This lecture describes the detailed processes of single-step and multiple-step clinching; it shows the differences of the various clinching methods concerning the amount of shearing; it illustrates the major differences in mechanical properties of clinch joints compared with resistance spot welds. General mechanical engineering background and familiarity with the subject matter covered in TALAT This lecture 4101 is assumed.

1. TALAT Lecture 4102
Clinching
13 pages, 14 figures
Basic Level
prepared by Lothar Budde, Universität-Gesamthochschule Paderborn
Objectives:
− to describe the detailed processes of single-step and multiple-step clinching
− to show the differences of the various clinching methods concerning the amount of
shearing
− to illustrate the major differences in mechanical properties of clinch joints compared
with resistance spot welds
Prerequisites:
− General mechanical engineering background
− TALAT Lecture 4101
Date of Issue: 1994
 EAA - European Aluminium Association

2. 4102 Clinching
Table of Contents
4102 Clinching .............................................................................................................2
4102.01 Definitions and Classifications................................................................. 3
• Definition of the Term Clinching With or Without Local Incision ....................3
• Trade Names for Clinching Methods...................................................................3
• Selected Standard Tool Combinations for Clinching ..........................................4
• Criteria for Classifying Clinching Processes .......................................................5
4102.02 The Clinching Process .............................................................................. 6
• Process Steps in Single-Step Clinching with Local Incision ...............................6
• Process Steps During Two-Step or Multi-step Clinching with Local Incision...7
• Geometry of a Clinched Joint Formed by Clinching With or Without Local
Incision.....................................................................................................................8
• A Comparison of the Properties of Clinched Joints and Spot Welded Joints.....9
• Process Steps of a Single-Step Clinching Process without Local Incision (Die
with Movable Parts).................................................................................................9
• Process Steps of a Single-step Clinched Joint without Local Incision (Die
without Movable Parts)..........................................................................................10
• Formation of a Flat Clinch Element without Local Incision..............................11
• Comparison of Clinch Elements with Varying Local Incisions and Formed Parts
12
• Holding and Stripping Systems for Clinching ...................................................12
4102.03 Literature/References ............................................................................. 13
4102.04 List of Figures............................................................................................ 14
TALAT 4102 2

3. 4102.01 Definitions and Classifications
• Definition of the term clinching with or without local incision
• Trade names for clinching methods
• Selected standard tool combination for clinching
• Criteria for classifying clinching processes
• Definition of the Term Clinching With or Without Local Incision
Compared to the state of development of conventional fastening methods, the clinching
technology for joining shaped sheet components and sections is still new, although the
first patent for this process was granted as early as 1897.
Clinching is a direct joining of materials using the forming technology. A flattening or
material flow (impact extrusion) creates a quasi form locked joint (Figure 4102.01.01).
With Local Incision
Clinching
is a direct forming technology for joining materials
in the form of sheet, tube and profiles using a
single or multi-step fabricating process with a
common displacement combined with local
incision or plastic deformation and folowed by
cold compression, so that a quasi form locking
Without Local Incision joint is produced by flattening or flow pressing.
Source: Budde
alu Definition of the Term Clinching 4102.01.01
Training in Aluminium Application Technologies with or without Local Incision
• Trade Names for Clinching Methods
Within the scope of the general definition for clinching, each company is free to choose
an own name, which generally reflects the tool design used for the fastening process.
As a result, the individual process variations used in the metal processing industry are
better known under their trade names (Figure 4102.01.02).
TALAT 4102 3

4. • Selected Standard Tool Combinations for Clinching
A selection of standard tools for clinching based on local incision and/or forming
processes illustrates the high state of the art for these mechanical fastening methods
(Figure 4102.01.03).
The joint strengths that can be attained depend, among others, on tool design so that the
tools for the individual clinching processes are being constantly developed and
improved.
(Single or Multi-Step) Clinching
With Local Incision Without Local Incision
- "CLINCH" - System - "TOX" - System
- "S-" and "H-DRUCKFÜGE" - System - "O-" and "R-DRUCKFÜGE" - System
- "LANCE-N-LOC" - System - "TOG-L-LOC" - System
- "STITCH" - System - "RIVET" - System
- "T-SPOT-CLINCHING" - System - "R-SPOT-CLINCH" - System
- "PUNKTFÜGE" - System - ...............................
- ................................ - ...............................
- ................................ - ...............................
Source: DIN 8593, Part 5
alu
Trade Names for Clinching Methods 4102.01.02
Training in Aluminium Application Technologies
TALAT 4102 4

5. Clinch-Process DRUCKFÜGE-Process RIVET-Process TOX-Process
Cutting Punch Punch Forming Punch Forming Punch
O-Rings
Compressing Cutting
Punch Laminae
Wedging
Anvil Punch
Cutting Die Spreading Die Form Die Form Die
Source: Budde
alu
Training in Aluminium Application Technologies
Selected Standard Tool Combination for Clinching 4102.01.03
• Criteria for Classifying Clinching Processes
Based on the DIN standard 8593, part 5, it is possible to characterise clinching either
according to the kinematics of the tool components (single or multi-step clinching) or
the shape of the joint itself (clinching with or without local incision, see also Figure
4102.01.04).
Classifying the Clinching Process
According to the Kinematics of the Tool Parts
In Single and Multi-Step Clinching
According to the Joining Element Form
In Clinching with and without Local Incision
alu
Criteria for Classifying Clinching Processes 4102.01.04
Training in Aluminium Application Technologies
TALAT 4102 5

6. 4102.02The Clinching Process
• Process steps in single-step clinching with local incision
• Process steps during two-step or multi-step clinching with local incision
• Geometry of a clinched joint formed by clinching with or without local
incision
• A comparison of the properties of clinched joints and spot welded joints
• Process steps of a single-step clinching process without local incision (die
with movable parts)
• Process steps of a single-step clinched joint without local incision (die
without movable parts)
• Formation of a flat clinch element without local incision
• Process steps of a multi-step clinched joint without local incision
• Comparison of clinch elements with varying local incisions and formed
parts
• Holding and stripping systems for clinching
• Process Steps in Single-Step Clinching with Local Incision
Clinching with local incision creates an undetachable (permanent) joint under the
combined action of shear and penetration processes, in which the penetration and
incision limit the joint region, and a cold compression process, in which the sheet
material pushed out of the sheet plane is compressed and flattened in such a manner that
a quasi form locked joint is created.
The single-step clinching process derives its name from the fact that the joint is created
during an uninterrupted stroke of a single tool component (Figure 4102.02.01).
TALAT 4102 6

7. Punch
Joined parts
Die
Source: Budde
alu
Process Steps in Single-Step Clinching
Training in Aluminium Application Technologies with Local Incision 4102.02.01
• Process Steps During Two-Step or Multi-step Clinching with Local Incision
The clinch joining element of a two-step or multi-step clinch process with local incision
is created under the action of successive motions of the tool components .
Although the multi-step clinching process works, unlike the single-step clinching
process, with a single tool combination for the corresponding joint geometry, this
process, because of its more complicated alignment technique, has not been very
successful till now (Figure 4102.02.02).
TALAT 4102 7

8. Cutting Die
Compressing
Punch
Parts to be
joined
Cutting
Punch
Source: Budde
alu Process Steps during Two-Step or Multi-Step clinching 4102.02.02
Training in Aluminium Application Technologies with Local Incision
• Geometry of a Clinched Joint Formed by Clinching With or Without Local
Incision
In recent years, a large number of fastening elements, based on the principles of the
clinched joint element, have been developed.
Characteristic for all these recent developments is an increase in the joint strength
resulting from the enlarged shear area as well as from the reduction of the locally
incised part which is replaced by a corresponding increase in the plastically formed part
(see Figure 4102.02.03).
increasing th
e sheared a
rea
decreasing th
e sheared ar
ea
Source: Budde
alu Geometry of a Clinched Joint Formed by Clinching 4102.02.03
Training in Aluminium Application Technologies with or without Local Incision
TALAT 4102 8

9. • A Comparison of the Properties of Clinched Joints and Spot Welded Joints
Results of experiments with single-element clinch fastenings with various locally
incised and formed parts as well as various shear areas demonstrate that under quasi
static and dynamic impact loadings, these joints do not attain the strength of a single
spot welded joint (see Figure 4102.02.04). This result is also valid for clinch joints with
enlarged clinched elements.
On the other hand, in the case of dynamic loading, the strength of clinched joints is
superior to that of spot welded joints, especially if the local incision is reduced in favour
of the formed part, thereby reducing the notch action.
1 SW 2 CL with
Local Incision 3
CL with Reduced 4 CL without
Local Incision Local Incision
% AlMg5Mn % %
s = 1.25 mm
180 180 180
Reapted Cycle Force
Fracture Strength
160 160 160
V = 5.3 m/s
Fracture Work
120 V=10 mm/ min 120 120
80 80 R=0.0 80
f=80Hz
40 40 40
1 2 3 4 1 2 3 4 1 2 3 4
0 0 0
Source: Budde
A Comparison of the Properties of Clinched
alu
4102.02.04
Training in Aluminium Application Technologies Joints and Spot Welded Joints
• Process Steps of a Single-Step Clinching Process without Local Incision (Die
with Movable Parts)
In the clinching process without local incision, a combined penetration and clinch
operation (whereby the fastened region is limited by the penetration) is followed by a
cold compression process (whereby the displaced volume of material is flattened by
compression) leading to a quasi form locked joint formed by material flow (impact
extrusion) (see Figure 4102.02.05).
The displaced material of the clinch joint, relevant for the fastening strength, is formed
by the varying flow characteristics of the material on the die and punch sides.
TALAT 4102 9

10. Parts to be
joined
Die with
Movable
Parts
Rubber
Ring
Source: Budde
alu Process Steps of a Single-Step Clinching Process
Training in Aluminium Application Technologies without Local Incision (Die with Movable Parts) 4102.02.05
• Process Steps of a Single-step Clinched Joint without Local Incision (Die
without Movable Parts)
Tool systems with and without moving parts have been designed for the single-step
clinching process without local incision .
During the single-step clinching process with movable die parts, the different flow
characteristics of the material of the parts to be joint is caused by a yielding of the
sheets. On the other hand, in the single-step clinching process without movable parts, a
grooved ring in the die forces the displaced material of the sheets to flow differently
(Figure 4102.02.06).
The advantage of the die without moving parts lies in the absence of wear of the
components. The disadvantage is that oiled aluminium sheets can lead to the formation
of a "hydrostatic cushion" in the closed die, leading eventually to the destruction of the
die.
Punch
Joined
Parts
Die without
Moveable Parts
Source: Budde
alu
Process Steps of a Single-Step Clinched Joint
Training in Aluminium Application Technologies Without Local Incision (Die Without Moveable Parts) 4102.02.06
TALAT 4102 10

11. • Formation of a Flat Clinch Element without Local Incision
New variations of the clinching process which overcome the process limitations of the
single-step and multi-step clinching process with and without local incision, are being
developed constantly. The basic principle, however, remains unchanged.
Thus, it is possible to flatten the typical edged form of the clinch element without local
incision in a second operation, so that this side can be used for the visible surface
(Figure 4102.02.07).
Starting Condition Intermediate Stage End Condition
Round Form Flat Form
Fixing
Punch
Joined
Parts
Counter
Punch
Source: Budde
alu
Formation of a Flat Clinch Element
Training in Aluminium Application Technologies without Local Incision 4102.02.07
Similar to clinching with local incision, it is possible, in a two-step or multi-step
process, to produce a clinch element without local incision (Figure 4102.02.08).
The two-step or multi-step process for clinching uses about 20 % less energy than that
required for single-step clinching, due to the fact that the penetration and compression
(flattening) steps of the former occur in consecutive steps.
Displacing
Punch
Parts to be
joined
Displacing
Die
Compressing
Punch
Source: Budde
Process Steps of A Multi-Step Clinched Joint
alu
without Local Incision 4102.02.08
Training in Aluminium Application Technologies
TALAT 4102 11

12. • Comparison of Clinch Elements with Varying Local Incisions and Formed
Parts
As illustrated in the comparison of clinch elements with varying local incisions and
formed parts, reducing the local incision part in favour of the formed part is coupled
with a reduction of notch effect - i.e. primarily an improved behaviour of the joint under
dynamic loading - as well as reduced chip production. At the same time, however, this
leads to the need for tools able to meet the added requirements.
Clinching Tool Chip Joining Infuence of Local Formed Geometric
Tool Control Production Element Joining Part Incision Part Notch
Surface Effect
Source: Budde
Comparison of Clinch Elements with Varying
alu
4102.02.09
Training in Aluminium Application Technologies Local Incisions and Formed Parts
This means that reducing the incision part amounts to an increased effort in aligning
punch and die (Figure 4102.02.09).
In order to align clinching tools accurately for joints without local incision, special
clamps with double-C frames have been developed, making the use of clinching robots
possible.
• Holding and Stripping Systems for Clinching
A faultless holding system, a prerequisite for producing high quality clinching, must
clamp the aligned parts, so that the material flow during the clinching process does not
cause a movement of the position of joining groups relative to each other.
Appropriate holding systems can be used to clamp the joining parts as well as strip the
finished part from the dies.
TALAT 4102 12

13. Just as in the case of clinching, holding systems must also be adapted for use in punch
riveting (Figure 4102.02.10).
Single-Step Clinching
with Local Incision
Single-Step Clinching
without Local Incision
alu
Holding and Stripping Systems for Clinching 4102.02.10
Training in Aluminium Application Technologies
4102.03Literature/References
1. Budde, L. Untersuchungen zur Kombination quasi-formschlüssiger und
stoffschlüssiger Verbindungsverfahren. Dissertation Uni-GH-Paderborn, 1989
2. Liebig, H.P. Nieten und Durchsetzfügen. Blech Rohre Profile 39 (1992) 3, 220-221
3. Boldt, M. Mechanisches Verhalten von Durchsetzfüge- und
Punktschweißverbindungen bei quasistatischer und dynamischer Beanspruchung.
Dissertation Uni-GH-Paderborn, 1992
4. Steimmel, F. Einfluß der Blechoberflächen auf das Festigkeitsverhalten. Bänder
Bleche Rohre 31 (1990) 11, 33-36
5. Schmid, G. Methoden der Qualitätssicherung beim Durchsetzfügen. Bänder Bleche
Rohre 32 (1991) 61-64
6. Schröder, D. Neue Verbindungstechniken für Aluminiumwerkstoffe. Bänder
Bleche Rohre 32 (1991) 5, 83-87
7. Beyer, R. Kostengünstig und technisch interessant - Druckfügen. Industrie-Anzeiger
110 (1988) Nr. 16, 26-29
8. Reuter, H. Erfahrungen mit dem Durchsetzfügen in der Automobilindustrie.
Tagungsband “Umformtechnisches Fügen von Blech“, Chemnitz 1990
9. Bober, J. und Liebig, H.P. Prozeßanalyse beim Druckfügen. Bänder Bleche Rohre
31 (1990) 10, 143-146
TALAT 4102 13

14. 4102.04 List of Figures
Figure No. Figure Title (Overhead)
4102.01.01 Definition of the Term Clinching with or without Local Incision
4102.01.02 Trade Names for Clinching Methods
4102.01.03 Selected Standard Tool Combination for Clinching
4102.01.04 Criteria for Classifying Clinching Processes
4102.02.01 Process Steps in Single-Step Clinching with Local Incision
4102.02.02 Process Steps during Two-Step or Multi-Step Clinching with Local Incision
4102.02.03 Geometry of a Clinched Joint Formed by Clinching with or without Local
Incision
4102.02.04 A Comparison of the Properties of Clinched Joints and Spot Welded Joints
4102.02.05 Process Steps of a Single-Step Clinching Process without Local Incision (Die
with Movable Parts)
4102.02.06 Process Steps of a Single-Step Clinched Joint without Local Incision (Die
without Movable Parts)
4102.02.07 Formation of a Flat Clinch Element without Local Incision
4102.02.08 Process Steps of a Multi-Step Clinched Joint without Local Incision
4102.02.09 Comparison of Clinch Elements with Varying Local Incisions and Formed
Parts
4102.02.10 Holding and Stripping Systems for Clinching
TALAT 4102 14