1. Understanding the Forces Acting on the Brick
1. Clamping Force (Fc):
The normal compressive force delivered by the pneumatic or servo cylinder across the gripper fingers to pinch the brick.
2. Tangential Friction Force (Ffriction):
The vertical resistive force generated by the contact rubber pads. With 2 active jaws:
Ffriction = 2 × μ × Fc
3. Vacuum Pull Force (Fvacuum):
The negative differential pressure acting across the sealed contact surface:
Fvacuum = ΔP × Area × η
4. Required Dynamic Load (Fr):
Total downward force to overcome during upward acceleration:
Fr = m × (g + a)
2. Sizing Formulas & Safety Factor
Safety Factor Criterion:
Sf = Fholding / Frequired
• Sf ≥ 1.5 : Safe, reliable robotic transfer in industrial conditions.
• 1.0 ≤ Sf < 1.5 : Critical / marginal hold; vibration or jerks cause slipping.
• Sf < 1.0 : Mechanical failure! The brick slips mid-air, drops, and fractures.
3. The Two Robotic Gripper Architectures
| Feature |
Case ā : 2-Jaw Parallel Clamps |
Case ā”: Vacuum Foam Area Gripper |
| Workpiece Orientation |
Perpendicular to arm (Length l along depth) |
Parallel to arm (Length l along width) |
| Gripping Action |
Pincer clamp across narrow width w (L > w) |
Top-surface suction seal across area (l × w) |
| Contact Material |
High-friction Polyurethane Rubber Pads (μ = 0.40 - 0.65) |
Closed-cell EPDM Porous Sealing Foam |
| Best Applied For |
Dry bricks, unmortared blocks, high accelerations |
Palletizing, bricklaying (sides free for mortar) |
4. Indian Standard (BIS) Masonry Specifications
| Specimen |
Standard Reference |
Dimensions (l × w × h) |
Typical Mass |
| Modular Brick |
IS:1077 (BIS) |
190 × 90 × 90 mm |
3.0 - 3.4 kg |
| Traditional Red Brick |
Non-modular Indian |
230 × 110 × 70 mm |
3.5 - 4.2 kg |
| Fly Ash Lime Brick |
IS:12894 |
230 × 110 × 75 mm |
3.2 - 3.8 kg |
| AAC / Concrete Block |
IS:2185 |
300 × 150 × 100 mm |
10.0 - 14.0 kg |
