Special Screws for Plastics
When developing moulded parts from plastic, very early in the planning,
construction and design phase consideration is given to screw
joints.
Standard screws with threads for steel sheets, chipboard or similar
applications are however completely unsuitable for plastic materials.
There is a risk of damage to bore holes and mandrels, arbors,
shafts whereby the workpiece is no longer of any use.
Against this background Menschel has developed the MEPLAST 30
screw. MEPLAST 30 is a reliable and cost-effective screw solution
for permanent joints either between plastics and other materials or
between different kinds of plastic. There is a thread angle of 30°
which prevents bending, overturning or even destruction of the
screw.
With thread forms in plastic materials mass is displaced whereby
the “eye” extends radially.
In numerous experiments with different shaft geometries depending
on the thread pitch a thread angle of 30 ° has proved to be the
best for reliable joints in plastics. The tube is not destroyed and
excellent positioning of the screw is ensured. The displaced plastic
can relax in a polygonal cross section which altogether leads to an
extremely durable and firm screw joint.
Nevertheless the screw joint can be loosened again and can even
be reconnected repeatedly without causing damage to the workpieces
and the MEPLAST 30 preformed thread.
In the overview of our products we would like to inform you about
the technical properties and benefits of MEPLAST 30 and provide
you with valuable advice on planning and construction.
Benefits of the Product
- MEPLAST 30 is suitable for all types of plastic – duroplastics and thermoplastics.
- The slim thread profile maintains the very low insertion torque
required.
- The trilobular cross section of the screw body enables the plastic to recede into flattened zones.
- The 30 ° thread angle guarantees non-destructive connection of
the workpieces.
- The large thread pitch ensures low-wear screw connections
which are optimally resistant to tearing.
- With its extremely high overturning and fracture torque
MEPLAST 30 achieves a very favourable insertion torque ratio.
Applications with Plastics
MEPLAST 30 was subjected to detailed test analyses in the department for plastics technology at the University of Erlangen under
Professor Dr. Ing. Gottfried W. Ehrenstein. All the statements in this
overview of our products are based on verifiable results documented
in the test analysis report which we would be pleased to send
to you on request.
According to these tests MEPLAST 30 is excellent for use with
amorphous and semi-crystalline plastics. The university institute
specifically tested plastics which are used in the electrical, household
electrical and automotive industries where parts are screw
together directly. A conscious decision was taken in the selection
of materials with extremely different properties: ductile, brittle,
fibre glass reinforced. The most important properties of these plastics
are listed in the following table.
According to this MEPLAST 30 shows optimal screw joint parameters
for different plastics. This is seen in the results achieved in a
variety of screw insertion and hardness tests with tearing, oscillation
and load capacity experiments. |
