Molding the Future of Large Iron CastingsJan 16, 2013
The challenges of the highly engineered casting market have created more stringent quality specifications than previously encountered for large iron castings. To meet the required quality levels, and particularly to control inclusion and oxide defects, foundries producing large iron castings must control sand entrainment and minimize molten metal turbulence in the mold. They do this using modern foundry simulation programs to optimize their gating and methoding practice, and by incorporating ceramic tile runner systems and ceramic filter encasement systems at the lowest point in the mold, near the in-gate. It is common for foundries to incorporate ceramic hollowware runner materials on castings larger than one ton.
A new lightweight runner system — HOLLOTEX™ EG Runner resin-bonded, carbon fiber-reinforced refractory systems, available in North America and Europe, exclusively from Foseco — provides the benefits of ceramic tile without some of the negative side effects. Investigation and customer feedback have confirmed the system as a replacement for ceramic tile in many large ferrous casting operations.
The Hollotex EG Runner system is available in diameters ranging from 30 to 70 mm. Push-fit, in-gate break-off and diameter conversion adaptors comprised of a low-density core-shot material are available also, to connect or terminate sections.
The particular features of Hollotex EG Runner systems provide several benefits to the metalcasting process.
Ease of assembly. Each tube, elbow, and t-junction has a flange at one end. With these ends, Hollotex EG Runner system components are easy to assemble with male/female push-fit connections. The entire gating system design can be assembled without glue, tape, or supporting rebar.
Reduced weight. Hollotex EG Runner components are 90% lighter than conventional ceramic tile. Due to the low weight of the components, they are extraordinarily easy and fast to assemble; therefore, the productivity of the molding facility increases.
The ergonomic value is based on the reduction in physical strain for workers who now have only to push-fit such lightweight gating systems. Because of its light weight, it is possible to connect multiple tubes without tape, hot wax, adhesive or glue. It also eliminates the use of steel rebar support systems, so there is no need to collect and straighten the supports after shakeout.
Easy to cut. Hollotex EG Runner components are simple to shorten with a hacksaw. A scale for easy measurement is formed on the exterior of the tubes when manufactured. There is far less airborne dust compared to dry cutting conventional ceramic parts. When ceramic parts are wet cut they need to be dried before use. With Hollotex EG Runner components, the remaining cut-off portions can be used with adaptors. This will consume most scrap pieces that would otherwise be discarded.
Reduced inventory costs. The product’s flexibility simplifies inventories. Because they are easy to shorten, only one tube length may be required. This reduces stocking many different lengths of the same diameter tile, and improves cash flow.
Reduced contamination and dumping costs. As a result of the composition and lightweight of Hollotex EG Runner products, virtually no additional material remains post-shakeout, and contamination of the sand system is not an issue. Consequently, there is no need to remove ceramic fragments during reclamation. Disposal costs for clay ceramic tube fragments/remnants often are very expensive. By eliminating hard ceramic fragments in the sand, wear on downstream activities like the shakeout machine, sieves, transport belts, and sand coolers is reduced, lowering the costs for service and maintenance of these facilities.
Hollotex EG Runner components can withstand the weight of the surrounding sand during molding. Unlike ceramic tile materials, which are fragile, the components will not break when dropped on the ground or tipped over on the pattern plate. There is little scrap from application. All remaining pieces from cuts can be connected and used. Adaptors are formed at the ends of all elbow and t-junction tubes that can be cut off and used to connect all the remaining pieces.
Low-density core-shot adaptors are available for conversion, to link one diameter tube to another, and in-gate break-off adaptor rings are available, too. This allows most gates to practically fall off in shakeout. There is also a reduction of “ceroxide” defects related to turbulence in standard ceramic tile systems.
The ease of handling Hollotex EG Runner systems offers many benefits, including productivity improvements and cost reductions. The service and maintenance of foundry equipment will be reduced too, and there will be savings by eliminating the disposal of ceramic runners as normal foundry waste. Adopting Hollotex EG Runners in large iron foundries has helped to simplify everyday molding operations and helped customers meet the rising quality requirements of their customers.