WCA March 2024

Technical Article

Laser printing materials for wire and cable applications: a technology overview By Stacey A Saba, Paul J Brigandi and Mohamed Esseghir, The Dow Chemical Company

Abstract Trends in 5G, cloud computing and the Internet of Things are driving technology evolutions in communications infrastructure. Cable designs are evolving to accommodate higher fibre counts and reduced installation costs, and to enable future expansion in dense communications networks. This is leading to significant reductions in cable diameter and the use of thinner jacket walls. Laser printing provides the necessary fine print character and excellent mark contrast needed for marking and identification of these down-gauged cable designs. These cables are often deployed by jetting into installed ducts, where the durability of laser marks is advantageous. However, conventional carbon black UV-stabilised jacket compounds are not inherently laser printable. This paper provides an overview of materials technologies for enabling laser printing on wire and cable jacket compounds. The effect of laser marking additives, resin selection and laser printing speed on laser mark contrast were studied on selected compositions. The advantages of a laser printable formulation are demonstrated, including abrasion resistance and UV performance, while meeting the other material needs of a jacket compound. 1. Introduction Cable print markings are employed to identify the cable type, manufacturer and date of manufacture, and to mark out the length to ensure adequate length is available during installation. To serve this function during the service life of the cable, the print must withstand the mechanical abrasion of installation and the erosion conditions present in the cable’s environment. Print resiliency to these conditions is important to allow outside plant personnel to determine cable length during installation and to allow for the identification of the cable during its lifetime. Cable designs are evolving to accommodate higher fibre counts and reduced installation costs, and to enable future expansion in dense communications networks. This is leading to significant reductions in cable diameter and the use of thinner jacket walls. Therefore, cable identification is evolving and required to withstand a variety of installation and in-service conditions. Traditional methods of cable marking have included print wheels and hot stamp systems as well as continuous inkjet printing. [1] While the traditional marking methods have advantages, there are several disadvantages particularly for mini- and micro-cable designs with small diameters and down gauged jackets. For inkjet printing, the disadvantages can be poor adhesion of common inks as well as significant scrap and downtime due to printer malfunctions. Mechanical hot stamp and embossing are not practical and should be avoided for small diameter cables as they would damage the thin wall jacket and can add stress on the fibres.

Laser printing is advantageous over traditional marking technologies in durability, absence of hazardous materials, and fine font character, making it an emerging trend in cable jacketing technology. However, traditional black jackets are not laser printable due to the presence of carbon black for UV resistance. Therefore, this work extends upon earlier work to further investigate multiple aspects of laser printing technology for wire and cable applications. [2] Previous work demonstrated laser printing on selected compositions; here, various aspects of laser marking additives, resin selection and print conditions are discussed in detail. UV and abrasion resistance of these compositions is demonstrated. 2. Experimental 2.1 Cable jacket compounds The compounds used in this work are designed for use in fibre optic cable jackets. The material properties of the compounds are summarised in Table 1 . Laser-printable (LP) compounds LP1 and LP2 were developed to demonstrate the effect of additives on laser printing. The control compound BK1 is a commercially available black jacket compound used in fibre optic cable applications.

Carbon black (wt%)

Laser marking additive

Resin density (g/cm 3 )

LP1

<1

No

0.945

LP2

<1

Yes

0.945

BK1

2.5

No

0.945

LP: Laser printable. BK: Conventional black jacket

Table 1 : Material properties of laser-printable compounds

2.2 Property testing Laser marking was performed at IPG Photonics on 102 x 102mm compression-moulded plaques with nominal thickness 1.3mm. A fibre laser of wavelength 1,064.6nm, pulse energy of 1mJ and beam diameter of 7.794mm was used. The focus lens was a Linos 245mm F-Theta-Ronar. A Lanmark Controls controller and software were used. A mapping of pulse frequency (x axis) vs pulse intensity (y axis) was carried out, providing a matrix of laser marks. Each mark represented a unique frequency and intensity. The marking speed was 2,000 or 4,000mm/s. Scanning electron microscopy (SEM) micrographs were obtained on a FEI Quanta 200 with an accelerating voltage of 20kV and a working distance of 12mm.

77

www.read-wca.com

March 2024