A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Burr side
Burr formation cannot be completely avoided on the outlet side of the hole punch.
It is kept as low as possible, but absolute freedom from burrs can only
be achieved through reworking.
Conveyor direction
When perforated plates are used for screening purposes it is essential
to provide the conveyor direction with regard to the blank dimensions
Cylindrical or conical perforations
In normal punching processes the hole is cylindrical in the top
third only and is slightly conical on the lower two thirds. This
conical form is often required in screening plates, because it
reduces the danger of the holes becoming clogged. Absolutely
cylindrical holes can only be made with fine punching, drilling, etc..
Dimensions and tolerances
General stock sizes (normal shapes) are levelled mechanically and are not re-cut.
This means that there may be slight deviations from the corresponding DIN standards,
in particular because the plate stretches during punching.
The values set in the DIN standards apply otherwise for all tolerances.
Fiberglas
Various types of plastic can be drawn over glass fibre. Polyvinyl chloride (PVC)
is usually used. PVC is actually a hard, brittle substance. However,
if larger amounts of plasticiser are added products similar to soft rubber are obtained.
PVC becomes brittle at extremely cold temperatures. It does not burn,
or only weakly, does not drip, causes soot and smells of hydrochloric acid.
Its use causes problems because large amounts of hydrogen chloride are released
when it burns. PVC is resistant to acids and solvents and can be deep-drawn
and welded. The main field of application for glass fibre is the use as technical
threads and fibres.
Free cross-section = Open screen area
This is understood as the percentage share of open area (holes)
in the size of the perforation field. The free cross-section
is important for each determination of sieving and throughflow quantities,
and is also important for the load-bearing capability and weight-saving.
Hole length
The hole length is the length of an oblong hole.
Hole shapes
We differentiate between the following hole types:
round holes, square holes, oblong holes, special holes, decorative holes.
Hole width
The hole width is the diameter of a round hole,
the edge length of a square hole or the width of an oblong hole.
Materials
In principle we machine all punchable materials, such as steel,
non-ferrous metals, plastics, wood, etc. Steel is the most
widely-used of these, from plain carbon steel through to corrosion-
and acid-resistant or heat-resistant stainless steel. Machining
abrasion-resistant steels through to austenitic manganese steel
and composite steel plays an important role in our business. On
request, we can carry out heat treatment (stress relief annealing,
normalising, hardening, hardening and tempering) to achieve defined
mechanical properties.
Polyamides
Polyamide is a plastic fibre which is sensitive to acids but is very resistant
at room temperature to lyes, alkalis and many organic solvents and fuels and oils.
Characteristic are the narrow melting and solidifying range, the toughness,
the abrasion and wear tolerance, the stiffness and the creep resistance.
Application temperatures are between -40oC and +120oC.
With longer interaction times and higher temperatures polyamide turns yellow
and loses strength. Polyamides melt and drip when burning, burn brightly and
smell of burnt horn. All polyamides absorb water. They are physiologically
generally recognised as safe and without colorants are approved for use as foils,
e.g. in the food industry.
Polyester
Polyester is a plastic fibre which is very resistant to most mineral acids and
weak lyes. However, it dissolves in heavy lyes at higher temperatures.
Its melting point is around 250 to 260oC. Polyester is very light-
and weather-resistant, has good wear resistance and is very fragile. It burns
with a bright flame, carbonises and smells sweet leaving glass fibre residues.
The main area of application for polyester is use as chemical fibres
in the clothing industry and as a moulding compound
for manufacturing technical plastic articles.
Sound proofing
Sound absorption is silencing and can be achieved with very thin absorbers with
suitable flow resistance. With silencing, the sound propagation is cushioned,
whereby the sound energy is converted into heat. Materials such as acoustic
nonwoven with sound-absorbing properties are referred to as sound-absorbing
materials. In combination with perforated plates this is an excellent way of
providing sound insulation.
Strand
The strand is the smallest distance between two adjacent holes. With
oblong holes we differentiate between top strand and side strand.
Unpunched edge
The unpunched edge is the clearance from the edge of the plate to the first
row of holes. It corresponds to the spacing dimension and the respective
plate dimension. If an unpunched edge is not wanted, the blank must be
larger and a cut made through the holes after punching. If a wide
unpunched edge is required tensions are found in the edges which do not
stretch as well during punching which cannot always be eliminated by machining.