Olmec UK, a vision systems integrator, has worked with a vehicle manufacturer to develop an inspection device to verify the position of piston valve roller rocker arms in commercial automobile engines.
During engine assembly the roller rockers must be correctly located onto the push rod seat at one end, and the valve spring at the other end. This is a vital inspection, since incorrect assembly leads to a catastrophic failure of the engine the first time it is started. The automated system speeds the inspection process by removing any initial visual inspection requirement.
The vision system consists of two cameras mounted on a saddle that moves into position above the engine block. The cameras are positioned so that one of the cameras views a roller rocker in one row of pistons as the other camera inspects the rocker in the parallel row.
The cameras are then moved on a linear ballscrew guide using a stepper motor to inspect each of the roller rockers at the eight piston positions to give a total of 16 measurements. Once the measurement cycle is completed, the saddle moves out of the way to allow the next engine block to move into place.
High dynamic range cameras are used to produce high-quality images, even in the presence of reflections from the metal parts. Illumination is provided by an LED bar light. Measurements are made on the minimum and maximum angle of the rocker position at each location as well as classifying any detected defects against a stored library. Measurements need to be able to accommodate any variation in compression across the rockers in the inspected sets.
Pass/fail results are displayed on the control screen, with each rocker position showing either green or red according to their status. Any red indicators mean that a visual inspection must be made before the engine block can proceed further.
