Automated Guided Vehicles (AGVs) are more in demand than ever. They are a central component of modern intralogistics solutions.
What is their core task?
↔️ They independently transport loads from point A to point B.
↕️ They lift and lower loads.
Where they operate, people are also present. Therefore, SAFETY is the top priority to ensure no danger to people.
Critical Points in Lifting and Lowering that Can Pose a Danger to People:
Safety: AGVs move freely through the hall where people are present. Therefore, the lifting elements must be safe and must not simply collapse in the event of an emergency stop. Otherwise, there is a risk of life-threatening danger to people.
Our Safe Solution: Our spindle lifting gears are self-locking. In the event of a power failure, the spindle lifting gears will not simply collapse but will hold the position stably. The load remains securely at the previous level. For additional safety, it is recommended to use four support points, i.e., a lifting system with four screw jacks. This prevents the AGV from tipping over due to unequal load distribution. The advantage: no additional elements are needed for the lifting movement.
Stability: To lift heavy loads, the lift table must be stable. Stability comes, for example, from the scissor mechanism in the lift table.
Our Solution: The spindle is stable enough to absorb lateral forces (such as from the acceleration of the load). A complex guide in the lift table is not necessary—the scissor mechanism can be omitted. However, it should be noted that lateral forces during long lifts can be a challenge for spindles under compressive load. If the energy from the mass acceleration becomes too great, it can lead to plastic deformation of the spindle—at least in the extended state. But since most AGVs only perform lifting movements of up to 200 mm, two advantages arise: the customer has more space, and costs are reduced.
Speed: Modern manufacturing systems require the shortest cycle times and high speeds. The 24V motor quickly reaches its limit.
Our Solution: We can vary the speed through different gear ratios, spindle pitches, and spindle types. Generally, spindle lifting gears are not exemplary in terms of high efficiency. Nevertheless, due to self-locking or a brake on the motor when power is off, the lifting system consumes no energy as long as no lifting movement is performed. Since the AGV only uses a fraction of the cycle time for the lifting movement, energy requirements can be relatively easily calculated. The advantage: short cycle times and high speeds are possible. The self-locking feature makes energy requirements more predictable.
lifting system
To ensure optimal dimensioning, we explicitly recommend considering the following points:
- Long Lifts and Stability: Long lifts compromise buckling safety. Spindles under compressive load face stability issues with increased length. Calculations using Euler's or Tetmajer's formulas provide insight here. Combined with lateral acceleration, the calculation of equivalent stress must be considered.
- Higher Speed and Efficiency: Achieve higher speeds through higher pitches. Higher pitches also result in better efficiency. However, note that with a spindle pitch over 4.5°, self-locking is no longer assured.
- Use of Linear Chain Systems for greater lifts: For larger lifts, we recommend push chain systems. To keep the AGV as narrow as possible, linear chains provide an appropriate solution for lift heights exceeding 300mm. The advantage is that the linear chain can be deflected 90° behind the drive housing, requiring significantly less space. Caution: Linear chains cannot serve as guides. Check out our demonstration video: GROB Trade Fair News - Day 1.
