Tending CNC Machines? Here's How to Do it With a Cobot

See how machine tending tasks like loading and unloading parts and running CNC machines can become the daily work of a cobot in your shop.


cobot tending Haas CNC machine

Automation is a big buzzword in manufacturing, and for good reason. Adding robots, cobots (or collaborative robots), and other automation equipment is a game changer. They save time, increase production, and can even improve the quality of parts and assemblies thanks to their repeatability and precision.


If you’ve ever seen banks of robots working on a production line, the idea of bringing automation into your machine shop might seem a bit more complex than your resources will permit.


However, it doesn’t have to be that way. Sometimes the best way to venture into automation is to look for the “low hanging fruit” – in other words, look for the easiest tasks and automate those first. In our experience, tasks that are very repetitive, not too complex, or that cause slowdowns or bottlenecks in production are great starting points.


CNC machine tending is a perfect example. By using a cobot, you can quickly and easily automate the work of loading, running, and unloading CNC machines. This reduces loading errors, speeds up production, and might even help fill in gaps in your labor force, among other benefits. Keep reading to learn how to get started.


CNC Machine Tending in Action


Most CNC machine operations are subtractive manufacturing processes in which material is removed from a blank or part. In a traditional manual process, an operator loads a workpiece into the machine and secures it in a fixture. The fixture either holds the workpiece still or rotates it, while cutting tools remove material. All the cuts and other movements of the CNC machine are guided by a computer program for extremely precise and repeatable results each cycle. Then the operator removes the finished part and reloads a new one.


This work is known as machine tending, and it can also be accomplished by a cobot, like the OB7 from Productive Robotics. Some commonly automated examples include:


Milling machines. In a CNC mill, the stationary workpiece is held in place by fixtures and rotating multi-point cutting tools shape the piece.


Lathes/turning machines. A lathe has one or two fixtures that hold both ends of the workpiece and rotate it. The cutting tool remains stationary as it cuts. When two fixtures are used, they can usually be adjusted to the correct length to keep parts secure.


EDM (electrical discharge machining) machines. This machine makes cuts with electric spark erosion, in which sparks are created between the conductive workpiece and an electrode. The workpiece is placed in a bath of deionized water during cutting. This non-contact cutting method is used for intricate parts or those that are very difficult to cut with traditional milling or turning CNC machines.


CNC laser cutters. In this process, a high-temperature laser melts and cuts the material. The heat remains in an extremely localized area, so there is minimal heat-related distortion to the part. It also leaves smooth edges and requires little to no additional finishing.


How to Get Started With CNC Machine Tending Automation


Because the motions for CNC machine tending are straightforward (e.g., pick up and load blank, close CNC machine door, run the machine, unload the part, etc.), it’s usually a simple matter to assemble the cobot and set it up. However, there are some important considerations to keep in mind, such as:


Creating a highly structured, predictable, fixed workspace. This means blanks must be in same spot for the cobot to pick up each time, so you may wish to use positioners like a tray or dispenser to keep them aligned. It’s also important that worktables or benches remain a consistent distance from the CNC machine to accommodate the cobot’s reach. And be sure the work area has no unplanned obstacles or changes, like someone setting down a coffee mug in the arm’s path or moving the stack of blanks from its usual location.


Note that a structured workstation can be rearranged if necessary; however, the cobot will need to have its work instructions and movements adjusted.


Selecting the right gripper. While it’s possible to use multiple grippers, switching them out can add time to manufacturing processes. Many grippers can adapt to pick up different sizes, shapes, and types of materials. In general, parts with two parallel sides (e.g., rectangular or cylindrical prisms) are easiest to pick up with a pincer-style gripper. Vacuum suction cups are another option, especially for thin, delicate, or flat items.


Calculating payload. This is the amount of weight the arm can lift and it includes the weight of the gripper as well as the part before it is machined. Keep in mind that depending on the specific application, the amount of weight can affect the speed with which the arm moves and the amount of time it takes to come to a complete stop.


Planning for reach and axes of motion. Reach is how far the arm can extend and stretch out. It dictates how far the cobot can be placed from the CNC machine. Axes of motion are like joints on a human arm and they allow the cobot to reach over, under, through, between, or around obstacles. While six axes of motion are common, the OB7 cobot has seven. This gives it even more dexterity for loading, unloading, and moving machine hatches in a variety of workstation configurations and sizes.


Cross training for flexibility in production. Because they are compact and quick to set up, cobots can be switched between multiple workstations. This can make your production schedule more efficient and allows you to make on-the-fly adjustments to production, for example:

  • Increase volume production as needed to catch up or get ahead

  • Take on new, larger orders

  • Fill in for operators who are out sick or on leave to avoid diverting other workers

  • Fill jobs that would remain open due to worker shortages

Working in the dark? Adding a cobot to one or more CNC machines makes it possible to run those operations without a person tending the machine, even after hours or overnight. Some shops take advantage of this capability to get ahead by building up back stock, take on larger orders, or add new parts and part families to their offerings.


DIY Automation with Productive Robotics