Machine tool monitoring? Do not discount DNC


The newer machine tools are designed to be monitored, and many of them offer dashboard displays of critical performance metrics as a standard feature. However, going beyond rudimentary machine monitoring capabilities may be easier for manufacturers starting out with more established technology: a Distributed Numerical Control (DNC) system to transfer part programs to CNCs. “You get 90% of the way with what comes out of the box, but you need tools for that last 10%,” says Rich Hefner, president of the developer of the FactoryWiz machine monitoring system. “DNC is an essential tool for this. “

As an example, Hefner cites the machining of screws of different sizes on Swiss type machining centers. Rather than creating separate sets of toolpaths for each size, a CAM programmer can use a macro to modify a few key variables in a common program. However, he says tracking quantities and cycle times for individual screws can be complicated when monitoring is separate from DNC.

The reason is that many communication protocols used to collect CNC data, which differ from manufacturer to manufacturer, would not recognize

With tablets and PCs more and more common in the workshop, the integration between monitoring and DNC can eliminate duplicate data entry (possibly on different terminals) by standardizing and consolidating the processes on each workstation. of work. Image courtesy of FactoryWiz.

the individual part programs created by the macro. Consider MTConnect. MMS has covered this standard extensively for a good reason: it makes a significant contribution to making machine monitoring accessible by providing a common “language” for a diverse mix of machine tools and other workshop equipment. However, MTconnect is a read-only standard. That is, it is designed to extract data from the CNC, but not to send data to it. It cannot issue the command necessary to modify variables to monitor parts as well as to machine them. Returning to the example of screws machined in Switzerland, “You will get the same program header regardless of which screw you make out of the 50 different screws,” Hefner explains.

DNC has no such restrictions. Decades ago, vendors of these systems essentially experimented with reversing the flow of data to get a rudimentary level of intelligence out of the shop floor. One of the means to this was the DPRNT (“data print”) command, which inserted a language into the G code for outputting the selected data to a printer via the RS232 wired connections of the time. Modern DNC systems work essentially the same, he says, although the software is much better and more user-friendly, and the connection is generally faster (and often wireless).

In any case, the ability to reach the “last 10%” of Hefner’s capacity is inherent in a system born out of the DNC. DNC connects through the control’s native protocol and can become a data source for machine monitoring or other analysis software. He argues that this capability can be advantageous even when it is also native to the latest CNCs connected to Ethernet. After all, machine tools in production today come from different eras.

Machine monitoring aside, stores also seem to be rediscovering the value of full-fledged DNC, says Domenic Lanzillotta, vice president of sales. DNC helps put in place consistent and standardized processes for managing and distributing CNC programs, he explains. This proposal is of particular interest to those looking to comply with quality control certifications. Likewise, DNC can alleviate cybersecurity issues with practices such as transferring programs via USB stick. “I have installed more DNC systems in the past two months than in the past two years,” he says.

Adding machine monitoring amplifies these benefits, even when monitoring ambitions don’t go beyond tracking downtime and other basic metrics. Machine monitoring has come a long way since the days of linking PLC hardware to lamps in the machine tool stack to produce DPRNT commands. Today’s software offers a range of features for automatic remote alerts and notifications, job progress tracking, and even direct text communication between workstations and departments. “Why not take the DNC component and include it in this same operator interface? Hefner asks. “Why shouldn’t (the same tablet or workstation computer used for monitoring) be where they can click and select the file to send to the machine?” “

Add other software to the mix, such as an enterprise resource planning (ERP) system, and tablets or workstation computers can provide a common interface for a range of different tasks, from ” connection ”to jobs through notification to quality control that the parts are ready. “When we started with monitoring, we were just collecting information and providing reports, and we were just looking at productivity from a strictly analytical perspective,” Hefner explains. “As we moved forward, we really looked to this as an information hub – like a communications infrastructure within a company.”


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