Valve-spring fractures not wholly avoidable - Scherdel GmbH

REPORTS ON RESEARCH AND DEVELOPMENT, MANUFACTURING, MATERIAL TECHNOLOGY AND THE PRACTICAL APPLICA- 

TIONS OF ENGINEERING SPRINGS AND ON THE SYSTEMS, MACHINERY AND TOOLING DIVISIONS OF THE SCHERDEL GROUP 

Dear reader, 

As you will see from this new 

edition of SCHERDELnews, we are 

continuing to act in accordance with 

our corporate motto "Progress based 

on tradition" and also "Growth thanks 

to innovation". Here, we are constantly 

striving to achieve our most 

important corporate aim: customer 

satisfaction. Of course, this also 

includes the improvement of the 

services we offer. Since SCHERDEL 

has expertise in almost all branches 

of technology relating to engineering 

springs, we can guarantee optimum 

customer service, from a single 

source and on a worldwide basis, 

for just about all engineering-spring 

problems. 

So far we have been able to maintain 

the profitability of our Group, 

despite the widespread difficulty in 

obtaining raw materials. Here, I 

would like to point out that transferring 

the production of new parts to 

low-wage countries is not always an 

acceptable alternative, since these 

countries often lack the necessary 

specialist staff to ensure a faultless 

production process. 

As far as our global activities are 

concerned, I can report that the joint 

venture in China relating to "coilspring 

manufacture" is running to 

schedule, and that additional projects 

in India and Poland are currently at 

the planning stage. 

I am sure you will find several 

points of interest in the following 

articles. I look forward to continuing 

our fruitful cooperation and to developing 

new synergy effects for the 

maximum benefit of our customers. 

Valve-spring fractures 

not wholly avoidable 

SCHERDEL conducts intensive research 

into optimized production processes 

S 

ince manufacturers began using 

steel produced in accordance with 

the "Superclean" process, valve-spring 

fractures due to inclusions have become 

rare but, unfortunately, as far as 

current scientific and technical knowledge 

is concerned, they are not wholly 

avoidable. 

"Superclean" means: 

• deoxidation of the molten crude steel 

with silicon 

• generation of the types of inclusion 

which have a low melting point and 

good ductility within the range of the 

eutectic of the ternary phase diagram 

CaO / Al 2 O 3 / SiO 2 

• Observance of a given number of inclusions 

of the sizes 5-10 µm and 

10-15 µm, and no inclusions > 15 µm 

in the metallographic rod-wire examination. 

The durability of a valve spring depends 

on the complex interplay of engineering 

design, stress during use, 

manufacturing method employed and 

the quality of the material used. However, 

even the use of the "cleanest" 

steel of the highest quality class will not 

completely prevent fractures due to inclusions. 

Tests have shown that even a 

25-gram specimen of such steel contains 

14 inclusions ranging in size from 

20 to 50 µm. A method ensuring the 

complete avoidance of spring fractures 

would require an engineering design 

Walter Bach 

resulting in a suitably low level of 

Group Managing Director 1 

stress. However, for the construction of 

today's engines this requirement is unrealistic. 

As far as current technical knowledge 

is concerned and in view of the facts 

mentioned above, no valve-spring supplier 

can give a warranty and assume 

responsibility for spring fractures due to 

inclusions in the steel. Of course, we 

regard it as a priority task to continue 

analysing all the above-mentioned influential 

factors and to develop methods 

which will enable us to provide the 

customer with a more reliable product. 

We are devoting a great deal of effort 

to the achievement of this aim. 

TECHNOLOGY AND PRODUCT DEVELOPMENT - NEWS AND INFORMATION EDITION 2/2007 E

COMPANY NEWS 

SCHERDEL puts new coati ng installation into operation 

TLZ-1 installation ensures a dynamic sequence of operations - optimum coating is now possible, 

even for delicate parts and for those with complex geometry 

TECHNOLOGY AND PRODUCT DEVELOPMENT - NEWS AND INFORMATION 

View of the interior of the new 

TLZ-1 installation, whose special 

feature is its dynamic sequence 

of operations. 

C 

orrosion is a decomposition 

process mainly affecting metallic 

materials and caused by chemical or 

electrochemical influences. The Delta 

MKS coating system employed by the 

company known as Sigmund Scherdel 

Surface Finishing in Marktredwitz - 

a member of the SCHERDEL Group - 

enhances the durability of technical 

components to a considerable extent. 

By altering the material characteristics - 

e.g. by reducing a component's frictional 

resistance, providing protection 

against acids and caustic solutions, or 

preventing contact corrosion - the system 

can also be of great benefit to the 

customer. Coating in special colours is 

also possible and orders for small 

quantities are no problem. 

Sigmund Scherdel Surface Finishing 

has invested heavily in a state-of-theart 

coating installation which, thanks to 

quence of operations - this is provided 

by the new TLZ-1 installation. Once the 

coating basket has been filled, the dipping, 

coating and spinning procedures 

are carried out automatically. Since the 

unit is completely enclosed, no solvent 

can escape. An ingenious air-circulation 

system is used for preheating, heating 

and cooling. 

DELTA PROTEKT KL 100 

An inorganic base coat which provides 

a micro-layer consisting of zinc and aluminium 

flakes. The component is given 

a coating with a silvery metallic sheen 

which provides excellent corrosion 

resistance and can withstand temperatures 

up to 180°C. Here, several protective 

mechanisms are involved: 

galvanic protection - barrier effect 

provided by zinc and aluminium flakes - 

reaction of the binding system with 

the base - cementation of the Delta 

Protekt KL 100 coating when subjected 

to corrosion. 

DELTA TONE 9000 

This is a largely inorganic base coat. 

The product is very similar to Delta 

Protekt KL 100. The differences relate 

to the binding system and the temperature 

stability. 

DELTA SEAL AND DELTA 

SEAL GZ 

Enhances the characteristics of a 

material and provides colouring as 

required. It has an insulating effect and 

provides protection against contact corrosion. 

The coating is resistant to acids 

and caustic solutions, and is approved 

for use in connection with foodstuffs. 

It also provides a distinct reduction of 

the frictional resistance. 

Parts which have been treated with the Delta 

MKS coating process. 

The new exhaust-air cleaning installation contributes to environmental protection. 


2 

the Company's own efforts and the support 

of the SCHERDEL subsidiaries 

AFEMA and ZARIAN, went into operation 

recently. Here, consideration was 

also given to the environment: the integration 

of an exhaust-air cleaning installation 

ensures that all production 

processes in the factory meet the most 

exacting environmental standards. 

A coating process which ensures firstclass 

quality and a high degree of flexibility 

combined with a dynamic se- 

Previously, coating installations of this 

type could only be used for treating 

bulk items. Until now, springs hooking 

on to each other, sensitive or easily 

dented workpieces with complicated 

surface geometry, or heavy components 

were a problem. Thanks to the 

new TLZ-1 installation this is a thing of 

the past. Depending on customer requirements 

and technical specifications, 

Sigmund Scherdel Surface Finishing 

uses the following coating procedures: 

Further information 

available from: 

Oberflächentechnik 

Sigmund Scherdel 

GmbH & Co. 

c/o Herr Schörner 

Meußelsdorfer Str. 27 

95615 Marktredwitz 

Tel. 09231/603800 

Fax 09231/603802 

www.oftm.de 

info@oftm.de 

3

COMPANY NEWS 

AFEMA equipped with 

new CAD/CAM system 


View of the factory at AFEMA Automation 

and Control Technology 

Optimized construction of special machines, 

thanks to networked processes for design 

and production 

I 

n order to achieve a more effective 

production process for modern, 

special high-tech machines, AFEMA 

Automation and Control Technology 

has put a new electronic data processing 

system for process optimization into 

operation at its company headquarters 

in Marktredwitz. 

Postprocessor Assistant". In addition to 

the great saving in time for programming 

the machines, the potential source 

of error presented by manual data input 

no longer exists, thus avoiding the tiresome 

business of searching for programming 

errors. In addition, there are 

new possibilities regarding the sequence 

of operations: for example, the 

integrated software "EdgeCam Simulator" 

provides a realistic image of the 

surface of a workpiece, which makes it 

possible to visualize the removal of 

4 

Four 3-D workstations with a common 

server provide networked data access 

to engineering drawings, component 

drawings, parts lists, operating instructions, 

technical specification sheets or 

tenders. In order to optimize the interface 

between the 3-D engineeringdrawing 

department and the control of 

the processing machines, the Company 

has acquired the CAM software product, 

"EdgeCam Solid Machinist", which, 

as far as programming the machines is 

concerned, makes manual operation 

more or less superfluous. This means a 

considerable reduction in programming 

time for the Company's lathes and 

milling machines, as well as for the 

modern turning and milling centres. The 

data from all the leading CAD manufacturers 

can be imported directly for further 

processing. The basic versions of 

all the most frequently used control programs 

are integrated in the "EdgeCAM 

material during the machining process. 

When installing the new CAD-CAM 

system, AFEMA paid particular attention 

to ensuring that the hardware and 

software were adapted to suit in-house 

working procedures to an optimum degree. 

In addition to the improvements 

already achieved, and the resulting advantage 

for the customer, the way is 

now paved for the use of further new 

developments in the technical field.

COMPANY NEWS 

Fine-blanking technology 

extends range of expertise 

GL-Spezial Platinen GmbH in Chemnitz makes 

precision components for heavy-duty service 

A 

s a result of the take-over of the 

company known as GL-Spezial 

Platinen GmbH in Chemnitz, 

SCHERDEL has extended its range of 

expertise in the field of stamping and 

bending technology. This company, 

which is now an established member of 

the Group, was founded in 1921 and, 

initially, it made a name for itself as a 

supplier of needle-guide elements for 

the construction of textile machinery. In 

Chemnitz they can call on four decades 

of experience in the field of fine-blanking 

technology and, on the basis of the 

sound technical knowledge and motivation 

of the staff, they can guarantee the 

high quality of their products. Customers 

specializing in the manufacture 

of automobiles, in the making of household 

and recreational appliances, in the 

electrical and electronics industry, or in 

the field of medical technology can 

build on cost-optimized solutions for 

the development and manufacture of 

precision metal components which are 

ready for installation. In the automotive 

field the products include components 

for locking systems, brakes, exhaust 

systems, gear mechanisms, and motion 

and safety systems. 

Fine-blanked components are produced 

in a single operation on presses 

with three effective-force parameters. 

The special features of this process are 

the very smooth cutting surfaces, the 

observance of extremely fine tolerances 

and the high level of angular 

precision plus a workpiece with an optimum 

degree of evenness. The resulting 

products are in fact "ready-to-use". 

Depending on customer requirements, 

processes involving thermal treatment, 

or surface treatment and surface coating 

are available. An in-house prototype 

and tool-making shop ensures an 

efficient sequence of operations from 

the development stage right through to 

series production. Here, cold-forming 

processes can even be integrated into 

the tooling equipment. The machinery 

at GL-Spezial Platinen GmbH includes 

presses with a pressure force of 80 to 

880 tonnes. It is possible to process 

material with a thickness of up to 

12 millimetres. Here the maximum 

strip-processing width is 450 millimetres. 

Depending on requirements, the 

basic materials used are: steel, copper, 

aluminium and a wide range of alloys. 

By investing in new machinery, 

SCHERDEL intends to develop the 

field of fine-blanking technology further. 

Follow-on production unit 

Fine-blanked parts are suitable for 

heavy-duty service. 


stamping 

fine blanking 

F S 

F R 

F R 

F S = cutting force 

F R = vee-ring force 

F G = counter force 

F S 

F G 

F S 

The diagram shows the differences 

between stamping and fine blanking. 

5

RESEARCH 

Potential of modern spring materials for spring components 

subjected to dynamic stress in the valve train 

Staff profile 

We'd like to introduce staff members 

to you who will act as your 

contact if required. 

New engine designs require springs with improved cha racteristics and enhanced load-bearing capacity - 

Choice of material is crucial - paper presented at the co nference of the Association of German Engineers (part 2) 


6 

Fig. 4: Shot-peened surface 

Fig. 5a: Fatigue test for springs 

B 

oth the quality of the different steel 

suppliers and the ability of the individual 

wire drawers vary. The worldwide 

requirement for valve-spring wire 

can be produced by an average steelworks 

in less than two weeks. This 

shows how difficult the situation is with 

regard to this highly specialized steel 

market and the exacting technical standards 

it involves. It requires very close 

co-operation between the spring manufacturer 

and the supply chain for the ingoing 

material. In particular, the development 

of new types of steel - something 

in which our Company is also involved 

- and the ongoing optimization 

of the ensuing wire-drawing processes 

require perseverance and the kind of 

co-operation between the material supplier 

and the spring manufacturer which 

is based on sustained effort and partnership. 

The high level of technological 

expertise and the profound specialized 

knowledge required for the design of 

new materials and their processing 

methods is something which, on a global 

basis, is possessed by very few 

spring manufacturers today. In addition 

to the sound technical know-how and 

experience of the staff, one of the main 

requirements is a sound financial basis. 

Here, it should be mentioned that 

SCHERDEL is active at the forefront of 

worldwide developments and that, during 

the past years and decades, our 

Group has contributed to important 

ideas and innovations in many areas, 

thus establishing today's quality requirements 

and today's quality standards 

in relation to valve-spring wire. 

It should also be mentioned that the 

IVSWMA (International Valve Spring 

Wire Manufacturers' Association) has 

repeatedly pointed out that in the steelmaking 

process inclusions are unavoidable. 

Our customers have received written 

information to this effect. That 

means that today, despite intense efforts 

and the ongoing improvement of 

the steel-making processes and the ensuing 

machining technologies, it is still 

not possible to ensure that the material 

is completely free of inclusions. To a 

great extent, these "natural defects in 

the material" can be offset by the developments 

in the spring-manufacturing 

process which are taking place hand-inhand 

with the development of the materials. 

Design 

The design of the valve spring is 

largely determined by the predefined 

cam contour, which determines the 

excitation of the valve spring, as well as 

by the load being moved and, finally, by 

the dimensions and the overall dynamics 

of the valve train. Using modern 

design tools - Finite Element Method 

(FEM), Multi-Body Simulation (MBS) 

and calculation programs developed 

in-house - combined with efficient measuring 

and test stands, it is possible to 

achieve a dynamically optimum design 

of the valve spring within the given 

dimensions. As mentioned at the beginning, 

lightweight construction, reduction 

in mass and thus reduction of the frictional 

resistance in the valve train are 

the main topics. Here, the valve spring 

is only one of many elements which 

determine these dynamic characteristics. 

However, it is one of the most sensitive 

components, which directly shows 

the designer that there is a problem 

relating to the dynamics. It functions, 

as it were, as the dynamic sensor of 

the valve train. It reflects alI the dynamic 

events in the form of excessive 

dynamic increases by means of the 

characteristic frequency response. The 

design of valve springs and the design 

tools used for this purpose is a topic 

which has already been dealt with in 

previous editions of SCHERDELnews. 

These design tools are now able to 

achieve an even greater degree of conformity 

between simulation and measurement, 

in order to determine precisely 

the dynamic behaviour of valve 

springs and spring elements in the 

valve train, whereby this is reflected not 

only in the design of the spring but, in 

particular, in the optimum choice of 

materials and in the shape of the wire. 

Today, MultiArc profiles combined with 

a beehive-shaped design, for example, 

make it possible to design a valve 

spring for highly dynamic valve trains 

with excellent dynamic characteristics, 

combining a distinct reduction in size 

with extremely fine manufacturing tolerances. 

Techniques and processes 

Of course, the processing of higherstrength 

valve-spring materials means 

that the existing manufacturing infrastructure 

has to be adapted accordingly. 

In addition to adapting the different 

tools in the spring-coiling process, it is 

necessary to select not only the appropriate 

thermal-treatment parameters but 

also suitable shot-peening parameters, 

for example. The greater degree of 

hardness of the higher-strength materials 

and, especially, of the nitrided surfaces 

calls for a suitable shot: that 

means an shot with a suitably adapted 

hardness and shape, so that it can induce 

compressive residual stress in the 

region of the boundary layer without 

damaging the surface. 

In order to shot-peen the component, 

modifications must also be made to the 

shot-peening installation and, in some 

cases, other materials must be selected, 

to ensure adequate stability of the 

surfaces in question. 

It is therefore clear that the existence 

of a new material alone will not result in 

a more efficient component. In order to 

gain the full benefit of the material's efficiency 

in the component, this material 

must be used in conjunction with extensive 

process modification and suitably 

adapted installations. Here, the majority 

of the processes and the accompanying 

installations are developed and built by 

SCHERDEL in-house. This is one of 

the main reasons why, from a technological 

point of view, SCHERDEL occupies 

a leading position in the market. 

Finally, this means a benefit for the 

customer, who has the opportunity of 

using these new materials without delay. 

In this connection it should be mentioned 

that today we carry out an extensive 

release procedure for new materials 

and processes. As a rule, this release 

procedure is carried out separately 

with each OEM and it involves long 

trial runs as well as high costs for the 

suppliers and automobile manufacturers 

themselves in relation to experiments 

and tests. The wire and valvespring 

suppliers, for example, carry out 

a rotating bending test (100 million 

cycles) to test the surface quality and 

cleanness, fatigue tests with springs 

(including exposure to heat) and also 

extensive engine tests with the engine 

manufacturer. 

Surface-finishing techniques provide 

another possibility for enhancing the 

durability of springs exposed to a higher 

level of stress. One example is the 

nitriding process, which is carried out 

in-house at SCHERDEL. In this case 

Fig. 5b: Rotating bending test for wires 

too, the specific installations and 

processes have to be adapted to suit 

the new materials and an overall inhouse 

process-development system 

has to provide a secure technological 

basis. Once these processes have 

been mastered, the components can 

be given the careful treatment required 

to ensure top quality, without the need 

for additional transport to external service 

companies. 

Thomas Regnet 

General Manager of Innotec GmbH 

Since 1st July this year, Thomas 

Regnet (graduate in business administration) 

has been General 

Manager of Innotec GmbH, the 

SCHERDEL subsidiary in Poppenreuth 

near Marktredwitz which is 

responsible for research, development 

and innovation. 

Thomas Regnet was born in 

Bernstein near Wunsiedel in 1963. 

He attended the grammar school 

in Wunsiedel and obtained his 

A levels there in 1984. After military 

service he trained as a commercial 

employee in industry from 

1986 to 1988. During the following 

years Thomas Regnet studied industrial 

engineering and business 

economics at the Würzburg- 

Schweinfurt Vocational College, 

his main subject being marketing. 

During this period he gained 

business experience by working 

at various times as a student employee 

with an internationally 

active enterprise in Upper Franconia 

and also with SCHERDEL. 

From 1993 to 1999, as a graduate 

in business administration, he 

worked in the Sales and Marketing 

Division at SCHERDEL. 

From 1999 to 2001, Mr Regnet 

worked as Head of Sales and 

Marketing with an automotive 

parts supplier specializing in plastics. 

During the next six years he 

took over the management of the 

Sales and Marketing Department 

of an automotive parts supplier 

for the German market and then 

became Director of Sales & Marketing 

specializing in Seat Comfort, 

with responsibility for the 

whole European market and for 

a turnover in the three-digit 

million range. 

7 

TECHNOLOGY AND PRODUCT DEVELOPMENT - NEWS AND INFORMATION

Expertise 

around the automobile 

The SCHERDEL Group works out solutions tailored to customer requirements in the following divisions: 

Engineering springs, Vehicle components, Stamping and bending technology, Connection technology, Assembly technology, 

Machines and systems, Automation and control technology, Tools and equipment, Surface finishing and Research 

and development. Here we would like to show you the most important products in the automotive field: 


Expertise in Vehicle Drive 

injection system 

compression springs 

piezo-injection stamping parts 

variable valve drive 

torsion springs 


stamping and bending parts 

spiral springs 

double-body springs 

assemblies 

fine-blanking parts 

belt tensioners 



torsion bars 


basic engine 

coil expanders 

valve springs 

springs for valve clearance compensation / 

switchable tappets 

springs for vibration absorber 


circlips 

ignition 

magnetic sleeves 

contact springs 

rolled bushes / sleeves 

ignition plug protection covers 

EMC shielding 

hose and stud connections 

hose clamps 

transmission / coupler 



spring packs 

disk springs 

stamping and bending parts 


assemblies 

compression springs dualmass flywheel 

Expertise in Vehicle Interior 

central arm rest 

metal structures with and 

without snap mechanism 

safety of passengers 

springs for belt 

height adjustment 

springs for belt lock 

stamping / bending parts for airbag 

seat system 

metal structures seat frames 

metal structures backrest frames 

sport frames 

side upholstery / upholstery wires 

spring systems for backrests and seats 

lumbar support springs 

supporting and connecting elements 

isofix connectors 

seat connectors / guides 

panel holders 

headrest bows 

holder for fire extinguisher 

actuating devices 

assemblies 

(e.g. seat height adjustment, pedals) 


disk springs 

torsion bar springs 

Expertise in the Areas Body, Brakes 

and Chassis 

brake system actuation 

booster springs 

spring packs 

control units 

brake system foundation 

pad holder springs 

housing holder springs 

spread locks 

tension / compression springs drum brake 

fine-blanking parts drum brake 

annular counters for ABS 

mechanical wear display 

cable holder 

chassis 

rolled bushes for chassis damping 

disk springs / fine-blanking parts bumper 

rebound springs 

comfort springs steering column regulation 

body 

spare wheel holder 

compression / tension / torsion springs 

for lock systems 

active and passive pedestrian 

protection systems 

assembly plates 

coating of structure components 

opening systems 

spring supports tailgate / rear lid 

tension springs tailgate / rear lid 

hinges 

clamps 

8 

SCHERDEL GmbH, PO Box 4 40, 95604 Marktredwitz, Germany, Phone: +49 9 23 16 03-0, Fax: +49 9 23 16 03-4 62

Valve-spring fractures not wholly avoidable - Scherdel GmbH

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