102
N
ovember
2014
Article
THE Machines Yvonand SA
Furthermore, the use of conventional inkjet printers hardly
assures acceptable results at line production speeds higher
than 100m/min.
Further negative factors are seen in the maintenance and
consumables costs, such as inks and solvents – significant
additional cost factors that must not be neglected. Thus to
minimise, for instance, any potential equipment down-time
a second (standby) unit must be acquired and be ready
on-call and at a moment’s notice. All in all, the use of inkjet
printers will necessitate and accrue additional costs calculated
between 50,000 and 60,000 CHF.
In order to eliminate the above mentioned disadvantages,
laser marking equipment was developed through which high-
speed, permanent and abrasion-free printing is achieved.
There are no on-costs for additional maintenance or necessity
for supplementary consumable items. The printing and
marking is done without problem on all current products and at
production speeds up to 300m/min while there is no external
or surrounding contamination with ink, and no solvents are
used.
A prerequisite nevertheless is the use of a special laser
technology. The use of CO
2
lasers will initiate a thermal
etching (engraving) of the printing into the pipe wall. This may
well lead to issues, especially with thin-walled products where
the prescribed and specified minimum wall thickness can no
longer be attained or maintained. In order to overcome this
problem the overall tube wall thickness must be increased,
which leads to additional costs in the form of material usage
on-costs amounting to some 100,000 CHF and more annually.
The ‘special’ laser marking used provides the advantage
to print a product in such a way that the marking and
identification is readable even after prolonged and extensive
use of the product in the field. It should be added that many
international standards now specify a permanent marking.
The laser marking as described can be used safely and
assuredly at speeds up to 300m/min for the production of
black polyethylene tapes, tubes and pipes without the use
of any supplementary products and consumables. A typical
marking unit is depicted in Figure 2.
For the laser marking unit type MTL the advantages can best
be summarised as:
•
No consumables such as inks and solvents
•
The surface pre-treatment of the PE pipes with flame or
corona discharge is no longer needed
•
The printing is fully abrasion resistant
•
The marking does not penetrate into the actual pipe wall –
thus no wall thickness reduction
•
Considerable cost savings in maintenance are achieved
compared to inkjet printing solutions
•
No health hazard or risk to operators
•
No operational safety hazards or issues (eg fire, explosions,
contamination, etc)
Quality assurance
The following steps are envisaged for quality assurance:
•
Spool weight control (spool, coil or reel)
•
End product diameter control
•
End product wall thickness control
•
Water emitter rate per position
•
CV value
•
Burst pressure
The data detailed above is captured and stored in the
QC system of the DFC unit, and is transferred or can be
made available for call-off and retrieval by a central data
management system.
Figure 2: Laser marking unit
type MTL – laser-marked tube
Figure 4: Process flow of an integrated QA and QC system
Figure 3: QA test equipment DFC
and typical test bench set-up
