Blog

15 July 2020

Reset gravity, to go faster!

The combination of high speed and precision requires extreme efforts in the construction and implementation of High-speed robot systems.

It is essential to take this into account in the motion control strategy and the mechanical design of the actuators.

 

Many automatic systems are operated and maintained at relatively low speeds to ensure repeatability and mechanical stability

 

The moving mass should be kept as low as possible to limit the accelerations, and consequently, the forces involved (and to avoid deformation of the moving structure).

 

What are the most common applications on pick and place robots?

 

As already mentioned, in all those cases where it is necessary to decrease the moving masses to obtain greater dynamics; for example on high-speed robot Pick & Place with linear motors.

The idea is to make our pick and place robot believe that the moving mass is lower (at least on the z-axis)...

In this article, I talk about the advantages of a pick and place robot with linear motors.

Serialpicker l'high-speed robot pick and place sviluppato per automazioni ad alta cadenza
L'high-speed robot Serialpicker, dettaglio dell'azzeratore di gravità montato parallelamente all'asse Z.

How do you get gravity compensation?

Gravity compensation is a well-known technique in robot design. It achieves balance over the entire range of motion - as a result, the loads on the actuator are lower.

Are there any other advantages that help the performance of pick and place robots?

Let's not forget safety: By adopting a gravity compensation system on the z-axis of our robot, in the event of a power failure, our vertical axis cannot descend to the lower-end position, even if the robot is fully loaded.

When designing the robotic system, we will choose a gravity compensator (or zero gravity compensator) that has a capacity slightly greater than the load to be transported. It will overcome the force of gravity by keeping the load in the upper-end position.

In this other article, you will find a comparison between the pick and place robots with linear motors and the pneumatic ones.

Passive support

Since gravity compensators are passive elements, once the idle position has been defined, the vertical axis and the load remains safe in position even in shutdown condition: we will consequently avoid mechanical damage to the system in case of power failure.

Energy saving

In fact, for as long as the system remains in the idle position the vertical axis motor will not be in action, avoiding unnecessary overheating and waste of electricity.

Operating principles

Although the operating principle of a gravity compensator device is very similar to that of a mechanical spring, the physical principles that characterize it are very different.

A mechanical spring stores energy as potential elastic deformation energy.

The Serialpicker gravity compensator is a device with magnetic action.

Magnetic springs store potential energy in the magnetic field of permanent magnets.

No mechanical mechanism is involved that is subject to failure or fatigue. These devices, therefore, have a virtually infinite life expectancy.

As a result, they are ideal candidates for industrial applications with high dynamics and durability requirements.

Posizione di montaggio dell'azzeratore di gravità sul robot pick and place Serialpicker

No energy source needed

No electricity or compressed air.

The Serialpicker gravity compensator can help to raise the safety the safety standard of the robot pick and place

They exert a constant force over their entire working range - the slider is pushed out of the stator and the force rises from zero to the nominal value in a short distance and remains constant throughout the entire stroke.

When applied in a vertical axis, the motor acts in applying forces only necessary for positioning and, as already mentioned, not for supporting the weight in the idle position.

it can be said with some measure, that a vertical axis, thanks to the Serialpicker gravity compensator, behaves neither more nor less like a horizontal axis.

 

Let's see the salient features

  • It is merely passive, requires neither electricity nor compressed air.
  • Simple design
  • Forces up to 60 N
  • Strokes up to 350 mm
  • Can be easily applied using a mounting kit

How can it be installed?

It's done by mounting the Serialpicker gravity compensator device on its support without tightening the locking screw. The vertical slider of the vertical axis should be moved to the idle position, and after that, the screw that fixes the device must be tightened.

This will be the starting position in reference to which we will tighten the gravity resetting clamp.

The motor will only come into action when it is necessary to lower the vertical axis, and the force at stake will only be that to overcome the force of the gravity compensator: which will be equivalent to the load to be carried.

The Serialpicker gravity compensator is supplied with a complete mounting kit including a compensation system for misalignment and parallelism errors.

When an appropriate gravity compensator system is used to compensate for the moving mass, the power required by the electric drive is reduced.

Hence, when designing the system, a smaller drive can be considered, and thus also the power supply.

The moving mass is smaller

Starting and stopping the load is smoother and the vertical guidance system is subjected to less load.

Maintenance-free

There is no fatigue failure mechanism involved.

Want a closer look? Request an appointment with one of our Technicians! !

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Andrea Milan
About Andrea Milan
Appassionato di nuove tecnologie e robotica industriale, cultore di viaggi e musica Jazz. Co-fondatore di Omas srl.