Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(vol.43 no.495 April 2002)
Development of Forging Process Optimization System Using Wear Model
Hisayoshi KOJIMA, Shin-ichiro FUJIKAWA and Akira ISHIHARA
(Received on March 15, 2001)
We describe how we developed a system called gYOURS-PROh, which is designed to optimize the forging process. YOURS-PRO is a two-dimensional die design system for the front wheel hub, a forged-axle component. This system can be used in designing the best preform processes to ensure long die life. We first identified the object to be optimized and the required system specification by both FTA (failure tree analysis) and QFD (quality function deployment) methods. Then, we developed a new equation for calculating the amount of forging die wear. The new equation was derived from the equation proposed by Felder and Montagut, which takes the effect of contact time into account. The wear distribution on the surface of forging dies was measured. Then, the constant moduli were determined by applying the experimental results to the basic formula. We developed a new algorithm for predicting wear distribution based on the FEM results. We applied the wear prediction system to optimize the preform shape design. The geometrical relationship between the preform and finisher die designs was obtained. Our new automatic die design system gYOURS-PROh was completed, together with the new FEM module for quality assurance.
Key words : forging, FEM, die design system, die life, FTA, QFD, optimization, die wear
Prevention of Seizure by Oxide Coating
in Multi-Stage Deep Drawing of Pure Titanium Sheets
Takuji MURAO, Ken-ichiro MORI, Yasunori HARADA,
Koji KATO and Fujio OKUBO
(Received on February 5, 2001)
Long pure titanium cups with a high resistance to corrosion are formed by preventing seizure in multi-stage deep drawing processes of titanium sheets. The titanium sheets have sufficient ductility and high r-value for the deep drawing, whereas the seizure tends to occur during the deep drawing due to high reactivity with other materials. For the prevention, pure titanium sheets are treated by electrochemical and heating oxide coatings, because the coated titanium is not in direct contact with the die during the deep drawing due to the existence of the oxide layer. The effects of the coating methods and conditions and die materials on the occurrence of seizure in the multi-stage deep drawing are examined. Long pure titanium cups with the height which is 6 times larger than the diameter were successfully formed by using bronze dies or oxide re-coating.
Key words : sheet metal forming, deep drawing, multi-stage drawing, titanium sheet, tribology, seizure, oxide coating, bronze die
Incremental Forming of Sheet Metal into Spherical Shapes which Have an Undercut
-- Study of a Numerical Control Forming System Driven in a Cylindrical Coordinate System --
Yutaka AIHARA and Shigeo MATSUBARA
(Received on April 5, 2001)
In this study, the authors aim to develop a method for forming shapes with undercuts. First, a shape without an undercut is formed by the incremental backward bulge forming method, which has been developed by one of the authors. Several drawing processes follow the first process to make an undercut. A forming device of lathe type is made and used in order to avoid interferences between the forming tool and work material in the forming. Rotation of the workpiece and movement of the forming tool are numerically controlled with their synchronization. Possible shapes of products will, therefore, not be limited to rotational symmetric ones. In the forming of a sphere with a diameter of 80mm, two types of tool paths for drawing are used and the results are compared. For the forming from a commercially pure aluminum sheet of 1mm thickness, the forming limit by arc paths is larger than that by linear ones. The maximum limit obtained is such that the spherical surface of the product reaches 85% of that of the whole sphere.
Key words : production system, incremental forming, spherical shapes, cylindrical coordinate drive system, undercut