Efficiency, sustainability and cost-effectiveness: these are the principles on which Kohler is driving the further development of its machines and systems. With the new generation of strip straighteners, the company relies on proven technology paired with innovations and a new design. Hugo Kern und Liebers GmbH & Co. KG, a technology leader in the manufacture of highly complex parts and assemblies, has invested in two identical strip straightening lines at locations in China and India.
Kern-Liebers, based in Schramberg in the Black Forest, is one of Germany’s large, independent family-owned companies. The Group manufactures precision strip steel and wire products at over 40 locations worldwide with more than 7,700 employees. About two-thirds of all passenger cars contain at least one piece of core Liebers. As a supplier to the automotive, textile and consumer goods industries, Kern-Liebers generates nearly 700 million euros in annual sales.
The new Kohler strip straightening lines at the Taicang (China) and Tumkur (India) sites have played a major role in the flexibility of customer-specific production, process reliability, and the exploitation of optimization potential.
Stamped and bent parts that Kern-Liebers manufactures on behalf of customers must meet high quality standards and strict specifications. This requires that the sheets are straightened and stress-relieved before punching and bending. This is because only precisely straightened plates form the basis for further processing that is gentle on the tools and of the best quality without costly manual reworking.
The strip straightening lines used at Kern-Liebers straighten aluminum and steel strip in a material thickness of 1.5 mm to 12 mm and a strip width of 50 mm to 450 mm. The coiler and decoiler support 5 tons. The reel is designed so that the strip can be unwound both from above and from below.
At the customer’s request, Kohler integrated a nibbler into the lines – a separating device between the decoiler and the straightening machine. This allows the already unwound strip to be cut off manually before the straightening machine. This is particularly practical when a coil is not completely processed.
In such a case, only the cut strip has to be rewound between the straightener and the reel, but not the part of the strip that is in the straightener or on the strip loop – a time saving that cannot be neglected. In both lines, the strip is transferred to the downstream press above ground.
For uncomplicated cleaning and maintenance of straightening rolls and back-up rolls, both strip straightening lines were equipped with Kohler’s proven advanced cleaning system. This means that the upper and lower slide plates with the rollers and support rollers can be extended independently of each other by electric motor. The cleaning work can now be easily performed by a Kern-Liebers employee.
Innovation, precision and economy go hand in hand
The heart of the strip straightening line is the precision straightening machine, which, with its high rigidity and 21 hard-chrome plated straightening rolls, allows the best straightening quality to be expected. This straightening machine does not use the usual transfer gearboxes to drive the straightening rolls. Instead, Kohler relies on an energy-efficient drive concept with direct drives without cardan shafts.
This significantly reduces the amount of maintenance required, as the absence of cardan shafts means that recirculating oil lubrication is no longer necessary. And: the innovative direct drive of the straightening rolls enlarges the straightening area while at the same time being gentle on the surface of the material.
It is also used for the belt puller, so here, too, there is no need for drive via cardan shafts. The consistent use of the new drive concept also reduces energy consumption – which saves costs in ongoing operation.
The control of the plant runs with Siemens S7 TIA and can be easily operated via a modern control panel with touch screen. The intelligent machine controller is Industry 4.0-ready, has an OPC UA interface and can be integrated into existing communication environments.
Wide yoke type track rollers are found in all Kohler equipment: These have a significantly longer service life and, unlike many narrow back-up rollers commonly found on the market, need to be replaced much less frequently. In addition, the straightening quality is increased.
With the new generation of strip straighteners, Kohler relies on proven technology paired with innovations and a new design. On the one hand, the drive concept was renewed and, on the other, the design was modernized and optimized. The new strip straightener requires a good 20 percent less floor space.
Kohler also placed particular emphasis on an easily accessible and tidy interior. Should inspection or maintenance work be required on the leveler, the drive motors are easily accessible.
More flexibility through options
Kohler strip straighteners with direct drives can be flexibly equipped: They process material in thicknesses from 0.2 mm to 14 mm and material widths from 50 mm to 2100 mm. The precision strip straighteners can be supplied with 21 straightening rolls. The diameter can range from 40 mm to 65 mm, depending on the application.
As an option, additional intermediate rollers can be installed to ensure gentle processing of particularly sensitive surfaces. The 9” display is also available as a 15” version on request. A machine hood is also available as an option. The systems can be equipped with individually adjustable belt loops.
Plants with conventional drive are available with straightening rolls from 18 to 30 mm diameter. The product portfolio includes strip straighteners in short and long design for strip widths from 35 mm to 2200 mm and strip thicknesses from 0.1 mm to 12 mm, expandable with upright straighteners.
Kohler belt straighteners and straightening material at Kern-Liebers:
Coillade chair, load capacity 5 tons
Decoiler movable, load capacity 5 tons, designed for decoiling from above or from below
Insertion aid, designed for unwinding from above or below
Nibbler cutting device, between decoiler and straightener, for strip thicknesses up to 12 mm
Precision leveler with 21 leveling rolls hard chrome plated, roll diameter 65 mm
Direct drives for straightening rolls
Advanced cleaning and quick change device
Tape take-off with own direct drive
Belt transfer above ground
Material to be straightened:
Tensile strength: up to 600 N/mm²
Material thickness: 1.5 to 12 mm
Material width: 50 to 450 mm