A vacuum gripper is used to lift hard, flat objects such as boards, doors and metal discs. The gripper reviewed in particular can be viewed as a beam construction consisting of three parallel beams combined with a fourth beam orthogonal to the first three. On each end of the three parallel beams there is a vacuum cup, adding up to a total of six cups. The aim of this report was to analyze the strength of a ProWood Maxi with tilt by Lifts All AB made of steel with a yield strength of 355 MPa and to further develop it.
The development process of the gripper aimed to produce a concept of a steering or warning system to prevent undesired tilts of the gripper to avoid injuries on the user as well as damages on the load. A requirement on the construction was an ability to be able to withstand a load of 200 kg.
The project was restricted to only analyze the beam construction of the gripper with the main focus on the stresses and deformations. Calculations were performed including free body diagrams, force and torque equilibria as well as shear force and internal torque diagrams. Following this, computer analyses were done with the aim to find more realistic forces on the vacuum cups by letting those stay fixed and apply forces on the suspension devices corresponding to 200 kg. These forces were then used to analyze the stresses and deformations of the construction using ANSYS. For the concept of steering and warning system, strain gauges were placed on the beam construction. These gauges image the distribution of the load on the gripper and prevents usage if the load exceeds predefined critical values.
The results of the analysis showed that the maximum stresses were about 50 MPa and that the maximum deformations in the steel construction ended up at 2.3 mm.
In conclusion, the total deformation of the steel construction is small compared to the deformation in the elastic vacuum cups. The steel construction will be able to hold a load of 200 kg with a safety factor of n=7 considering the yield strength of the steel. It is also possible to enable a simple control system to prevent undesired tilting using strain gauges via a warning system, however using an active balance system would not be practical.
2016. , 32 p.