Cobot interfaces What greater lift capacity will mean for CNC machine tool operation

October 7, 2021   /   daniel@d2seattle.com

As the challenge of finding skilled manufacturing labor persists, some companies have had to look to automation to solve their workforce challenges. 

But the use of robots in the manufacturing space often requires additional strict safety procedures because of the strength, power, and inflexibility of robots while carrying out the tasks they are programmed to conduct.

An alternative viable option for many manufacturers are collaborative robots or “cobots.” While they do not have the power and strength of their larger robot cousins, cobots provide a much safer environment and are designed to work side by side with a human counterpart to enhance a worker’s capabilities by carrying out repetitious and tedious tasks. 

You will not find a cobot moving large-scale automobile parts in an assembly line, but they perform well when tasked to move and manipulate smaller and lighter objects. This makes them ideal in support of small and medium size CNC operations.

Cobots equipped with optical sensors or that are dealing with predictable production process are capable of loading parts into a CNC machine tool and removing them after the operation is complete.  This allows the machine operator to focus their attention on machining and reduces the risk of human error in the loading and unloading process. 

There are limitations, however. The two main factors that impact the optimal environment for cobot use are the payload capability of the robot (how much it can lift) and its reach (how close does it need to be to the items it is lifting or manipulating).

And, as it turns out, these two factors have an inverse relationship.

The greater the reach of the cobot’s arm, the further it can access parts and the deeper it can place those into a machine center. However, the further it needs to extend, the lower the weight of the payload it can handle. Proper placement and positioning will alleviate this challenge, but it is important that prior to acquiring a cobot solution that its limitations and capabilities are clearly understood.  

Of course, the primary reason for the development of cobotic solutions is the safety of workers near the cobot during operations. Operators can work closely with their machines when using a cobot solution, rather than repeatedly exiting a safety cage when traditional robots are employed.

Cobots have torque sensors and programming that allows them to sense when a collision occurs, and to react quickly to prevent injury to bystanders. Where a normal robot arm requires personnel to be out of reach, a human operator can work safely in the same workspace with a cobot.

As with the inverse relationship between payload and reach, the safety of a cobot also bears a cost.  Because cobots are pliant and force sensing to meet safety needs, they are often weaker than their robot counterparts, limiting their payload lift capacity.

In its optimal role in support of CNC operations, the lift capacity of a cobot will generally dictate the range of parts and tooling that it can support. Yet the payload capacity of a cobot does not consider the weight of a cobot’s end effectors, or hands. So, if the cobot is limited to 4kg (a little under 9 lbs.), and the cobot’s hand is 1kg, then it will only be able to manipulate parts that weigh 3 kg or less in any given operation.

Although cobots are still an emerging technology, their safety and ease of use as a force multiplier for machine operators is already pushing developers and manufacturers to improve the weight and reach capabilities so that they will become an increasingly integral part of the automated manufacturing space.