A vibro sifter looks simple – a round stainless steel drum with a screen and a couple of outlets – but its performance depends on how the vibration is produced and controlled. This article explains the working principle in plain terms.
Main Parts of a Vibro Sifter
- Base: houses the vibro motor and carries the springs; usually on castors.
- Vibro motor: a vertical motor with eccentric weights at the top and bottom of its shaft.
- Springs: isolate vibration from the base and let the screen assembly move freely.
- Screen frames and mesh: one, two or three frames, each with a tensioned mesh and its own outlet.
- Top cover and inlet: close the machine and receive the feed.
- Clamps: hold frames together; quick-release for cleaning.
The Gyratory Motion
The eccentric weights are deliberately out of balance. As the motor turns, the top weight creates a horizontal circular force at screen level, which spreads material outwards. The bottom weight acts lower down and tilts the assembly, adding vertical and tangential components. Together they create a three-dimensional gyratory motion: particles hop, rotate and travel across the screen, repeatedly meeting the mesh openings.
Particles smaller than an opening fall through to the next level and leave through the lower outlet. Larger ones keep travelling to the rim and leave through the side outlet above the mesh.
Lead Angle: Tuning the Travel Pattern
The angle between the top and bottom weights is called the lead angle. Changing it changes the path material takes:
- Small lead angle: material moves quickly outward – good for scalping where most material passes immediately.
- Larger lead angle: material spirals more and stays longer on the screen – better for fine separation.
Adding weight increases amplitude, which helps with heavier or coarser material but can reduce efficiency for very fine powders. The right setting is found during trials with your material.
What Affects Sifting Performance
- Particle size relative to mesh – particles close to the opening size pass slowly (near-size particles).
- Moisture and oil – make powders sticky and cause screen blinding.
- Bulk density – heavy material passes faster by weight; light, fluffy powders need more area.
- Feed rate – overfeeding forms a deep bed, so fines can't reach the mesh.
- Screen tension and condition – loose or damaged mesh reduces efficiency and can let oversize through.
Next: learn how to choose mesh size, or view the vibro sifter machine specifications.
Frequently Asked Questions
What makes a vibro sifter vibrate?
A vertical vibro motor with out-of-balance eccentric weights at the top and bottom of its shaft.
What is the lead angle?
The angle between the top and bottom eccentric weights; it controls how material travels across the screen.
