The manufacturing process of today involves many challenges, from mass production down to a lot size of one. The CNC controls in factories have to master this market trend without an adequate amount of skilled labor in the US manufacturing world. In essence, manufacturing is facing a renaissance in the CNC control technology shift.

Machining application utilizing the AFC function on a HEIDENHAIN TNC.

On one hand, many of the current CNCs used in factories are controlling machines with 3-axis motion or maybe 3+1 and relying on a CAM program to provide the right machine code (e.g., G-codes) to drive these machines. An operator just pushes the green button to start a program. When one operation is done, the worker stops the machine, repositions the part (or a cobot), and pushes the green button again to start the next machining program. This type of operation bears a few risks.

Also, the next generation of professional manufacturing machine operators will not be willing to just push a button. Many machine operators want to feel empowered to make a quality part. At the same time, advanced 5-axis machine CNC controls have arrived and many of today's operators expect that the part they see on the touchscreen comes off the machine at the exact size as the print or what the 3D model calls for. They do not want to rework or recut like the experience many machinists are used to. And quite frankly, that is how it should be if factory owners want to maximize the machine utilization and productivity output. In order to achieve this, the modern machine motion system has to be much more sophisticated than a simple 3-axis CNC with encoders on ball screws.

Improved Speed on the Factory Floor

Today's new 5-axis machine controls offer so much more on the factory floor including multiple touchscreens and the ability to import CAM files in IGES or DXF formats right into the CNC. This enables users to interactively create and simulate the machining process on a virtual machine with high-resolution graphics. The system gives the operator confidence that the part will be perfectly cut without a collision of the spindle or fixture of the machine setup quicker and more easily than ever before.

These new controls offer accessibility from the operator panel on the machine, right to the server system. Options now possible for control users include the ability to view setup sheets, workflow information, and even run the CAM system right from the machine as well as update programs, create new tool paths, and transfer data right into the CNC. In the age of mass customization, priorities and workflow change constantly, so the smart CNC needs to be able to adjust quickly and reliably.

HEIDENHAIN's StateMonitor in use via a remote tablet.

Another important function now available for use on the factory floor that speeds up the process is the ability to reprioritize manufacturing jobs automatically. This feature is programmed to determine if all the necessary machining programs and tools are available to complete the next job, and if they are, the machine does so. It even determines if the remaining tool life is adequate to machine the next job where the tool will be used. The control can accurately determine how long it will actually take to machine a particular job because it has the actual machine motion or kinematics stored in the CNC. This enables the operator or programmer to accurately calculate the machining time based on machine behavior and axis motion speed, hence optimizing machine utilization time and maximizing profits.

To ensure that parts are set up correctly on a machine tool, a new feature similar to face recognition found on some newer smartphones is now also in use on some manufacturing factory floors. Think for a moment of an operator at a 5-axis machining center connected to a robot or parts changer. The operator loads a pallet with the qualified part setup into the machine. In the machining center, a camera takes a high-resolution image of the perfect setup and stores it into the control. Now, when the operator starts the automation process to load the next part into the machine, the system will take another picture of that part, compare it to the stored image in the control, and determine if the setup is correct. If so, the machining process can begin. But if there is a problem, such as if someone left a wrench on the fixture or a feature like a bore is missing, the control will then trigger an error message and either stop the machine or load the next part, repeating the process. When an “all clear” is received, the part will be machined.

Improved Accuracy on the Factory Floor

The visual setup system called VSC (Visual Setup Control) from HEIDENHAIN.

Now, let's move from speed to accuracy. As in most cases, it is a tradeoff between the two during machining. This is no longer the case with advanced CNC functions.

Controls are available that allow a programmer to achieve both speed and accuracy. To do so, the user can define a tolerance band for the machine movement, allowing it to move as fast as possible around corners and critical features without radical speed changes. Radical speed changes are a problem as they generally leave marks on fine surface finishes and risk final part accuracy.

Picture a racetrack with many curves. The racecar driver wants to optimize the path he takes around the corners to be as close as possible to the curb and not lose speed, but not go too far over the curb that he's penalized by the officials. Advanced control systems compensate and control for that on a machine tool. When taken one step further, if the operator wishes to machine a part beyond the accuracy provided by the cutting tool shape (e.g., a bull nose radius tolerance), smart controls offer features to handle that.

Other important considerations now in place in today's advanced machine controls to ensure maximum part accuracy and superior surface finishes include the use of sealed linear glass scales and high dynamic motion systems that are critical, specifically in simultaneous 5-axis applications. Dynamic efficiency functions are advantageous if parts are machined without knowing how much stock material is really being removed.

Let's take, for example, 3D-printed parts or castings. A 3D model in a CAM system “assumes” how much engagement of the cutting tool in the material is happening and that determines the speeds and feeds that are written into the CNC program. The control has the capability to automatically adjust the optimum feed rate based on spindle load, optimizing material removal rate as well as extending the cutting tool life. This maximizes process reliability and efficiency even when cutting unknown material thicknesses and the operator is not at the machine.

Connected Machining on the Factory Floor

Today's smart controls can now often be connected to a company's network, allowing programmers and operators to communicate without paper and share files or other documents between the machining center and the office team. This encourages smoother and more efficient work than before possible.

In addition, a powerful monitoring system can be connected either via DNC, MTConnect Modbus, or OPCUA protocols. This plug-and-play solution offers instant analytics about machine performance and operation efficiency. The communication feature will e-mail at predefined times/dates the specific machine messages to the person with the right skill set (e.g., preventive maintenance staff) who then can take actions to ensure maximum machine utilization. All this can be viewed and operated not only on the local network but also on mobile devices like smartphones or tablets.

Conclusion

In summary, today's advanced smart CNC controls allow manufacturers to optimize the manufacturing process right on the factory floor like never before. At the same time, monitoring software provides valuable data and alerts to identify predictive maintenance or other error messages in real time, allowing operators or managers to maximize the ROI of the modern machine tool, from a large production down to small lot size applications.

This article was written by Gisbert Ledvon, HEIDENHAIN TNC Development Manager, at HEIDENHAIN, Schaumburg, IL. For more information, visit here .


Motion Design Magazine

This article first appeared in the February, 2020 issue of Motion Design Magazine.

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