Cranking Up Hole Inspection

Rosfer (rosfer.it) of Turin, Italy, has developed a novel system for inspecting oil holes in crankshafts. The traditional method of accurately inspecting such holes is to use a touch probe, but not all of the holes are accessible for probe-based measurement. In response, Rosfer has developed an inspection station that uses a video camera combined with three Heidenhain (heidenhain.us) components: a Quadra-Chek 3000 optical measurement system, an LS 388 linear encoder and an ROD 486 rotary encoder.

To perform an inspection, the operator places the crankshaft into a holder on the measuring station and clamps it into place. The camera traverses linearly above the crankshaft and stops over the hole to be measured. The Quadra-Chek 3000 displays the direction of movement and the position to be approached on a touchscreen, then the LS 388 linear encoder installed on the linear axis enables accurate positioning of the camera. 

Because the oil holes are arranged at different angles, the crankshaft must be rotated from one measuring point to the next. The operator receives the information required for this procedure directly on the Quadra-Chek screen. During rotational movement, the ROD 486 rotary encoder provides accurate position measurement. 

The diameter of each individual hole is inspected with an accuracy ranging from ±0.1 mm to ±0.5 mm, depending on the hole. The circularity of the hole and the quality of its chamfer are also checked, in addition to the location of the holes in the bearing (i.e., the correct distance to the sides of the main and connecting rod journals).

Results are provided in real time on the Quadra-Chek and if necessary, the operator can adjust the settings or perform additional measurements quickly and intuitively. An entire crankshaft can be inspected in seconds, according to Heidenhain.