How do you calculate part damage rate in mass finishing?

Divide the number of damaged parts by the total parts processed, then multiply by 100. With 8 damaged out of 250, the rate is 3.2%.

What is a good part damage rate for vibratory finishing?

For robust steel parts, under 1% is achievable. For thin-wall or soft aluminum and zinc parts prone to part-on-part impingement, 2 to 4% is more common, which is why a 3.2% result still leaves a wide gap to a 95% target.

What causes part-on-part damage in a tumbler?

Too few media relative to parts, overloaded bowls, oversized parts that nest, and high amplitude. Increasing the media-to-part ratio and separating parts is the usual first fix.

Damage rate vs scrap rate, what is the difference?

Damage rate counts every part marked by the process whether reworkable or not, while scrap rate counts only parts that cannot be saved. Damage rate is the earlier, broader warning.

How do I reduce part damage without losing finish quality?

Switch to gentler media shape or lighter media, lower amplitude, raise the media-to-part ratio, or add part separators. Each cuts impingement while still cutting burrs.

What does the gap to target mean here?

It is the distance between your good-part target and the computed rate. A 3.2% damage rate against a 95% target leaves a 91.8 point gap to close, signaling the recipe needs serious work before it qualifies.

Mass Finishing, Deburring & Polishing calculator

Part Damage Rate Calculator

Part damage rate is the share of pieces a mass finishing process nicks, dings, peens, or impinges badly enough to scrap or rework. In vibratory bowls, tumblers, and spindle finishers, parts collide with media and each other, and soft alloys, thin walls, and sharp edges are the first casualties. Quality engineers and finishing supervisors track this rate to decide when media is too aggressive, loads are too heavy, or part-on-part contact needs separation. It is the single clearest signal that a finishing recipe is damaging the very parts it is meant to improve.

What this calculator does

Calculate part damage rate for mass finishing, deburring & polishing planning, quoting, troubleshooting, capacity review, or process improvement.
Use it when part damage rate in mass finishing, deburring and polishing needs a clean rate and gap-to-target you can put on a tier board.
It divides damaged parts by total parts run to give a damage percentage, then compares that against a target good-part rate to show the gap.

Formula used

Part Damage Rate rate = affected amount ÷ total amount
Gap to target = target rate - calculated rate

Inputs explained

Parts damaged in finishing:
Parts run through the process:
Target good-part rate:

How to use the result

Use it after a finishing run to grade media aggressiveness and load density, or when qualifying a new recipe before it goes to production.
It treats every damaged part equally; a hairline edge ding and a scrapped impingement count the same, so pair it with severity grading for real decisions.

Common questions

How do you calculate part damage rate in mass finishing? Divide the number of damaged parts by the total parts processed, then multiply by 100. With 8 damaged out of 250, the rate is 3.2%.
What is a good part damage rate for vibratory finishing? For robust steel parts, under 1% is achievable. For thin-wall or soft aluminum and zinc parts prone to part-on-part impingement, 2 to 4% is more common, which is why a 3.2% result still leaves a wide gap to a 95% target.
What causes part-on-part damage in a tumbler? Too few media relative to parts, overloaded bowls, oversized parts that nest, and high amplitude. Increasing the media-to-part ratio and separating parts is the usual first fix.
Damage rate vs scrap rate, what is the difference? Damage rate counts every part marked by the process whether reworkable or not, while scrap rate counts only parts that cannot be saved. Damage rate is the earlier, broader warning.
How do I reduce part damage without losing finish quality? Switch to gentler media shape or lighter media, lower amplitude, raise the media-to-part ratio, or add part separators. Each cuts impingement while still cutting burrs.

Last reviewed 2026-05-12.