<strong>Why the Mix Ratio Matters in Shot Blasting</strong>

Steel grit does not work as a single particle size. Inside a shot blasting machine, the abrasive circulates continuously: each particle strikes the workpiece, returns through the recovery system, is cleaned by the separator and is accelerated again. During this cycle, particles gradually wear and break into smaller pieces, while the finest dust is removed by the separator and dust collector. A well-maintained operating mix keeps the balance between coarse particles, which deliver impact energy, and fine particles, which provide coverage and surface finish. When this balance is lost, cleaning speed drops, abrasive consumption rises and profile depth becomes unstable.

<strong>Signs of an Improper Mix Ratio</strong>

Watch for these warning signs in daily operation:

- Cleaning speed slows down and the time needed to reach Sa2.5 keeps increasing;

- Surface profile depth drifts outside the 40-75μm range required by most epoxy primer systems;

- Abrasive consumption per ton of steel rises noticeably;

- Patches of unremoved scale or rust remain on the workpiece;

- Excessive dust in the separator discharge, indicating too many fine particles in the mix.

<strong>Building the Initial Operating Mix</strong>

For a new machine or after a full abrasive change, build the mix according to workpiece thickness and cleaning requirement:

Application | Recommended steel grit size | Typical profile

Thin sheet (below 6mm), light cleaning | G40-G50 (0.4-0.6mm) | 30-50μm

Medium plate (6-20mm), general anticorrosion | G25-G40 (0.6-1.0mm) | 40-75μm

Heavy sections and thick scale (above 20mm) | G16-G25 (1.0-1.4mm) | 60-100μm

For most structural steel work aiming at Sa2.5, a blended mix of G25 and G40 at HRC 40-50 hardness offers a good balance of impact energy and durability. Start with a graded blend, for example 60% coarse and 40% fine, so the mix can fill in naturally as particles break down in service.

<strong>Replenishment: Add Small, Add Often</strong>

The key to stable performance is continuous replenishment:

- Add fresh grit in small amounts — typically 10-15% of the machine's abrasive capacity per shift — instead of dumping in a full batch at once;

- Base replenishment on actual consumption: track kilograms of grit used per ton of steel processed;

- If profile depth trends downward, increase the share of coarse grit; if the surface becomes too rough, raise the share of fine grit;

- Always confirm that fresh grit hardness matches the in-service mix. Mixing HRC 40 and HRC 55 media causes unpredictable wear behavior.

<strong>Daily Checks That Keep the Mix Healthy</strong>

- Separator air flow: adjust the air curtain so usable grit is not carried away with the dust — a badly set separator wastes good abrasive;

- Screen the mix weekly: take a sample and sieve it to confirm the particle size distribution stays within the target range;

- Inspect blades, control cage and liners regularly — worn impeller parts reduce shot velocity and can mask mix ratio problems;

- Keep the dust collector in good condition; excessive fines in circulation reduce the impact energy per kilogram of abrasive.

A disciplined mix ratio routine usually lowers abrasive consumption clearly while keeping Sa2.5 quality stable — the savings become visible within weeks of consistent operation.

<strong>Need Help Optimizing Your Shot Blasting Operation?</strong>

If you want to confirm the right grit size, hardness and mix ratio for your production line, our engineers can support you with abrasive selection and operating parameters. Contact us for free samples and technical consultation.