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1

Investigation of the suitability of a fused filament fabricated tool for incremental sheet metal forming

Weise Dieter, Langner Christian, Pierer Alexander, Kraeusel Verena, Petru Jana, Koziorek Jiri, Prauzek Michal

Computer Methods in Materials Science

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2023

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Vol. 23, No. 1

43--49

EN

Incremental sheet forming (ISF) is a flexible manufacturing process for sheet metal parts in small to medium quantities. Successive movements of a stylus create the geometry of the sheet metal part. ISF can be performed with or without a counter tool. By using counter tools, the geometry deviation of the formed sheet metal part can be reduced. To achieve the broader application of ISF, counter tools must be cost-effective, fast, and individually producible, even for batch sizes of only one part. In addition to milling, which has been the main method used to date, additive manufacturing (AM) also makes it possible to meet these requirements for flexible counter tool production. To investigate the suitability of AM for the production of counter tools for the ISF and to learn more about the load on the counter tool, a cylindrical counter tool made of polylactic acid (PLA) was produced using the fused filament fabrication (FFF) process. This counter tool was used for the ISF of drawing steel. Based on the force measurement results, a first step towards suitability evaluation of 3D-printed counter tools for ISF was taken, and possibilities, as well as application limits for such counter tools were discussed.

2

Influence of input parameters on the coefficient of friction during incremental sheet forming of grade 5 titanium alloy

Szpunar Marcin, Szawara Paulina, Myśliwiec Piotr, Ostrowski Robert

Advances in Mechanical and Materials Engineering

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2023

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Vol. 40, nr 1

113-123

EN

This research paper focuses on investigating the influence of input parameters on the coefficient of friction (COF) during incremental sheet forming (ISF) of grade 5 titanium sheets. Titanium alloys are widely used in various industries due to their corrosion resistance and strength to weight ratio. ISF is a flexible and cost effective process for producing complex shapes. The aim of this study was to gain insight into the frictional conditions during ISF that affect formability, surface quality, and overall process performance. The experiments were carried out using a combination of MoS2 lubrication and friction stir rotation-assisted heating. COF was measured using a high precision piezoelectric dynamometer, taking into account axial and horizontal forces. A split-plot design was used and 25 runs were performed to obtain the COF for each run. The results of the study provide valuable information on the relationship between input parameters and COF, contributing to the understanding of the frictional conditions in the ISF.

PL

Niniejszy artykuł badawczy koncentruje się na badaniu wpływu parametrów wejściowych na współczynnik tarcia podczas przyrostowego formowania blach tytanowych grade 5. Stopy tytanu są szeroko stosowane w różnych gałęziach przemysłu ze względu na ich odporność na korozję i korzystny stosunek wytrzymałości do masy. Kształtowanie przyrostowe to elastyczny i opłacalny proces produkcji elementów o złożonych kształtach. Celem tego badania była analiza warunków tarcia podczas kształtowania przyrostowego, które wpływają na formowalność blachy, jakość powierzchni i ogólną wydajność procesu. Eksperymenty przeprowadzono przy użyciu kombinacji smarowania MoS2 i ogrzewania materiału blachy wspomaganego obrotami narzędzia. Wartość współczynnika tarcia wyznaczono na podstawie składowych siły kształtowania (siły osiowej i sił poziomych), które mierzono za pomocą precyzyjnego dynamometru piezoelektrycznego. Zastosowano plan split-plot i wykonano 25 prób w celu uzyskania wartości współczynnika dla każdej z nich. Wyniki badania dostarczają cennych informacji na temat związku między parametrami wejściowymi a współczynnikiem tarcia, przyczyniając się do zrozumienia warunków tarcia występujących podczas kształtowania przyrostowego.

3

Shape accuracy in single point incremental forming of conical frustums from titanium CP2 sheets

Szpunar Marcin, Balcerzak Maciej, Żaba Krzysztof

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

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2022

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z. 94

63--75

EN

This paper presents frustum cone drawpiece analysis made of titanium CP2 sheet by a single incremental sheet forming. Central composite design has been adopted to carry out an experiment containing 20 runs, then multi-criteria parameter optimization has been done. Optimal parameters have been validated and responses deviations do not exceed 4% compared to created models. For the drawpiece formed with optimal parameters, AGRUS optical measurement and X-ray tomography has been applied to check the obtained of the part wall thickness and general deviations compared to the CAD model. The wall angle discrepancy of the cone generatrix has also been analyzed. No gaps or ruptures have been confirmed by X-ray. The blank rolling direction has a significant effect on the drawpiece deviations. The measurement results showed deviations of the drawpiece wall angle +0.27°/- 0.06°, sheet thickness on the cone +0.012/-0.04 mm and +0.151/-0.096 mm from the reference CAD geometry.

PL

W pracy przedstawiono analizę wytłoczek w kształcie stożka ściętego wykonanego z blachy tytanowej CP2 metodą jednopunktowego przyrostowego kształtowania. Do przeprowadzenia eksperymentu obejmującego 20 przebiegów przyjęto centralny plan kompozycyjny, następnie dokonano wielokryterialnej optymalizacji parametrów. Dokonano walidacji optymalnych parametrów, a uzyskane wyniki nie przekraczają 4% w odniesieniu do stworzonych modeli. Dla wytłoczki uformowanej z optymalnymi parametrami zastosowano pomiar optyczny AGRUS oraz tomografię rentgenowską w celu sprawdzenia uzyskanej grubości ścianki wytłoczki i odchyłek w porównaniu z modelem CAD. Przeanalizowano również rozbieżność kątów ścian tworzących stożka. Za pomocą skanu rentgenowskiego potwierdzono brak szczelin i pęknięć wytłoczki. Kierunek walcowania półfabrykatu ma istotny wpływ na odchyłki. Wyniki pomiarów wykazały odchylenia kąta ścianki wytłoczki +0,27/-0,06°, grubości ścianki na stożku +0.012/-0.04 mm oraz +0.151/-0.096 mm od geometrii referencyjnej CAD.

4

Research on Forming Parameters Optimization of Incremental Sheet Forming Process for Commercially Pure Titanium Grade 2 Sheets

Szpunar Marcin, Trzepieciński Tomasz, Ostrowski Robert, Zwolak Marek

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 4

1411--1418

EN

This study aims to determine optimal forming parameters for Incremental Sheet Forming process Commercially Pure titanium Grade 2 sheets in terms of formability improvement, force reduction, and efficiency of forming. Based on the central composite design, data were collected during 20 runs and then variation analysis was performed. The experiments were performed on a 3 axis CNC milling machine equipped with a Kistler dynamometer plate. Subsequently, regression models have been developed to describe process responses by input factors. As crucial parameters, the relative velocity and step size of the tool that affect the forming force and the height of the fracture have been determined. Finally, the application of optimization algorithm has emerged optimal input factors in terms of selected multi-criteria goal. The results of this study suggest that there is a process window that allows the formation of 45° wall angle drawpieces of commercially pure titanium Grade 2.

5

Manufacture of Bead-Stiffened Panels Using the Single Point Incremental Sheet Forming Technique

Krasowski Bogdan, Kubit Andrzej, Trzepieciński Tomasz, Slota Jan

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 4

1305--1314

EN

This paper presents the results of experimental research on the fabrication of thin-walled panels with longitudinal stiffening ribs by the single point incremental sheet forming technique. The bead-stiffened panels were made of Alclad 2024-T3 aluminium alloy sheets commonly used in aircraft structures. The influence of forming parameters and tool strategy on surface quality and the possibility of obtaining stiffening ribs with the required profile and depth was tested through experimental research. Two tool path strategies, spiral with continuous sinking and multi-step z-level contouring, were considered. The results of the experiments were used to verify the finite element-based numerical simulations of the incremental forming process. It was found that the main parameter which influences the formability of test sheets is the tool path strategy; the tool path strategy with multi-step z-level contouring allowed the rib to be formed to a depth of 3.53 mm without risk of cracking. However a greater depth of rib equal of 5.56 mm was achieved with the continuous tool path. The tool path strategy was also the main parameter influencing the surface finish of the drawpiece during the single point incremental forming process.

6

Investigating the capability of the Lemaitre damage model to establish the incremental sheet forming process

Kumar Pavan, Tandon Puneet

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e66, 1--18

EN

This paper presents the numerical and experimental investigation of the incremental sheet forming (ISF) process with the Lemaitre damage model to incrementally form parts of conical shapes. The Lemaitre damage model was prepared as a material subroutine (VUMAT) and linked to Abaqus/Explicit. The elastic–plastic parameters for the simulation were identified through tensile testing of the ASTM E8 specimen. The digital image correlation (DIC) was performed during the tensile testing to identify the damage parameters of the Lemaitre damage model. Scanning electron microscopy (SEM)-based area method was used to identify the area fraction vis-a-vis the variation of the strain. Thereafter, the identified area fractions with respect to strains have been calibrated to obtain the damage parameters through an inverse analysis approach. The identified parameters were used to form conical objects of Al1050 H14 sheets of 2 mm thickness through finite element (FE) simulation. The results obtained through FE simulation were compared with the experimental outcomes to investigate the efficiency of the Lemaitre damage model to simulate the ISF process. The responses obtained through FE simulation and experiments have been discussed in terms of limiting wall angle and forming depth, damage evolution, deformation mechanism, forming limit diagram, geometrical accuracy, forming forces, thickness distribution, and surface roughness.

7

Właściwości przetłoczeń usztywniających kształtowanych w cienkich blachach z lotniczego stopu aluminium 2024-T3 metodą formowania przyrostowego

Kubit A., Wydrzyński D., Bucior M., Kluz R.

Technologia i Automatyzacja Montażu

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2018

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nr 4

28--32

PL

W pracy przedstawiono wyniki badań eksperymentalnych, dotyczących podłużnych przetłoczeń w cienkich blachach, pełniących rolę ryfli usztywniających. Zagadnienie dotyczy przetłoczeń kształtowanych w blachach z lotniczego stopu aluminium 2024-T3 obustronnie platerowanych, o grubości 0,4 mm. Przetłoczenia wykonano relatywnie nową technologią tzw. kształtowania przyrostowego, która polega na punktowym odkształcaniu materiału poprzez narzędzie w formie trzpienia stopniowo zagłębiane w materiale, zgodnie z określoną ścieżką determinującą kształt finalnego przetłoczenia. Formowanie prowadzono przy użyciu trzy-osiowej frezarki numerycznej stosując narzędzie o średnicy 6 mm z promieniem na czole o wartości R3. Kształtowano przetłoczenia o długości 120 mm oraz szerokości 20 mm. W ramach badań rozpatrywano różne głębokości przetłoczeń stopniując je co 1 mm w zakresie od 1 do 5 mm. Największą wartość głębokości o podanej wartości przyjęto, ponieważ przy większej głębokości od 5,5 mm kształtowana blacha ulegała pękaniu, dlatego wartość 5 mm uznano za maksymalną, dla której prowadzono analizy. Dla opisanych przetłoczeń przeprowadzono statyczne próby wyboczenia, a na ich podstawie stwierdzono, że głębokość przetłoczenia równa 4 mm, jest wartością krytyczną, gdyż siła wyboczenia dla przetłoczeń w zakresie od 1 do 4 mm wzrasta wprost proporcjonalnie do głębokości przetłoczenia, natomiast przy głębokości równej 5 mm siła ta ulega spadkowi.

EN

The paper presents the results of experimental research on longitudinal ribbing in thin sheets, made as stiffening ribs. The issue concerns ribbing formed in 2024-T3 aluminum alloy plates, 0.4 mm thick. The embossing was made using a relatively new technology, the so-called incremental sheet forming, which is a point of deformation of the material through the tool in the form of a plunger, gradually penetrated into the material in accordance with a defined path that determines the shape of the final embossing. Forming was carried out using a three-axis numerical milling machine using a 6 mm diameter tool with a head radius of R3. Embossments 120 mm long and 20 mm wide were formed. As part of the research, different depths of embossing were considered, grading them every 1 mm in the range from 1 to 5 mm. The highest value of the depth with the given value was assumed, because above the 5.5 mm depth the shaped sheet was cracking, so the value of 5 mm was considered the maximum for which the analyzes were carried out. For the described embossments static buckling tests were made, on the basis of which it was found that the embossing depth of 4 mm is a critical value, because the buckling force for extrusions in the range from 1 to 4 mm increases in direct proportion to the depth of the ribbing, while at a depth of 5 mm force this falls.

8

General overview of sheet incremental forming

Tisza M.

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 55, nr 1

113--120

EN

Purpose: The aim of this research paper is to give a general overview on sheet incremental forming as an emerging field in small and batch production. Design/methodology/approach: First the historical and literature background of sheet incremental forming will be given, and then some theoretical and practical issues of the incremental forming processes will be described including the research work done by the author at the University of Miskolc. This research is part of an international EUREKA project with the main focus on formability and accuracy in incremental sheet forming. Findings: In this research paper some important findings on the critical wall angle which is a characteristic formability feature in incremental sheet forming will be discussed. New specimen geometry was elaborated to reduce the great amount of experimental work to determine the formability limits. The main conclusions are that in incremental forming the formability is significantly higher compared to conventional sheet forming. The process is very flexible and economic due to the low tool costs. Research limitations/implications: One of the main target areas of further research work is the determination of technological window for sheet incremental forming of various materials and to introduce this novel process into industrial practice. Practical implications: In practical applications besides the economy of the process due to its very low tool expenses, the flexibility should be mentioned which is very important in small batch production and particularly in rapid prototyping. Originality/value: The results achieved within this research work are equally important both from the point of view of theoretical and practical aspects of sheet incremental forming.