Using edge finders correctly - here's how it works.
Edge finders are used during milling to be able to approach reference surfaces or edges. This means that the work spindle of a milling machine can be precisely aligned with the edge of a workpiece using an edge finder. There are different types of edge finders, which are based on different operating principles:
- Mechanical edge finders
- Optical/acoustic edge finders
Our guide shows you how these two types of edge finders work and how to use them correctly to optimally align the work spindle of your milling machine with the edge of the workpiece.
Mechanical edge finder
A mechanical edge finder consists of two offset cylinders that are connected internally by a spring. The scanning head of the edge finder can have different diameters (e.g. 4 mm).
The operating principle of the mechanical edge finder is the centrifugal force that is generated at 500 to a maximum of 600 revolutions per minute on the milling machine. In order to achieve an exact result, the working spindle of the milling machine must therefore be switched on at 500 to a maximum of 600 revolutions per minute.
How to use mechanical edge finders correctly:
Slowly approach the edge of the workpiece with the edge finder. You will see that the edge finder "wobbles" a lot at first. However, the closer you get to the edge of the workpiece, the more precisely the cylinders will align. As soon as the edge of the workpiece is reached, the lower cylinder of the mechanical edge finder runs to the side and the two parts run round offset to each other (picture).
Now you need to consider the diameter of the probe head. In this example, this is 4 mm. Accordingly, another 2 mm must be subtracted in order to align the centre of the work spindle exactly with the edge of the workpiece.
The values of the edge finder can be read with the help of a measuring system. The edge finder shows exactly the same value on the Y-axis for several passes and therefore has a very high repeat accuracy.
Edge finders can also be used to determine the edge of the workpiece on the other axes (example: on the X-axis).
Optical/acoustic edge finder
Optical/audible edge finders emit an optical and acoustic signal as soon as the probe head touches the reference edge of the workpiece to be approached. While the work spindle must be switched on at 500 to a maximum of 600 revolutions per minute when using mechanical edge finders, this is not necessary with optical/audible edge finders. These work with an electrical contrast.
Please note that optical/audible edge finders can therefore only be used with conductive or slightly conductive material surfaces.
How to use optical/audible edge finders correctly:
The procedure is similar to the mechanical edge finder. Use the edge finder to slowly approach the edge of the workpiece on the desired axis. As soon as the probe head touches the edge of the workpiece, it emits a signal tone and lights up at the same time.
Even with optical/acoustic edge finders, you must observe the diameter of the probe head and subtract half of it in order to align the centre of the work spindle exactly with the edge of the workpiece.
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