Machine Tending: The Advantages and Disadvantages

24 September 2020
Machine tending: Robots overseeing machines

Why read this: Machine tending can increase productivity and improve the working environment. However, demanding safety regulations and expensive vision systems might make investments in the popular application more challenging. This article highlights the advantages and disadvantages of machine tending.

Advantages

Machine tending refers to a robot overseeing a machine, for example a CNC machine. A typical machine tending application consists of a robot loading and unloading the parts while the machine operates on them.

Machine tending reduces the risk of injury

Machine tending assists in making the production floor a safer space. By using a robot instead of a human to feed a machine with material or parts, the probability of injury is significantly decreased. In case an employee approaches the cell, the robot can be programmed to slow down, further eliminating the risk of injury. In addition, it frees employees from the tedious job of loading and unloading and gives them time to focus on more productive tasks. This creates more value for the company and encourages employees to further develop their competences.

Machine tending can raise productivity

Use of robots for machine tending raises speed and decreases part cycle time (the time needed for one piece to be finished) as a result. Usually, it is only a matter of difference in seconds compared to a human operator, but over weeks and months this can prove as a major boost in productivity as a whole. Especially because a robot can work for weeks in a row without stopping. The robot can also run a couple of hours after normal workday unattended, thus providing more capacity without the need for further operators.

The robot can have more uses than just loading/unloading

By default, the robot just moves the material from point A (e.g. bin) to point B (e.g. CNC machine) during a machine tending application. However, some of the robots used for machine tending applications are often cobots (collaborative robots), meaning that they have a flexibility which can be used for other tasks in the factory such as finishing applications. Depending on the fragility of the product, tasks like polishing, sanding, deburring etc. are often better done by a robot than a human employee, as robots are typically more faster and more consistent.

(See also: The Pros and Cons of Collaborative Robots – Flexibility vs. Efficiency)

Robots can tend more than one machine

Given the right mounting such as rail, floor or ceiling mounting, a robot can tend multiple machines at the same time (also known as parallel machine tending). The robot can be strategically placed between two machines or above them and load and unload parts to both of them. If the machine is big enough, the robot can even be placed inside the machine. In any case, all those options could save space on the factory floor and reduce movements between processes.

Parallel machine tending: One robot tending several machines at once.
Parallel machine tending: One robot operating several machines.


Disadvantages


Machine tending sometimes calls for vision systems which can be very expensive

The use of a robot com­es with a high cost, including the robot itself, maintenance costs, different tools corresponding to different pieces fed to the machine, and sometimes the need for a vision system. Such a system is crucial to verify if the material is successfully processed by the machine.

If the robot picks up parts that are in a fixed position, a vision system is optional but recommended, as it can detect and discard bad parts before they are further processed. However, if the robot needs to pick up parts that are scrambled around, a vision system is essential. Vision systems can cost up to 50.000 dollars and therefore raise the cost of the investment significantly.

Robots may find it hard to handle different kinds of material

Depending on whether the robot tends more than one machine or different parts, materials and shapes are used, the robot might fail in grasping all those parts efficiently.  Therefore, different grippers need to be placed on the robot each time. A solution to that problem is to have all of them already mounted and just rotate the end-effector of the robot to get the correct tool in front, ready to grasp.

RObot with two grippers.
By rotating the end-effector, one robot with more grippers can pick up different parts.

 

Machine tending and CE marking

According to European Union requirements, every machine needs to be CE marked before being marketed in the EU. This includes a risk assessment as well as preparing an instruction manual and other documents stating that all safety requirements are met. Similar rules apply for machines outside of the EU as well. Now if two new machines are combined or assembled (e.g a robot and a CNC machine), apart from the individual risk assessment of each machine, a new assessment must be carried out based on the application. This complicates things of course. In case of parallel machine tending, things get even more challenging.

Conclusion

Machine tending is an automation solution that can be worth applying to your production floor. It can improve productivity and relieve employees from tedious task. However, potential challenges like complications with CE marking or an expensive vision system could turn this into a more challenging investment.