Roller spinning forming regularity

2.1. Spinning principle

During the spinning process, the blank and the mandrel are fixed together in some way, the mandrel is rotated at the same speed as the blank, and the swivel can feed the blank in either direction. In the process of forming the blanks continue to plastic deformation, and finally spin out the parts to meet the conditions.

2.2. Classification of spinning process

According to the process of spinning plastic deformation of the rough situation, spinning technology is generally divided into two kinds of ordinary spinning and strong spinning. Common spinning is called the general rotation, the main categories include: stretch spin, shrinkage spin and expand spin and other forms of processing.

In the spin form, the stretch spin is widely used. Modern machine tool equipment hydraulic profile device, by controlling the wheel feed ratio to adjust the wheel path, pressure, can eliminate the metal radial deformation caused by thinning. In the shrinkage spinning process, the blank is fixed on the spinning machine, so that its radius gradually reduced. The spinning process is to fix the blank to the mandrel with the spindle rotating, and the rotating wheel moves axially along with the rotation of the blank. Expand Spinning is that the hydrodynamic force on the spinning machine causes the preformed blank to radially symmetrically expand. Most of the parts formed by the form of expand spinning are thin-walled components such as drum agitators, wheels and so on.

Fig. 2The classification of strong spinning

a) Spinning of the Cone pieces

b) Spinning of the cylindrical member

c) Spinning of the tubular part

Strong spinning, also known as thinning spinning. In the forming process, the thickness and shape of the blank have undergone a corresponding change, that is, volume deformation. According to the difference of the shape and the ways of plastic deformation of the workpiece, strong spinning is generally divided into tapered parts and cylindrical parts of the strong spinning. According to the direction of rotation of the metal and the direction of the same wheel or not, can be divided into two kinds of positive spinning and anti-spinning. The former refers to the direction of the same, the latter is the opposite direction. The positive spinning is used to spin.

Based on the temperature in the spinning process, the spinning is divided into two types: cold spin and hot spin. The so-called cold spin, that is, the temperature during the spinning process at room temperature, generally used for some material plastic deformation of the workpiece is very good. Different from the cold spin, hot spin refers to the spinning in the heating, in order to achieve the best plastic deformation of the blank in the case of spinning, for the deformation of the larger resistance and plastic deformation of the workpiece material is more applicable.

4.1. Building the model

The ABAQUS software was used to establish the preformed finite element model. In the simulation process, the blank is assumed to be elasto-plastic deformation, the core mold and the rotating wheel are assumed to be analytical rigid body. The outer surface of the core mold is in contact with the inner surface of the workpiece. The contact and separation between the two are judged by the contact theory. The mandrel plays the role of material diversion in the process of deformation.

The friction between the core and the workpiece is calculated according to the law of Coulomb friction, the friction coefficient is 0.3. And the friction between the surface of the rotor and the workpiece is negligible in this paper. The mandrel drives the blank at the same time to rotate, and the rotor rotates both the axial and the radial feed to the blank so that the metal flow of the blank material causes the plastic forming of the blank. In the pulley spinning, the blank, the core mold and the rotating wheel are both dynamic contact, and the rough metal material flows continuously, thus selecting ABAQUS / Explicit dynamic explicit module to simulate the process.

Pulley materials often used gray cast iron, steel, aluminum or engineering plastics. Gray cast iron is the most widely used, when $v$ ≤ 30 m/s, with HT200; when $v$ ≥ 25-45 m/s, it is appropriate to use ductile iron or cast steel [6]. In this paper, 45 steel is selected as the V pulley material. The properties of the pulley material and the mechanical properties are shown in Table 2.

For the sake of calculation, the following assumptions are made for the model:

1) The workpiece material is homogeneous and isotropic;

2) The effect of gravity and inertia on the forming is neglected.

The rotary wheel should have sufficient rigidity, hardness, strength, abrasion resistance, dimensional accuracy, reasonable structural shape and smooth working surface, so the wheel material is selected as Cr12MoV. According to the pulley spinning process requirements, the rotating wheel is selected, the schematic diagram of the wheel shape is shown in Fig. 3. The radius of the wheel is 30 mm, the thickness of 10 mm, ${\gamma }_{\rho }$ for the rounded fillet radius, $\alpha$ for the rotary wheel operating angle.

Fig. 3Schematic diagram of the wheel shape

In the finite element numerical simulation analysis, the grid division has great influence on the analysis speed and the result. In the process of plastic deformation of the blank material, the occurrence of excessive deformation led to the finite element numerical simulation does not converge, thus forming a reasonable analysis results. Therefore, the use of reduced integral hexahedron element division grid, that is, C3D8R partition grid. According to the pulley spinning process, the spinning geometry model is established. As shown in Fig. 4. The three-dimensional finite element model is shown in Fig. 5.

Fig. 4Spinning geometry model

Fig. 5Three-dimensional finite element model

Fig. 6The geometry of the contact

In the process of pulley spinning, in order to obtain the pulley with the condition, the blank and the mandrel rotate at the same speed, and the rotating wheel must simultaneously move in both axial and radial directions. In the ABAQUS finite element model, the core and the blank are fixed together in the form of tie (the blank and the clamping device are bound together, in the forming process, to eliminate the relative rotation between them, you can eliminate the displacement of the rigid body); And apply a rotational load to the reference point of the mandrel, the mandrel drives the blank to rotate, thereby realizing the rotation of the blank around the main shaft. The geometry between the rotary wheel and the workpiece is defined as the general contact relationship.

4.2. The influence of the working angle of the rotary wheel on the forming of the pulley

In order to obtain high-quality processed products must be appropriate to select the rotary wheel working angle $\alpha$, fillet radius ${\gamma }_{\rho }$, wall thickness reduction rate ${\psi }_t$, wheel feed rate $V_f$, processing temperature and other parameters. In order to analyze the effect of the working angle $\alpha$ on the spinning process, the following analytical scheme is initially developed. See Table 3.

Three groups of parameters under the analysis shown in Fig. 7.

Fig. 7The analysis of results

a) Rotary working angle is 10°

b) Rotary working angle is 20°

c) Rotary working angle is 30°

As can be seen from Fig. 7, as the rotational angle $\alpha$ increases, the higher the uplift of the blank metal in contact with the front end of the rotor, resulting in non-stable flow of the metal. Therefore, the working angle of the rotary wheel during the spinning process should be smaller in a certain range, that can achieve the purpose of reducing the bulging of the rough surface and the irregular flow of the metal.