Automating the CNC machine process is a great way to keep the spindle turning and increase throughput. These tips will help you get it right in your shop.
In past blogs, we've explained how collaborative robots (cobots) and flexible automation benefit CNC machine shops. You might have also seen examples of cobots at work with CNC machines, like this one above.
If you're thinking about automating your CNC machining processes with a cobot, you might wonder exactly how to go about it. We'll explore the details you need to know here.
Break the CNC Process into Steps
In order for your cobot to work in tandem with the CNC machine, you’ll give it detailed instructions for all the steps and associated motions in the process. Each step will be stored in the cobot’s memory. But first you must make a list of all the actions in the current manual process, that is, all the steps an operator takes when tending the machine, in the correct order.
In a typical example, the steps may include:
Picking up a blank or component from a tray or conveyor
Loading and securing the blank in a vise or other fixture
Closing the machine door
Pressing the start button
Waiting for the cycle to finish
Opening the machine door
Releasing and removing the finished part
Putting the finished part on a tray or conveyor
Depending on the process or type of CNC machine, additional steps may be involved, such as inspecting a completed part, cleaning a part, or clearing chips from inside the machine. Be sure to take all of these steps into account and determine if the cobot or an operator will be carrying them out.
Connect the Cobot to the CNC Machine
The cobot and CNC machine must be able to send and receive signals. In the simplest setup, if your CNC machine has a single output, you can use an M-code to signal the cobot when the machining cycle is finished. This tells the cobot it’s time to open the door, remove the workpiece, and continue the rest of its stored instructions to start the next cycle. In this example, the cobot arm opens and closes the machine door and presses the start button.
If your CNC machine has multiple outputs and/or an autodoor feature, it’s possible for the cobot and machine to send signals back and forth when each has finished a step, thereby integrating their actions back and forth. For example, first the cobot loads a workpiece and signals the CNC machine to close the door, then the CNC machine door closes, the cycle runs, the door opens, and the CNC machine signals the cobot to remove the workpiece and resume its saved instructions.
The OB7 cobot package from Productive Robotics includes a General Equipment Interface (GEI) with eight digital inputs, eight digital outputs, and four analog inputs to help manage air, ethernet connectivity, and signals between the cobot and CNC machine.
Minimize the Variability of Inputs
Unlike a human being, a cobot can’t make real-time adjustments to its actions or split-second decisions about how best to perform a task. Cobots require a consistent and uniform environment in order to function optimally. This applies to the blanks or components it handles and loads, the manner in which the components are presented, and the place it will put completed parts.
For example, if three different employees manually cut blanks to size and deliver them to the cobot for CNC machining, all three employees must cut the blanks to uniform size and shape and deliver them to the same place, oriented the same way. This ensures the cobot will always be able to pick up the blank and load it correctly every time.
Now is the time to arrange the workstation and delivery system to be uniform and consistent. This careful planning also minimizes defects and out-of-tolerance machining, and keeps the flow of parts steady. As a result, quality and throughput are increased, and scrap and rework are reduced.
Inflow and Outflow
Just as parts need to be uniform and consistent, how they flow in and out of the CNC workstation is critical too. The instructions in the cobot’s memory tell it exactly where to turn, reach, and grasp for a blank or part, and that is exactly where and how it will move. It’s not able to notice that someone used a different kind of tray or set a tray down on a different cart.
The same principle applies to finished parts, too. For example, if they are to be stacked on a cart, the cart must be in the same spot all the time. The cobot is not able to look around and find it if someone accidentally puts it back even a few inches too far away.
Plan for Monitoring Tools and Equipment Over Time
While automating CNC machining can bring opportunities for running equipment unattended or 24/7, it’s still not a “set and forget” process. It’s still necessary to monitor tools and equipment including:
Monitoring cutting tool life cycle to ensure parts are within tolerances
Ensuring proper chip control is in place
Monitoring fluctuations in temperature or forces
Proper activation of safety systems
Inspection for wear and tear on tools, lines, and connections
Checking for proper alignment of the cobot arm with the CNC machine, tools, fixtures, etc.
This is especially important if the machines will be running unattended for long periods or overnight. It can be helpful to write out a process or checklist to ensure everything is in correct working order throughout the run time. Be sure the checklist includes details about what to monitor, who is responsible, and what to do when adjustments are needed.
Train your Operators
A cobot like the OB7 is easy to teach, but one of the biggest keys to success is making sure the operators are comfortable working with it and adjusting work instructions. After all, it’s one thing to tell someone the cobot is easy to work with and another for them to try it and see it really is that easy.
Everyone who will work with the cobot must spend time using it, teaching the arm a series of movements, and updating the steps. It’s also crucial each operator understand the proper flow of parts in and out of the workstation, and how their daily work will change. Instead of tending the CNC machine themselves, they are now responsible for overseeing and troubleshooting the cobot/CNC machine pair, and keeping the larger workflow moving smoothly.
Hopefully, you see how just a little investment of time and thoughtful planning can greatly impact your CNC machining operations. If you have questions about specific cobot applications, want to learn more, or are ready for a demo, please contact us!