Its modular design and, above all, its multifunctional head make the DVS UGrind 800 a universal workshop machine with which the hard fine machining of workpieces of small or medium batch sizes can be realized with high precision, quickly and cost-effectively. How efficient micromachining with the DVS UGrind 800 can also be easily implemented for a special requirement is shown by a solution for machining the frogs of gear pumps, with which we at DVS Universal Grinding were able to convince a long-standing customer just in terms of quality and economy.

What are gear pumps?

In a gear pump, two equally sized intermeshing gears run in a housing between the two housing covers. The housing covers contain the plain bearings for the two gears, one of which is the drive gear whose shaft protrudes from the housing to drive it externally. Opposite the points where the gears mesh are the pump's inlet and outlet, respectively. When the driving gear moves, it creates suction, which draws in the medium and conveys it back out through the discharge. This simple principle leads to considerable technical challenges in practical production.

To avoid pressure loss due to leakage currents, the flat surfaces of the gears must be as close as possible to the housing covers. For this reason, the width of the gears has a very narrow tolerance of a few µm. To ensure low-friction running, the face surfaces must also have only a low surface roughness.

Since the tip circle diameter of both gears is tightly enclosed in the housing, this must also be ground to within a few µm after gear cutting.

• Width of the gears: 3.3 mm, toleranced with +/- 4µm,
• plane parallelism 4µm
• Cylinder, diam. 8h6, concentricity 5µm, cylindrical form 5µm, perpendicularity to the face of the gears 4µm.
• Roughness of cylinder: Rz 1.5, roughness of face Rz 1.3
• tip diameter 17,25 (0 / -0,01)

Gear pumps are used in a variety of industrial applications - e.g. as metering pumps or for pumping viscous liquids at high pressures and under high temperatures, as hydraulic pumps in construction or agricultural machinery, or in vehicle construction as injection and oil pumps.

Efficiency and precision for the heart of the gear pump

• Machining the gears of the pump poses particular challenges for production:
• In order to maintain the tight tolerances and ensure the required throughput, the parts must be completely machined in just one setup.
• Due to the high surface qualities required, especially on the flat surfaces, there is a risk of grinding burn.
• Pure machining time, approx.24 sec, non-productive time (loading, unloading see below)

The Micromachining Solution with the DVS UGrind

• The component is driven and securely entrained in its own gear teeth by a gear driven by a servo motor.
• This constellation enables machining between fixed centers. Compliance with manufacturing tolerances is ensured by in-process measuring systems.
• Two machining stations, each operated by its own robotic system, ensure the throughput of the machine. While the machine is machining a part, the finished part is simultaneously removed at the other station and a new blank is clamped.

The high-precision yet highly efficient machining of the core elements of gear pumps once again demonstrates the adaptability of the DVS UGrind 800. Its modular design, with two tailstock consoles with fixed centers per station, allows the universal machine to be adapted for different special manufacturing tasks. Its multifunctional head can be equipped with up to two external grinding wheels for face and diameter machining depending on the application.