MACHINING TECHNOLOGY
MACHINING TECHNOLOGY Productivity without limits for timber construction Thinking big The latest SCM technological solution has been developed for the industrial production of large format CLT panels. High productivity, precision and reliability are the main advantages of this new CNC machining centre AREA XL is the new 5-axis CNC machining centre designed and manufactured by SCM for the industrial production of large format CLT panels. This solution, an evolution of the already popular and appreciated AREA model, was developed to meet the needs of those companies requiring high productivity, accuracy and reliability. The processing of large format CLT panels is characterized by heavy duty stock removal, process automation in the handling and referencing phases, as well as cleaning of the work area: The new AREA XL has been designed taking into consideration these specific requirements. High productivity With this machining centre, size and thickness of CLT panels are no longer a problem. Elements up to 16,000 mm long x 3,600 mm wide and up to 400 mm thick can be processed, in particular thanks to an electro-spindle of high power and torque: 63 kW in continuous operation. The overall productivity can also be further increased by equipping the machining centre with a second machining head unit, capable of executing several operations simultaneously. Another plus is the possibility to perform transversal throughfeed-drilling operations even on the maximum panel size, thanks to optional auxiliary units. Maximum comfort of use, cleaning and safety AREA XL offers up to 60 tool stations in total, including two sawblades for each machining head unit. The operator’s work becomes even easier, both during the process, thanks to automatic workpiece handling and referencing systems, and during chip removal from the work area, thanks to innovative cleaning systems. AREA XL also allows to work in total safety, thanks to the full enclosure and a protected access system to the work area through laser barriers. The exclusive SCM’s approach for sustainable timber construction As noted by Tommaso Martini, SCM Business Unit Manager for CNC machining centres for timber construction, the use of cross-laminated timber (CLT) is increasingly widespread within the construction industry. “This is a modern, ecological, resistant product that can adapt to the most diverse design requirements and, thanks to these special features, can also be used for the construction of multi-storey buildings of considerable heights. SCM is able to offer this market a strong knowhow and expertise, thanks to a long experience in high technology solutions gained over the years with the OIKOS and AREA cnc machining centres dedicated, respectively, to the processing of modular and large format panels. A path that finds today, in the new AREA XL, a further evolution to respond to the needs of companies that demand to combine increasing productivity with high levels of accuracy and reliability”. www.scmgroup.com 12 No. 1 • March 2021
MACHINING TECHNOLOGY Patented Twin-Shaft Cutting System Precision with maximum efficiency The way a twin-shaft shredding unit works is fairly simple: two tools moving in opposite directions draw in the collected waste material for shredding and crush it all together into smaller pieces. If it is purely about volume reduction, for example for easier transport, this can be achieved with conventionally designed shafts. Some applications, however, require specific particle sizes for their processes. Plants that recover energy from waste wood, for example, are usually designed with a standardised particle size in mind. Oversized particles in the material stream can block the conveyors or safety systems such as rotary valves. In addition, too many fines negatively affect combustion and very small particles might lead to lumps jamming the facility. Therefore, if the required size is not obtained in the first shredding step, the material must be treated further. The crux of the matter is that additional processing is costly, reduces the recycler’s profit margins and, in the worst case, leads to customer complaints. To avoid these problems, Lindner’s patented SF synchronous fine cutting system is specifically designed based on the following two simple principles. Scissors and Archimedes’ Screw The easiest way to achieve smaller particles sizes would be to reduce the gap between the individual cutting tools. Conventional shaft pairs crush the material with rippers acting in parallel. If, in this case, the effective working range were extended, the amount of force required and thus the energy consumption would increase significantly. However, if the angle between the knives is changed, they act just like scissors, effectively applying force to a much smaller area. This massively increases the individual tools’ impact while maintaining the same energy consumption. Thanks to the ingenious arrangement of the knives, rippers and small blocks on Lindner’s SF cutting unit, the material is shredded up to four times in one pass. This results in smaller particles with a low percentage of fines. Since less force is needed, the shafts are subject to less stress, which in turn reduces maintenance and increases the cutting unit’s service life tremendously. If we now look closely at the entire shaft, we see that the cutting edges are not aligned in parallel. Thanks to this arrangement the two shafts act just like two Archimedean screws rotating in opposite directions. What the ancient Greeks used to transport water over great heights with the help of gravity, positively affects the way the shredding unit pulls in the material. This aggressive intake increases the throughput enormously and also mixes the final fraction once again for an output that is as homogeneous as possible. Lindner’s SF synchronous fine cutting system cuts the material twice in one pass thanks to its scissor action. Additionally, the chips are crushed twice more by the rippers. What needed to be proven Past experiences show that, with just one single pass, Lindner’s shredders from the Urraco or Miura series equipped with these tools produce a standardised P100 particle size according to ISO 17225-1 with less than 4 % fines during waste wood shredding. This standard basically describes in detail the percentages to be achieved as well as maximum specifications for the main fraction, oversized particles and fines. During the production of these standardised particles, depending on the configuration, Lindner’s extremely efficient twin-shaft shredders achieve 20 up to 120 metric tons per hour ‐ an incredible result. www.lindner.com
