CNC Machine Resource Management: Perfect World Versus Reality

Summary

When it comes to CNC machine resource management, there are two sides to that coin: the theoretical environment and the physical environment. Both have tools and tool programming, and both benefit from functionality like program management, tool wear monitoring and tool breakage monitoring. Each employs that functionality differently, and each feeds back information to the other. Digitalization brings those worlds together.

A real-world tool instance passed from programmers to engineers into a digital environment will be used to create CAD/CAM simulations—theoretical environments made up of perfect tools that never wear. “When you’re managing a theoretical environment, you’re working in a perfect world,” said Steve Fruehe, solutions consultant at Siemens. “But perfect-world tooling and programs still needs to be managed, even if they’re in a perfect environment where there’s no wear and tear, there’s no operator error, and everything is controlled and virtual, with no real-world consequences.”

When the work done in the theoretical world—the tooling and bill of materials—is transferred to the shop floor, you have the real-world challenges to be managed. “After realizing that you don’t have any of those perfect world-tools, the challenge is to manage tool inventory,” Fruehe said. “Questions to consider are, ‘How many tools do we have? How quickly do we remove tools? How quicky do these tools break? What do these tools cost?’”

Questions about real-world tooling accumulate over time, as do questions regarding part programming. Users can design parts in a perfect world, but soon realize the program they created doesn’t run on a particular machine. Tooling and program questions are inherent to CNC machine resource management and bridging the theoretical and the physical while maintaining consistency between the two is essential.

Digital solutions that can build that bridge and maintain consistency do exist and pursue a very important goal: “We’re trying to remove operator error and communication barriers to establish best practices,” explained Fruehe.

Tool wear and breakage monitoring

Operators in the real world can monitor tool wear by measuring between every cut (Figure 1), trial-and-error style, or by replacing a tool after a designated number of runs or actual machining time. The other way to monitor tool wear is through what Fruehe calls “responsiveness.”

“If SINUMERIK controllers are used, we can monitor spindle torque during the cutting process. By doing this, [users] can monitor how the tool changes over time,” Fruehe said. “A new tool uses less energy to cut than a tool nearing its end of life.”

More torque applied to the spindle typically indicates tool wear. However, no torque feedback also indicates a problem. “The machine expects force feedback. If there is no force, the machine sends an alarm to the controller,” Fruehe explained. “Typically, that’s an indication of tool breakage. Digitalization and data collection give users more information to make the machining process much easier.”

Fruehe explained that if a tool continues to wear, breakage is inevitable. “Our job is to determine when a tool will break and how to prevent it from causing a catastrophic problem on the shop floor. We want to get ahead of problems before they occur,” he said.
 

Smart shop floor

Digitalization extends the programming done in the theoretical world to the real world of the shop floor (Figure 2). Digitalization is what allows a fleet of CNC machines on the shop floor to leverage functionality like program management, tool wear monitoring and tool breakage monitoring. “Digitalization is connected to our lives in ways we don’t even think about,” Fruehe said. “People may not be aware of how ingrained our lives have become with digitalization and machine learning.”

“Consider that each application could save a few seconds. If you have a fleet of 100 machines and those few seconds saved occur multiple times throughout the day, hundreds of times throughout the week, and thousands of times throughout the month, the time saved becomes exponential,” Fruehe said. “With this trend, [users] start to see the dollar signs come to life. Five seconds over the course of a year can be 10 more parts; 10 more parts at the cost of $10,000 can be $100,000 more in your bank account.”

Digitalization allows users to identify where gaps are in the process. However, no one knows the machine better than the original equipment manufacturer (OEM). Having their hand in commissioning or building out a new machine can be beneficial.

“OEM partners assist customers in providing the digital twin or use software to use their machine as a test bed for the digitalization journey. It is common for OEMs to remote into machines for troubleshooting and maintenance,” Fruehe said. Siemens software is designed to integrate with third-party solutions.
 

Getting started

The first step to digitalization is connecting machines to a network so they can communicate. Other scenarios are removing expired part programs or running a large quantity of the same part and fine tuning the feed overrides to optimize automatically—each step done without human intervention, which minimizes time and human error.

Fruehe encourages users to start small; just start collecting data. “It doesn’t have to be a grand plan,” he said. “Just start seeing when your machine is on and off, and then go from there. My role at Siemens is to help in that process.”

Digitalization allows more data to flow between the theoretical and real worlds of CNC machining, and more data is better when making business-critical decisions that enable users to be more productive and proactive.
 
This is the fourth article in the Machine Tool Digitalization series sponsored by Siemens. The other articles in the series include:

• Machine Tool Digitalization Benefits CNC Builders and Users
• Edge Computing Enables Smart CNC Machine Digitalization
• Digital Twins Validate Real-World CNC Machines