Universal grinding machines for precision manufacturing tasks

Precision grinding applications increasingly require manufacturers to accommodate a wider variety of workpiece sizes and geometries while maintaining tight tolerances, consistent surface quality, and efficient production. This is particularly important when the same manufacturing environment must handle internal and external surfaces, contours, tapers, or more specialised operations such as out-of-round and thread grinding. A machine platform that can combine these capabilities can help manufacturers reduce the need for multiple dedicated machines while providing greater flexibility as production requirements change.

EMAG’s UG Series was developed with these requirements in mind. The universal grinding machines combine internal, external, and out-of-round grinding capabilities with a modular machine concept designed for precision, flexibility, and process reliability. With grinding lengths ranging from 400 to 1,500 mm, the series covers applications from toolmaking and small-batch production to the machining of longer shafts and complex workpiece geometries. Depending on the application, workpieces can be machined between centres or held in a chuck.

The series comprises four models: the UG 400 with a grinding length of 400 mm, the UG 630 with 630 mm, the UG 1000 with 1,000 mm, and the UG 1500 with 1,500 mm. This range allows users to select a machine according to workpiece dimensions and production requirements rather than adopting a single configuration for widely different applications.

All four machines share a technical foundation that includes linear guides in the X and Z axes, servo drives with recirculating ball screws, and direct-drive motorized grinding spindles. The standard centre height is 175 mm, while the UG 1000, for example, can accommodate workpieces weighing up to 120 kg. Larger centre heights and workpiece capacities can be specified as options for applications requiring additional flexibility.

Direct-drive technology for precision grinding

At the centre of the UG Series is a grinding head equipped with direct-drive motor spindles providing up to 11 kW of power. By eliminating belt drives, the design removes a potential source of vibration and transfers torque directly to the spindle. This contributes to uniform power delivery and stable grinding conditions, factors that are particularly important when dimensional accuracy and surface finish must be maintained consistently.

The automatically swivelling B-axis further expands the machine’s application range. It provides infinitely variable positioning from –15° to +225° with an accuracy of 0.0005°, enabling the grinding wheel to be positioned for different surfaces and contours without extensive manual adjustment.

Grinding wheels can operate at peripheral speeds of up to 50 m/s. For internal grinding applications, the machines can be equipped with high-speed precision spindles using oil-air lubricated bearings. These spindles enable the machining of smaller bores while maintaining the stability required for precision internal grinding.

The workhead is similarly designed with accuracy and rigidity in mind. Precision tapered roller bearings provide concentricity accuracy of 0.5 µm, while a swivel range from 0° to +30° supports cone grinding strategies. A pneumatic lifting device assists with workpiece setup and handling.

For applications requiring additional process monitoring, optional acoustic emission (AE) sensing can detect contact between the grinding wheel and workpiece. Identifying the point of contact allows the machine to reduce unnecessary approach movements and idle time. For more specialised operations, an optional workpiece spindle with C-axis functionality enables out-of-round and thread grinding by synchronising workpiece rotation with the machine’s axis movements.

Supporting accurate workpiece positioning

When grinding between centres, accurate positioning and support of the workpiece are essential to achieving the required geometry. The UG Series tailstock incorporates a 63 mm quill for MK4 centres and is designed to operate with minimal backlash.

Fine adjustment of ±40 µm allows operators to compensate for taper and maintain concentricity. Depending on production requirements, the tailstock can be supplied with manual or hydraulic actuation. The hydraulic version automatically retracts the quill, helping shorten workpiece changeover times in applications involving repeated loading and unloading.

Integrated sensing can also be used to monitor correct positioning of the workpiece tip. This provides an additional level of process control by confirming that the workpiece is correctly positioned before grinding begins.

Dressing and measuring options

Grinding wheel condition has a direct influence on surface finish, dimensional accuracy, and process consistency. As the wheel wears, its geometry and cutting characteristics must be restored through dressing. EMAG therefore offers several dressing configurations for the UG Series, allowing the system to be matched to the grinding wheel, workpiece geometry, and production volume.

A table-mounted dresser provides flexible positioning for different wheel diameters and geometries. For batch-production environments requiring more automated processes, a dressing spindle can be mounted on the workhead and incorporated into the machining cycle. Dressing-tile holders can also be installed on the tailstock or workhead for applications where a simpler dressing arrangement is sufficient.

Beyond dressing, the modular machine concept provides options including NC synchronous tailstocks, in-process measuring systems, hydraulic steady rests, and automatic NC-axis tailstocks. In-process measurement can be particularly useful in applications with tight dimensional tolerances, allowing the grinding process to be monitored without relying solely on post-process inspection.

CNC control for different grinding requirements

Machine operation is based on FANUC CNC technology. The standard FANUC 0i-TF controller uses a dialog-oriented human-machine interface intended to simplify programming and operation. Frequently used functions can be accessed directly, while structured operator guidance helps reduce the complexity associated with setting up different grinding operations.

For applications involving more demanding contours, out-of-round components, or thread grinding, the FANUC 31iB Plus is available. Its higher computing capability and synchronised motion control support precise coordination of multiple machine axes, which is required when the workpiece profile depends on the relationship between axis movement and workpiece rotation.

The use of established CNC technology can also simplify integration into manufacturing environments where operators and maintenance personnel are already familiar with FANUC controls.

A modular approach to grinding

An important aspect of the UG Series is its ability to be configured around specific manufacturing requirements. Rather than limiting the machines to a single type of grinding operation, the combination of different grinding spindles, workholding arrangements, dressing systems, measuring technology, and axis configurations allows users to adapt the platform to particular components and production volumes.

EMAG can also provide turnkey packages incorporating the machine, tooling, workholding equipment, cutting fluids, and finished workpiece programs. This approach can reduce the amount of process development required after machine installation and provide manufacturers with a production-ready grinding solution.

With four machine sizes and a range of configurable technologies, the UG Series addresses applications extending from relatively compact precision components to longer shafts and complex geometries. Its combination of internal and external grinding, contour machining, and optional out-of-round and thread grinding gives manufacturers the flexibility to perform different precision grinding tasks on a common machine platform.

For manufacturers facing a growing mix of component geometries and production requirements, this flexibility can be as important as the machine’s individual performance specifications. By combining precision grinding technology with modular automation, measuring, dressing, and workholding options, the UG Series provides a platform that can be configured around both current production needs and changing manufacturing demands.