by Young-Wook Chae, AnyCasting Seoul, Korea
The necessity of simulation
Recently, rapid technological development of the vehicle, electricity, and electronic industries means that the demands on product design have become more complex. Users want ever shorter development times, while demanding better quality in all parts of the product.
Software simulation is being used in almost all processes, and has now extended to polyurethane products made by foaming. The simulation extends from initial product design to product moulding, and can be applied in the foaming process and to mould design — aspects which are the basis of making foamed products.
In conventional foam part making, the product is developed from a trial object, requiring much trial and error and expense.
By using simulation in the design step, we can apply the result to the product and the process conditions, and so minimise trial and development times and expense.
Computer simulation is being used to raise productivity and improve the quality of foam products. It can predict all the physical phenomena that could happen in the process of getting the materials into the mould, and during the foaming process in the mould, in order to apply the right parameters to the mixhead and vent etc. But if simulation programs consider only change of material density, the simulation result is inaccurate.
Previous simulation software has suffered from other problems such as high cost, long calculation time and difficulty in use, and so has not achieved widespread use.
Development of AnyFoam
AnyFoam is a process simulation program that can be applied to urethane foaming, to give a total analysis for any system. AnyCasting developed it over the last seven years, and has spent three years applying it to real polyurethane products.
AnyCasting is targetting the software at users making automotive and train seat pads, building and container insulation and refrigerators.
In the software, the CAD/CAM (computeraided design and manufacturing) interface includes mould, nozzle and system design.
It is focused on simulation of the foaming process, including the chemical reaction and setting up the database for the foaming material, according to the mixing ratio.
One way it has enhanced the accuracy of the simulation result is through back-pressure calculation, considering gas loss, vent and parting line. It can calculate the density distribution during and after foaming, and predict air pocket defects during foaming.
Users can analyse the simulation result faster and more exactly because the software enables three-dimensional observation of the product.
Contents of AnyFoam
AnyFoam is composed of six modules; foamPRE, foamSOLVER, foamPOST, foamMESH, foamDBASE, and Batch-runner.
foamPRE (Pre-Processor) foamPRE is the pre-processor for AnyFoam. It imports CAD (computer aided design) data in a wide variety of file types, generates the FDM (finite difference method) mesh, and sets the simulation conditions for operation of foamSOLVER — the foaming simulator itself.
The 3D graphics environment uses OpenGL, a Windows-based, intuitive, easy-to-use interface that lets the user analyse the shape of the product and easily set the conditions.
The path for the foaming material can be input with only a click for position and also working conditions (head diameter, injection mass rate, temperature and the injection time).
Also, use of multiple mix heads is possible, and users can change the injection conditions such as time and location.
Using a fast-meshing algorithm, it takes only a second to generate a million meshes, giving extremely rapid mesh generation for simulation.
In the X, Y, Z axes, users click on the area they want, and designate the number of the mesh. For the rest of the area, meshes are then generated automatically. For a product that has thin areas locally, users can minimise the number of meshes, so reduce the calculation time and gain a more accurate simulation result.
foamSOLVER (Flow & Foam Solver)
foamSOLVER realises the multi-physics that solves the four equations below. It does this by linking the dynamic analysis that calculates flow and the dynamic/chemical reaction analysis and the so calculates progresss of foaming process.
- Three-dimensional compressibility Navier- Stokes equation.
- VOF (volume of fluid) equation for tracing the free surface.
- Energy equation that considers exothermic and endothermic reactions (the gelling reaction and chemical and physical blowing).
- Concentration equation — considers the change of composition as the chemical reaction takes place.
To predict the location of defects accurately, AnyFoam considers the back-pressure inside the mould, with respect to the air vent and parting line, and the gas loss that happens in foaming the polyurethane mix.
foamPOST is the post-processor of AnyFoam, and is designed so that users can easily observe the simulation result. They can show the data as filling and foaming pattern, foaming time, isolated air pockets, temperature, density, velocity, chemical species and distribution of gas etc, with two- or three-dimensional shapes.
Also, by setting the sensor in any location, calculation data can be displayed, such as the temperature, rise profile, foaming pressure etc.
It is also possible to export that data.
foamPOST has an auto-reporting function so that the user can easily document the simulation result, and classify it automatically, producing presentation data, as well as animations/pictures for documents for reports.
foamMESH (Mesh Editor)
With foamMESH, users can directly edit errors on the CAD or edit the necessary part of CAD, without changing the 3D CAD model itself.
foamDBASE (Material & BC Database)
foamDBASE is the software’s database management system. It contains all the thermal properties of the materials for the mould, pipework, and of the materials being foamed, together with their physical properties. It arranges the properties of general materials according to international standards.
The mould material category includes ferrous and non-ferrous alloys. In the structural material category, users can add properties of polyurethane as well as other materials.
The foamDBASE is composed of a general database and a user database, which can be easily modified and extended. The user’s material database can consider polyol and isocyanate mixing ratio, specify cream times and gel times, mix ratio, hydroxyl value, and water content in the polyol, etc.
Batch-Runner is a program that can manage several simulations at the same time. In general, it takes several hours to simulate one product and changing the simulation conditions will give several simulations. Batch-Runner allows several projects to be run at once. When using Batch- Runner, users manage the project list beforehand and automatically run foamSOLVER.
AnyCasting’s AnyFoam software has made computer simulation of foaming processes a reality, allowing accurate prediction to replace a process that previously involved much trial and error in the conventional development of foaming processes and foamed part production.
Conventional foam simulation programs run only on a workstation. In contrast, AnyFoam can run on any computer of Pentium IV 2Ghz and over. It takes users only two to three days to learn to operate the software.
Users of AnyFoam can optimise the design process and solve problems in process technology and control defects, and more. Also, by minimising trial and error in the process, users can dramatically reduce the development time for new products and cut defect rates.
Users can also share simulation data with each other, building a comprehensive database to apply the variables from the field process.
AnyFoam aims for a total solution of the foaming process, to help users to rapidly develop technical processes and products, and so improve their competitive position.