Flexible Stretch Forming Technology for Sheet Metal Based on Discrete-Gripper and Multi-Point Die

To solve the problem of low material utilization in traditional stretch forming process, a flexible stretch forming method was proposed, which can be realized by interaction of the multi-point stretch forming die with discrete-gripper stretch forming machine. The principle and characteristics of sheet metal flexible stretch forming technology was introduced, structural composition and working principle of the multi-point stretch forming die and discrete-gripper stretch forming machine were expounded, and the technology experiments was carried out with a self-designed flexible stretch forming technology equipment for sheet metal. The experimental results indicate that structure of multi-point stretch forming die and discrete-gripper stretch forming machine are reasonable, and flexible stretch forming technology can be realized by above-mentioned die and machine, stretch forming parts has a good quality and its shape error can satisfy requirements of production.

Download Full-text

A New Stretch-Forming Process Based on Loading at Discrete Points and its Numerical Investigation

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.423-426.737 ◽

2013 ◽

Vol 423-426 ◽

pp. 737-740

Author(s):

Zhong Yi Cai ◽

Mi Wang ◽

Chao Jie Che

Keyword(s):

Sheet Metal ◽

Three Dimensional ◽

Discrete Point ◽

Stretch Forming ◽

Sheet Metal Part ◽

Metal Part ◽

Forming Process ◽

Loading Trajectory ◽

New Process ◽

Forming Defects

A new stretch-forming process based on discretely loading for three-dimensional sheet metal part is proposed and numerically investigated. The gripping jaw in traditional stretch-forming process is replaced by the discrete array of loading units, and the stretching load is applied at discrete points on the two ends of sheet metal. By controlling the loading trajectory at the each discrete point, an optimal stretch-forming process can be realized. The numerical results on the new stretch-forming process of a saddle-shaped sheet metal part show that the distribution of the deformation on the formed surface of new process is more uniform than that of traditional stretch-forming, and the forming defects can be avoided and better forming quality will be obtained.

Download Full-text

Comparison between an Advanced Numerical Simulation of Sheet Incremental Forming Using Adaptive Remeshing and Experimental Results

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.554-557.1375 ◽

2013 ◽

Vol 554-557 ◽

pp. 1375-1381 ◽

Cited By ~ 5

Author(s):

Laurence Giraud-Moreau ◽

Abel Cherouat ◽

Jie Zhang ◽

Houman Borouchaki

Keyword(s):

Numerical Simulation ◽

Numerical Model ◽

Sheet Metal ◽

Metal Forming ◽

Tool Path ◽

Incremental Forming ◽

Computation Time ◽

Experimental Results ◽

Forming Process ◽

Adaptive Remeshing

Recently, new sheet metal forming technique, incremental forming has been introduced. It is based on using a single spherical tool, which is moved along CNC controlled tool path. During the incremental forming process, the sheet blank is fixed in sheet holder. The tool follows a certain tool path and progressively deforms the sheet. Nowadays, numerical simulations of metal forming are widely used by industry to predict the geometry of the part, stresses and strain during the forming process. Because incremental forming is a dieless process, it is perfectly suited for prototyping and small volume production [1, 2]. On the other hand, this process is very slow and therefore it can only be used when a slow series production is required. As the sheet incremental forming process is an emerging process which has a high industrial interest, scientific efforts are required in order to optimize the process and to increase the knowledge of this process through experimental studies and the development of accurate simulation models. In this paper, a comparison between numerical simulation and experimental results is realized in order to assess the suitability of the numerical model. The experimental investigation is realized using a three-axis CNC milling machine. The forming tool consists in a cylindrical rotating punch with a hemispherical head. A subroutine has been developed to describe the tool path from CAM procedure. A numerical model has been developed to simulate the sheet incremental forming process. The finite element code Abaqus explicit has been used. The simulation of the incremental forming process stays a complex task and the computation time is often prohibitive for many reasons. During this simulation, the blank is deformed by a sequence of small increments that requires many numerical increments to be performed. Moreover, the size of the tool diameter is generally very small compared to the size of the metal sheet and thus the contact zone between the tool and the sheet is limited. As the tool deforms almost every part of the sheet, small elements are required everywhere in the sheet resulting in a very high computation time. In this paper, an adaptive remeshing method has been used to simulate the incremental forming process. This strategy, based on adaptive refinement and coarsening procedures avoids having an initially fine mesh, resulting in an enormous computing time. Experiments have been carried out using aluminum alloy sheets. The final geometrical shape and the thickness profile have been measured and compared with the numerical results. These measurements have allowed validating the proposed numerical model. References [1] M. Yamashita, M. Grotoh, S.-Y. Atsumi, Numerical simulation of incremental forming of sheet metal, J. Processing Technology, No. 199 (2008), p. 163 172. [2] C. Henrard, A.M. Hbraken, A. Szekeres, J.R. Duflou, S. He, P. Van Houtte, Comparison of FEM Simulations for the Incremental Forming Process, Advanced Materials Research, 6-8 (2005), p. 533-542.

Download Full-text

Principle and Simulation Study on Multi Point-Single Point Incremental Combined Forming for Sheet Metal

Materials Science Forum ◽

10.4028/www.scientific.net/msf.626-627.273 ◽

2009 ◽

Vol 626-627 ◽

pp. 273-278 ◽

Cited By ~ 1

Author(s):

X.J. Li ◽

Ming Zhe Li ◽

C.G. Liu ◽

Zhong Yr Cai

Keyword(s):

Sheet Metal ◽

Single Point ◽

Experimental Result ◽

Work Piece ◽

The Novel ◽

Forming Process ◽

Explicit Finite Element ◽

Forming Defect ◽

Forming Technology ◽

Elastic Cushion

Based on Multi-Point (MP) forming technology and Single-Point Incremental (SPI) forming technology, MP-SPI combined forming method for sheet metal is proposed, the principle and two different forming techniques are illustrated firstly. Then the paper is focused on numerical analysis for the novel forming technique with explicit Finite Element (FE) algorithm. During simulation of spherical work-piece, dimpling occurs as a main forming defect in MP-SPI combined forming process. Simulation results show that the dimpling defect can be suppressed effectively by using elastic cushion. An appropriate thickness of elastic cushion is necessary to prevent dimpling. And also the deformation of the work-piece is sensitive to the shape of elastic cushion. The combined forming test shows that the numerical simulation result is closed to the experimental result.

Download Full-text

The Effect of Swinging Ball Heads with Different Arrangements in Multi-Point Stretch-Forming Process

Materials ◽

10.3390/ma12030337 ◽

2019 ◽

Vol 12 (3) ◽

pp. 337 ◽

Cited By ~ 1

Author(s):

Jian Xing ◽

Yan-yan Cheng ◽

Zhuo Yi

Keyword(s):

Numerical Simulation ◽

Finite Element ◽

Sheet Metal ◽

Strain Distribution ◽

Finite Element Models ◽

Stretch Forming ◽

Forming Process ◽

Forming Quality ◽

Staggered Arrangement ◽

Simulation Results

To improve the effect of multi-point stretch forming of sheet metal, it is proposed in this paper to replace a fixed ball head with a swinging ball head. According to the multi-point dies with different arrangements, this research establishes finite element models of the following stretch forming, i.e., fixed ball heads with conventional arrangement, swinging ball heads with conventional arrangement, swinging ball heads with declining staggered arrangement, and swinging ball heads with parallel staggered arrangement, and then numerical simulation is performed. The simulation results show that by replacing a fixed ball head with a swinging ball head, the surface indentation of the part formed was effectively suppressed, the stress and tension strain distribution of the part formed was improved, and the forming quality was improved; the thickness of the elastic pad was reduced, the springback was reduced and the forming accuracy was improved; and when the ball head was applied to a multi-point die with staggered arrangement, a better forming result was achieved, where the best forming result was achieved in combining the swinging ball heads with the multi-point die with a parallel staggered arrangement. Forming experiments were carried out, and the experimental results were consistent with the trend of numerical simulation results, which verified the correctness of the numerical simulation.

Download Full-text

TENDENCIES IN FORMING SHEET METAL PARTS USING INCREMENTAL FORMING ADVANCED TECHNOLOGIES

Journal of Engineering Studies and Research ◽

10.29081/jesr.v25i3.327 ◽

2019 ◽

Vol 25 (3) ◽

Author(s):

CATALINA CIOFU ◽

BOGDAN CHIRITA ◽

ROXANA LUPU ◽

COSMIN GRIGORAS ◽

CRINA RADU ◽

...

Keyword(s):

Sheet Metal ◽

Incremental Forming ◽

Stretch Forming ◽

Micro Forming ◽

Forming Process ◽

Metal Parts ◽

Sheet Metal Parts ◽

Advanced Technologies ◽

Metal Materials ◽

Forming Methods

Stretch forming of sheet metal materials is a highly required process in aerospace industry for manufacturing skin parts. Automation of some processes such as cutting, punching, forming, shearing and nesting in conventional manufacturing tends to combine these forming methods. Some researches are made on the formability of sheet metal materials obtained in incremental forming process with stretch forming and water jet incremental micro-forming with supporting dies. This paper is an attempt to review the newly researches made on optimization of manufacturing metal skin parts to achieve geometrical accuracy.

Download Full-text

Study on the Surface Quality of Fender NC Incremental Forming

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.335-336.523 ◽

2011 ◽

Vol 335-336 ◽

pp. 523-526

Author(s):

Liu Ru Zhou

Keyword(s):

Sheet Metal ◽

Sheet Metal Forming ◽

Metal Forming ◽

Process Time ◽

Forming Process ◽

Forming Technology ◽

Starting Point ◽

Incremental Sheet Metal Forming ◽

Metal Deformation ◽

Improvement Method

The NC incremental sheet metal forming technology is a flexible forming technology without dedicated forming dies. The forming locus of the forming tool can be adjusted by correcting the numerical model of the product. Because the deformation of sheet metal only occurs around the tool head and the deformed region is subjected to stretch deformation, the deformed region of sheet metal thins, and surface area increases. Sheet metal forming stepwise is to lead to the whole sheet metal deformation. The principle of NC incremental sheet metal forming and the forming process of the fender are introduced. The effect of process parameters on forming is analysed. The improvement method of the forming quality is suggested. The groove is created in the starting point of tool moving when the starting point of tool moving locus at all layers is identical. The groove can be eliminated when the starting point of tool moving locus at all layers is different. The feed pitch p increase, the process time decrease, production rate and surface degree of roughness increase. In general, the feed pitch is 0.25mm.

Download Full-text

Tool Path Design of the Counter Single Point Incremental Forming Process to Decrease Shape Error

Materials ◽

10.3390/ma13214719 ◽

2020 ◽

Vol 13 (21) ◽

pp. 4719

Author(s):

Kyu-Seok Jung ◽

Jae-Hyeong Yu ◽

Wan-Jin Chung ◽

Chang-Whan Lee

Keyword(s):

Sheet Metal ◽

Tool Path ◽

Incremental Forming ◽

Single Point ◽

Optimization Method ◽

Single Point Incremental Forming ◽

Shape Error ◽

Forming Process ◽

Two Stage ◽

Shape Errors

Incremental sheet metal forming can manufacture various sheet metal products without a dedicated punch and die set. In this study, we developed a two-stage incremental forming process to decrease shape errors in the conventional incremental forming process. The forming process was classified into the first single point incremental forming (1st SPIF) process for forming a product and the counter single point incremental forming (counter SPIF) process to decrease shape error. The counter SPIF gives bending deformation in the opposite direction. Furthermore, the counter SPIF compensates for shape errors, such as section deflection, skirt spring-back, final forming height, and round. The tool path of the counter SPIF has been optimized through a relatively simple optimization method by modifying the tool path of the previous step. The tool path of the 1st SPIF depends on the geometry of the product. An experiment was performed to form a circular cup shape to verify the proposed tool path of the 1st and counter SPIF. The result confirmed that the shape error decreased when compared to the conventional SPIF. For the application, the ship-hull geometry was adopted. Experimental results demonstrated the feasibility of the two-stage incremental forming process.

Download Full-text

Statistical Study on Correlation between Design Variables and Shape Errors in Flexible Stretch Forming Process

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.652-654.1994 ◽

2013 ◽

Vol 652-654 ◽

pp. 1994-2001

Author(s):

Young Ho Seo ◽

Jun Seok Yoon ◽

Beom Soo Kang ◽

Jeong Kim

Keyword(s):

Material Behavior ◽

Radius Of Curvature ◽

Curvature Radius ◽

Regression Equations ◽

Shape Error ◽

Stretch Forming ◽

Forming Process ◽

Tensile Direction ◽

Design Variables ◽

Shape Errors

In order to reduce the elastic recovery of a sheet material and eliminate a great number of solid dies used in the forming process of various shapes, a flexible stretch forming process (FSFP) is considered in this study. Especially, the relationship among design variables, such as the punch size, objective radius of curvature, and elastic pad thickness is quantitatively evaluated to find out their respective influences on the shape errors of a formed sheet plate using the statistical method based on the FE simulation result planned by the three-way factorial design. The shape errors are divided into two types based on the material behavior according to the widthwise- and tensile- directions. The correlations of the shape errors and the design variables are estimated through the Pearson correlation analyses. The punch size has a strong positive linear correlation with the widthwise- and tensile- shape errors, and the correlation between the objective curvature radius and tensile-direction shape error is weak and negative. Although the effect of the elastic pad thickness is less than those of the other variables, it prevents effectively surface defects. Subsequently, the mathematical model is assumed to clarify their relationship. Two regression equations are estimated in terms of the design variables regarding the widthwise- and tensile- shape errors. The shape errors could be inferred by the assumed model in the particular combination of the design variables; then, the acceptable punch size and elastic pad thickness can be determined according to the objective curvature radius.

Download Full-text