Cases for the high-efficiency gearboxes produced by Fertigungstechnik Nord in Gadebusch, Germany, are machined from solid castings. By locating all of the bearing bores in the one-piece cast case, the Nord “Unicase” housing eliminates all torque and lateral forces from the sealing faces of the bolted-on cover, producing a compact yet extremely robust gearbox. As might be expected, however, this design approach requires extremely high accuracy in the production machining processes that produce the cases. It also creates a very challenging environment for the subsequent quality assurance gauging operations required.
Nord machines their “Unicase” housings in a single setup on large CNC machining centers and gauges the bores at an adjacent workstation. Total Unicase production is more than 280,000 units annually, in a variety of sizes and configurations. Each of them requires 12 or more different quality assurance gauging operations. (Figure 1)
Gadebusch Plant Manager Steffen Timm has extensive experience with networked automatic gauging systems used in the plant’s shaft manufacturing area. These systems, supplied by Marposs, automatically measure production shafts and provide compensation feedback to the controls to maintain quality.
That approach is not feasible in the case machining area. “Equipping them all with fully automatic measuring devices would be too expensive and economically unfeasible,” he explains. But Timm has been able to obtain many of the same benefits by changing from conventional cable-connected plug gauges to the new M1 Wave Wireless gauges from Marposs.
The most obvious benefit of moving to a wireless solution is the elimination of cables, and that is no small advantage when a typical workstation has a dozen or more gauges, each with several yards of cable attached. The safety impact of removing those cables from the working environment is self-evident, and eliminating the maintenance cost associated with them produces significant operating cost savings as well.
Timm has found that the new gauges also have other important benefits. For example, eliminating the cables also eliminates a major source of interference and incorrect gauge readings that cost his employees precious time at the machines. “There were bores that would be detected as out of range owing to an error linked to the cabling system,” he says. “This would lead to defective goods and incorrect tool settings. The new wireless gauges have substantially reduced the error rates. Combined with the display electronics in the form of networkable PC technology and the process-oriented software solution, the new measuring systems ensure a high measuring reliability. In addition, we implement traceable documentation of the measured data we manually collect in our casing manufacturing plant.”
Flexible, Reliable, and Accurate
The completely self-contained Marposs M1 Wave wireless gauges use proven Bluetooth® wireless technology for data transmission. Unlike other wireless systems that use plug-in transmitter dongles, the M1 Wave allows full freedom of movement to inspect the cases while they are still clamped in the machine, and all with no risk of false readings due to cable interference or defects. (Figure 2)
M1 Wave wireless gauges are based on the Marposs M1 Star EBG (Electronic Bore Gauge), which features interchangeable heads mounted on a common handle. The EBG heads incorporate an electronic measuring cell that directly generates the measured value, eliminating the conventional mechanical transmission using tapered needles or push rods to actuate a transducer. The handle contains the Bluetooth electronics and power supply to produce a completely self-contained gauging system.
Because the M1 Star EBG eliminates all of the delicate mechanical components used in a traditional gauge, it provides exceptional precision. The electronic transducer ensures a reproducibility of ≥ 0.5 μm. The system is highly resistant to mechanical damage and virtually impervious to coolant-induced wear or sticking, providing high reliability in even the most difficult operating conditions. Adding to the flexibility of the system, a single handle can use any M1 Star EBG interchangeable head. This makes it easy to change diameters and also reduces the amount of bench space required to store the gauges on the production floor. (Figure 3)
Transmission of the measured value is triggered by pressing a button on the handle. Three transmission rates between 10 and 40 measurements per second can be selected via software, with the lowest selection yielding a battery life of more than 220 hours of active transmission. A programmable automatic power saving function is also available to ensure maximum battery life. In most applications battery changes are required every 8-10 weeks of production.
Easy Analysis, Ease of Use
M1 Wave wireless gauges can be connected to various Marposs display devices including the E4N Wave column, the Merlin mini-PC, or the E9066T™ thin panel industrial PC as used by Nord. Measuring only 50 mm thick, the E9066T can be wall or swivel mounted, integrated into a control panel, installed on a swivel arm, or even used as a table-top device as it is at Nord. Marposs offers a 17″ touch screen for the E9066T as an alternative to the standard 15” LCD TFT display used by Nord. The gearbox manufacturer also uses the integrated Ethernet network adapter to connect bench top units to a plant computer for higher-level data collection and analysis.
Nord displays and analyzes measured data using Marposs’s Quick SPC™ software for Windows operating systems. Timm especially appreciates the menu-driven test processes that guide the operator step by step through the measurement sequence. The program is so user-friendly that operators can program their own work processes on site using the Windows interface. (Figure 4)
The system is intelligent enough to monitor trends and adjust inspection frequency based on process stability. This eliminates the need for 100-percent inspection of every part, and guides operators through dynamically generated partial test routines via on-screen prompts. An integrated Q-Das statistic server is used for data analysis. The system also supports archiving in a variety of formats via network or external data storage media. “These new wireless measuring systems ensure top measuring reliability,” Timm says.
In the production environment at Nord, operators have found them to be extremely sturdy and precise. And, with the recent introduction of an inductively charged battery system for the M1 Wave wireless gauges, they promise to be nearly maintenance free as well. Altogether, a good outcome for a project that started out simply to eliminate a bunch of troublesome cables.