Advantages and disadvantages compared with conventional cylindrical grinding

Advantages

High productivity There is no need to clamp the workpiece. This results in very short auxilary times related to loading and removing the workpieces, and even those are typically much shorter than the process for clamping between centres. For centerless throughfeed grinding, one workpiece is immediately followed by the next. Auxilary time for infeed are thus very short.

Stable workpiece support: The workpiece is supported for a substantial portion of its length, or its entire length, by the regulating wheel and workpiece support. This is extremely advantageous in particular for longer workpieces with very small diameters. A powerful rough grinding can be undertaken without concern about bending and torsional stress. There are no harmful deformations caused by grinding forces. The metal removal rate can also be increased. During finishing grinding, the stable support of the workpiece allows for high precision grinding, meaning workpieces with low tolerances can still be produced with process safety.

Doubled accuracy: The configured infeed amount corresponds during centreless grinding corresponds to the diameter measurement for the workpiece. When grinding between centers, the infeed amount instead works radially. This means that, for the same infeed amount, the diameter is reduced by approximately double the value. The process accuracy for centerless grinding is thus much higher. Infeed errors, such as those caused by wear on the grinding wheel or thermal accumulation within the machine, are only half as significant.

Reduction of pre-work: Less work is required for centerless grinding, as there is no need to prepare the workpiece by establishing the centering.

Reduced grinding allowance: During centerless grinding, the machining process starts with the workpiece finding its rotational axis based on its existing shell surface. Because the highest points on the workpiece are the first to be touched, centerless grinding involves the largest diameter in the current state being ground to completion. This means that the grinding allowance during centerless grinding can be smaller than grinding between centers as in the latter process the position of the centers to the shell surface determines how much grinding allowance is needed.

Disadvantages

Regenerative effect: During the shaping process, this effect can lead to unstable behavior. These interrelationships have long been known and can be managed by choosing a suitable grinding zone geometry.

Coaxial / Concentricity issues: The concentricity of the external surface to any centering bores that may potentially be on the workpiece is not assured. This may cause problems if the subsequent work steps dictate work from a center again.

No grinding in reverse direction: It is not possible to run the machine in the opposite direction. The friction force on the regulating wheel is insufficient to overcome both the friction on the workpiece surface and the cutting force on the grinding wheel.

Fundamentals of Centerless Grinding - Other Topics

Fundamentals of Centerless Grinding

Centerless grinding or centerless cylindrical grinding is a special form of external cylindrical grinding. Unlike conventional cylindrical grounding, the workpiece does not require double sided centering and is ground "centerlessly."

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Plunge grinding

For centerless plunge grinding, the workpiece is ground using a plunge method, whereby the grinding wheel is fed along the workpiece. For this reason, the grinding and regulating wheel have a negative profile of the workpiece, provided with the help of a dressing tool.

More about plunge grinding
Throughfeed grinding

Centerless throughfeed grinding, also called traverse grinding, is one of the most economical grinding techniques for mass production. The workpieces run continuously with an axial feed through the grinding zone.

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