Motor solutions that are faster, more accurate and more energy-efficient help with the understanding of machines and devices. This has a positive effect on their quality and longevity and has the potential to reduce their ecological footprint. Operating costs and therefore the unit costs of the manufactured products are also reduced.
Fast, precise movements play a key role in the cost-effectiveness of machines and equipment used for the production, packaging or transport of goods. The two developments described below enable significant improvements in the agility, accuracy and energy efficiency of movements. As a result, they can lead to significant product innovations in mechanical engineering.
Mechanical engineering is becoming mechatronic
In the past, machines or devices were seen as mechanical structures that had to be moved in some way. This resulted in separate development paths for mechanical component, controllers and motors, as well as for sensor technology and software. Most of the time, mechanical components were defined and designed first, and often even described in greater detail. Only then were the motors and the electrical engineering constructions, including the hardware for the process, motion and safety controls as well as the visualisation, selected and designed. Right at the end came the creation of the programs—often delayed and under enormous time pressure—intended to bring the whole thing to life.
This separation of disciplines led to inefficiencies as a common basis for communication was lacking. Each department worked mainly for itself, and the necessary exchange to achieve better targets together simply was not there. One of the main developments of the past few years has therefore been to look at machines and systems as complete mechatronic works. This promotes interdisciplinary, joint development with deeper integration of software, electronics, sensors, actuators and mechanical components, and thus higher efficiency.
Acceleration through method reversal
The key to the successful development of more efficient machines and systems is reversing the traditional order of development. This means that since the movements within a machine or system are its most essential core, it is good to define the motion axes first.
The process logic of the axis movement can then be defined. During this step, also known as sequence logic modelling, the description of the machine behaviour is created as a sequence of states, essentially as an extension of the requirements description. Since this only follows the logic and is not linked to the linguistic conventions of the individual departments, it can be used as a common basis for technicians of all disciplines. They are able work on this at an early stage and use it as a reference for their detailed work.
Separate software tools now exist for this purpose. These support developers in designing motor components and come with the appeal that PLC programs can be automatically derived from the behavioural description of the machine later on.
From mechatronic concept to digital twin
The next step in creating mechatronic concepts is to build a physics-based model. It is sufficient to define the dimensions and masses of the objects to be moved and the transport kinematics.
Well before time and costs have gone into the detailed design or programming, or even prototyping, the consistency of the kinematic design has been checked, and, for example, any collisions can be detected or avoided. The physical variables used for this purpose also serve as parameters for component design and automatic program creation.
All additional work must be carried out to the same extent as before. However, it can be done in parallel. This not only speeds up the overall process, but, together with the description of the machine’s behaviour as a common basis for discussion, it also enables constant coordination between the disciplines. This tends to lead—especially in terms of motors—to better solutions than the later “revival” of a preset, constructed mechanical component.
A gradual process from model to reality
The mechatronic, model-based development allows for the creation of a digital twin, whose proximity to reality is gradually growing. The fact that a complete, all-encompassing model does not have to be created from scratch makes it far less daunting.
Since it can be used for position determination simulations in every phase, this also helps very athletic development goals to be met reliably. The good thing about this is that motor solutions can be created in a short time — without the high costs of physical (error) tests.
Embedding for efficiency
Designing machines and systems as mechatronic units using embedded computer hardware and sensor technology as well as electrical motors has the potential to increase the efficiency of movements. If, as with race cars or spacecraft, the motors and drives are seen as central elements and the mechanical components are constructed all around them, so to speak, less dead mass needs to be moved.
Not only are fewer auxiliary kinematics required than drives added to a given mechanical component, but more than anything, the drives can often be used as part of the structure and the remaining mechanical components can be smaller.
This method comes with another significant advantage: It allows the construction of modular machine assemblies and their integration into comprehensive control and automation solutions. The departure from monolithic machines reduces the effort and time required for the development of customer-specific machines and systems, as only the special components need to be redesigned.
Prerequisite for electrification
To a large extent, another major development of the recent past is a prerequisite for changing methods in mechanical and plant engineering: the electrification of motors. As we have already seen in the automotive industry, modernising the motors leads to huge technical advances and achieves new efficiencies. The basis for making similar things possible in mechanical engineering comes from product innovations from the past few years, which are replacing previous methods.
Many drives that were previously implemented mechanically, hydraulically or pneumatically can therefore be replaced. Where this does not make sense, the addition of electrical sensors and drives already brings improvements that lead to significant efficiency gains compared to traditional implementations.
Mechanical drives reaching the end of the road
Unlike with automotive construction and power generation, internal combustion engines and turbines do not play a role in mechanical and plant engineering. For decades, manufacturers have focused mainly on electric motors for primary drives.
Until today, mechanical secondary drives were used to drive smaller units within machines and systems. The advantage of this is their comparatively low manufacturing costs and energy losses. In contrast, they come with a lack of flexibility and greater need for maintenance, for example, for lubricating the moving parts. They also pose an obstacle to modularisation.
Today’s electric motors have efficiencies far beyond 90 percent, and the costs of the control units required have fallen enormously. This is why electric drives can replace mechanical drives everywhere, just as large motors once replaced transmission belts for main drives.
This results in efficiency gains by eliminating mechanical auxiliary structures and their moving mass, as well as freedom from maintenance. At the same time, electric drives make it very easy to realise differentiated, precisely controlled movements in small machine parts. As a cable as the only connection needed, electric drives also facilitate the construction of modular machine concepts.
Is it the right time for pneumatics?
Pneumatic drives are very common in mechanical engineering, primarily for generating short linear movements. They play to their strengths where very high speeds are required. High retention forces at the end positions can also play a role. Classic electromechanical drives often did not have a high enough stroke to replace them, rotary electric motors were usually too slow and linear motors were too expensive.
Low-cost linear motors and modules are now available with the ability to directly replace pneumatic cylinders because they help it reach similar speeds. Controlled by—sometimes integrated—servo drives, this allows for more precise positioning and much more differentiated movements, even at variable speeds, opening up additional possibilities for the realisation of complex machines. A further contribution to this comes from rotary-stroke motors, which combine linear and rotary movements in one single drive.
The complexity of valve assemblies and the pipework of pneumatic drive systems is increasing at an exponential rate. This impedes functional expansion and a modular design and keeps flexibility low. Replacing pneumatic drives with electrical counterparts does away with these limitations and allows the construction of machinery and equipment with greater efficiency and productivity.
Electrifying hydraulics
Traditionally, hydraulic drives are preferred where large forces are required. But even in diesel locomotives for the railways, power is now usually transmitted from the combustion engine to the wheels via a generator and electric motors instead of a hydraulic converter gearbox.
In mechanical engineering, too, the availability of sufficiently strong but compact electric motors should first be checked. Torx motors, which have been available for around a decade, provide powerful and precisely controllable alternatives. Electric linear drives that are suitable as replacements for hydraulic cylinders now also exist.
The same advantages apply here as with pneumatics: In addition to the more precise positioning, this includes above all the elimination of the pipework, which boosts flexibility and design freedom.
Hybrid forms of energy
However, there will continue to be applications of pneumatics and especially hydraulics that cannot be easily replaced by electric motors. Here, at least, the notoriously lossy pressure provision needs to be converted to more economical methods. Instead of generating the system pressure by means of piston pumps and maintaining it stably at a high level, it should be generated on a needs basis.
This has been possible for several years now, since highly reactive motor controllers drive highly efficient internal gear pumps for pressure generation via fast servo motors. This allows media pressure to be delivered sufficiently quickly when needed. Compared with classic hydraulic pressure generation, this not only leads to an energy saving of more than 50 percent, it also significantly reduces the space requirement.
These methods are ideal for increasing the service life, productivity, precision and efficiency as well as the sustainability of production facilities. In the case of drive electrification, this applies not only to new developments, but equally to retrofitting existing machines and systems.
Images: reichelt elektronik
