A IMPLEMENTATION OF A SAFETY SYSTEM FOR A REBAR UNCOILING MACHINE WITH INTEGRATION OF AN AUTOMATED PRODUCTION COUNTING SYSTEM

Resumo

This study presents the retrofit of an AVAKORT AK 12 rebar decoiling machine, including production-control automation and a functional evaluation of protective measures. The objective was to modernize the control system, incorporate guards and interlocks intended to reduce operator exposure to crushing hazards in the traction and straightening areas, and automate the counting of cut rebar pieces. The solution integrated a Delta TP04P-32TP1R Programmable Logic Controller (PLC), an integrated Human-Machine Interface (HMI), a PNP inductive sensor, four flexible-stem limit switches, a latching emergency-stop pushbutton, contactors, and mechanical guards. The methodology consisted of applied and experimental research involving equipment characterization, identification of the main hazards, implementation of protective measures, and operational tests. Counting performance was evaluated in five tests with programmed quantities of 5, 10, 15, 20, and 25 pieces, totaling 75. A total of 71 pieces were counted, corresponding to an overall correct-count rate of 94.67%; the mean correct-count rate across tests was 95.87%, with a standard deviation of 4.33 percentage points. Functional tests of the protective measures indicated a mean complete physical stopping time of 450 ms, measured with a mobile-phone stopwatch. Available speed records indicated that the mean values for diameters of 6, 9, and 12 mm changed from 4.0 to 5.2 m/min, from 3.5 to 4.5 m/min, and from 2.8 to 3.64 m/min, respectively, corresponding to increases of 30.0%, 28.6%, and 30.0%. The results indicate that the retrofit integrated protective measures, production control, and operational improvement under the evaluated conditions. However, they do not support claims of full compliance with safety standards or economic feasibility because no formal assessment of the required safety category or performance level and no cost analysis were conducted.