In vibratory finishing, cost per part can be calculated. Not exactly, but close enough to make a decision.

You start from one thing: how many parts fit in a batch.

Step 1: how many parts go in

Part volume in the bowl comes from the machine’s working volume and the load ratio.

The usual ratio for deburring is around 1:3 to 1:4 — one volume of parts to three or four volumes of media.

Example. Machine with 350 litres working volume, ratio 1:4.

Part volume = 350 / (1+4) = 70 litres.

Divide by the volume of one part and you know how many fit.

Step 2: how long a batch takes

Cycle time is established during trials, on your part. It depends on the media, the settings and the required result.

Add loading, separation and unloading time. This is routinely underestimated: on a 30-minute batch, 10 minutes of handling is a third of the cycle.

Step 3: what a batch consumes

Media. Not replaced, topped up. Consumption is measured as the daily addition needed to keep the level constant.

Compound. Dosed against the mass of media in the bowl — the order of magnitude is tenths of a litre per hour for each kilogram of media. In a closed circuit, flow increases.

Water and energy.

Labour — loading, supervision, separation, unloading.

Step 4: cost per part

Add the consumption per batch, add labour and machine depreciation over the cycle, and divide by the number of parts in the batch.

What changes the result most

The load ratio. Going from 1:4 to 1:9 nearly doubles the cost per part, because you load fewer parts into the same cycle. Justified only when the result demands it.

Cycle time. More aggressive settings shorten the cycle but can spoil the finish.

Handling. On small parts in high volume, automating loading and unloading changes more than any consumable.

Compare against subcontracting

With the per-part figure in hand, you have your benchmark. Ask for a subcontracting price on the same part and see where you stand.

The difference, multiplied by annual volume, tells you how quickly the machine pays back.

What vibratory finishing costs per part