Drilling; Further Processing Methods; Bonding; Thermoforming - Vetus Poly-wood Instrucciones De Instalación

a Clearance [degrees]: 5-15
g
Rake angle [degrees]: 5-15
Cutting speed[m/min]:
up to 1000
Feed [mm/tooth]: 0.2-0.5

2.5.4 Drilling

Spiral drills can almost always be used. Angle of fluting should be
20-30° and point angle 110-120°. A considerable level of heat is gen-
erated by drilling, which must be taken away with the swarf or by
further cooling. For deeper drilling it is helpful sometimes to remove
the drill from the hole to empty out the swarf. If high precision is re-
quired, it is advisable to pre-drill the item and put into intermediate
storageas appropriate. A reamer should be used for precise drilling.
a Clearance [degrees]: 10-12
g
Rake angle [degrees]: 15-25
j Point angle [degrees]: 60-90
Cutting speed [m/min]: 30-70
Feed [mm/rpm]: 0.2-1.0
3

Further processing methods

3.1

Bonding

The high chemical resistance of Poly-wood means that there is no
bite on the surfaces at room temperature and only adhesive joins are
possible. Pre-treat ment of joint surfaces notably improves wettabili-
ty. This activation can be achieved by singeing with a flame set to ex-
cess oxygen by dipping in a bath of chromosulphuric acid at 60-80°C
or electric surface discharge. See DVS Information Sheet 2204 page 2
'Sticking Polyolefins' for detailed instructions on sticking polyolefins.
Experience to date has shown that the following adhesive is suitable
for bonding Poly-wood: 3M™ Scotch-Weld™ DP8005.
This is a two-part acrylic based adhesive. After the adhesive is ap-
plied, substrates must be mated within the worklife of the adhesive,
2-2.5 minutes for one-sided applications. The bonded should be fixu-
red or clamped for at least 2 hours. For further information, please
visit the website: www.3m.com/bonding.
3.2

Thermoforming

Poly-wood sheets can be processed by thermo forming, which is of-
ten described - not entirely correctly - as a deep drawing process.
'Deep drawing' is in fact a metalworking term and means a process of
deformation whereby the sheets are not firmly clamped at the edges
and can still flow. In thermoforming, on the other hand, the edges
are firmly clamped.
Heating, forming and cooling are all vital stages, but the quality of
the semi-finished product is vitally important for the thermoforming
process.
A controllable heating system will be required, designed to provide
even heat to each point of the sheet. Excessive differences of tempera-
ture cause surface flaws. Poly-wood is generally heated on both sides.
Temperature range for forming Poly-wood: 140°C - 150°C
Poly-wood
α
γ
polywm003
γ
β
α
ϕ
After heating the plates, the next stage is forming. In principle, there
are two methods:
- Negative forming into a female mould
- Forming over a male mould.
The process used will depend on wall thickness distribution and fin-
ishing at the edges, and what side of the surface is designed for use.
To obtain an item with a stable form, formed parts should cool in the
mould. Various air cooling systems can be used, e.g. water spray with
air or cooled moulds.
Semi-finished products for thermoforming may not have any major
deviations of dimensions parallel to or across the direction of extru-
sion after maintaining at 170°C (as per DIN 16925, Section 4.5). In par-
ticular there should be not positive change in dimensions in the cross
direction. The level of shrinkage will depend on sheet thickness.
The homogeneity of the semi-finished product is decisive for the
quality of the formed parts. Streaks, exu dation marks and corruga-
tions, which can be overcome by smoothing rolls in the extrusion
process, show up again after thermoforming. Homogeneity is tested
by the shrink age test.
3.3

Printing

Surfaces of Poly-wood parts can be printed after correct pre-treat-
ment.
Colours and paints do not adhere readily to Poly-wood parts. This ne-
cessitates intensive surface pre-treatment. Pre-treat ment is possible
by ordinary or Corona discharge methods. Both increase surface ten-
sion by producing polar groups within the sheet surface. Only this
makes any form of colour adhesion possible. Pre-treatment should
be carried out when at its most effettive, i.e. immediately before
printing. When parts are stored far any length of time, pre-treatment
should be repeated.
To print, the usual machines and processes are used such as flexog-
raphic, rotogravure, offset and litho. Good adhesion and even spread
of colour depends on good pre-treatment.
3.4

Painting

We do not advise painting. Standard paints are more rigid and harder
than the thermoplastic material. Large expanses of paint burst and
come away from the material. If painting is required, we recommend
direct contact with the paint manufacturers.
3.5

Hot stamping

Surface pre-treatment is not required for hot stamping. Good results
are largely determined by print pressure, temperature and contact
time of the hobbing punch.
3.6

Hot gas welding

The process uses heated gas (usually air) to plasticise the original
material and filler and weld them to the joint surfaces under a given
pressure. The air is heated to the re quired temperature by electric ele-
ments. The following rules should be followed for optimum welding:
• Joint surfaces and weld rod should be cleaned before working
• Smooth, even surfaces improve seam quality
• Use correct welding nozzle with correct profile weld rod
• Seam should have no notches or fusion defects
ENGLISH
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