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Centerless cylindrical grinding
and centerless cylindrical grinding machines 3

Fixed grinding center

A laterally fixed grinding gap is a prerequisite for machining bigger bars or tubes on centerless cylindrical grinding machines. For this to work, the grinding and regulating wheels must be able to move horizontally, and the workrest blade vertically, relative to the workpiece center. Bars and tubes are fed in and out via bar tables.

The “fixed grinding center” also simplifies the setup of centerless cylindrical grinding machines for other applications.

Stationary grinding center in the Ebert C-3070– Centerless cylindrical grinding – stationary grinding wheel

 

 

Simple machines

In centerless cylindrical grinding machines without a stationary grinding wheel, the main motor and grinding wheel are fixed. As the grinding wheel wears, the guide rail and regulating wheel are moved towards the grinding wheel. Here, the regulating wheel is mounted on the top slide and can be moved relative to the guide rail.

These centerless grinding machines are relatively inexpensive and compact, but complex to set up and unsuitable for large workpieces. Feeding workpieces is difficult.

Movable grinding media in simple machinesCenterless cylindrical grinding – movable grinding wheel

 

 

Control disc

For through-feed grinding (centerless cylindrical grinding of long workpieces or short material in succession), the regulating wheel is inclined by approximately 3°. For plunge grinding, it is inclined by 0° to 1°; here, axial movement of the workpiece can be prevented with a stop.

The control disk must be dressed “hyperboloid” so that it – even when tilted – touches the surface of the workpiece in a straight line.

 

 

grinding wheel

Depending on the application and the desired grinding result, the grinding wheel is dressed cylindrically or in different zones: entry, grinding and exit zone.

 

workpiece feed

The workpiece feeding and removal process must be positionally and repeatably accurate and suitable for the grinding type and process. Workpieces must not be damaged. In practice, various methods have become established:

Through-loops:

The workpiece is continuously fed within the machine using the control disc. No additional holding devices are required.

  • Manual feeding:
    – The workpiece is pushed by hand onto the guide rail into the grinding gap; transport through the regulating disc begins
    – cost-effective, suitable for small batch sizes, but may involve a risk of injury depending on the workpiece geometry

 

  • Gravity feeding
    – suitable for through-grinding in a closed loop
    – via inclined feed rail
    – workpieces slide along
    – often with singulation via pawl or stop
    – robust and cost-effective, good for high production volumes

 

  • Step conveyor
    – Depending on the conveyor’s design, the workpieces lie either in an ordered or chaotic manner in a raw parts bunker
    – One or more blades move upwards and lift one or more workpieces from the bunker onto a feed belt towards the grinding machine

 

  • Belt or chain conveyor

 

  • Bar tables

 

  • Vibratory conveyors
    – For small, short workpieces
    – spiral or linear conveyors
    – with singulation and alignment of the workpieces

 

plunge grinding:

  • The workpiece must be placed in the grinding position on the guide rail, in front of the axial stop. This can be done, for example, in the following ways:
    – Blowing in small workpieces via hose or pipe.
    – Gantry loader for one or more workpieces simultaneously.
    – Manually, again for small batch sizes, with a risk of injury.
    – From a magazine with singulation.

 

  • The workpieces can be unloaded in the following ways, for example:
    – Manually
    – Portal loader
    – Axially with an ejector
    – Downwards by retracting the control disc”