Consumables: the real cost per part

The cheapest consumable per kilogram is often the most expensive per part. This is where most money leaks in a finishing shop, and the leak is quiet.

Why price per kilogram misleads

An abrasive costs 30% less but is consumed twice as fast. You paid more, but each invoice looks better, so nobody notices.

The correct comparison is cost per part processed, or per tonne of material treated.

How to calculate it, for blasting

You need three things:

1. Abrasive consumption per tonne of parts or per square metre treated
2. Abrasive price
3. Output over the measured period

Reference consumption varies widely between fields — several times higher on contaminated castings than on clean sheet. You will find them in the dedicated article.

If you are far above the reference, the problem is rarely the abrasive. It is the settings, the separation or leakage.

How to calculate it, for vibratory finishing

Media is topped up daily. Real consumption is the daily addition needed to keep the level constant — not the quantity bought in one order.

Measure it over a month and divide by the parts processed that month. That is your figure.

Compound is dosed against media mass, not part count. In a closed circuit, consumption rises compared to open circuit, but the waste water treatment cost disappears.

Where the money goes

Wrong mix. In blasting, an unbalanced mix — too much new shot added at once — worsens cleaning and raises consumption.

Angular grit used without reason. It wears far faster. If you do not need a rough profile, keep it out of the mix.

Faulty separation. Good abrasive discarded with waste is pure cost. Blocked separator holes are the most frequent cause.

Leakage. Abrasive leaving the circuit, at the separator or on the parts themselves.

Unsuitable media. Too aggressive spoils the surface and forces a second pass. Too fine lengthens the cycle.

The check that costs nothing

Once a month: record the consumable quantity added and the number of parts processed. Divide.

If the figure rises month over month with no change in output, you have a mechanical problem. You find it before it costs you a whole quarter.

Related reading

• Which blasting abrasive should you use? A guide by type
• Vibratory Finishing Consumables
• How much abrasive you actually consume in blasting
• Cut wire or cast shot: choosing the abrasive