 |
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Technical Data |
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The technical data presented here refer mainly to the ELESA Standards, made
of engineering plastics.
The main technologies used for the manufacture of these products are:
compression/transfer moulding for Duroplasts
injection moulding for Technopolymers.
This primary process may be followed by secondary operations such
as machining, finishing, assembly, decoration to customize the product
(tampoprinting), packaging to guarantee adequate protection during
transportation and identification of the product.
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PLASTICS |
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DUROPLASTS: Phenolic based (PF) thermosetting plastics that harden during moulding due to
irreversible polymerization.
TECHNOPOLYMERS: Thermoplastic polymer materials in which the chemical composition of the
molecular chain provides a wide range of mechanical, thermal, and technological properties. The
transformation process is based on the melting and subsequent hardening by solidification of the
material in the mould. The material itself has a low environmental impact because it can be recycled
(reversible solidification).
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| The main TECHNOPOLYMERS used by ELESA |
| PA |
PA-T |
PP |
POM |
PC |
PBT |
TPE |
Glass-fi bre
reinforced
polyamide,
glass reinforced
polyamide,
polyamide-based
super-polymers |
Special
transparent
polyamide |
Glass-fi bre
reinforced
polypropylene
or with mineral
fillers |
Acetal
resin |
Special
polycarbonate
|
Special
polyester |
Thermoplastic
elastomer
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Mechanical Strength |
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DUROPLASTS: The use of a mineral filler and natural textile fibres, and optimum selection of the
base resin give this material an excellent mechanical strength and a good impact strength.
TECHNOPOLYMERS: The rich selection of basic polymers available and the possibility of combining
these with reinforcing fillers or additives, make a wide range of performance levels possible in terms
of mechanical strength, impact strength, creep and fatigue.
For an indication of the mechanical strength of components moulded with the plastics listed above,
see chapter 4. MECHANICAL PROPERTIES OF PLASTIC PRODUCTS.
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Thermal Resistance  |
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The use of thermosetting materials and reinforced thermoplastic polymers with a high thermal
resistance, enables ELESA to obtain products with great thermal stability and a limited variation in
their mechanical properties at both high and low temperatures.
The recommended operating temperature range for each plastic product in this catalogue is
indicated by the “Temperature” symbol.
Within this temperature range:
The material is stable and no significant degradation takes place.
The user does not normally encounter any problems with the basic function of the product.
The mechanical strength, impact strength, maximum torque and maximum
working pressure values indicated in the catalogue were obtained from tests
carried out under laboratory conditions (23°C - relative humidity of 50%).
These values may vary over the working temperature range indicated.
Customers are therefore themselves responsible for checking the product’s
actual performance in their specific thermal working conditions.
A very general indication as to the working temperature range for the various types of plastics is
given in the table below: |
|
| Duroplasts (PF) |
from -20°C to 100°/110°C |
Special, high-resilience polypropylene-based (PP)
technopolymers |
from 0°C to 80°/90°C |
Glass-fi bre reinforced polypropylene-based (PP)
technopolymers
|
from 0°C to 100°C |
| Polyamide-based (PA) technopolymers |
from -20°C to 90°C> |
Glass-fi bre reinforced polyamide-based (PA)
technopolymers |
from -30°C to 130°/150°C |
Glass-fi bre reinforced polyamide-based (PA)
technopolymers for high temperatures |
from -30°C to 200°C |
For some types of products with specific functional requirements, narrower operating temperature
ranges are recommended.
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Strength and surface
hardness |
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DUROPLAST: The material and its glossy finish enables the surfaces to be kept in perfect condition,
even after prolonged use in the presence of metal machining residues or in abrasive environments
like those, for example, of metal machining applications with machine tools.
TECHNOPOLYMER: The surface hardness values are lower than those of Duroplast, but are still
within the 60-98 Rockwell range, M scale. Technopolymers are however tougher and have a greater
impact strength than Duroplasts.
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Resistance to chemical agents |
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Some of the tables in Chapter 12 describe the resistance of the plastics used for ELESA products at
an ambient temperature of 23°C, in the presence of the various chemical agents they may come
into contact with in an industrial environment (acids, bases, solvents, lubricants, fuels, and aqueous
solutions).
The tables on page A23, A24 and A25 indicate 3 classes of resistance:
Good resistance = the product’s functional and aesthetic properties remain unchanged.
Fair resistance = the functional and/or aesthetic properties are affected to a degree that depends
on the type of product and the working conditions. Some limitations in specific applications.
Poor resistance = product susceptible to chemical aggression. Not recommended for use.
As a general rule, chemical resistance decreases as the working temperature
and mechanical stresses to which the product is subjected increase.
Testing of the product’s resistance to chemical agents is essential for use in the
presence of high temperatures and high levels of mechanical stress.
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Resistance to atmospheric
agents and UV rays |
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In most cases, ELESA plastic standards are used for indoor applications. In any case, due to the
properties of the materials and the measures taken during the design stage, these products may also
be used for outdoor applications, where they are exposed to various atmospheric agents.:
Rapid changes in temperature: within the working temperature range recommended for
each product, rapid changes in temperature do not create problems due to the impact strength
of the materials used.
The presence of water or moisture may result in processes of hydrolysis and the absorption
of a certain percentage of the water/moisture until a state of equilibrium is reached. This may
alter some of the material’s mechanical properties. Examples of materials that absorb water
include polyamides (PA), transparent polyamides (PA-T, and PA-T AR) and duroplasts (PF).
Products made of these materials may undergo slight changes in size due to the absorption
of water, which may affect dimensional tolerances. During the design stage, ELESA normally
takes these possible variations into account in order to minimise their effects and to guarantee
compliance with the technical specifications. The absorption of water results in a significant
increase in impact strength.
The following polymers do not absorb water: polypropylene (PP), thermoplastic elastomers (TPE),
and acetal resin (POM).
Occasional contact with rainwater followed by “drying” does not generally pose any problems
in terms of the strength of the product.
When used in outdoor applications, it is advisable to prevent water accumulating on the product
by installing in such a way that water runs off it quickly.
Exposure to the sunlight and UV rays in particular. Specific resistance tests have been
carried out using specific equipment for accelerated ageing testing, in accordance with the
ISO 4892-2 standard, and setting the following parameters:
- Radiation power: 550 [W]/[m]2
- Internal temperature (Black Standard Temperature, BST): 65°C
- OUtdOOR filter that simulates exposure to the open air, with low shielding against UV rays.
- Relative humidity: 50%.
The relation between the hours of testing and the hours of actual exposure to an outdoor
environment (“Equivalent Hours”) obviously depends on the weather conditions of each
geographic area. Taking the Average Radiant Exposure per Day (ARED) as a basis for
comparison, the reference values adopted on an international scale include:
- Miami Equivalent Hours = high intensity exposure, typical of countries with a tropical or
equatorial climate (ARED = 9.2 MJ/m2)
- Central Europe Equivalent Hours = mean intensity of exposure, typical of continental climates
(ARED = 2 MJ/m2).
At the end of prolonged tests carried out at the ELESA laboratories, the variation in mechanical
strength was measured (tensile/compression breaking, and impact breaking) was measured.
In general, the results show that the mechanical strength of polyamide (PA), polypropylene (PP) and
Duroplast (PF) products is not significantly reduced by exposure to UV rays.
As to the aesthetic appearance of samples exposed to the action of the UV rays, in some cases
a slight variation in the surface appearance of the product was found, on completion of the tests.
For further details on UV ageing tests on specific products, contact the ELESA Technical
Department.
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Flame resistance |
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The universally recognised classification used to describe the reaction of plastics to flames is
obtained from two tests defined by UL (Underwriters Laboratories, USA). These tests are called
UL-94 HB and UL-94 V, which define four main types of reaction to flames: HB, V2, V1 and V0 with
progressively increasing levels of flame resistance.
UL-94 HB (Horizontal Burning)
The test consists of putting a set of three standardized samples of the plastic (in a horizontal position
set at an angle of 45° with respect to their own axis) each one in contact for 30 seconds with a
flame applied at their bottom free edge. Two marks are present on the samples at standardized
distances from the free end.
A material may be classified HB if, for each of the three samples, the following conditions are
applicable:
- the speed of burning between the two marks does not exceed a given standardized value that
depends on the thickness of the samples being tested
- the flame is extinguished before the fire reaches the furthest mark from the free edge (that is, from
the point of application of the flame).
UL-94 V (Vertical Burning)
The test entails putting a set of five standardised samples of the plastic (in a vertical position) into
contact each one twice for 10 seconds with a flame applied at their bottom free edge. A sheet of
cotton wool is placed underneath the samples. The following parameters are measured:
- the time required to extinguish each individual sample each time the flame is applied
- the sum of times required to extinguish the five samples (considering both flame applications
specified)
- the post-incandescence time of each individual sample after the second flame application
- whether any material drips from the sample onto the cotton wool set underneath it with a risk of
igniting it.
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UL Classification of plastics |
| UL-94 HB |
For each of the three samples, the speed of combustion between the two marks does not
exceed the standardized speed that depends on the thickness of the samples |
For each of the three samples, the fl ame is extinguished before it reaches the further mark
from the point of application of the flame |
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Time required to extinguish each individual sample
after each flame application |
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Sum of times required to extinguish the five
samples (considering both fl ame
applications specifi ed) |
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Post-incandescence time of each individual
sample after the second flame application |
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Presence of any material dripping from the sample onto the cotton wool beneath it with the risk
of igniting it |
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The variables that determine the reaction to the flame include the thickness of the samples and the
colouring of the material (in fact, there may be differences between materials with their natural
colour and those with an artificial colour and differences depending on the variation in thickness of
the sample with the same colour).
Yellow Card: This is a document issued by the Underwriters Laboratories that certifies the reaction
of a plastic to flames, following laboratory testing. This constitutes an official recognition of the
product’s flame resistance.
The “Yellow Card” indicates the trade name of the product, the manufacturer and related ID number,
known as a UL File Number. The flame resistance is certified for specific material thickness and
colour.
Some material manufacturers carry out flame resistance tests in independent laboratories, using the
same test methods as the Underwriters Laboratories.
In such cases, a declaration of conformity but
no “Yellow Card” is issued by the manufacturer.
There are groups of ELESA standards with UL-94 V0 classification, identified as AE-V0 by the
symbol.
Most of the other ELESA products for which no specific indication is given in this regard belong to
the UL94-HB category.
ELESA products identified as AE-V0 are made of environment-friendly plastics and are free of
PBB (Polybromine Biphenyl), PBDE (Polybrominediphenyl Ether) and in particular of Penta-BDE
(Pentabromodiphenyl Ether) and of Octa-BDE (Octabromodiphenyl Ether).
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Electrical properties |
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Plastics are generally good electrical insulators. This is particularly useful in certain applications in
the electromechanical field, making plastic products preferable to similar metal products.
The extent of a material’s insulating properties is determined by:
Its surface resistivity
Its volume resistivity
The table below classifies the materials on the basis of their surface resistivity [Ω]. |
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Where specific resistivity characteristics (ESD - Electro-Static Discharge applications, conductive
products, anti-static products) are required, contact ELESA’s Technical Department, who are
specialized in designing specific customized solutions.
Typical values for a few of the plastics used by ELESA are: |
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| Material |
Property |
State of material |
Measuring Method |
Value |
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Conditioned
(50% RH equil.)
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Conditioned
(50% RH equil.)
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Conditioned
(50% RH equil.)
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Surface Finish and Cleanability |
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When moulding technopolymers, it is technically easier to make products with a rough matte surface
finish, which hides any aesthetic defects such as shrinkage cavities, flow marks, or joining marks
caused by non-optimum moulding processes.
However, a rough matte finish makes it more difficult to clean and handle the component after
prolonged use.
ELESA technopolymer standards have a very fine matte finish so that the product remains easy to
clean in time, and is easier to handle for the user. Some groups of technopolymer products have
recently been developed with a completely glossy finish, so that they remain clean for a long time.
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Compliance with
International Standards |
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Over the past few years, the national and international regulatory authorities have laid down a
series of regulations for the control of substances that are harmful to man or the environment and
for the environment safety management in the industrial field.
ELESA’s Technical Department is able to give any kind of assistance also providing any techinical
information required on the following International Standards:
European Directive 2000/53/CE, also known as the ELV (End Life of Vehicles) directive, which is
applicable to the automotive. This provides for a gradual reduction in the quantity of heavy metals
(Pb, Cd, Hg, and Cr6) present in vehicles.
European Directive 2002/95/CE, also known as the RoHS, Restriction of Hazardous Substances,
directive, which is applicable to the field of electrical and electronic equipment. This provides for a
gradual reduction in the quantity of heavy metals (Pb, Cd, Hg, and Cr6) and PBB and PBDE type
halogens present in the components used in the electrical and electronic industries.
European Directive 94/9/CE (known as the ATEX directive), for products used in a potentially
explosive atmosphere.
WEEE Directive (Waste of Electrical and Electronic Equipment).
European Regulation REACH (Registration, Evaluation, Authorisation and Restriction of
Chemicals) n.1907/2006 of 18/12/2006 for the use of chemical substances.
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Competence of ELESA’s
Technical Department |
| |
Ongoing research and experimentation with new materials that offer increasingly high levels of
performance is part of the principle of continuous improvement on which Elesa’s Quality System is
based.
Our partnership with leading plastics manufacturers in the world and the use of mechanical and
process simulation programs, also allows us to offer the material that best suits the Client’s specific
application.
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metaL MATERIALS |
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Plastic elements very often contain inserts or functional components made of metal.
The tables in chapter 12 describe the chemical composition and mechanical strength as per the
reference standards for the metals used.
Surface treatments for metal inserts and parts: the surface of metal inserts or functional
parts is generally treated to ensure maximum protection against environmental agents, in order to
maintain the product’s aesthetic and functional qualities.
The protective treatments normally used include:
Burnishing of steel bushings and hubs
Zinc-plating of threaded studs (Fe/Zn 8 in compliance with the UNI ISO 2081 standard)
Matte chromium plating of lever arms and revolving handles shanks.
Metal parts made of brass or stainless steel do not normally require surface treatment.
On request and for sufficient quantity, inserts subjected to other types of protective surface treatment
may be supplied: black zinc-plating, nickel-plating, Niploy-Kanigen process, nitriding and others.
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OTHER MATERIALS |
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Gaskets: ELESA normally uses gaskets made of synthetic nitrile butadiene rubber (NBR) or
acrylonitrile butadiene rubber (BUNA N) for its products, with hardness values ranging from 70 to
90 SHORE A depending on the type of product considered.
The working temperature range for continuous use is -30°C to +120°C. Where a higher chemical
and thermal resistance is required, that is, for products in the HCX.INOX, HCX.INOX-BW and
HGFT.HT-PR series, gaskets made of FKM fluorinated rubber are used.
For an indication of the chemical resistance values, see the table in chapter 12 on page A24-A25.
The working temperature range is -25°C to +210°C.
On request and for sufficient quantity, flat washers and O-rings made of special materials such as
EPDM, silicone rubber, or others may be supplied.
Air filters for filler breather caps (SFN., SFP., SFV. and SFW. series):
TECH-FOAM type filters: polyester-based polyurethane foam mesh, degree of filtration 40
microns, recommended for temperatures of between -40°C and +100°C for continuous use, and
brief peak temperatures of +130°C. This material does not swell in contact with water, petrol,
soap, detergents, mineral oils or grease. Some solvents may cause slight swelling of the foam
(benzene, ethanol, and chloroform).
TECH-FIL type filters: made of zinc-plated iron wire (quality as per
DIN 17140-D9-W.N.R 10312, zinc-plated as per DIN 1548), degree of filtration 50-60 microns.
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MECHANICAL
PROPERTIES OF
PLASTIC PRODUCTS |
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LThe mechanical properties of a moulded plastic component may vary significantly according to its
shape and the technological level of the manufacturing process.
For this reason, instead of providing tables containing specific data on the mechanical strength of
test pieces of various types of material, ELESA has decided to inform designers of the forces which,
in the most significant cases, may cause the component to break. For most products the mechanical
strength values indicated in the catalogue are therefore breaking loads.
For some products for which deformation under a load is not negligible and may therefore
jeopardise their performance, two load values are provided.
“maximum working load” below which deformation DOES NOT jeopardise the
component’s performance.
“load at breakage” in accordance with the concepts outlined above.
In these cases, the “maximum working load” will be used as design data to guarantee correct
performance while the “load at breakage” will be used for safety tests, applying the relevant
coefficients.
Working stress has been taken into account (e.g. the transmission of torque in the case of a
handwheel, and the tensile strength of a handle) as well as accidental stress (e.g. an impact with
the component), in order to provide designers with a reference for determining suitable safety
coefficients, according to the type and importance of the application.
All the strength values supplied were obtained from tests carried out at ELESA’s Laboratories, under
controlled temperature and humidity conditions (23°C - relative humidity of 50%), under specific
working conditions, and applying a static load for a necessarily limited period of time.
The designer must therefore take into account an adequate safety coefficient
according to the application and specific operating conditions (vibrations,
dynamic loads, working temperatures at the limits of the allowed temperature
range). In the end, however, the designer is responsible for checking that the
product is suitable for its intended purpose.
For some thermoplastics, for which the mechanical properties vary significantly in relation to the
percentage of moisture absorbed (see paragraph 1.5), the resistance tests on the element are
carried out in compliance with ASTM D570, so that the moisture absorbed is in equilibrium with
respect to ambient conditions of 23°C and a RH of 50%.
Compressive strength for levelling elements (working stress):
the levelling
element is assembled on its threaded metal stud and placed on special testing
equipment. The element is then subjected to compressive stress with repeated and
incremental loads until it breaks or undergoes a permanent plastic deformation.
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Resistance to transmission of torque (working stress):
Use is made of a electronic dynamometer that
applies increasing torque values as shown in Figure 1.
Here the dynamometric system is shown in
a traditional way to make the comprehension
easier.
The mean values of the torque C, obtained in
the breaking tests are shown in the tables for the
various components and expressed in [Nm]. |
Impact strength (accidental stress):
The special equipment shown in Figure 2 is used.
The mean values obtained in the breaking test,
shown in the tables for the various models and
expressed in [J], correspond to the breaking work
L of the element subjected to repeated impacts, with
the falling height of the percussion weight being
increased by 0.1 m each time.
Percussion weight: metal cylinder with a rounded
ogival shaped end and weighing 0.680 kg (6.7N). |
 |
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Tensile strength of U-shaped handles (working stress):
this test entails fitting the handle to be tested on a dynamometer, and applying two types of stress:
perpendicular to the mounting screws (F1).
Here the stress on the handle is a combination
of pulling and bending
parallel to the mounting screws (F2).
The load applied by the electronic dynamometer increases
gradually in order to obtain a deformation of the tested
element within a limit of 20 mm/min.
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PROPERTIES OF MOULDED-IN METAL INSERTS |
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With a view to ensuring the most effective anchoring of the metal inserts to the plastic and the best
possible mechanical operation of the element, use is normally made of diamond knurling, of a
shape, pitch and depth suited to the stress to be applied. This type of knurling ensures both axial
anchoring (that contrasts axial tensile stress) and radial anchoring (to avoid rotation during the
transmission of torque) (Fig.3).
For studs, instead of using a common screw available on the market, use is normally made of a
specially shaped threaded insert which protrudes a few tenths of mm from the plastic body so as to
form a metal face on the screwing plane, thus freeing the plastic of all stress. |
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Types of assembly
of elements with threaded inserts |
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Types of assembly that create optimum clamping conditions:
The plastic base on the clamping knob should never rest on the clamping surface. In this way the
stud or threaded boss are never subjected to abnormal twisting (“corkscrew” effect) when axial
tensile stress is applied. The metal stud (or boss) is therefore only subject to the torque applied to
the knob to tighten it. |
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 |
 |
| 1. Tapped hole, without any chamfer or countersinking. |
2. Tapped hole with chamfered edge or countersinking
of a smaller diameter than that of the face on the stud, in
order to ensure an adequate overlap between the metal
insert and the clamping surface. |
 |
 |
| 3. Plain cylindrical hole of a smaller diameter than that
of the face on the stud, in order to ensure an adequate
overlap between the metal insert and the clamping
surface. |
4. Plain cylindrical hole of a larger diameter than that
of the face on the stud, setting in between a steel washer
whose hole has a smaller diameter than that of the
face of the stud. This guarantees an adequate overlap
between the metal insert and the clamping surface. |
Incorrect types of assembly:
The plastic base of the clamping knob rests directly on the clamping surface and the stud or threaded
boss are therefore also subject to an axial load (“corkscrew” effect), which could jeopardize its
anchoring. The values of this force are always higher, with a broad safety margin, than those that
may be applied by normal operations performed by hand, but designers who wish to take into
account cases of improper use should avoid the situations illustrated in cases 5-6-7. |
 |
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| 5. Tapped hole and champfer or countersinking with a
larger diameter than that of the face on the stud. |
6. Cylindrical through hole with a larger diameter than
that of the face on the stud. |
 |
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| 7. apped hole without any chamfer or countersinking,
setting in between a steel washer whose hole has a
diameter larger than that of the face on the stud. |
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Through holes |
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For knobs in which through holes (FP type) have to be made, the insert is set in such a way that the
machining of the hole or the broaching of a keyway only affects the metal part, without the plastic
having to be machined in any way.
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End of threaded studs |
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All threaded studs of the ELESA elements have a chamfered flat end in compliance with
UNI 947 : ISO 4753 (Fig.4). |
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On request and for sufficient quantity,
studs with different kinds of ends may
be provided. These ends may be of the
types shown (Fig.5), as indicated in the
UNI 947 : ISO 4753 table for
“Fixing elements: ends of elements
with ISO metric outside threading”. |
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*IT = international tolerances |
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MACHINING
TOLERANCES |
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THE REFERENCE TOLERANCE SYSTEM IS THE ISO SYSTEM - BASIC HOLE |
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TOLERANCES FOR HOLES AND THREADS IN THE metaL INSERTS |
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Plain holes in the bosses and hubs of knobs and handwheels.
For the most widely used models, there are various kinds of standardized holes available so the
user has a wide selection and is saved the costly task of remachining the hole on assembly. The
tolerance of these holes is normally grade H7, but in a few cases it is grade H9. The degree of
tolerance is always indicated in the tables of each article, in the hole size column. For cases in
which it is more difficult to propose a standardization of the holes that satisfies the broadest range
of assembly needs, either a pre-drilled hole with a simple roughing tolerance (hole with a smaller
diameter than that of the shaft on which it is expected to be assembled), or a hub with no hole (not
drilled) is used.
Tapped holes in the bosses and threads of the studs.
Machining in accordance with the ISO metric threads (UNI 5545-65) for a normal screwing length
(see table in chapter 12).
- tapped holes of built-in metal bosses = tolerance 6H.
- metal studs or ends of shanks for revolving handles = tolerance 6g.
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TOLERANCES OF HOLES AND THREADS OBTAINED FROM MOULDED PLASTIC |
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Plain holes (for handles with a through hole for assembly in an idle condition on pins).
Despite the considerable difficulties encountered in maintaining the tolerances in a machining
process in which numerous factors influence the end result, the size of the diameter of the axial hole
is normally respected with a tolerance of C11. The handles may therefore also be assembled on pins
made from normal drawn parts. If the pin is obtained by turning from a bar with a greater diameter,
a machining process with a tolerance of h11 is recommended, as this gives a suitable free coupling,
with the advantage of a quick, simple and inexpensive machining process.
Inside threads (for handles with no metal bushing to be screwed in and fixed to threaded
pins).
They are normally kept undersized so that assembly is slightly forced at ambient temperature.
Outside threads (for filler breather caps or level indicators with a threaded connector).
In this case, for reasons related to the process technology and the type of plastic, which may absorb
small amounts of moisture from the outside environment, the tolerances must be interpreted taking
this into account though the tightening of the component assembled is never actually jeopardized
in practice.
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SPECIAL
CONSTRUCTION
FEATURES |
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Ball knobs
On all ball knobs or handles of other types, the knurled band indicated as an example in Fig.7 has
been ruled out on principle.
This solution is used to hide the burrs that form on the joining line of the mould, thus eliminating the
cost of deburring and finishing. From the functional and ergonomical points of view, this solution is
not rational, however, in that it causes considerable irritation to the operator’s hands after prolonged
use. In addition, apart from this ergonomic consideration, which is, in any case, important, the
knurled band accumulates dust and dirt which is almost impossible to remove, with the result that the
handle made in this way always appears “dirty” and is therefore not at all “inviting” to the touch.
The solution of facilitating the elimination of burrs by creating a raised edge along the joining line
of the mould (Fig.8) presents the same problems, though to a lesser extent. |
Consequently, the following two solutions have been exclusively adopted:
- completely smooth finish: (Fig.9) which entails a higher cost for deburring (to remove the joining
line of the mould), subsequent smoothing (to join the surfaces) and polishing (to restore the gloss)
but makes the handle comfortable to hold and makes it look always ”clean”; |
 |
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| - finishing with an equatorial groove: (Fig.10) which represents a more economical solution in
that it reduces the deburring to simply eliminating the joining line of the mould by turning a small
equatorial groove, without having to join the surfaces by lapping and also without any need for
polishing. |
Elongated handles
For elongated handles both for fixed assembly (at the end of levers) and for revolving assembly
on shanks, smooth shapes free of grooves and knurls have been adopted exclusively (Fig.11), this
benefits the operation of the handles, which is to be used only for gripping a mechanical part
that is to be subjected to translating movements. Also in the case of the revolving handles on a
shank, knurls, grooves and edges simply irritate the hand of the operator who has to hold it and
accumulates dust and dirt. |
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Fixed handles: types of
assembly. |
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Various kinds of couplings are used for securing fixed handles to the shaft:
Handles with brass boss for screwed assembly on a threaded shaft.
Handles with the nut screw moulded into the plastic for screwed assembly on a threaded shaft.
Handles with built-in self-locking boss made of special technopolymer (original ELESA
design) for push-fit assembly on a plain shaft (unthreaded) made from a normal drawn rod
(ISO tolerance h9). This solution prevents spontaneous unscrewing in time due to the vibrations
to which the lever is subjected or the rotary forces exerted inadvertently by the operator’s hand
while handling the lever itself.
For executions with threaded holes obtained from the plastic in the mould, the measure of keeping
the thread undersized with respect to the specifications laid down in the standards has been
taken.
This enables the threads of the nut screw to adapt slightly to the screw, when tightening at ambient
temperature, thus creating a coupling with an elastic reaction that gives an effective locking effect.
Even better results may be obtained by hot assembly: the handle is heated to 80÷90°C before
being screwed onto the threaded pin. This method of assembly initially facilitates the screwing
operation in that the thread of the nut screw is expanded when screwed in and subsequently enables
an extremely efficient locking effect to be obtained from shrinkage on cooling, due to the slight
roughness of the surface of the thread on the shaft. |
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The solution with a self-locking bushing made of special technopolymer (Fig.12) is, in any case, the
most effective against spontaneous unscrewing in that the elastic coupling is not susceptible to any
vibrations or rotary forces exerted by the operator’s hand.
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The lock is also such as to ensure that the handle does not come out even when subjected to a normal pulling action along its axis. In relation to this, the results of the research work and tests carried out
at the ELESA laboratories are provided and they confirm the technical validity of the coupling with
self-locking bushings made of special technopolymer (Fig.13 and 14).
The graph in Fig.13 shows the variations in axial translation effort expressed in [N] as a function
of the variations in diameter of the shaft (mm), dry and degreased with trichloroethylene. The two
curves represent the minimum and maximum values in hundreds of tests conducted on a type of
self-locking handle with a hole having a Ø 12 mm. The area A contains the values that refer to shaft
with a commercial diameter of 12 mm (tol. h9).
The graph in Fig.14 shows the variations in axial translation effort (mean values) as a function of
the surface area of the shaft. As may well be imagined, the presence of lubricating or emulsifying
oil on the surface of the shaft lowers the handle removal effort. It may however be readily noted
that, even in this unfavourable condition, the axial effort required to slide the handle out is always
such as to ensure that this cannot actually happen in practice.
The use of this kind of handle ensures a considerable saving in that it does not entail machining
thread on the end of the shaft. The self-locking bushing made of special technopolymer enables an
elastic coupling to be obtained and the handle itself maintains all its surface hardness and wear
resistance typical of thermosetting materials.
Assembly instructions: fit the handle onto slight chamfered shaft end and push as far as possible
by hand or by means of a small press. Alternatively it is possible to tap the handle with a plastic
or wooden mallet until firmly in place. In this case we strongly recommend to use a cloth or other
suitable soft material over the product to avoid any surface damage. |
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MEASURES TO BE
TAKEN IN ASSEMBLING PLASTIC PARTS |
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Plastic is a poor conductor of heat and has a different thermal expansion coefficient from that of
the metal inserts so measures must be taken, while remachining the hole, to stop the hubs and
bushings from overheating: in fact, the heat produced is not dissipated and the metal parts expand
and create stress inside the body of the plastic which has a damaging effect on the strength of the
assembly (Duroplasts).
In addition, for thermoplastics (Technopolymers), temperatures close to their softening point could
be reached with the risk of the metal insert coming loose.
It is therefore always necessary to adopt cutting and feed rates that do not produce marked
localized heating and to cool intensively when the holes have a large diameter and depth with
respect to the size of the bushing.
To conserve maximum gloss of the surfaces, we recommend, once machining has been completed,
to avoid leaving the plastic wet for a long time, by removing all residual emulsified water from the
surfaces; use oil only, if possible.
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Types
of machining process |
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The machining processes commonly required for the assembly of handwheels or knobs are:
Remachining of axial hole in the bosses (blind hole). When remachining the hole of a builtin
metal boss, always avoid operating as shown in Fig.15, because both during the drilling
operation and during the insertion of the small shaft, an area of the plastic covering may be
subjected to stress, with the risk of cracking or detaching the part indicated with cross shading.
The operation shown in Fig.16 is the most rational. |
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Note that in the ELESA parts, remachining of the axial hole may be performed under the correct
conditions indicated above in that the length of the built-in bushings is always indicated in the
table of each article so, for the depth of the hole, reference should simply be made to the basic
plan.
Remachining of the axial hole in the bosses (case of a through hole). If the drilling operation
affects not only the metal boss but also a layer of the covering material, the handwheel must be
centred carefully and drilling should be started from the plastic side otherwise, chipping may
occur when the tool is removed.
transversal threading in the boss for grub-screw. To be performed in accordance with the
instructions given above. Avoid threading both the metal and the plastic: it is better to drill the
hole in the plastic part and thread the metal part only.
Drilling or threading operations to be performed entirely in the plastic are exceptional. Bear in mind
that the difficulty with which the heat produced locally is dissipated, also through the abrasive action
of the plastic on the tool, worsens considerably the latter’s working conditions, resulting a rapid wear
of the cutting edges (use hard metal tools). |
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SPECIAL EXECUTIONS |
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The range of ELESA elements is extremely broad and offers designers valid alternatives as regards
designs, properties and performance of materials, sizes..., to satisfy the most diverse applicational
needs. The customer may however need to ask for changes to the standard part or have it made in
different colours to adapt it to special applications. In these cases, the ELESA engineers are at the
customer’s full disposal to satisfy these requests for specially designed parts which, as such and for
the modifications they may entail to the mould, must be required in sufficient quantity.
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THE COLOURS OF PLASTIC ELESA STANDARDS |
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In addition to black, which represents the most commonly used colour for plastic components, a
large number of standard elements in this catalogue are available in the following colours: |
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The RAL code is indicated indicatively in that the tone of the colour of the moulded part may differ
slightly, depending on various factors such as the base of the polymer pigments (polyamide or
polypropylene), the finish (glossy or matte), the thickness and the shape of the product.
Warning: the RAL table refers to the colour of paints and are therefore colours with a glossy
surface.
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TEST VALUES |
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All the information about the test values are based on our experience and
on laboratory tests conducted under specific standard conditions and in a
necessarily limited time interval.
Any values indicated must therefore be taken only as a reference for the
designer who will apply adequate safety coefficients to them according to the
application of the product. The designer and the purchaser are responsible for
checking the suitability of our products for the purpose for which they are to be
used under the actual operating conditions.
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TECHNICAL TABLES |
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CONVERSION TABLE |
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DIN 6885/1 KEYWAYS |
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EN 110 TRANSVERSAL HOLES |
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An operating element is normally mounted on an axis using a transversal grub-screw or a
security dowel. For the type, position and size of these holes, ELESA refers to the drawings
and table shown above. |
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THREADS |
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MVK |
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Fixing the threads (by self-gluing).
Coating with microencapsulated hardener (red). |
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The torque values respect the DIN 237 standard, part 27, and are based on clamping tests without
preloading, with a 6H nut and at ambient temperature.
With a thread of l0 <l2, the length l2 is reduced to the point that one or two of the last threads are left
uncovered (l1).
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The glue is made up of a liquid plastic and a hardener contained in microcapsules of polymer
coated with a red film visible on a part of the thread.
During the screwing operation, the capsules open under the pressure caused by the friction
between the two threads.
The liquid plastic and the hardener react chemically with one another to lock the thread in
position.
The setting and positioning operations must be completed within a period of about 5 minutes,
as the glue will start to set after about 10-15 minutes. An initial hardening sufficient to fix the
thread is reached after about 30 minutes while complete hardening of the fixture will take
place over a period of 24 hours.
The threaded element glued in this way may be unlocked by applying a torque equivalent to
the one indicated in the table for each thread or by heating the element up to a temperature
of over 180°C.
Reuse after unlocking is not recommended.
Threads free of oil and grease guarantee the maximum fixing effect of the glue.
Elements treated with this glue may be stored for a period of up to 4 years, without any
deterioration in their properties.
Threads with MVK microencapsulated glue are generally used on machines subjected to
vibrations, in order to prevent spontaneous unscrewing.
The working temperature range is from -40°C to +170°C.
To order an article with microencapsulated glue, add the abbreviation MVK to the product
description.
Example:
GN 615-M8-K-MVK
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PFB |
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Fixing threads with locking action.
Polyamide-based coating (blue). |
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The torque values respect the DIN 237 standard, part 27, and are based on clamping tests without
preloading, with a 6H nut and at ambient temperature.
With a thread of l0 <l2, the length l2 is reduced to the point that one or two of the last threads are left
uncovered (l1).
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Application of the PFB polyamide-based coating is a process in which the elastic plastic
(polyamide) is applied to a part of the thread, to create a locking action while a screw is
being tightened.
The play between the screw and the nut screw is filled with polyamide, thus ensuring a high
degree of contact between the remaining uncoated threaded surfaces. The coating contrasts
accidental unlocking and accidental unscrewing. The parts locked together may always be
separated by applying a minimum unlocking torque.
There is no need to wait for it to be activated as the locking action between the threads is
instantaneous.
Elements threaded with PFB polyamide-based coating may be stored for a virtually unlimited
period.
The working temperature range is from -50°C to +90°C.
To order an article with the polyamide-based coating, add the abbreviation PFB to the product
description.
Example:
GN 615-M8-K-PFB
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PROPERTIES OF METAL MATERIALS |
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STAINLESS STEELS |
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The characteristics described should be treated as guidelines only. No guarantee is made.
The user is responsible for checking the exact operating conditions. |
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PROPERTIES OF METAL MATERIALS
CARBON STEELS, ZINC ALLOYS, ALUMINIUM AND BRASS |
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PROPERTIES OF PLASTIC MATERIALS |
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DUROPLAST |
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Resistance to chemical agents at ambient temperature (23°C) |
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● = good resistance
�� = fair resistance
(limited use according
to working conditions)
▲ = poor resistance
(should not be used)
Blanks stand for data
not available |
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The characteristics described should be treated as guidelines only. No guarantee is made.
The user is responsible for checking the exact operating conditions.
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TECNOPOLYMERS AND RUBBERS |
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Resistance to chemical agents at ambient temperature (23°C) |
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The characteristics described should be treated as guidelines only. No guarantee is made.
The user is responsible for checking the exact operating conditions.
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● = good resistance
�� = fair resistance (limited use according to working conditions)
▲ = poor resistance (should not be used)
Blanks stand for data not available
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Conc. = concentration
Sol. = solution
Liq. = liquid
Sat. = saturated
Swell. = swelling |
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The characteristics described should be treated as guidelines only. No guarantee is made.
The user is responsible for checking the exact operating conditions. |
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ELESA models all rights reserved in accordance with the law. Always mention the source when reproducing our drawings. 
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