduces noise emissions and emulsion vapors can be extracted. At the same time, it forms the core of the safety concept so that the system can be operated in full compliance with CE regulations.

Hot Forming and Its Significance

In addition to mastering the actual forming process, hot forming required special design measures. The integration of several water circuits for cooling the upsetting heads and the thread roll is particularly noteworthy. Several air-water heat exchanger systems are used here, which actively cool and can be precisely controlled.

In addition, the oil and grease vapors that arise during the induction heating of the blanks must be extracted. This is the primary reason for enclosing the system once it has been installed at the customer's premises.

New Approach: Integrated Hot Forming

The new series of stud machines is designed to cold form wire with a diameter of up to 12 millimetres (~0.5 inches)  as before and to hot form material up to 18 millimetres thick (~0.7 inches) . Even for experienced designers, the dimensions initially posed a challenge: The transition from 10 to 12 millimetres results (~0.4 to 0.5 inches) in forming forces that are around 40 percent higher than those of the predecessor model BM 10.

To get these forces under control, Amba integrated hot forming - a first in the company's history. This entailed a fundamental redevelopment of every single station: starting with the insertion of the wire with the WFS Wire Feeding System, the straightening and cutting of the blanks, the upsetting of the heads and the rolling of the thread. The forming tools also have to be cooled and other components protected from the intense heat radiation. The bearing shells of the transport spindles must also be cooled in order to minimize expansion effects due to the heat input via the blanks.

In order to ensure that the machine achieves the required performance, extensive numerical simulations of the forming behavior were carried out in advance, which were confirmed by real tests.

The Function of the System in Detail - From Wire to Bolt

The wire rod is brought from the coil to the target diameter in an unwinding system provided by the customer via a pre-drawing device, pre-straightened in a rotating wire straightening system, cut to length and deposited in the transport system.

Before the first upsetting stage, the ends of the blanks are heated from room temperature to over 1,000 degrees Celsius (~1,830 °F) over a distance of 450 millimetres (~17.7 inches) in around 13 seconds. An induction heating system has been integrated into the machine for this purpose. The temperature of the preheated area of each workpiece is checked inline by a pyrometer to ensure that the required minimum temperature has been reached before the next work step.

The screw head is formed in two stages. In the first forming unit, one end of the blank is formed into a pre-volume, in the second, the finished square head is produced. The upsetting heads work with a force of up to 100 tons.

The newly developed thread rolling station is designed for more than 400 millimetre long thread rolling tools (~15.8 inches) provided by the customer in accordance with industry standards. The Amba tool concept allows the synchronous rolling of the thread as well as the form rolling of a large chamfer at the bolt tip and is compatible with common standard dies, enabling integration without individual solutions. The finished billets leave the system via a chain conveyor.

Compact Drive with Plenty of Power

The new compact press drive is 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 adjustability in set-up mode. Despite a reduction in external dimensions of over 50 percent, the drive is significantly more powerful due to the high flywheel speeds and provides the machine with power reserves. In addition, the BM 12 has been equipped with a mechanical overload clutch integrated into the main shaft, which prevents damage to the drive unit in the event of an overload.

The system also features optional process monitoring and the option of remote maintenance. The process monitoring is part of a configuration that can be selected by the customer and detects trend behavior in the process. If there are signs of tool wear, for example, the machine is automatically stopped to prevent machine damage and avoid the production of rejects.

*Michael Köhlbach is Product Manager at Aachener Maschinenbau GmbH (Amba)