Fig 2 - uploaded by Zygmunt Mikno
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Simplified diagram of primary inverter welding machine circuits. where-NR-network rectifier,-I – inverter,-CS-current sensor (Rogowski coil),-F-electrode force.
Source publication
This article is concerned with controlling a servomechanical force system applied in the joining of thin-walled metal elements when manufacturing e.g. car bodies. The new, i.e. servomechanical electrode force control system is both an element and a parameter of a technology used for joining metal elements by means of resistance welding. The project...
Contexts in source publication
Context 1
... use of a servomotor (instead of a pneumatic actuator) as the electrode force system decreases the weight of the force-exerting element by approximately 50%. Moreover, the use of a high frequency inverter (10kHz), due to its location outside the mobile part of the welding machine, enables the reduction of the transformer weight by almost 50% (see Fig. ...
Context 2
... control should lead to the optimisation of welding power spatial distribution in the welding area and, consequently, to the improvement of welded joint quality. Figure 2 presents a simplified diagram of inverter welding machine circuits and units, i.e. i) three-phase input rectifier (D 1 D 6 ) with a capacitive filter (C f ), ii) inverter (T 1 T 4 ) based on IGBT transistors, iii) transformer (Tr) with an output rectifier (D 7 , D 8 ) and iv) electrodes with a pneumatic actuator/servomotor. The operation of the inverter is monitored by a related control system. ...
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... pre-set quantity (i.e. the control of electrode travel instead of electrode force (particularly during the flow of welding current) enabled the obtainment of very advantageous changes. As a result, the distribution of temperature in the welding area was significantly more convenient (Fig. 6b), particularly at the beginning of the welding process (Fig. 6b2). Also, the time of projection height reduction during the flow of current was conveniently extended (Fig. 4). Figure 7b below presents the profile of electrode travel (i.e. the pre-set quantity). As a result of the new approach to the control of the process, it was possible to obtain the profile of force. Fig. 7. FEM calculation ...
Context 4
... (Fig. 5a) and power density in the contact area during welding were higher. As a result, the power and energy in the whole welding area were higher as well. Consequently, the projection material underwent melting in the most convenient place, i.e. in the projection cap (Fig. 8b); the weld nugget was initiated in the centre and grew outwards ( Fig. 6 ...
Context 5
... second step of the optimisation (Fig. 10, step 2) consisted in changing the manner of electrode control. The control of electrode force was "replaced" by the control of electrode travel. The determination of welding process parameters applied during the flow of welding current was followed by the determination of profile "B" of electrode travel. The electrode travel profile "B" was ...
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Citations
... In a study carried out by Singh and Vijayakumar [5], the impact of welding current, the number of cycles, hold time and cooling time parameters on the amount of dent, an indicator of welding quality defined in terms of the resistance, nugget size and penetration of AISI 301L stainless steel sheet in point welding, was investigated by Taguchi method, and the mentioned parameters were optimized. Mikno et al. [6] examined the movement of welding machine electrodes and controlling the force they exert by servo-mechanical system. In a recent study, Kong and Kang [7] investigated the effect of alloying elements on expulsion limit current in electric resistance spot welding (RSW) of advanced high-strength steel. ...
A new Mamdani-type fuzzy inference system with four input variables such as weld current, electrode force, a transformed variable of weld time + sheet thickness, and projection height was proposed for both DC 04 and DP 600 steel sheets to predict the degree of expulsion and spattering (conjugate) index (E) and the maximum push-out load of weld (weld strength) (Fk) in projection welding. In the computational analysis, trapezoidal membership functions were constructed for the fuzzy subsets of each model variable. The product (prod) and the center of gravity (centroid) methods were implemented as the built-in AND method and defuzzification method, respectively. Fuzzy logic outputs were compared with the predictions of multiple regression analysis-based models derived within the scope of this work. Model performances were quantified by means of various statistical performance parameters. Linear regressions between the outputs of the fuzzy logic model and the experimentally measured values yielded very high determination coefficients (R² = 0.967 − 0.994). The well-correlated results reveal applicability of the fuzzy logic model for predicting the expulsion and spattering (conjugate) index, and weld strength, as well as determining the optimal combination of the process parameters to conduct the projection welding operations resulted in desired weld quality.
... Practically it is n1:1 ratio, where the secondary is single turn winding or multiple turns connected in parallel. Additionally transformers have two secondaries connected to two diode rectifier [4]. Such specific operation and design causes that proposed transformers and results of their analysis have been reported in literature very occasionally and selectively. ...
... The criterion of the optimization has been assumed as the same full weld nugget diameter and weld strength as those obtained using the pneumatic force system [20]. ...
The paper is focused on the control of resistance projection welding process applied in joining of thin-walled metal elements. The motion of electrode is generated by electric servo actuator that controls the force exerted on electrode or alternatively, just travel itself of electrode. The projection welding has been discussed for welding of 1.5 mm thick DX53 steel sheets where one sheet contains an embossed projection. Apart of electric servo actuator, another source of force has been described, i.e. pneumatic actuator (classical one), for the reason of comparison. The solution where the electric servo operates together with appropriate algorithm makes the new solution that is alternative for classical, pneumatic one. Optimized motion of electrode due to new proposed source of electrode force or/and travel, based on relevant algorithm yields improved quality of joints.
