Profile Ring Rolling

I explained that the rotation speed of the main roll is constant in the ring rolling machine( Rotation speed control of axial roll ). But it isn’t constant in the CALTEK ring mill. I’ll tell you why the rotation speed of the main motor is not constant in our ring mill. Increasing the rotation speed of the roll during rolling can reduce the rolling force because the coefficient of friction between the roll and the workpiece becomes smaller.  That’s why I always ask the ring mill operators to make the rotation speed of the main roll as fast as possible.  However, if the size of the ring is small, the ringmill operator should not rotate the main motor in the maximum speed. I’ll explain the reason with this ring mill belows: * Main motor rpm : 0 ~1,200 * Main roll gear box reducer ratio : 1/40 * Axial roll cone angle : 40 * Axial roll gear box reducer ratio : 1/10 * Axial motor rpm : 0~1,400 * TR range : 200~600 Tis is a graph of the rotational speed of the axial motor according t...

The driving force that rotates the ring in the ring mill is generated by the main roll and the axial roll. Of these two rotational speeds, the rotational speed of the main roll is used as a reference, and the axial roll is controlled according to the rotational speed of the main roll.  Normally, the rotation speed of the main roll is fixed and the rotation speed of the axial roll is controlled according to the position of the ring. In the previous, we have understood the concept of linear velocity( What is linear velocity ) and studied how to obtain the linear velocity of the main roll( The linear velocity of main roll ) and the linear velocity of the axial roll( The linear velocity of axial roll ). The linear velocity of the main roll(V m ) is fixed and constant and we control the rpm of axial roll to match the linear velocity of the axial roll(V a ) with that of the main roll. The linear velocity of the main roll(V m ) is, V m = R m x ω m The linear velocity of the a...

I posted on this blog about the linear velocity of the main roll.( The linear velocity of the main roll in ring rolling ) The formula for calculating the linear velocity of an axial roll is a bit more complicated than that of the main roll because the axial roll is a cone shape. As you know, the linear velocity is the product of the rotation radius and the rotation speed. V = R x ω (V : linear velocity, R : rotation radius, ω : rotation speed) 1. The rotation radius of the axial roll The rotation radius of the main roll(R m ) is constant, but the rotation radius of the axial roll(R a ) varies with the position of the ring. The rotation radius of the axial roll(R a ) is, R a   = TR x sin(θ/2) (TR : the encoder value of the Tracer Roll, θ : the cone angle of the axial roll) I explained in the previous post about the TR encoder( The encoders of the ring mill ). 2. The linear velocity of the axial roll The linear velocity of the axial roll is, V a = R...

The linear velocity is proportional to the rotation radius and rotation speed.The linear speed of the main roll is obtained by multiplying the radius of the main roll by the rotational speed of the main roll. V=r × ω There are a motor, gear box and main roll in the main roll assembly. The main roll assembly has a main motor, gear box and main roll. In general, the main speed displayed on the ring-mill program screen is the rotation speed of the main motor.  The main roll assembly has a main motor, gear box and main roll. In general, the main speed displayed on the ring-mill program screen is the rotation speed of the main motor. The rotation speed of the main roll( ω M ) is calculated by the rotation speed of the motor( ω m ) and the reduction ratio of the gearbox(R). ω M = ω m ×R Therefore, the linear velocity of the main roll(V) is, V=R x  ω M  ( R : reduction ratio of the main gear box,   ω M  : rotation speed of the main motor) L...

There are usually three ways to express the speed of rotation. They are rpm , angular velocity and linear velocity .   rpm is the number of revolutions per unit time. The unit of rpm is rev/min.   Many people confuse linear velocity with angular velocity.  I will explain the difference between linear velocity and angular velocity, and how to calculate linear velocity. Angular velocity is the angle of rotation per unit time.  The unit of angular velocity is rad/s.  Linear velocity is the distance traveled per unit time.  The unit of linear velocity is m/s. The formula of angular velocity( ω)  is belows: ω= θ/t ( θ : angle, t : time) Linear velocity is the distance of the arc that moves per unit time. The length of the arc is as follows: ℓ=r θ The linear velocity( V)  is as follows: V= ℓ/t= r θ/t=r ω Linear velocity(V) is proportional to rotation radius(r) and angular velocity( ω). ...

The three main rolls in the ring mill are the main roll, the mandrel and the axial roll. This means that these three rolls wear quickly and that these rolls should be replaced frequently. And among these three rolls, axial roll is the most expensive roll. Because the axial roll is cone shape, it is difficult to machine.   Why is the axial roll not a cylindrical shape that is easy to machine, but a cone shape that is difficult to machine? I have to explain the linear velocity of the axial roll to tell the reason. I explained the linear velocity of the main roll before  YouTube(What is the linear velocity) In the ring mill, the main roll and axial roll rotate the ring.  The linear velocities of the ring by the main roll(V1) and by the axial roll(V2) should be same.  This ensures that the ring remains in the center of the ring mill. When the linear velocity(V2) of the axial roll is faster or slower than the linear velocity(V1) of the main roll, the center of the ...

1. Cause of the ring climbing There are some reasons for the ring’s climbing up and down(Rippling). In this case the bad shape of the preform is the main cause of the ring’s rippling. I explained the process of making preform at my blog before. The process of making preform is cogging→upsetting →p unching →p iercing as I explained at that post. When you press the punch too much and don’t make the preform flat, you will have this bad shape of preform. When the axial roll press down the preform, the other side of the preform will go up. It’s not easy to make the ring stable if this happened. 2. Result of the ring climbing You can see a gap between the stacked rings. And you need to add more excess material for the ring. It makes the ring expensive 3. How to solve this problem If you have to press the punch deeply to save the material, you have to make the preform flat after piercing it. The quality of the preform is very important. It aff...

I got a call from the ring mill operator of my company. He told me that the main roll stopped rotating while rolling a ring. But the main roll was rotating when I arrived at the ring mill shop. I wasn’t at the sight so I couldn’t see the problem.  I looked over the technical data saved in the PC. And I could find the cause of this problem as soon as I saw the data. * Technical data of CALTEK ring mill I found the main motor was rotating at high speed and the motor current went down suddenly. If the motor is over current, it could be stopped. But the current is not high in this case. I could guess the motor had no problem, it was normal. But why didn’t the main roll rotate? There’s a gear box between main motor and main roll. It transfer the motor’s driving power to the main roll. Motor rotates but main roll doesn’t rotate.   I can guess there’s something wrong in the gear box. We checked the gear ...

There are 3 kinds of dimension to design the ring rolling product. They are machining, cold and hot ring dimensions. The first step to design the dimension of ring rolling products is analyze the customer drawings. There may be some different ODs, IDs and Hs in the drawing for the customer products. Among the many ODs, IDs and Hs, the maximun OD , minimun ID and maximun H come to the dimension of machining ring. The machining ring dimension of this item should be   OD 1,500 * ID 980 * H 150 . You need to design the dimension of the cold ring by considering the additional dimension. You decide the hot ring dimension by considering shrinkage from the hot ring to the cold ring. You can use this expression to calculate the hot dimension: Hot dimension = cold dimension ×100÷(100- shrinkage rate) The shrinkage rate can be different depending on the ring dimension, material, the atmosphere temperature of the factor...

The process for manufacturing ring rolling products is as follows: Cutting →  Heating →  Blanking →  Ring Rolling →  Heat treatment →  Machining The blanking and ring rolling processes are main forging processes among these processes. I’ve introduced the ring rolling process before, I’ll introduce the blanking process this time. Blanking is the process of making a preform for ring rolling. Blanking processes are 1. cogging, 2. upsetting, 3. punching and 4. piercing. The cogging process is a process to make a square material into a circle, and it is not necessary if you use a round bar as a raw material.  The upsetting process is the process of compressing the material in the longitudinal direction.  The punching process is the process of inserting a punch to make holes in the material.  A piercing process is a process of punching holes in a material.  This is the finished prefor...