TPT September 2022

AR T I C L E

ISTech

overheating of certain parts of the machinery; to overcome this problem, minimal lubrication systems can be studied or, alternatively, the sawing machine can be designed with materials able to withstand high temperatures without losing efficiency. For certain uses where the use of liquids is not possible due to the complexity of decontaminating the waste, such as nuclear power plants, air cooling systems can also be studied. Other arrangements can be studied to optimise cutting efficiency and quality in the case of very delicate materials such as chromium-plated metals. In addition to the hardness of the material, the size of the workpieces to be machined can also lead to different design choices. In the case of automated systems, which cut large workpieces, the automatic loading of bars is certainly a great advantage, but if in the morning operators have to unload all the production of the previous shift, they can take hours, not to mention the hard work. An in-depth study of the process of unmanned plants also allows the unloading and palletising of cut pieces to be automated; the operator thus finds everything in order and proceeds to the next machining operation seamlessly. The reliability of cutting times is much greater and the company is able to meet last-minute requests on time, with an excellent return in terms of image as well. Depending on whether the focus of production is on cutting speed, the ability to handle the transport of even very heavy bars, or other aspects, the adjustments to be made in the design of the system will lead to machines which, although similar at first glance, in reality incorporate very different technologies, customised for each situation. In the case of particularly difficult machining operations, in order to preserve materials from damage, which could be caused by cutting errors, the plant may be equipped with automatic systems to stop machining before the damage occurs, so as to minimise waste and maximise the efficiency of the production process. If the cut pieces have to meet particularly stringent quality requirements, the adoption of sensors can safeguard the quality of the processing: for example, laser measurement systems allow the positioning of the piece by checking its size and congruence with the cut and stopping the machinery in the event of deviations beyond a predetermined limit. The elements of the sawing machine What are the main elements of the sawing machine and what characteristics of these elements can influence the performance of the finished system? Let us start with the base frame: the study of this part of the sawing machine is very important as this is where chip management takes place. In high-speed cutting systems, where chip generation is very intense, studying a base that allows the chips to be conveyed to disposal in an efficient manner is fundamental. Sliding columns are also fundamental to give solidity and rigidity to the cutting head: compared to linear guides, double columns of large dimensions made of chrome-plated metal minimise

customisation of the software is fundamental; for plants, in addition to the IT aspect, it is also important to customise the mechanical solutions for the management of incoming and outgoing material. For sawing machines intended for unmanned use, it will be crucial to automate process control activities as far as possible. For this reason, it is important to include sensors in the design phase to verify that the process is stable. A blade deviation sensor, which allows the quality of the cut to be evaluated during the process, will, for example, avoid cuts which do not conform to quality standards, correcting and self-adjusting; if the deviation proves impossible to correct without operator intervention, the sensor will interrupt the cut, avoiding the creation of non-conforming pieces, which would entail a waste of the metal being processed. Other sensors (unloading cells) evaluate the cutting pressure; it is also possible to check the power absorption of the blade motor. If these parameters are exceeded, the machine is able to introduce corrective measures, signal the anomaly or, in the event of a deviation that could damage the workpieces, interrupt the process. Another aid in the case of unmanned machining is the automation of the positioning of the motorised chip cleaning brush. The brush is subject to wear; a fixed positioning would mean a very rapid reduction in effectiveness, but the automated positioning system brings the brush closer to the teeth of the blade as the brush itself wears down, keeping the cleaning constantly accurate. The ideal solution The characteristics of sawing machines also vary, of course, depending on the material to be processed predominantly or exclusively. For aluminium, for instance, cutting is much faster than for stronger materials; therefore, the gearbox first of all changes, but not just that. The cutting speed means that considerably more swarf will be generated in a given time frame, so the chip conveyor is designed with a higher capacity. Furthermore, aluminium being the light metal par excellence, it produces chips which float; the coolant filter system must therefore be designed with this in mind. If the material to be machined is cast iron, cutting generally takes place without the aid of coolants, but this can lead to

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SEPTEMBER 2022