Success Story - Die Casting - G.A.RODERS
Röders Develops an Innovative New Gating Concept Using a Virtual Experimental PlanG.A. Röders, known for its high quality die-cast parts, applied a virtual experimental plan to develop an innovative gating concept for gearshift domes, in order to optimize flow behavior and material efficiency. As a result, the jury of the International Aluminum Die-Casting Contest (GDA) bestowed this new, simulation-based methodology their 2014 “Special Recognition” award for sustainability and energy efficiency.
For the German foundry G.A. Röders, innovation and optimization are part of their daily routine. “Each reduction in delivery time is a strong argument and helps to meet increasing customer needs“, says Gerd Röders, company CEO. “Requirements regarding surface quality, heat treatment of thin walled structural components and weldability of die-cast parts are continuously increasing. What counts is the time from placement of the order until approval of the sample including all development iterations – always staying in compliance with the ordered quality, of course.“ At the same time, work must be efficient, quick and cost effective to keep a competitive edge. In this context, numerical simulation is a decisive factor. “Simulation allows for improvement as early as in the construction phase and saves us costly time consuming development iterations after mustering the die“, states Gerd Röders.
During the second stage, initial problem areas were highlighted. Based on the inputs made by the Godrej design engineers, the part design was changed while maintaining the client‘s requirements. At this early stage, simulation played a vital role as communication tool with the customer.
Subsequently, the position of the ingates was determined. A rib running through the entire length of the casting was used as an obvious channel for fast transfer of molten material to the hard-to-fill sections of the casting. The first die filling simulation revealed a non-uniform filling pattern. A reversal of the flow of the metal front was detected at the rib area near the ingate. Further analysis clearly demonstrated an increased danger for air entrapment in the location of the ribs. By studying the complete shot profile, it was seen that a small bore and the adjacent cup filled first before the second cup area got filled.
In the fourth stage, a radical modification of the design was implemented to shift the main feeding location to the big bore flange on the machining face. In addition, one ingate location was retained at the rib to divert the flow towards the cup area. The simulation showed a significant temperature drop in the cup areas and, in addition, a reverse filling was observed in the cup area near the small bore. As a result of this evaluation, further design changes were introduced.
Specifically, the designs of the main runner and the fan gate were heavily reworked. In total, more than 40 variations based on this parameterization were created and then were formed into a virtual experimental plan using MAGMASOFT ® to identify the best solution. The flow optimization of the runner system was paramount and specified through objective functions within the software. The volume of the gating as well as the MAGMASOFT ® results ‘Air_Entrapment’, ‘AirContact’ and ‘Porosity’ were chosen as quality criteria and subject to minimization in the final design. Conventional means to evaluate the numerous die filling and solidification results were either not efficient or essentially impossible to execute, due to the sheer quantity of results. Therefore, the ability to compare results directly within MAGMASOFT ® provided a decisive aid. The quality criteria can easily be displayed and swiftly evaluated by means of influence diagrams. This way, the best compromise can be selected after viewing the differences between the selected properties.
The best versions were chosen for further refinement in a second round of optimization in MAGMASOFT ®. Ultimately, an unconventional variant was identified as the best outcome, proposing an asymmetric runner concept for the two-cavity die. This final solution was realized in a new die and used in actual production.
The following assessment of the cast part quality as well as material and energy savings showed positive results. The mass produced parts confirmed the predictions of the simulation regarding the casting quality. At the same time, the weight of the runner and gating system was reduced by 44 %. Based on a yearly production of 85,000 cast parts, this equals 13 % less molten metal required, for an annual savings of 24 tons of aluminum plus a decrease in oxidation related material losses by 1.5 tons. The energy consumption in the melt shop was significantly reduced as well: G.A. Röders will save 33,000 kWh worth of gas each year. In total, the optimization of this part alone amounts to annual savings of about 15 tons of CO2.
According to Gerd Röders and Peter Kohlmeyer, the application of MAGMASOFT ® was of great importance for the positive outcome of this study. “The successful evaluation of the results in this short amount of time was only possible through simulation. This work also helped G.A. Röders significantly expand its scope of application for MAGMASOFT ®”, says Gerd Röders. “Today, MAGMA is an integral part of our optimization. In addition, the automatic optimization of the casting process by means of simulation is becoming more and more important for reducing the key factors development time and overall cost of our die-cast parts.”
G.A. Röders has already started the optimization of 15 additional projects. Gerd Röders closes: “MAGMA 5 Rel. 5.3 offers new functions to set up robust processes and automatic optimization. We are looking forward to increasingly deploying MAGMASOFT ® in the planning of new dies as well as die revisions in the future.”
G.A. Röders from Soltau, Germany, was founded in 1814 and has been owner-managed ever since. Together with its customers, the company operates along the whole process chain, from design to production. The 170 employees in Soltau are responsible for development and small series castings, while mass production is carried out by the 120 employees at Mesit & Röders in the Czech Republic. Both sites produce high-quality parts made of zinc, aluminum and plastics. Applied research in cooperation with universities and institutes generates new know-how. An own in-house tool shop allows for quick responses and short processing times. G.A. Röders is certified according to ISO TS16949. By strict implementation of international standards, the company presents itself as a partner for the automotive, aerospace and medical as well as the measurement and control technology industries. Quality is paramount for G.A. Röders – for products as well as for employees.
Text and images courtesy of G.A. Röders, Germany
Optimization is now the norm for new parts and dies at G.A. Röders. Parts and dies already in production are also re-evaluated for optimization. On the occasion of a die change, the runner and gating system of the aluminum die-cast gearshift part considered here was chosen for improvement.
The intention was to maximize the casting yield while still meeting or surpassing the customer’s quality specifications. A change of the runner geometry from a rectangular to a circular profile was chosen as the technical approach. Given the same cross-sectional area, a circular profile possesses a smaller surface area, reducing thermal losses while preserving the filling performance - with less total mass in the casting system. Peter Kohlmeyer, specialist for development and department head of mechanical finishing at G.A. Röders, reflects: “At the start of our work, we did a parameterization of the complete casting system and developed different versions of the runner and gates based on variations of these parameters.”
Stage Parameterized runner and gating geometry based on circular cross sections
Stage CAD-Model with conventional rectangular runner system (start design, left) and CAD-Model with optimized asymmetric circular runner system (end design)
Optimized quality criteria: ‘Temperature’ and ‘Porosity