The selection methodology and table shown here provide examples of how to calculate and compare the mixed-sand costs-per-ton of two different formulations when incorporating a sand additive into your process.

In the first example, 1.8% binder is being used (a high binder percentage, but sometimes that’s necessary to offset the core strength degradation some sand additives cause.) If you multiply 1.8% by 55% — which is the ratio for Part 1 — you end up with 0.99%, which is the total Part 1 binder being added to the sand mix.

Next, multiply 0.99% by the cost-per-pound of the Part 1 binder ($1.40), which yields a result of $0.0139 cost-per-pound of mixed sand. Multiply that cost times 2,000 in order to determine the cost-per-ton of mixed sand. Repeat this calculation for the Part 2 binder. Then, multiply the catalyst cost by two.

To calculate the sand-additive cost-per-ton of mixed sand, multiply the percent being added (in this case it’s 10% times 2,000.) This will give you the number of pounds of additive per ton, or 200 lbs. Multiply the price of the sand additive ($0.75) by 10% to figure out the cost-per-pound of mixed sand.

In order to calculate the cost-per-ton of mixed sand, multiply the pounds-per-ton (2,000) by the cost-per-pound of the sand additive ($0.75) to get $150. Add together the cost-per-ton for mixed sand for the binder Part 1 and Part 2, catalyst, sand, and sand additive. Repeat these calculations for the second sand additive and compare the values.

In this example, using Sand Additive 1 will cost $247.51 per ton of mixed sand; whereas, Sand Additive 2 will cost $115.16 — meaning a savings of $132.35 per mixed ton of sand used. Therefore, Sand Additive 2 would be the much more economical choices based not only on a lower price per pound but also the additional value of being able to use considerably less additive to get similar casting quality.

The ability to use lower amounts of additive can have the additional benefit of reducing the overall amount of binder to be used because of the lesser effect on tensile strengths as well as reducing the foundry’s environmental footprint.

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