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Pri aditivnih tehnologijah na osnovi oblikovnega obločnega navarjanja s klasičnimi MIG/MAG postopki, je varilna šoba pritrjena na industrijskega robota ali na CNC stroj, ki jo med navarjanjem po programu premika v 3D prostoru. Za doseganje ustrezne geometrije depozita, mora biti medvarkovna temperatura ustrezno nizka. S tem namenom je razvit krmilnik temperature, ki temelji na IR temperaturnem senzorju. CNC krmilnik je povezan z varilnim virom in krmilnikom temperature. Razvito je krmiljenje celotnega sistema. Za hitrejše ohlajanje objekta je dodan tudi elektromagnetni pnevmatski ventil, s katerim se avtomatsko vklaplja prisilno hlajenje s komprimiranim zrakom. Učinek hlajenja s komprimiranim zrakom je testiran z navarjevanjem ravnih sten. Učinkovit je predvsem pri izdelavi višjih objektov s kratkimi zvari oz. pri manjših izdelkih. Sistem je bil testiran tudi z izdelavo lupinskih objektov. Pri tem velik izziv predstavlja predvsem doseganje konsistentnih vžigov varilnega obloka. Izkaže se, da so nekonsistentni vžigi eden od glavnih dejavnikov za pojav napak na izdelku in za posledično odstopanje geometrije izdelka od predpisane. Wire and Arc Additive Manufacturing is a manufacturing process where welding torch is used together with a robot arm or other CNC manipulator to produce parts. During weld cladding, the torch is moved in 3D space according to the CNC program. To achieve a desired geometry of the weld bead when making small size parts, previously deposited weld has to be cooled down beneath a certain temperature. For that reason, temperature controller based on an IR thermometer was developed. Temperature controller and welding source communicate with the CNC controller, which is responsible for coordinated operation of the system. Custom control programs had to be developed. To remove excess heat from the welded part faster, automated cooling with compressed air was added to the system. Cooling effectiveness was evaluated by manufacturing multiple vertical walls. The results show that such cooling is especially effective when welding high parts with short welding trajectories. Welding system was also tested by welding different shell objects. It turns out that inconsistent ignitions of the welding arc can drastically effect the quality of the welded part. They are one of the main reasons for surface defects that also lead to deviations in the welded part geometry from the programmed geometry. |
