No.000174 Transfer Mechanism

Good IDEA!

7

Application Overview

Purpose

• Purpose
  • To utilize suction cups for transporting different shape plastic cases while maintaining orientation of the workpiece.
• Operation
  • The spherical bearings and air cylinder allow the suction cups to be tilted, so they are flush against the workpiece.
  • By using regulators and electromagnetic valves, the floating pressure can be adjusted during the transfer process.

Points for use

• The angle of suction cups can be retained by locking the air circuit.

Target workpiece

• Shape: Plastic case
• Size: W 100 x D 120 x H 20 (max) mm
• Weight:0.3kg

Design Specifications

Operating Conditions or Design Requirements

• Spherical bearing deviation angle 13°
• Cylinder stroke: 8.3 + 3 = 11.3 mm
• Output 11.3 x 70％ = 7.91 N・m (air pressure 0.4 MPa)
• Spring force at 15 mm stroke 3.66 N
  7.91-3.66=4.25N
• External size: 96 x 100 x 130 mm

Required Performance

• Allowable weight: 1.38 kg

Selection Criteria for Main Components

• Air Cylinder
  • Output at least 3.76 N at stroke of 15 mm or more.

Design Evaluation

Verification of main components

• Verify the air cylinder output
  Force conditional values at maximum tilt of the workpiece
  Workpiece weight: M=0.3kg
  Gravitational acceleration: g = 9.8m/s²
  Workpiece maximum tilt: θ₁=13°
  Distance between rotation center and workpiece center of
  gravity: L₁ = 25mm = 0.025m 
  Distance between rotation center and cylinder mounting: L₂ = 18mm = 0.018m 
  Cylinder output: F = 4.25N
  Suction cup diameter:d=φ20
  Vacuum level: p = 70 -kPa = 0.07 -MPa
  Safety factor at suction: S=4
• Air cylinder selection
  
  Moment by the workpiece：M₁  
  
  M₁=M×g×sinθ₁×L₁=0.3×9.8×sin13°×0.025=0.017N・m
  Force F₂ applied to the cylinder by moment M₁
  M₁ = F₂' x L₂ = F₂ x cosθ₁ x L₂ Thus, we have the following:
  F₂=M₁/(cosθ₁×L₂) =0.017/(cos13°×0.018)=0.017/(0.97×0.018)
  =0.97N  
  Thus, select an air cylinder with cylinder output of F.
• Check the load by the selected cylinder.
  Moment M₂ by the air cylinder at maximum tilt
  M₂=F'×L₂=F×cosθ₁×L₂
  =4.25×cos13°×0.018=4.25×0.97×0.018=0.075N・m
  Therefore, M₂＞M₁. Thus, meeting the condition.
• Check the suction force.
  Vacuum level: p = 70 -kPa = 0.07 -MPa, cup diameter: d = φ 20mm
  Safety factor at suction: S = 4, number of cups: n = 4
  Suction force:W=π/4×d²×p×1/S×n=π/4×20²×0.07×1/4×4=22N
  Therefore, W > M x g　　⇒ 22N > 3N Thus, the suction force satisfies the condition.

Other Design Consideration

• By using a guide pin with spherical bearing, floating suction hand can be tilted in a desired direction to grip the workpiece.
• The suction hand is free floating after the workpiece is released. Therefore, it is recommended to use the four cylinders to lock the hand in place when it is not gripping a workpiece.