Simple Solutions That Work! Issue 15

18 LOCATION CONSIDERATION If the riser is not physically located close enough to the last metal to solidify (hot spot), it will not feed the casting. Ideally, the riser should be connected to the hot spot of the casting and placed directly above the given casting section. Depending on the casting geometry, molding constraints and other considerations, this may not always be possible. When top feeding isn’t possible, side risers will likely be used. This location aspect also takes into consideration feeding distance, which is the distance a feeder can supply metal into a casting and is controlled by casting geometry, alloy type, and section thickness. By applying some basic risering knowledge with the appropriate casting parameters, you can rig castings with a high likelihood of success. Large, complex castings and those with unusual alloys may still require solidification software for rigging. In these cases, the cost and time requirement for simulation work can be absolutely justified. To illustrate the concept briefly discussed, let’s apply these principles to a simple iron hub casting. (See EXAMPLE on previous page) Based on the calculations, and assuming a single feeder for this casting, we can select a feeder based on the following: • Volume : 507.3 in³ X .04% volumetric shrinkage suggests you need 20.3 in³ of feed metal. Chemex feeders reliably provide 50% of the contained metal, so this translates to a minimum feeder volume using Chemex product of 40.6 in³. • Modulus : The largest modulus occurs in section X (which is 1.018). In the case of ductile iron, we want a feeder modulus 10% larger than the section so a feeder should be selected with a minimum modulus of 1.12. • Location : In this case, a single feeder in the middle is determined to be sufficient. An alternative may be considered to use a smaller feeder on the center section and additional feeders and/or chills on the outer ring section. Recommendation: Chemex Tele 500-40(60) For the purpose of this discussion, we can use simulation software to confirm the manual calculations. As expected, the Tele 500-40(60) generates a good simulation result. Simulations may also compare the Tele- Feeder result to what might be expected with a natural (sand walled) riser a traditional slurry product. Simulations confirm the result from traditional rigging method: The Tele-Feeder clearly provides the correct feeder volume and modulus. It’s the most efficient of the three in the simulations performed. As expected, it provides the smallest riser and the smallest casting contact area of the three risers. Rigging castings manually is not only relatively simple but also generates good results. Shrink defects in can be used to troubleshoot why a problem is occurring. We can also validate the results of a simulation to check our work before a new casting is put into production. The benefits of accurate risering translates directly to foundry yield improvement, riser removal efficiency and many other benefits that lead to better results for the foundry. Chemex Tele-Feeders should be considered in any foundry where yield, efficiency and profitability are considered crucial to the success of the foundry. No matter the struggles facing the foundry, be it commercial, technical, or production, improved feeding practice will improve your foundry’s operations. Contact: JONATHAN ERMAN [email protected]