Robot, bottom pour ladle drastically reduce melting labor, scrap costs.

In the past, melting and pouring by hand at TPi Arcade, Arcade, N.Y., was a difficult job that required two people per shift. Scrap rates were high at the shop, which specializes in V-process aluminum casting. But the implementation of a robotic pouring system with a bottom-pour ladle has helped reduce melt labor costs by 50% and scrap by 30%.

In the past, TPi Arcade had difficulty automating pouring using a traditional tilt-pour ladle because the robot was unable to duplicate the manual pouring process and avoid impurities that float to the top of the melt. The company investigated bottom-pour ladles, which have the advantage of delivering cleaner metal and maintaining a constant head pressure, but discovered that most companies that had tried them had problems with leakage and reliability. Then the foundry asked Taylor Metalworks, Inc., Orchard Park, N.Y., to design and build a custom bottom-pour ladle capable of handling pour weights that range from 8-140 lb. The new bottom-pour ladle, integrated with an ABB industrial robot, successfully completed the automation at a cost of $93,000 and helped the firm achieve a cost savings within a year.

The primary motivation of automating was to make the pouring more consistent and safer. Pouring with a hand ladle was successful, but some impurities almost always managed to get into the ladle, which means they go into the mold and then migrate to the top of the casting. An even greater concern is line challenge of filling long, thin sections in the mold. Tilt pouring docs not produce a steady head pressure so there is the possibility the melt would freeze before the part is filled. The only way to correct this problem was to use funnels or pouring cups to maintain head pressure, but that would create safety concerns, take extra time and require extra equipment.

A number of foundries have attempted bottom pouring but most have run into problems with leakage and reliability due to the sealing components used to open and close the ladle. They must tolerate a temperature of 1300F (704C) and still fit together to seal off the ladle. In other cases, the refractory materials failed. Taylor Metalworks addressed the material issues by working with Pyrotek, Spokane, Wash.

For the ladle, a recommendation was made to use Pyrocast AR castable refractory, a material that can easily be formed into complex shapes and is not wetted by molten aluminum. The stopper rod that seals the ladle was made from O'Sialon, which is a silicon nitride and silicon carbide composite ceramic with high thermal shock resistance and excellent abrasive wear.

Another major challenge was keeping the stopper rod aligned to and seated in the hole in the ladle as both components expand and contract when the operating conditions change. A unique bracket that locks the two components together was then designed. The testing showed that storing the rods at 160F (71C) eliminated any tendency for them to absorb moisture, extended the rod life to 6000-8000 molds and virtually eliminated leakage, with the bottom pouring ladle working successfully, the firm implemented robotic pouring with little to no problems.

The biggest advantage of the robotic pouring system is that operators are no longer exposed to hot metal. The company's employees have not experienced a single injury in the melt shop since the robot was implemented. In addition, the number of employees needed to operate the melt shop has been reduced from three per shift to just one.

The new ladle provides constant head pressure, which has substantially reduced problems with filling long, thin cavities in the mold. Pouring from the bottom of the ladle also largely eliminates impurities from entering the mold. This has greatly reduced the amount of casting cleaning and weld repair that is required. Since the new system was implemented, the value of saleable product produced per hour worked in the cleaning department has risen substantively. This has made it possible to reduce the number of people in the department while maintaining the same volume of work.

Select No. 102 at www.moderncasting.com/info