Using Energy Efficiently

Everyone is talking about energy efficiency, and about how we can use and convert energy in the most cost-effective way possible. However, the cheapest technology is not necessarily the most economical solution. Costs for operation, maintenance, repair and disposal also have to be taken into account. When it comes to electric drive solutions, it is important to choose the right technology.

Energy saving potential exists at all stages in the working process. However, in order to create energy efficient solutions for handling tasks, a comprehensive analysis is first required. Festo supports users in creating energy efficient machine and system designs and also helps them to optimise their costs in the process.

Avoiding wasted energy
Poor design leads to energy being wasted. This can be avoided by selecting the right components and having a comprehensive overall concept of machines and systems. Even at the design stage of electric drive solutions, energy is wasted due to the fact that the individual components such as the drive mechanics, gear unit and motor are configured separately. Safety factors in the range 1.3 to 2 are used in the design process to cover all eventualities. Consequently, a single axis incorporates this safety factor several times and the motor is often twice the size that it needs to be – frequently resulting in a drop of over 50 % in efficiency.

Another risk lies in examining the efficiency of only one specific technology without incorporating the other electrical components into the calculation. This can lead to incorrect assumptions being made. With electric drive solutions it is important to take into account not only the axis mechanics, toothed belt, lead screw or ball screw, but also the gear unit, servo motor and motor controller, whereby overall efficiency is calculated by multiplying the individual degrees of efficiency.

To support users in selecting the best possible solution and matching components, there is now software available to perform the calculations known as “Positioning Drives”. This software calculates the characteristic load values for the selected drives quickly and reliably – in a maximum of four steps. Simply enter the application parameters and required cycle times, edit the motion cycles and select the desired solution package. The program then outputs the detailed results such as motor characteristic curve, system data, product data and parts list. Users can then use this information for ordering and machine documentation.

Switching without power when at rest
Frequently in handling and automation technology, only positioning movements such as the insertion of a part in a machine for processing are required. This usually involves holding a position, and the electric drive remains under control without doing any work. Lead screw spindles with a self-locking design are suitable for ensuring minimal energy consumption when at rest. When using the electric piston rod cylinder DNCE with lead screw spindle from Festo, for example, you can hold a position for a long time without using any energy, thus keeping efficiency more or less at the optimum level. It accelerates smoothly and judder free and its positioning is freely programmable. The new type DMES axes with trapezoidal threaded spindle represent the latest generation of electrical servo drives. They offer compact dimensions with high rated loads and high mechanical torques with a feed force of up to 1000 N.

All other electric drives require an additional holding brake to prevent movement at rest. However, this efficiency can only be achieved if the electric drive is switched off when at rest.

Avoiding oversizing
Given the fact that electric drive systems are operated most efficiently at their nominal power rating, their operating point should also lie within this range and transmission losses between the motor controller and load should be as small as possible. This can be achieved by keeping the cables between the motor controller and motor as short as possible. A highly efficient motor controller such as the CMMP-AS together with servo motors EMMS offer additional optimisation potential. Avoiding mechanical power transmission components also contributes to efficient use. In this case, Festo’s design takes into account the fact that with standard axes, motors without gear units are sufficient for most applications. Another possibility for saving energy lies in better utilisation of the short-term thermal overload of electrical systems – frequently allowing use of a smaller motor. Considering all components at all times during the design phase prevents oversizing, as the motor needs only to be adapted to the required mechanical transmission capacity.

Electric drive solutions do not often make sufficient use of energy-saving potential. Festo supports its customers in identifying this potential, optimising systems and machines and, consequently, saving money.

Courtesy of  Festo