CASTING INNOVATIONS
Figs. 1 and 2. A no-fill defect occurring on one of Grupo Bocar’s cores was indicated during core simulation.
Core Simulation Solves Core Defect Issue The production of sand cores is a
complex process filled with technical challenges that can delay produc- tion, create scrap and rework, and increase the overall cost of a fin- ished casting. As casting geometries become more challenging, the de- mand for intricate and high quality sand cores will continue to increase. Additionally, facilities that produce cores are required to adhere to increasingly rigorous environmental regulations that seek to decrease the amount of emissions generated by the core making process. Many metalcasters have a dif-
ficult time determining how to efficiently produce a quality core at an economical price. In most cases, coreboxes are laid out based on past experience or by using a trial and er- ror method of testing different tool- ing set-ups and process parameters. The process of optimizing the core- box layout and coremaking process parameters requires numerous time- consuming and expensive sampling cycles. This trial and error approach to process development may require multiple tooling modifications to achieve the desired results and does not provide quantitative information about the actual cause of problems observed during trials. Grupo Bocar Automotive Sys-
tems, Los Reyes, Distrito Fed- eral, Mexico, produces a variety of complex automotive castings with complex cores. The metalcaster used MAGMASOFT’s add-on module
MAGMAc+m (MAGMAcore + mold) to evaluate a core with an incomplete filling issue. Through coremaking simulation, Grupo Bo- car conducted root cause analysis to detect and eliminate tendencies for core defects. The complexity of the coremak-
ing process is due in part to the large number of variables that inter- act to determine the final quality of a core. In the core shooting process, the total number of nozzles and vents, as well as their size and loca- tion, often has an impact on final core quality. Process parameters such as the amount of pressure applied during shooting, total shot time and sand-to-binder ratio also can affect how the corebox fills. Once the corebox is filled, the
binder then must be cured, or hardened, to give the core sufficient strength. In the case of phenolic urethane coldbox (PUCB) binder systems, the number, size and loca- tion of vents, along with the amount of curing gas and pressure profile used to apply the curing gas, will de- termine if a core is cured sufficiently. To further complicate the PUCB coremaking process, a venting sce- nario that will work well for the core shooting process may not be optimal for the subsequent curing process. Grupo Bocar determined the areas
in the core with low sand fraction values at the end of the initial simula- tion correlated with defects observed in production (Figs. 1 and 2). Te casting engineers considered changes in the core geometry and the size and location of nozzles but ultimately determined changes in the location of vents would lead to a significant improvement of the sand density distribution at the end of the core shooting process (Fig. 3). Te 3-D visualization of compli-
Fig. 3. Simulation results for a core design using optimized vent locations indicated a defect-free core.
cated physical processes provided by simulation was useful for analyzing and better understanding the effects of complex interactions between different process variables at Grupo Bocar. Te impact of tooling and process changes on core quality were evaluated without costly real world trials, and the time and cost to opti- mize the corebox layout and process
parameters were reduced. Visit
www.magmasoft.com for more information.
April 2012 MODERN CASTING | 45
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60