The Nature of Rolling

Abb. Roll forming: product and flower pattern
Roll forming: product and flower pattern

Rolling – A diverse process for (metal) forming

Rolling is a continuous or non-continuous pressure forming process with one or more rotating rollers. Additional tools can be used, such as plugs, mandrels etc. Molding occurs either through motorized rollers or by pulling rollers .

Rolling is one of the most diverse forming processe in the forming technology. It is used for the production of semi-finished as well as finished products. Rolling processes are used in all areas of forming technology, both in hot forging and cold forming, and of course in sheet metal forming.

There is a multitude of rolling processes. Some are named here: flat rolling, profile rolling, tube rolling, roll forming, forge rolling, cross-wedge rolling, wire rolling, and cross-row rolling.

Typical pass sequence for a railway track with partially asymmetrical cross-sections at a right angle to the roller

(Quelle: By Cschirp.Cschirp at de.wikipedia [CC BY-SA 3.0 de (http://creativecommons.org/licenses/by-sa/3.0/de/deed.en)], from Wikimedia Commons)

Products and Target Industries

Flugzeug (Quelle: Moses - Fotoalia.com)

The diversity of rolling is reflected in the diversity of products and the great range of applications these products have. Typical industries and products are:

  • Vehicle construction (cars, trucks, tractors)
  • Aircraft construction
  • Shipbuilding
  • Building construction and civil engineering
  • The offshore industry
  • The machine and plant building industry
  • The mining and tunneling industry
  • Carriage construction
  • Bearing industry
  • The petrol and gas industry
  • The furniture industry

Trends and Developments

Where is the development of rolling heading?

Rolling companies operate in a fiercely competitive market and under high cost pressures. They are confronted with steadily rising energy costs, rising laboratory costs in research and development and fluctuating prices for the raw materials. Investment costs for equipping rolling mills are the highest, when compared to other classic metal forming processes. Only a high degree of automation in the rolling process chain guarantees high margins.

This factor plays a considerable role in the future development of rolling technology when put together with demands for the economical use of resources. Driven by the automotive industry, one of the essential design principles is lightweight construction. Lightweight construction can be obtained through the use of better materials, the realization of optimized, complex forms (special profiles), or the integration of additional functions.

Allerdings stellt die Umformung von hoch- oder höchstfesten Stählen durch Walzen sowohl aufgrund der Festigkeit als auch aufgrund der auftretenden Rückfederung eine Herausforderung dar.

However, the forming of high-strength or super high-strength steels by rolling remains a challenge because of the stiffness as well as the occurring spring back.

 An example of the future development of rolling technology are tailored rolled blanks that are produced by flexible rolling. The roll-gap is adjusted during the process, resulting in a semifinished product with different thicknesses. The process design of tailored rolled blanks implies new challenges and developments for rolling technology.

Rolling mills are forced to confront these challenges and to develop and apply new approaches in their engineering environment.

Typical Challenges when Rolling

Rolling mill operators commonly use analytical calculation programs to compute pass schedules or pass sequences. There is a multitude of different solutions in this area, but all have the common problem that they only take into account some aspects of theschedule or sequence, which are then often based on simplifications and idealizations of the process. Process simulation should not be understood as a replacement for these established analytical models, but as a modern tool for the verification of analytically calculated pass sequences. The goal of this simulation is the optimization of the process at an early stage – especially given the fact that components have ever shorter product life-cycles. This simulation tool allows you to learn more about your process and to “look inside the component”.

Simulation example: Rolling of a rim profile

Analytical programs, such as those mentioned above, do not offer a sufficient solution for highly asymmetrical passes as decreases  cause twisting in the rolling stock. This impedes the process's stability and causes not only an increased technical effort (calibration, aligning), but very often an increase in waste, too.

By means of a simulation of different variants the profile of the pre-cut can be optimized and twisting during the roll pass can be significantly minimized. Reworking costs are reduced, the surface properties of the rim profile  are substantially improved and the set-up time for the calibration of the rolling mill is shortened considerably. As well as this the customer profits from higher product quality, decreased production costs and a shorter delivery time.

Profile rolling of a rim base profile with and without optimized pre-cut.

 

 

Applications

Further essential applications of simulation in the field of rolling technology:

  • Feasibility studies for component production (geometrical precision, crack formation)
  • Avoidance of rolling mistakes
  • Assessment of spring back effects
  • Analysis of strain and stress
  • Prediction of the geometry formation of the rolled stock during caliber rolling (profile filling)
  • Prediction of edge formation when slabbing or rolling by a coil line
  • Assessment of the number of passes and of the decreases during the passes
  • Selection of reasonable pass schedules
  • Optimal utilization of rolling passes
  • Prevention of twisting  or warping of the rolled material
  • Analysis of the effects of roller deflections
  • Consideration of the elastic roll stand deflection
  • Differing local distribution of field sizes, especially for microstructure characterization
  • Simulation of the process chains

 

Stress distribution in the rollers of a four-high stand, FEM-model of roller deflection
Multi pass wire rolling process, illustration of the cross-sections

Our solution for Rolling

Module „Rolling“ in Simufact Forming

Who will get the customer’s commission? Depending on the client’s situation, there are differing, specific demands on the product that the supplier has to meet. The one that meets the customer’s demands most fully gets the contract. Different factors come into play here: delivery time, product quality, customer orientation, costs, product innovation, and service.

Today, numerical simulation of rolling is a fixture in a CAE-based development environment.

Simufact Forming unites simple and intuitive usability with reliable predictions of rolling processes. The simulation’s results find their application not only in the development of products and processes, but also in the continuous improvement of processes.

Simufact Forming offers you programming interfaces that allow you to simulate even special rolling processes such as pilger rolling in a user-friendly way. The recurring movement of the tube blank during pilger rolling can be implemented through specific close-loop controlss. With a little programming (which we would happily do for you during customization), practically every process can be simulated.

Take advantage of SimufactForming Rolling for the simulation of your rolling processes:

  • Shorter development times with less trial runs
  • Comprehensive process understanding
  • Higher process stability and quality
  • Predictions of component properties
  • Higher machine utilization, cost reduction
  • Expand your product range
  • Optimum adjustment of the different process stages
  • higher yield
  • Avoiding rolling mistakes

 

For a functional discription of Simufact Forming Rolling, please read our product information: