Robots or a linear unit after all?
Effective automation technology is increasingly becoming a decisive competitive factor. To solve handling tasks, you can choose between robots and linear systems. IEF-Werner offers high-performance linear systems with which companies can also optimally fulfil very special requirements. Which solution is more economical depends on the individual application. But what needs to be considered?
Manufacturing companies rely on automation for efficient and economical assembly and handling. Industrial robots have proven to be a reliable aid in many applications. "But they are not always the right choice," Thomas Hettich, Product Manager at IEF-Werner, says. "There are applications in which the expensive robots can do far more than is actually required. And then the price-performance ratio is no longer right. Positioning systems made from standardised linear units can be a much more economical alternative." The automation specialist from Furtwangen in the Black Forest develops customised positioning solutions for its customers - from simple linear units to multi-axis, fully assembled systems in various sizes - with spindle drives, direct drives or toothed belt axes, depending on the application. "We offer both the appropriate solutions and the process expertise," Hettich promises. For effective automation, every solution has its place on the market. The only question is: Which technology is the most economical for which application?
"For up to two axes, a linear guide is generally the better choice," Hettich says. The two solutions can only be compared if they have to map a three-dimensional space - i.e. a combination of at least three axes or a robot is in use. It is then necessary to define which requirements the system should fulfil - for example in terms of speed, dynamics, the load to be moved or the length of the travel path. "Linear guides are always used when high positioning accuracy or fast and precise movements along a path are required, or when heavy components need to be moved," IEF expert Hettich explains.
When it has to be precise
Linear guides offer the same rigidity at every position, regardless of how heavy the load. This is because the distance from the axis to the left and right guide is the same everywhere - in contrast to a robot. The greater the distance between the gripper and the axis of rotation, the more frequently vibrations occur, which is detrimental to accuracy. The weight of the component to be handled also has a negative effect. "With a robot, I have the option of positioning it accordingly. However, this can restrict its freedom or bring other disadvantages," Hettich says. For example, one customer initially envisaged a robot for a particular application. However, due to the travel distances and the components, this had to be dimensioned accordingly, which would have had an impact on the dynamics. In order to fulfil the required precision, the products would have had to be placed in a circle around the robot. This would have required considerably more space. A robot would therefore not have been economical, and the costs for the required size and footprint would have been disproportionately high for the customer. In the end, he opted for a linear system. "Linear axes with a toothed belt or rack and pinion drive can potentially cover very large strokes and therefore move quickly and effortlessly between different processing stations. A linear system therefore offers significant advantages, especially in large installation spaces.
Simple or complex?
"When it comes to solving simple handling tasks and the requirements are geared towards speed, dynamics and precision, we usually recommend a linear system," Hettich explains. Compared to robots, they are often much more compact. IEF-Werner is able to combine different drive technologies. Depending on the requirements, spindle, direct or toothed belt drives are used.
Robots, on the other hand, are suitable for complex applications. A classic articulated robot has significantly more degrees of freedom. This means that it can also realise rotary and swivel movements. This means that the more movement options the application requires, the more the pendulum swings in the direction of the robot. It can also be positioned flexibly and does not require a complex substructure.
There are also cases in which it is worth combining linear technology and robotics," Hettich says. This can significantly increase efficiency in assembly and material handling: For example, a robot can be mounted on a linear unit in order to move from one production station to another. The linear axis thus significantly increases the robot's reach.
Safely controlled
"Linear systems and robots can be controlled differently," Michael Reißle, software developer for systems at IEF-Werner, reports. While robots have their own language, the main component of a linear system is a programmable logic controller (PLC). The programming effort for both systems is very similar, Reißle says. Robot programming is focused often on specific tasks. It can be time-consuming, but usually requires less complex programming structures. PLC programming, on the other hand, is more flexible and more complex in terms of controlling and monitoring processes - and recording process data.
The user is also on the safe side with a linear system when it comes to maintenance. This is because automation is put under a lot of strain, especially in applications that involve enormous quantities and high output. "With millions of cycles, a robot has to return to the manufacturer at some point for an overhaul, as the components are installed in the housing and are usually difficult to access," Hettich says. With an axis, repairs can usually be carried out in-house. This is a significant cost advantage. The linear units are made up of various individual parts such as deflection, planetary gears or guide elements, which can be replaced easily if necessary. "We have realised many applications for our customers that have been running for years and even decades," the IEF expert reports.
"Robot or linear system? The question is not always easy to answer and is very individual from case to case," Hettich summarises. "We are on hand to advise our customers. If more than three axes and movements such as turning or swivelling are required, we also recommend a robot if the application demands it. Ultimately, the important thing is that our customers receive automation that is optimised for them."
