Furthering the process of single point incremental forming

U ovome je radu proveden niz istraživanja kako bi se utvrdio stabilni tehnološki proces izrade tankostjenih proizvoda tehnologijom inkrementalnog oblikovanja u jednoj točki (SPIF - single point incremental forming). Pretpostavljeno je da je moguće primijeniti tehnologiju inkrementalnog oblikovanja na tankostjeni lim. Istraživanja su provedena na čeličnome limu TS230 (broj čelika prema EN 10027-2 je W. nr. 1.0371) debljine 0,155 mm i na limu TH415 (broj čelika prema EN 10027-2 je W. nr. 1.0377) debljine 0,24 mm s ciljem utvrđivanja optimalnih parametara u njihovoj obradi SPIF tehnologijom. Provedena su ispitivanja mehaničkih svojstava s ciljem utvrđivanja pouzdanosti ulaznih parametara kako bi se jasno definirala točnost izrade tražene geometrije krnjeg stošca pomoću SPIF procesa. Proveden je vlačni test kako bi se definirao konvencionalni dijagram naprezanje - deformacija, te Marciniak test kako bi se formirao dijagram deformabilnosti SPIF tehnologijom. Postavljeni su analitički modeli koji opisuju stanjivanje lima, kritične sile te pojavu trenja za ispitivane limove u SPIF procesu. Prema rezultatima analitičkog modela za izračun sile u SPIF procesu za tankostjene limove provedeno je ispitivanje trenja za odabrane materijale TS230 i TH415. Uzimajući u obzir rezultate vlačnoga testa i ispitivanja trenja postavljeni su uvjeti za modeliranje, analizu i simulaciju SPIF procesa u softveru ABAQUS. Za izradu modela odabran je oblik krnjeg stošca, simulacije su provedene kako bi se utvrdili uvjeti izrade uspješnog SPIF procesa za materijal TS230 i TH415. Na temelju prikupljenih podataka postavljen je plan eksperimenata za istraživanje u realnim proizvodnim uvjetima te je pristupljeno eksperimentalnoj verifikaciji modela. Odabran je CNC stroj, CNC-glodalica WEMAS VZ 750, te je projektirana specijalna radna naprava te su odabrani alati za inkrementalno oblikovanje. Postavljeni su modeli za izvedbu SPIF procesa na odabranom stroju pomoću softvera Solidcam i VeriCUT. Prema dobivenim spoznajama izveden je eksperimentalni plan izrade krnjeg stošca kako bi se utvrdilo funkcioniranje modela. Nakon uspješno izvedenog SPIF procesa i utvrđivanja optimalnih parametara obrade, postavljen je eksperimentalni plan mjerenja stanjivanja lima, ponovljivosti oblika te sposobnosti izvedenog inkrementalnog oblikovanja. Sposobnost inkrementalnog oblikovanja tankostjenog lima mjerena je metodom 3D fotogrametrije (digitalizacijski sustav ARGUS), a dobiveni su rezultati uspoređeni sa dobivenim rezultatima Marciniak ispitivanja. Sustavom 3D fotogrametrije kontrolirana je ponovljivost oblika i stanjivanje tankostjenog lima. Ustanovljena je maksimalna sposobnost inkrementalnog oblikovanja za ispitivane materijale s oblikom krnjeg stošca. Objašnjeni su parametri koji uvjetuju uspješnu obradu SPIF procesom tankostjenog materijala. Izvršena su dodatna mjerenja tvrdoće, hrapavosti i topline.In this work series of investigations were conducted in order to establish a stable technological process of manufacturing tinplate products with single point incremental forming technology (SPIF). In beginning of investigation it was assumed that SPIF technology is applicable on thin sheet metal. Investigations were conducted on two materials steel tinplate TS230 (W. nr. 1.0371 according to EN 10027-2) thickness of 0.155 mm and steel tinplate TH415 (W. nr. 1.0377 according to EN 10027-2) thickness of 0.24 mm with the goal of establishing optimal parameters in their manufacture with SPIF technology. Investigation of mechanical properties will be conducted with the goal to establish reliable input parameters in order to clearly define the accuracy of investigated truncated cone dimensions with SPIF process. A tensile test was conducted in order to define material stress - strain curve and Marciniak investigation in order to create forming limit diagram (FLD) for SPIF technology. Analytical models were defined in order to describe effect of sheet metal thinning, defining critical force and friction for investigated sheet metal in SPIF process. Friction investigation was conducted for materials TS230 and TH415 according to results obtained from analytical model for defining critical forces in SPIF process for thin sheet metals. Considering obtained results of tensile and friction investigation conditions for modelling, analysis and simulation of SPIF process in ABAQUS software are obtained. A truncated cone was selected for model development, a series of simulations were conducted in order to establish conditions for successful SPIF process of selected materials TS230 and TH415. On the basis of collected data a plan of experiments for real production conditions was proposed and verification of proposed was conducted. The CNC machine, CNC milling machine WEMAS VZ 750 was selected, the special work holder and tooling necessary for SPIF process proposed and created. Models for execution of SPIF process on milling machine were selected with softer Solidcam and VeriCUT. According to acquired know-how an experimental plan for creation of truncated cone was executed in order to confirm functionality of developed model. After successful execution of SPIF process and confirmation of optimal working parameters an experimental plan was prepared in order to measure with 3D fotogrametry. Thinning of sheet metal, geometry shape repeatability and FLD were measured with 3D fotogrametry system ARGUS. FLD diagrams for material TS230 and TH415 for selected geometry shape of truncated cone was defined. Obtained FLD diagrams of SPIF process ware compared with obtained FLD diagrams of Marciniak investigation. Explanation of influential parameters that influence successful SPIF process of thin sheet metal is given. Additional measurements of hardness, roughness and heat were conducted