G-force in vibratory screening is the gravitational force multiple generated by the screener's vibrating motor, typically ranging from 3G to 7G, that determines how aggressively material is accelerated on the screen surface. It is the primary tuning parameter that controls the balance between screening efficiency and throughput on every vibratory separator. A screener operating at 5G accelerates material on the screen surface at five times the force of gravity.
G-force is produced by the counterweights attached to the screener's vibrating motor. Adjusting the weight setting or motor speed changes the G-force output. In round vibratory separators manufactured by Sweco, Kason, Midwestern Industries, ScreenerKing, and others, G-force is the single most influential variable an operator can adjust to optimize performance. Too little G-force allows material to sit passively on the screen, reducing screening efficiency and promoting blinding. Too much G-force can throw material off the screen surface before it has a chance to pass through, reducing efficiency from the opposite direction while accelerating wear.
G-Force Calculation
G-force is calculated from the screener's stroke (amplitude) and motor speed (RPM) using the following formula:
G = (2 × π × RPM / 60)² × Amplitude / 9,810
Where amplitude is measured in millimeters (half the total stroke, peak to peak) and 9,810 is gravitational acceleration in mm/s².
Typical G-Force Ranges by Application
| Application Type | Typical G-Force | Mesh Range | Notes |
|---|---|---|---|
| Safety / scalping screening | 2 – 4G | 4 – 30 mesh | Low force sufficient; protects fragile product |
| General classification | 3 – 5G | 20 – 100 mesh | Standard operating range for most dry powders |
| Fine screening | 4 – 6G | 100 – 325 mesh | Higher force combats blinding and static |
| Ultra-fine screening | 5 – 7G | 325 – 500 mesh | Often paired with ultrasonic de-blinding |
| Wet / slurry screening | 4 – 6G | 50 – 400 mesh | Must overcome liquid surface tension |
| Dewatering | 5 – 7G | 100 – 325 mesh | High force drives moisture through mesh |
| Friable / fragile materials | 2 – 3.5G | Any | Low force minimizes particle breakage |
Why This Matters
G-force is the first parameter to evaluate when a vibratory screener is underperforming. It directly controls three critical outcomes:
- Screening efficiency — Proper G-force keeps the material bed in a fluid, stratified state so undersize particles can reach the screen surface and pass through. Low G-force creates a stagnant bed where fines are trapped above the screen.
- Throughput capacity — G-force works with the lead angle setting to control conveying velocity and residence time. Increasing G-force typically increases the rate at which material moves across and through the screen.
- Screen and machine life — Excessive G-force accelerates wear on screen cloth, bounce balls, springs, and bearings. Operating within the manufacturer's recommended range extends component life and reduces maintenance costs.
Related Glossary Terms
- Amplitude / Stroke — The displacement distance that, combined with RPM, determines G-force
- Vibrating Motor — The component that generates the G-force through counterweight rotation
- Resonance — A destructive condition to avoid when adjusting motor speed
- Screening Efficiency — The performance metric most directly influenced by G-force
- Blinding — Screen clogging that can be reduced with proper G-force adjustment
- Conveying Velocity — Material travel speed across the screen, driven by G-force
G-Force FAQs
What is G-force on a vibratory screener?
G-force on a vibratory screener is the gravitational force multiple produced by the motor's counterweights. It measures how many times the force of gravity the screen surface accelerates material. Most industrial vibratory screeners operate between 3G and 7G. Higher G-force means more aggressive material movement and better separation of near-size particles, but also increases wear on the screen and machine components.
How do you calculate G-force on a vibratory screen?
G-force is calculated from the motor speed (RPM) and the stroke amplitude. The simplified formula is: G = (2π × RPM / 60)² × amplitude / 9,810, where amplitude is in millimeters. Increasing either the stroke length (by adjusting counterweight angle) or motor speed increases the G-force output.
What G-force is best for fine screening applications?
Fine screening applications (100 mesh and finer) typically perform best at 4G to 6G. Higher G-force helps overcome surface tension and static charge that cause blinding on fine mesh screens. However, exceeding 7G on fine mesh can reduce screen life and cause particle degradation in friable materials. Ultrasonic de-blinding systems can supplement G-force to improve fine screening without increasing mechanical stress.
Optimize G-Force with the Right Equipment
ScreenerKing vibratory screeners — including the SiftPro, SiftPro 48, and SiftPro 60 — feature adjustable counterweights for precise G-force tuning from 2G to 7G. Need replacement springs, motors, or screens to restore proper G-force output? We stock parts compatible with Sweco, Kason, Midwestern, Cleveland Vibratory, Russell Finex, and Rotex.
