Cashing in on today's lost foam.

Inside This Story:

* Despite early struggles, recent improvements in the lost foam casting process have heightened its appeal to metalcasting facilities looking to expand their casting capabilities.

* Automation, improved compaction and better raw materials make it easier to consistently produce high-quality castings in lost foam.

* This article details the improvements made to the lost foam casting process and the dimensional capabilities it offers.

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For metalcasting facilities looking to expand their capabilities and enter new markets, adding the lost foam process to your shop is a viable option. Benefits of near-net shape casting, design freedom and the elimination of coring make the lost foam process attractive to customers because part designs can include more cast-in elements, minimal draft angles and tighter tolerances. Further, late developments in the technology have improved the manufacturing process to achieve higher quality castings more consistently.

When the lost foam casting process initially gained recognition in the metalcasting industry in the 1970s and 80s, the manufacturing technology was far outpaced by the interest and motivation of the industry, resulting in the failures of many lost foam startups. Today's lost foam casting process is not the same as it was in the 70s and 80s, however, and the remaining lost foam facilities and their suppliers improved their processes to achieve high-quality castings more consistently. Suppliers are providing better, more consistent coatings, the manufacturing process has become increasingly automated, and improvements in compaction make casting quality more consistent.

Honing Compaction

An important step in lost foam casting occurs at the compaction table, where compaction and vibratory forces cause the sand (or molding media) to flow around the pattern and into the internal passageways of the pattern and become rigid. For many years, compaction tables gave minimal measurement of variables, which generally were limited to the speed of the motor and the estimated energy output. Newer compaction tables, however, monitor nearly every variable that exists during compaction in real-time. This affords better prediction of equipment failures and lets the metalcaster know when a faulty flask has been made.

In addition, the newest generation of compaction tables is opening doors for casting design. Maneuvering the sand to flow uphill during compaction traditionally has been difficult and requires large amounts of energy, which limited designing for lost foam in the past. Casting designers for lost foam had to take into account the downhill flow of sand and design accordingly. Compaction tables using a vector flow system, however, make moving sand uphill much easier while requiring less energy, and they have the potential to open up parameters for the location of gating and risers, how the passageways are molded in the foam and how the foam is placed in the flask.

Automating Assembly

One of the areas that has been most improved by automation is building the lost foam clusters. Traditionally, the foam patterns for a particular component are glued by hand to an assembly tree before being dipped manually into the refractory coating mixture. Manual clustering, however, can lead to dimensional variation, internal casting defects, complete mold failures and low manufacturing efficiency.

With automation, clusters are built faster, and the consistency of the glue application and the location of each part on the assembly are more consistent. The level of repeatability also is better than what typically can be achieved by hand. Greater automation is possible today because the cost barriers that existed years ago are a lot lower.

Further, robotic technology has advanced the coating process, which when done manually, often requires individuals to make very precise actions in order to achieve proper coating (Fig. 1). This repetitive, strict motion can be taxing, and questions often arise on how consistent coating is applied day to day. The use of robots ensures the glued assembly will survive the dipping, ensures consistent application and requires minimal training (Fig. 2).

[FIGURES 1&2 OMITTED]

Shaping Up Shakeout 

Shakeout damage has become one of the largest sources of scrap for many lost foam facilities, but two pieces of equipment have entered the process to make shakeout more than simply swinging at the runner with a sledge hammer. The wedge and impactor are pneumatic devices that either separate the casting from the runner like the jaws of life (the wedge) or act like a mechanical sledgehammer hitting the runner to release the casting (the impactor).

Shakeout still is hot, hard and heavy work, but the wedge and impactor aid in reducing fatigue levels, injury rates and the amount of shakeout-related scrap. While this benefit is not specific to lost foam casting, the new shakeout tools greatly reduce what was once a large problematic aspect of the process.

Practical Success with Lost Foam

The tighter process controls and advances in manufacturing technology have taken the guesswork out of achieving the full benefits of lost foam. Lost foam casting can accommodate 01 degree draft angles, compared to 2 degrees for green sand and 3 degrees in permanent mold casting. In addition, the lost foam process calls for 0.015 in. (0.38 mm) cope and drag shift compared to .031 in. (0.8 mm) in green sand, offers a pattern mismatch tolerance of +/- 0.012 in. (+/- 0.3 mm) and achieves a surface finish of 9 microns (0.009 mm).

The lost foam process also provides weight reduction, eliminates or reduces machining and offers the freedom of designing castings with less scrap. While these advantages for lost foam are related to casting design and marketing, a simple example of success shows how the process can be beneficial to both you and the customer.

For instance, a variable pitch pulley, originally designed for green sand, was recently redesigned for the lost foam process. The original design (Fig. 3) included a threaded hub that required machining to achieve flat sides. Casting via lost foam allowed the flat surfaces of the hub to be as-cast due to good dimensional tolerances, which eliminated that machining operation (Fig. 4). Ribs also were added to the back of the pulley to maintain the mechanical strength. (Fig. 5).

[FIGURES 3-5 OMITTED]

In addition, the lost foam design included a wall thickness reduction and reduced stock material for machining (about 0.04 to 0.06 in. [1 to 1.5 mm]) (Fig. 6). The reductions in machine stock and removal of material from the back of the plate resulted in a 30% weight savings.

[FIGURE 6 OMITTED]

Component Integration

Because of the design freedom of lost foam and the ability to cast multiple parts as a single component, component integration is another major benefit to starting up lost foam capabilities at your shop.

When starting production of a new component, request to see the layout for the entire assembly, rather than just the drawing for a single part. Your facility then can pinpoint which parts can be incorporated as a single, complex foam casting. By viewing how the original component is meant to interact with the rest of the assembly, casting engineers will be able to show the customer how the lost foam process can save money and weight while producing a better part.

One successful lost foam component integration story centers on a direct coast clutch housing for an automotive manufacturer (Fig. 7). Originally a three-piece component, the lost foam process allowed holes and passages that previously were created by the combination of the three parts to be cast-in to the one-piece transmission component. At 8 lbs. (3.6 kg), the automotive transmission component features dimensional consistency across multiple tool cavities, reduced machine stock and resulted in a 70% reduction in landed cost. The component integration resulted in a weight reduction of 15% and led to $20 million in annual savings.

[FIGURE 7 OMITTED]

This article is adapted from the presentation, "Past vs. Future Manufacture and Marketing of Lost Foam Castings," by Mike Johnston, Citation Corp., for the AFS International Lost Foam Casting Conference, Toledo, Ohio, October 2004.

For More Information

"Finding a Niche with Lost Foam," K. O'Shaugnessy, MODERN CASTING, December 2004, p. 31-33.

RELATED ARTICLE: Outlook forecasts growth for lost foam.

With the lost foam casting process on the cusp of a large production growth, now is a good time to enter your own facility into the lost foam casting market. Lost foam production is forecast to grow from 275,000 tons in 2006 to 420,000 tons in 2009. Short-term production of lost foam aluminum castings is forecasted to grow from 180,000 tons in 2006 to 220,000 tons in 2009.

Eighty-five percent of the annual shipments of aluminum castings made by the lost foam process are for the automotive market. The gasoline engine market takes up 5% of the annual shipments, while diesel engines take up 3% and valve, electrical and aerospace take up 2%.

Fifty-five percent of iron lost foam castings are for the automotive market, while 20% go to the valve market and 10% go to the electric motor market. The valve market up nearly 100% of the end-users for bronze lost foam castings.

Mike Johnston is a sales manager at Citation Corp., Columbiana, Ala.