Rapid Prototyping for Sheet Metal Products DOI: http://dx.doi.org/10.5772/intechopen.88435

main drawback of this testing method. Therefore, considerable effort has been made to obtain FLCs theoretically. Swift [17] can be recognized as a pioneering study on predicting FLC. Hill [18] then proposed a way to improve the accuracy of FLC prediction by adopting necking point criteria. Stören and Rice [19] developed a solution for FLC prediction by applying a force equilibrium between necking and uniform deformed regions. Banabic et al. [20] observed and developed a pre-defect

Experiments of incremental forming for various square shape sizes with (a) 80° wall angle, (b) 85° wall angle,

Obtained forming limit based on the maximum wall angle versus maximum deformed height [18].

in the material and developed a theory of limited deformation based on

Figure 15.

Figure 16.

110

and (c) 60° wall angle.

Mass Production Processes

imperfections of material thickness. Hora et al. [21] upgraded the Swift diffuse necking criteria and set a modified maximum force criterion (MMFC) by effectively examining the instant deformation state changes until the forming force achieved a maximum value. Some new MMFC models proposed to improve the accuracy of FLC prediction based on theoretical models by solving systems of

Figure 17. Simulation and rapid prototyping of complex surfaces. (a) Intermediate deformations, and (b) Final shape.

equations. Currently, the finite element (FE) simulation is an indispensable tool to research, evaluate, and discern physical phenomena modeled by various theoretical and experimental equations. However, the current FLC curves are inconsistent with the experimental results in ISMF. To improve the fitting of experimental data with numerical data, Nguyen and Kim [22] upgraded and introduced Swift's equation to MMFC and predict FLD curve for cold rolled steel material. They imported obtained forming limit diagram curves to FEM software [23] in order to predict fractures of various square shapes and compare them with corresponding experimental results. In order to verify the effect of tool dimension on FLD at fracture, ductile fracture criterion of Clift et al. [4] should be adopted to predict FLC, simulated and confirmed by corresponding experimental results. After experimentally verified, FLC data were used to simulate different square sizes to show the effect of the wall angle to the maximum height of the square shape and established limits of formability based on the relationship between the maximum destructive height and the corresponding wall angle (Figures 15 and 16). The obtained limit curves could be used to indicate the failure of sound products through the relationship between the wall angles and corresponding maximum height of complex shapes for ISMF process.

3.4 Rapid prototyping application to complex surface products

• To accommodate with working space of CNC machine

corresponding to the forming height

possible to conduct a simulation beforehand to check.

prototyping of complex surface products by ISMF.

following specific conditions:

Rapid Prototyping for Sheet Metal Products DOI: http://dx.doi.org/10.5772/intechopen.88435

4. Conclusion

tool diameters decrease.

alloy sheet materials.

113

In order to perform ISMF for complicated surface products with various wall angles, the designed products must ensure the ability to be formed according to the

• To satisfy the plastic deformation by comparing the large wall angles

• To pre-simulate and verify the ductile fracture occurrence (Figure 16)

If it is found that there is a possibility of plastic destruction in a certain area, it is

Figure 17 shows the simulation process and the obtained results after rapid

To verify and compare the accuracy of the final shape between simulation results, experimental products with CAD-designed surface in ISMF, we can use different sections and measure the shape distribution at different wall profiles and angles as shown in Figure 18. From that comparison, it can be seen that different deviations appear in the process of ISMF such as incorrect tool path generation,

Thus, it can be concluded that the simulation method is a particularly useful method for understanding, predicting, and evaluating the phenomena that occur in the ISMF process. This rapid prototyping method also proves that this is a new and innovative method. ISMF method satisfies the task of researching and developing new products. The proposal steps in this chapter can be applied to the actual manufacturing industry. Products of ISMF are continuously designed and ordered for rapid prototyping sample; when traditional forming methods are not applicable due to limitations on the formability, cost money, and the time for the fabrication of molds, then the ISMF using CNC machine with simple forming tools combined with

• The forming limit curves of sheet materials for ISMF will be increased when

incremental sheet metal forming process will improve the formability of light

• To generate tool path for ISMF process in a simulation of complex surface,

• To predict and improve the formability of the ISMF process for industrial sheet products, pre-simulate based on the relationship between maximum wall angle

• The high-temperature generation at the contact area of the rotational

MATLAB code should be used to import to FEM input file.

versus maximum deformed height need to perform.

error due to tool radius, and error by springback and pillow effect.

FEM simulation will prove to be an effective and feasible method. Some obtained scientific outcomes from proposal chapter are:

#### Figure 18.

Types of errors occurring during ISMF process. (a) Deformation at tool stroke h = 8.5 mm, (b) Deformation at tool stroke h = 17 mm, and (c) Final results at tool stroke h = 22 mm.

equations. Currently, the finite element (FE) simulation is an indispensable tool to research, evaluate, and discern physical phenomena modeled by various theoretical and experimental equations. However, the current FLC curves are inconsistent with the experimental results in ISMF. To improve the fitting of experimental data with numerical data, Nguyen and Kim [22] upgraded and introduced Swift's equation to

Types of errors occurring during ISMF process. (a) Deformation at tool stroke h = 8.5 mm, (b) Deformation at

tool stroke h = 17 mm, and (c) Final results at tool stroke h = 22 mm.

MMFC and predict FLD curve for cold rolled steel material. They imported obtained forming limit diagram curves to FEM software [23] in order to predict fractures of various square shapes and compare them with corresponding experimental results. In order to verify the effect of tool dimension on FLD at fracture, ductile fracture criterion of Clift et al. [4] should be adopted to predict FLC, simulated and confirmed by corresponding experimental results. After experimentally verified, FLC data were used to simulate different square sizes to show the effect of the wall angle to the maximum height of the square shape and established limits of formability based on the relationship between the maximum destructive height and the corresponding wall angle (Figures 15 and 16). The obtained limit curves could be used to indicate the failure of sound products through the relationship between the wall angles and corresponding maximum height of complex

shapes for ISMF process.

Mass Production Processes

Figure 18.

112
