Sarclad Launches Rolltex EDT Multi-Servo Array As Demand Increases For Highest Quality Of Textured Rolls
Today’s leading steel and aluminum rolling mills need to consistently produce high quality textured strip, to satisfy increasing demand from market sectors such as automotive, white goods and packaging. Sarclad is the world-leading provider of roll texturing technology, having supplied over 120 Rolltex machines worldwide in its 45 year history. Sarclad is launching the next generation of Electrical Discharge Texturing (EDT) technology in April this year, featuring a Multi‑Servo Array (MSA) texture head. Rolltex EDT‑MSA will be targeted at applications that require the highest possible texture quality and consistency.
Author: Grant McBain, Sarclad
Electrical Discharge Texturing (EDT) is a well-established technology for producing textured strip. EDT produces a stochastic, isotropic surface texture on cold mill work rolls to high specific tolerances. These rolls then produce a textured surface on the strip that holds lubricant to aid forming during stamping procedures, while retaining excellent visual appearance after surface coating stages (Figure 1).
Fig 1 Schematic of rolling process
Arguably the demands of exposed automotive strip are the most exacting, with recent market trends requiring changes to textured roll specifications. High volume demand continues for textured strip with a medium roughness (2-3µm Ra) and a high peak count (Rpc) to optimise visual appearance. A new, rapidly growing market segment for automotive applications, seeks lower roughness rolls (1-2µm Ra). Lower textured roll roughness increases the demands on the texturing process to remove any defects remaining from the roll grinding process. Sarclad Rolltex EDT‑MSA machines will provide market leading textures for work rolls to the full range of surface texture specifications, for all tandem, temper and skin-pass mills.
PRECISION TEXTURING PERFORMANCE
Sarclad’s EDT‑MSA design (Figure 2) is unique in the world for roll texturing, combining individual servo control for each electrode, with an innovative formed array. This is delivered within a single or double texture station design, which then traverses the full width of the roll barrel.
Fig 2 Sarclad Rolltex EDT‑MSA
This industry first concept allows each electrode to be individually controlled both mechanically and electronically, to ensure optimal working performance, while still benefitting from the full and complete texture that the arrayed electrode design delivers. This combination provides the highest texturing consistency possible, combined with the highest possible sparking efficiency, to deliver world-class texturing speeds and quality.
The control system employs a novel closed-loop power delivery design, which ensures that the energy delivered by each spark is precisely controlled, ensuring greater consistency of the surface texture. The texturing process is closely monitored in real-time by an advanced digital control system, designed to provide the highest levels of process control, while simultaneously communicating detailed feedback to the control system and machine operator.
Fig 3 Multi‑Servo Array (MSA) electrode texture head
Each texture head (Figure 3) can be equipped with a range of custom options from 12 to 36 electrodes per station, with a double station machine providing a maximum capacity of 72 electrodes, for those seeking a roll texturing capacity in excess of 10,000 rolls per annum.
The package of technological innovations provides a step change in texturing performance, with the opportunity to tailor an application to each customer’s own specific set of requirements. This could be to obtain higher peak counts on standard roughness textures, for an application focussed on maximising visual appearance after paint system application, or for an application requiring removal of grinding defects at low roughness, where faster texturing times may be required. The Sarclad EDT Multi‑Servo Array concept provides roll shops with the ability and versatility to provide textures specific to their own needs and applications.
KEY PERFORMANCE STEP CHANGES
Sarclad has consciously targeted improvement in the areas of greatest benefit to the market, such as:
1. Higher Peak count performance.
Rolltex EDT‑MSA offers a 30% to 60% increase in peak count across the roughness range versus standard market EDT performance (Figure 4).
Fig 4 RPc vs Ra performance envelope
2. Improved speed and capacity
Rolltex EDT‑MSA offers a reduction in texturing time of at least 30% compared with the standard 72-
electrode Rolltex EDT. This increase in capacity means that one Rolltex EDT‑MSA could satisfy demand
where previously two machines might have been required.
Fig 5 Texture time per roll for Ra range
3. Removal of defects including scratches and water marks
Defects introduced by the grinding process can be removed more readily by Rolltex EDT‑MSA, due to greater texturing efficiency. For example, a severe defect such as the deep scratch shown in Figures 5a, can be removed even at low roughness, as shown in Figure 5b (1.2Ra in this example).
Fig 6a Scratch clearly visible before texturing
Fig 6b Scratch removed after 100% Texturing progress
CONSISTENCY AND RESILIENCE
In addition to increased texturing performance, Rolltex EDT‑MSA is also built to deliver improved texture consistency and operational resilience. Sarclad’s R&D team have shown that, each electrode contributes equally to delivering the full texture across the roll barrel surface area. Any difference in performance affects the full roll surface equally. In contrast, alternative EDT machines often have no contingency in the event of failure or imbalance of individual electrode channels, resulting in visible inconsistency appearing in the roll texture. Sarclad is confident that Rolltex EDT‑MSA offers a competitive advantage in the market, producing textures that are demonstrably 25% more consistent than standard EDT.
SUMMARY
With industry leading performance, Sarclad is positioning its latest technological developments to those wishing to produce strip with the highest possible surface texture quality. Launching in April 2022, Rolltex EDT‑MSA will complement Sarclad’s existing Rolltex product range, meeting demand across the global roll texturing market.
Grant McBain is Head of Sales & Marketing at Sarclad in Sheffield, UK
CONTACT: sales@sarclad.com