General Design Principles for DuPont Engineering Polymers - Module

Figure 11.91 Heading tool
Tool stroke
Heading
tool
D
d
Support
plate
Heading tool
Figure 11.92 Heading tool
0.7 t
t
0.1 t
0.2 t
0.7 t
90°
Pilot
D>d
1.0 t
Ø 1.4 t
Ø 2.5 t
Ø 1.5 t
Ø t
r 0.1
Figure 11.93 Riveting operations
1. Positioning of tool 2. Stroke
Pre-load
spring
Pre-load
sleeve
Plastic
fitting
Pre-load spring
Heading tool
Pilot sleeve
1.5 t
3. Finishing head
122
Riveting Operations
Permanent deformation is produced by pressure rather
than by impact.
The suggested tool and spring preload for various
shaft diameters are given in the table below.
t 2 mm 3 mm 4 mm 5 mm 6 mm 8 mm 10 mm
Pre-Load
Spring
20 kg 45 kg 80 kg 120 kg 200 kg 300 kg 500 kg
Tool-Load
(min.)
40 kg 90 kg 160 kg 240 kg 400 kg 600 kg 1000 kg
Relaxation of Shaft and Head
The tendency for a formed head to recover its original
shape after deformation depends upon the recovery
properties of material used and on environmental
temperature.
Caution
• When riveting unmodified Zytel ® nylon it is advisable
to have the part conditioned to equilibrium
moisture content before riveting, in the dry state the
material is too brittle. Impact modified materials
such as Zytel ® ST and Zytel ® 408 nylon resins can
be riveted in the dry-as-molded state.
• When riveting onto sheet-metal it is necessary to
remove all burrs from the edges of the hole in order
to prevent shearing of the head. To ensure no
recovery, as normally requested when joining sheet
metal to plastic, riveting should be effected by
ultrasonics.
Practical Examples
For examples of riveted parts, see Figure 11.94.
Design for Disassembly
To improve the recyclability of plastic parts, components
should be designed in such a way, that disassembly
is possible wherever possible. Aspects which
should be considered for this are:
• Use standard materials, whenever possible;
• When multiple materials have to be used in one part,
use assembly techniques which allow easy disassembly
at a later stage; see also Table 11.01;
• Disassembly, when applicable, should be possible
by using robots;
The design should allow easy cleaning and re-use of
the part;
• The part material should be recognizable by part
coding, for example >PA66-35 GF< for polyamide
66 with 35% glass fiber reinforcement;
• Inserts (other materials) should be easily removable,
for example by using “breaking out” techniques.