Simultaneous internal and external grinding

03/01/2007 - Oliver Hagenlocher


Hollow shafts and similar components, on which the alignment of bore to external diameter must be of the highest precision, are being complete-machined, ready for assembly, on the HG 208 CD Center Drive Grinder. Examples of this type of work include the gear shafts used in modern direct transmission systems in passenger cars. The machine simultaneously grinds the shafts inside and out in a single set-up. This process is far more accurate than alternative methods or producing the component on two separate grinders.

The HG 208 CD Center Drive Grinder simultaneously grinds hollow shafts of up to 400 mm length internally and externally. The top equipment specification for the machine features two internal and two external spindles mounted on two compound slides with B axis. This configuration allows for the internal machining of bores and end faces as well as of conical surfaces and slots.

The two external grinding wheels can also be used to grind diameters and adjoining end faces. Depending on machine requirements the grinding technology used can be conventional and/or CBN. A profiled dressing roll ensures that seats are ground without leaving tool marks. The work spindle operates on modern, maintenance-free AC motor technology. The chuck diameter is usually 160 mm.

An integral loader loads and unloads the workpieces and also serves upstream and downstream equipment components, such as the storage sections for raw-parts and finish-machined components, measuring devices, cleaning stations, workpiece recognition and orientation equipment, marking devices, the data collection for the statistical process control SPC, ... .

The HG 208 CD is based on the HG series of grinders, to which were added certain components from the VSC series of combined turning and grinding centers, many hundreds of which are in use across the globe every day.

Workholding and automation equipment too are made by EMAG. This allows for the HG 208 CD and its peripherals to be assembled strictly in accordance with customer requirements, using a range of well proven machine modules – all of them from a single source.

Upstream processes, in particular soft turning operations, as well as downstream processes, in particular the precision machining of hardened tooth profiles, are also covered by EMAG, the supplier of complete process streams and manufacturing systems. The after-sales and service network of the EMAG Group spans the globe, offering the user a high degree of security.

The monetary advantages the user can enjoy with the HG 208 CD are the result of:
- exceptional concentricity of external diameter to bore,
- low cycle and idle times,
- high degree of machine availability,
- great flexibility in the variety of workpiece geometries that can be produced,
- great flexibility in the selection of optimal grinding technologies,
- integrity of the process capability through the integration of in-process
gauging technologies according to manufacturing requirements,
- small footprint of the entire system.

In the past, such tasks were tackled with special purpose machines. The HG 208 CD is an example of how the demands of many users for individualised technologies – i.e. workpiece-specific manufacturing solutions – can be met with machines that come from a modular design.


Oliver Hagenlocher

Press and publishers

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