Centerless grinding is similar to centered grinding except that there is no spindle. This allows high through-put since parts can be quickly inserted and removed from the process. There are three main types of centerless grinding:
Through-feed grinding.
In-feed grinding.
End-feed grinding.
Through-Feed Grinding
In through-feed grinding, the part rotates between the grinding wheel and a regulating wheel as shown below.
For through-feed grinding, one or both wheels of the centerless grinding machine are canted out of the horizontal plane, as shown below. This imparts a horizontal velocity component to the work piece, so that outside feed mechanisms are not necessary.
The grinding wheel is canted with respect to the other two axes so that a component of its surface velocity pushes the part in the direction shown below. This auto feeding characteristic is useful for rapidly processing many parts in quick sequence. Because of the axial movement, through-feed parts can only have right circular cylindrical ground surfaces. The wheel cannot be dressed to grind more complex shapes. Below are parts produced with the through-feed centerless grinding process. As can be seen from the quantities produced, through-feed grinding is primarily a mass-production process because of its high throughput.
In-Feed Grinding
In-feed grinding differs from through-feed grinding in that the part is not fed axially so that the ground surface does not need to be a right circular cylinder. The grinding wheel can be dressed to accomodate the part. Once the work piece part is in place, the grinding wheel is fed in radially.
Because of the set up time involved for each part, in-feed griding does not have the high throughput of through-feed grinding. In-feed grinding is illustrated below.
End-Feed Grinding
In end-feed grinding, the part moves in axially between the grinding wheels, stops for grinding, and then moves out again. The wheel can be dressed to form more complex shapes, but the part can only get progressively smaller in diameter. End-feed grinding is illustrated below.
