GOOD TO KNOW

We can look back on a company history rich in tradition.
Since the foundation of the company in 1888, numerous developments and innovations have given KERN-LIEBERS what sets it apart today:  technical expertise, competence and reliability!
We want to share our experiences with you. Here you will find important background information on the subject of
safety, quality and service.

 

Materials

We pay particular attention at a very early stage to the definition of the spring material to be used.
Here we can fall back on the wide range of special spring steels already in use, and we can also offer other materials and special alloys.

We work together with our customers to determine the exact material specifications. We have a well-equipped materials laboratory for testing the material properties of spring steel. All incoming materials are tested and approved at this laboratory in accordance with the specifications. For the assessment of damage, the laboratory and its experts in fracture mechanics and analysis are on hand to provide assistance.


PRIMAFLEX” is a texture-rolled carbon steel similar to DIN 1.1525.

    
Given its special properties, this steel can also be used to achieve a particularly long service life.
⇒  For high demands on torque and service life

Appropriate greasing protects the spring against corrosion. 


SUPERFLEX” is a highly strain-hardened, austenitic, stainless spring steel strip similar to DIN 1.4310 with a specific rolling texture.
⇒  for high demands on torque and service life, and also suitable for a wide range of operating temperatures

The material quality of SUPERFLEX generally exhibits very good corrosion resistance.
 


Special materials for watch production

Nivarox

NIVAROX (non- variable oxide-proof) is a metal alloy developed by Reinhard Straumann in 1933. It is used to manufacture tension springs, as is the similar NIVAFLEXfor spiral springs. Nivarox is used mainly in the watchmaking industry. This alloy of nickel, chromium, manganese, titanium, beryllium, silicon and iron has properties that are advantageous in the manufacture of balance wheel spiral springs and drive springs. Springs made of NIVAROX are low-fatigue, virtually anti-magnetic, non-rusting and have a very low coefficient of thermal expansion.

NIVAROX makes the rate behavior of mechanical watches stable and almost temperature-neutral. These special properties made it possible to replace the complex and expensive compensation balance.

 

         

Nivaflex 

NIVAFLEX is a precipitation hardening special alloy based on cobalt. The material consists of iron, nickel, chromium, cobalt and beryllium. It is flexible and has a high level of corrosion resistance. The material properties are ideal for the production of break-proof springs in the smallest dimensions.

The alloy NIVAFLEX is used to manufacture springs for the watchmaking industry. NIVAFLEX was developed by Reinhard Strauman. Even today, watch mechanism components made of this special alloy are considered indispensable system parts in quality mechanical watches.

Bimetals

Abimetal (also thermal bimetal) is a metal strip consisting of two layers of different metals that are joined to one another by a material bond or a form fit. They are characterized by a change in shape when the temperature changes.
This manifests itself as bending. The reason for this is the different coefficient of thermal expansion of the metals used.
These metals can be for example zinc and steel or steel in combination with the alloy brass.

Two metals with different coefficients of linear expansion elongated by different distances when heated.
If the two ends of two metal strips are joined, for example by riveting or rolling, the difference in elongation causes the bimetal strip to bend.

Bimetals are used in certain spiral springs.

Non-ferrous metals

is a collective term for a subgroup of non-ferrous metals not including precious metals.
They include metals such as cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), tin (Sn) and zinc (Zn).

These base heavy metals are themselves colored or form colored alloys such as brass, bronze and gunmetal, with the alloys also classified as non-ferrous metals. Their color is often quite striking.

Processing

Steel cutting

On our modern strip cutting systems, which operate on the rotary shears principle, we cut custom spring strip widths to our
customers’ requirements in a just-in-time process.


Edge processing

To process the spring edges, we draw on a range of processes that have been proved in practice. For stainless spring steels in particular, the machining of edges in a process known as “chasing” is the preferred option.

For the processing of carbon steels, the spring edge is processed with a combination of section and hard rolling. This proprietary technology provides the best results in terms of the service life of the spring.


Spring shaping

To achieve the basic form, KERN-LIEBERS brings to bear the experience in tailored machine designs gained in over 130 years of spring production. We have specialty machines in place for everything from the smallest watch springs to large springs for railway systems. 

The “winding” or “coiling” operation is crucial to the performance of power springs and spiral springs. It can be used to selectively influence torque characteristics and operating behavior, specifically with respect to service life.

For constant force springs, the rolling process is the decisive factor in determining the spring force and service life. 


Heat treatment

Heat treatment after the forming of the spring is an important process step that fulfills two important functions:

1.  The internal stresses introduced during the plastic deformation process can be reduced.

2.  Depending on the choice of material, heat treatment achieves an increase in strength that stabilizes the shape,
giving the spring a high elasticity and guaranteeing the best possible use of materials.

We have suitable facilities in place for the heat treatment of the entire range of spring materials used. We set the properties of the springs to their optimum values with precisely defined heat treatment regimes. In addition to furnaces at normal atmospheric pressure, we also have facilities for treatment with inert gas or in a vacuum.

Quality assurance

KERN-LIEBERS is committed to the consistent implementation of the elements of the IATF 16949 standard in all phases of product development, from the first steps in planning to series production of the springs.

Here you will find a full overview of all current certificates held by the KERN-LIEBERS group of companies.


Right from the first stages of product definition,  the design of the springs is optimized to meet the customer’s specifications and the conditions in which they will be used. A range of tools specially adapted to our products is available for this purpose, with calculation programs for static design of the spring properties constituting the basis. The finite element method FEM and special software are used to look into the load on the springs and, for springs with dynamic use, a simulation is used to determine the movement behavior in the situation in which they are used.

This preliminary design stage is usually followed by the production of samples, which are manufactured under close-to-production conditions. These samples can be used to verify the spring characteristics determined theoretically, and they allow the customer to carry out initial testing of the spring in the customer’s application.


For verification of the spring characteristics, we have the usual measuring instruments in place for the determination of dimensions, forces, paths, torque and revolution characteristics. Where special customer-specific test equipment is required to verify the product characteristics, our equipment engineers can ensure that we are capable of implementing and providing it.

In the serial production stage, our focus is on stable processes that enable us to manufacture consistent product quality. These processes are monitored using the standardized tools of quality assurance, such as FMEA, capability assessment, and so on. Our processes are often designed to ensure that all important product characteristics are recorded inline where possible, in order to be able to identify potential deviations as early as possible at the point of origin. We also have a modern computer-aided quality assurance system in place to supports people working on site and enable regular documentation of all relevant production data.

For assembly modules, both purchased assembly parts such as plastic housings and auxiliary materials such as oils and greases are subject to regular inspection of delivery quality and consistent product characteristics. Suppliers are managed using a supplier management system. During fitting of the assemblies, automated inspection processes such as computer-aided image analysis are used to guarantee high product quality. The essential product characteristics are verified in a final inspection, and we also carry out a service life test, which KERN-LIEBERS runs on test benches developed specifically for this purpose. We inspect any special properties of the springs, sorted or classified by modern testing and sorting machines.

    

Spring setting

Due to the high stress level inside the spring, a relaxation and creep process occurs over the period of use, the so-called “spring setting”. The most important influencing parametres causing this setting process besides of the stress level itself are the type of stress (static or dynamic) and the duration (short term or permanent). Relaxation or the decrease in spring force is an age related change especially when it comes along with a higher working temperature. In a long term view it can be seen that the spring relaxes more at the beginning of its period of use, but then the loss of force gets continously less until the curve remains at zero growth.

With regard to classic power springs or MAXIMO power springs, a setting of 0 - 5% is expected with low stress, 5-10% with medium stress and 10-15% with high stress over several years of use.

Lubrication

Lubrication of power springs

Power springs operate with alternating coil contact. The friction this produces can be reduced with good lubricants applied to the surface of the springs. Depending on the application, the spring lubricant should have a friction-reducing effect at temperatures from - 40 °C to + 120 °C, and also a corrosion-protecting effect. However, even the best lubricants have an adhesive effect, which has a particularly unfavorable effect on thin, wide and long springs. This results in poor and jerky running with large hysteresis. This negative influence can be improved by using a support in the spring housing.

Because of their strong counter-curvature, MAXIMO power springs operate with less coil contact. Nevertheless, it is also advisable to oil or grease MAXIMO power springs, depending on what they are used for. In conjunction with a support, the lowest hysteresis can then be achieved.

    

 

The spring diagram shows a uniform torque curve, favored by the use of lubrication in conjunction with a spring support.
In the return motion in particular, the coils are less likely to adhere to one another. This means that the individual spring coils are released more evenly from the spring package, reducing the hysteresis. Because the hysteresis is low, a higher torque level can be achieved in the return motion.
At the same time, optimal conditions for reducing noise in the return motion are created.

Das Federdiagramm zeigt einen ungleichmäßigen Drehmomentverlauf infolge einer fehlenden oder geringen Schmierung und einer fehlenden Federstütze.

Dies hat zur Folge, dass aufgrund der größeren Hysterese ein geringeres Drehmomentniveau im Rücklauf erreicht wird. Durch das ungleichmäßige und ruckartige Lösen einzelner Federwindungen treten außerdem Geräusche im Federrücklauf auf.

Lubrication of constant force springs

Constant force springs operate without hysteresis because the spring strip is unwound and rewound without friction, so that lubrication would not actually be necessary. To reduce the risk of corrosion, however, oiling or greasing the springs is nevertheless recommended.

The situation is however different with two and more coiled constant force springs, because they move onto each other when extended, leading to relatively large frictional influences. In these cases, oiling or greasing is required. This also reduces surface wear, which can have a positive effect on service life.

Lubrication of spiral springs

Spiral springs operate without hysteresis due to the small angle of twist when properly supported.

To ensure good corrosion protection, they should however also be oiled or greased.

Corrosion

Greases and oils

The protective measures otherwise commonly used, such as painting or coating, are often not possible due to the shape of a spring. Depending on the application, the correct material and the correct grease must be selected for springs with regard to the other components and the application.

KERN-LIEBERS treats springs with special corrosion protection oils that provide protection against corrosion during production, intermediate storage and transport. 
The appropriate corrosion protection during operation of the assembly must be ensured by the design of the spring cartridge in conjunction with greasing, or a suitable material (steel, grease, plastic). The compatibility of the lubricants used (greases/oils) with the individual components (for example the plastic parts) under the specific operating conditions must be ensured in each individual case.


Corrosion protection papers

The VCl corrosion protection approach (“volatile corrosion inhibitor”) has held up extremely well over decades of practice. Corrosion protection papers are impregnated with chemicals that continuously release minute quantities of active substances. This does not eliminate the causes of corrosion, but does prevent their harmful effect on the surface of the goods to be protected; atmospheric oxygen, water vapor and sea air are passivated. The weak alkaline pH value of the impregnation neutralizes the effects of acidic substances such as wood acid, hand perspiration and industrial waste gases. Any corrosion that has already occurred is stopped.

There are many types of corrosion, which are described in detail in the specialist literature.
If the strip spring is not adequately protected, one of the following types of corrosion is most likely to occur, depending on the environment:


Surface corrosion

With this type of corrosion, the steel is affected more or less evenly over its entire surface, which under some circumstances can lead to a considerable weakening of the material cross-section. Surface corrosion is familiar to most people in the form of rust, which occurs mainly in unalloyed carbon steels when exposed to the influence of moisture in conjunction with oxygen without protection.


Pitting corrosion

This is a locally occurring corrosion process that produces crater-like or needle-like depressions. It depends heavily on the aggressive medium and occurs in particular on exposure to the influence of chlorides and halogen salts. These solutions also have a corrosive effect on alloyed and stainless spring steel strips.

Packing & labeling

Packaging

The packaging used not only has to adequately protect the springs during transport, it should also be easy to store at the customer’s production lines and make sense for the processing or assembly stations. The design of the packaging must be optimized for each product and contain quantities agreed for each package. The dimensions for containers, cardboard boxes and load carriers should be standardized where possible in accordance with VDA guidelines, and the goods must be correctly and completely labeled.

The optimum type of packaging depends largely on the type of spring.

 

1. Standard packaging
Packaging is in cardboard boxes. The boxes are stacked on reusable pallets and wrapped in film where necessary so that the goods can be moved directly by forklift or pallet truck in the warehouse or production area. In Germany, EURO pallets are exchanged by shipping companies. Where required, the KERN-LIEBERS Group uses only plastic straps or adhesive tape to seal the cardboard boxes,
in order to avoid the risk of injury from metal clips or straps. The dimensions of the pallets follow the EU standard of 80 x 120 cm; in exceptional cases also 80 x 80 cm and 60 x 80 cm. The packaging and filling materials comply with the international IPPC standard “ISPM-15”. For example, pallets are made of OSB (oriented strand board, a wood-based material) and marked with the appropriate symbols.
 

 


2. Disposable pallets
If the return of pallets is not possible, disposable pallets can also be used for the standard form of packaging described above.
 

3. Seaworthy packaging
For overseas shipment, the boxes are packed in OSB crates, which are lined with appropriate forms of paper to provide additional protection of the springs.
 

           

4. Honeycomb or individual packaging
For particularly sensitive products, we recommend the use of plastic trays (thermoformed plastic molds). These allow easy and/or automatic removal of the parts and provide optimum protection of sensitive springs against damage. Plastic trays are a form of returnable packaging that can be reused.

Particularly fine spiral springs are threaded onto a wire and packaged in plastic tubes.
 

 

   

5. Reusable packaging
Packaging in plastic containers (small containers as returnable packaging) is recommended if the packaging can be sent back and forth between customer and supplier. To protect the parts from dirt and damage, the transport box should be closed.
 

 

      

6. Customer-specific special packaging, such as blister, bags etc.


Labeling

There is a document pouch on each package containing the delivery note and customer-specific documents, as well as a label showing the address details. Customer-specific labeling is possible by arrangement.

For the labeling of our goods, we follow the standards set by the automotive industry (VDA or ODETTE) and use labels in accordance with VDA standard “4902 or 4994 Global Transport Label (GTL)”. The individual box  is given a Single Label (if required), while the pallet is given a Master Label (standard).

      

Safety instructions

Please exercise the greatest care and caution when handling technical springs.
By its nature, the spring is under constant tension and, depending on the design, can be extremely strong and sharp-edged.
Failure to exercise the necessary caution can lead to damage or injury.

Power springs should only be removed at the outer spring package (e.g. at the retaining ring or housing).
The inner end of the spring should not be pulled out. There is a risk of injury.

Environmental and energy policy

Our environment is our most valuable asset!  
That is why we are committed to the sustainable use of resources and to reducing our energy consumption.

We adhere to:
- The requirements set out in ISO 14001:2004 / AC:2009 and ISO 50001:2011.
- The legal obligations governing environmental and energy management and occupational health and safety.

We emphasize:
- Environmentally-friendly design and monitoring of products and processes
- Assessment of environmental aspects, risk analysis, implementation and maintenance
of improvement and corrective measures.
- Assessment of energy use and consumption, including natural resources.
- Measurement and review of results through regular audits.
- Reduction of the quantity of waste and waste water.
- Implementation of preventive measures in the form of an emergency preparedness and response plan.

Guidelines

In the production of technologically sophisticated springs and stamped, bent and fineblanked parts, we hold a leading position in our market segments and have established ourselves as a competent and reliable partner for industrial companies with global significance – We are extremely successful in implementing the zero-defect objective. Our company has been characterized by sustainability, so that our business today rests on a solid economic foundation that is capable of withstanding cyclical fluctuations. We also took advantage of the opportunities presented by globalization at a very early stage, becoming for example one of the first foreign companies to establish its own subsidiary in China, a move that today contributes significantly to our growth and success. In the internationalization of our business activities, the core competencies developed and established in Germany remain crucial to this day.

We are firmly convinced that this extremely successful development is based on the fact that we work consistently to realize our corporate objectives, and we will continue to do so in order to preserve and develop everything we have achieved so far.


As a family business operating globally, we are as conscious of our Black Forest origins and tradition as we are of the importance of our role internationally, and we are equally committed to both.

Our technological development work is consistent, is done in close cooperation with our customers, and continuous improvement of our products and processes is our everyday motivation. This is the only way we can grow profitably, generate income and ensure the continued viability of KERN-LIEBERS worldwide.

The element that binds all companies across the KERN-LIEBERS group of companies, each with their own local national cultures, is our framework of values. Our values guide us in our decisions and inform our conduct on a day-to-day basis.

Throughout the company, each of our employees is called upon to practice open communication – in their unit, at their production location and beyond – and to make a positive contribution to shaping the corporate culture of KERN-LIEBERS. The special role of our executives here is to lead by example.

By carefully observing our values, each and every one of us contributes to a fair and respectful approach to each other. In doing so, we also ensure that we achieve our most important corporate goal – sustainable economic success that is consistent with our social responsibilities around the world. This is the benchmark against which we want to be measured.

We, the companies of the KERN-LIEBERS group, take our corporate and social responsibilities very seriously and firmly believe that the long-term economic success of our companies requires a binding system of values. For this reason, we assume that our employees, customers, suppliers and business partners base their conduct and behavior on the following principles. The role of our executives here is to lead by example. Under certain circumstances, infringements may lead to consequences, including in contractual relations.


Products and laws

We make every effort to ensure that our high-quality products satisfy the interests of our customers in the best possible way.

We work continuously on innovation and improvement and examine potential cost savings.

We adhere to the legal provisions applicable to us, including any export and import restrictions.

We also expressly observe the United Nations Universal Declaration of Human Rights and support its enforcement, in particular through the Global Compact initiative.


Working conditions

We reject any form of forced or child labor and are committed to fair and safe working conditions.

We oppose any form of discrimination, in particular on grounds of nationality, ethnic origin, belief system, sexual orientation, religion, gender, age or disability.

We stand for equal opportunity and cultural diversity.

We want our employees to be able to develop their skills and qualifications accordingly.

We guarantee the right to freedom of association in accordance with statutory provisions.

We ensure that working hours and working conditions are at least in conformity with the statutory provisions or negotiated agreements applicable to us.


Confidentiality, intellectual property, data protection and data security

We ensure that both our own company and business secrets and those of our customers, suppliers and business partners are protected. We understand that in our relations with our customers and suppliers, we have as a rule committed ourselves to strict confidentiality, and we act accordingly, particularly in our approach to access permissions.

We respect the intellectual property of third parties.

We adhere to the data protection laws applicable to us and to the IT policies and standards in place at our company. We back up our work regularly in a manner that ensures that it remains usable for the company.

Click here to go to our privacy statement

We, the companies of the KERN-LIEBERS group, firmly believe that the economic success of companies for the benefit of all is prevented or made considerably more difficult by corruption, because decisions then no longer depend on objective criteria such as price, performance, quality or reliability.

For this reason, a commitment to fighting corruption is part of our value system. We must pursue this goal directly in our company. The purpose of the anti-corruption policy of the KERN-LIEBERS group is to define and prevent corrupt behavior. It applies to our employees and business partners alike, who we will also measure to establish whether and in what manner they support us in our efforts to achieve competitive conditions that provide equal opportunities to all.

From our executives, we expect a particular commitment to leading by example and translating the substance of this policy into their day-to-day business activities.


In many countries, corruption is endemic. But this is no justification for also being corrupt.
The fact that certain things have always been done this way, and that this is how they are done by others, is also unacceptable.

Our goal must be to take the company forward through quality, innovation, cost consciousness and integrity. There is no place for corruption here, even if that means that orders are lost. Management is well aware of this and is prepared to accept the consequences. The management of the KERN-LIEBERS group is resolute in its commitment to preventing and fighting corruption. It will not permit the misconduct of any individual employee to jeopardize the existence or reputation of the group.

Corruption is contrary to our interests.

To protect the KERN-LIEBERS group, every employee is obliged to make their contribution to the prevention of and fight against corruption.