Advanced Third Generation 3D-SIGMA Injection Moulding Simulation Multi-component and Multi-cycle Simulation with 3D-SIGMA
October 12, 2005
At the Fakuma 2005 Plastic and Rubber Exhibition in Friedrichshafen, Germany, Sigma Engineering developer of the 3D-SIGMA plastic simulation product suite, has officially released Version 4.4. High-light of the release is the completely reworked graphical interface for defining the process set-up for a multi-cycle multi-component simulation.
3D-SIGMA is a full 3D Navier-Stokes based plastic simulation solver, the filling solver is 3d, the cool-pack solver is true 3d, the shrinkage-warpage solver is 3d, and of course the geometry is 3d.
For critical moulding situations we have found that an accurate three dimensional thermal solver incorporating the mould is imperative; dr. Thornagel (manager application development at Sigma) states that the thermal situation does drive the resulting viscosity of the polymer. Although this is an open door we now start to understand the implications with the more challenging mouldings like multi-component. Our three dimensional solvers truly pay-off in our multi-component multi cycle simulation. We now start to understand the influence of the temperature of the mould and the influence of how the cavities are rotated on the temperature distribution in time.
From a simulation set-up point of view it gets quite challenging, the first component is simulated with a filling, cooling-packing and shrinkage-warpage simulation. Than the second material is moulded around the first component in a second cavity. The time necessary for switching from the first cavity to the second cavity and the way the first component radiates heat away into the first mould cavity and partly to the air is fully taken into the simulation. Subsequently a second simulation sequence will be performed, a simulation of the filling of the second material, simulation of the cooling-packing and simulation of the shrinkage-warpage. Subsequently the first component will heat-up again due to the filling of the second component so this means we perform a coupled shrinkage-warpage simulation taking into account the temperature distribution of the first- and the second component.
Our continuously challenging users quickly pointed out that two component moulding was a historic state-of-the-art and that the state-of-the-art in the tooth-brush market is three and four components. Therefore 3D-SIGMA can perform an unlimited number of component simulations.
Challenge was the development of an intuitive presentation for the set-up of a multi-cycle multi-component simulation. For this we developed a completely new GUI states mrs. Tina Niessen, developer at SIGMA; unique in this completely new GUI is the status indicator. The number of to be specified variables quickly becomes mind boggling, we are now talking four components for tooth brushes, which means we have to specify filling, cooling, packing and shrinkage-warpage for four components. And typically users run ten multi-cycles simulations, each comprising a filling, cooling, packing and shrinkage-warpage simulation, in order to determine when the mould reaches a quasi stationary temperature distribution. The status indicators will signal to the user whether all necessary specifications have been done or whether data still needs to be defined before he can execute his simulation.
We are quite proud of our new GUI continues mrs. Tina Niessen. When the user starts a simulation project the visible structure of the new GUI is clearly presented, the user can simply work his way down the presented tree structure and at the end he will have entered all the required data for a simulation. However after the first results have been studied, the user will continue to optimize his moulding by changing the necessary input variables. So advancing with his simulation work he needs a flexible graphical interface through which he has quick access to his specific project optimization variables. For a muti-cycle multi-component simulation this is challenging because on the actual moulding side quite a substantial number of input parameters have to be specified and on the simulation side also quite some specific variables have to be set. For instance does the user want to have the system automatically derive for one component the crystallization constants from the available pvT-curves or does he want to enter the Nakamura-Hieber coefficients himself.
Truly mind boggling are set-ups where inserts are surround moulded in a multi-component process. Dr. Michael Thiess explains; 3D-SIGMA is three dimensional in each aspect; this means that we do take into consideration the 'heat exchange coefficient' between inserts and the subsequent component mouldings. So one insert can have for instance three different HTC's because it makes contact with three different material groups. So with the going of the multi-component simulation the HTC definition will have to be changed from the first component moulding and its specific HTCs to the set-up for the second moulding to the HTC set-up for the third moulding.
Our driving force in the development of the simulation workflow and the representation in the GUI was to make it a pleasant thing to do; we did not want to make it a kind of stark bookkeeping exercise. For this reason we did develop our own graphical icons.
Dr. Marco Thornagel concludes that advanced mouldings will only become more complicated, these mouldings and processes will not become simpler. In essence this means that the simulation of these advanced processes will be more complicated, it is as whether the simulation becomes double so complicated. Because we have to deal with the process issues and we have to deal with the simulation issues. In our new GUI we have made extensive use of flow-diagrams and other graphical representations, our customers do report that we have kept the total complexity in check.
Company Background
Sigma Engineering was founded by Magma Giessereitechnology GmbH and Simcon kunststofftechnische Software GmbH GmbH in 1998. Magma develops Navier Stokes based simulation codes for the simulation of a variety of metal casting techniques. Simcon develops, markets and sells worldwide the plastic injection simulation code Cadmould.
