TPT November 2014

Article

THE Machines Yvonand SA

• 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:

Figure 2: Laser marking unit type MTL – laser-marked tube

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:

• 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 3: QA test equipment DFC and typical test bench set-up

Figure 4: Process flow of an integrated QA and QC system

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N ovember 2014