Simple Solutions That Work! Issue 18

The sand from the continuous mixer normally discharges into a storage hopper above the core machine. If there happens to be a tiny amount of sand that isn’t properly blended, it will blend into the existing sand. SINGLE OR DEDICATED MIXER PER CORE MACHINE In general, there are two ways to supply properly mixed sand to the core machines; a dedicated mixer for each core machine, or a system whereby the sand from a single mixer is delivered to multiple core machines. The dedicated mixer for each core machine is pretty straightforward. There is a mixer above the core machine surge hopper that discharges directly into the hopper. The advantages are that the sand can be custom mixed for the job that is running ensuring fresh sand. The surge hopper above the blow chamber valve can be comparatively small which is important on hot humid days. In the event of a mixer breakdown, only one core machine is not producing (instead of the whole core room). This ensures that enough sand is made for each job, regardless of size or cycle time. If a dedicated mixer is used for each core machine, a bulk transfer system (BTS) should be specified where the chemicals are in a location remote from the core room usually in a temperature controlled, fireproof room. A dedicated mixer for each core machine will also require a sand transporting system, with a valve feeding each hopper above each mixer. Level controls for each hopper as well as level controls and dust collection fittings/ ducting are also required for each mixer. There are a number of ways to deliver mixed sand to multiple core machines depending on the number of core machines, the distance they are from each other, and their respective layout. Three core machines can be fed with one mixer, either continuous or batch, where the mixer discharges either into the hopper above a core machine or onto a simple reversing belt. The level controls will keep all three hoppers full as needed by either running directly into one core machine hopper, or onto the belt that can reverse to go to another core machine. A single belt can be used to feed multiple core machines by using plows to take the mixed sand off the belt. This process, however, exposes the mixed sand to more air which can result in crusty, or hardened sand on hot humid days. A single continuous mixer can discharge onto a belt that pivots to reach any number of core machines that are oriented in a semicircular or circular layout. But the most popular single mixer, mixed sand delivery system is a shuttle car with all of the core machines in a straight line where the mixer discharges custom mixes for each core being produced. A shuttle car is a wheeled cart with a cone shaped polyethylene hopper on a track that is filled from either a batch or continuous mixer with each batch being custom designed for resin level, resin ration, powder additions, sand type, anti-veining product addition and release agents. There are many advantages to this design: • Only one raw sand hopper is needed with one discharge point for the transporter Contact: JIM GAULDIN [email protected] • Only one dust collection connection is needed • Only one set of resin supply tanks and level controls are needed The disadvantages to this system, is that if the mixer, transporter, or shuttle car are down, all core machines will stop producing as soon as the hopper above the core machine is emptied. Careful consideration is needed to determine mixer size and mix cycle time to fill the shuttle car taking mix time and travel time into consideration. If there are more than five or six core machines and they all are using a large amount of sand, multiple mixer and shuttle car systems may be needed. The mixer size, mix time, and travel time need to be carefully analyzed to determine the optimum system for your operation today and in the future. Sizing should always be determined by calculating the largest core possible on a given core machine at the highest production rate x the number of core machines. Whether you are building a new core room, enhancing an existing core room, or completely over hauling your operation, today’s technologies can ensure your core room is operating efficiently and economically. 42