The question comes up at every commissioning: how many parts do I put in the bowl?
The answer is not “as many as fit”. Parts always represent a fraction of the media volume, and the ratio decides what kind of processing you get.
The range
The volumetric ratio between parts and media sits between 1:2 and 1:9 — one volume of parts to between two and nine volumes of media.
1:2 — coarse processing. Many parts, little media, strong attack.
1:9 — superfinishing. Few parts, plenty of media, gentle and uniform attack.
1:3 … 1:4 — the usual range for deburring. Most applications work here.
How to calculate it
The formula is simple. Divide the machine’s working volume by the ratio plus one.
Example. The machine has a working volume of 350 litres. You choose 1:4, for deburring.
The denominator is 1 + 4 = 5.
Part volume = 350 / 5 = 70 litres.
The remaining 280 litres are media.
Why it matters
Too many parts and they touch each other. Impact marks appear, and processing becomes uneven — some areas are worked, others not at all.
Too few parts and you spend time and energy on a bowl running almost empty.
Processing without media
There are cases where no media is used at all. Processing happens part on part — the parts rub against each other.
It applies to robust parts with geometry that allows contact, and where no particular surface quality is required. It is the cheapest option, and the least controllable.
Related reading
- How to choose vibratory finishing media
- Vibratory Finishing Equipment
- What is vibratory finishing and what benefits does it bring?
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