Precise Z positioning of camera by using spot laser by luben111

Last crawled date: 3 years ago

The Video camera plugin in Mach3 is extremely powerful tool - you can position the tool precisely and quickly over the desired location of the detail. By knowing the distance between the camera cross hair and the spindle centre we can quickly switch between these two positions by using simple scripts (attached to the project). The camera is fixed to the CNC spindle head and if using objective with long focal length it's possible to get decent image magnification from distances of 100-200mm to the object. By using the camera it's possible to position the head with precision better than 0.025 over specific detail features, find the centre of holes, edges, etc. In two words: very useful for all everybody who uses CNC (attached are the camera scripts and the screen for Mach3).
There is one major problem with the camera - it's very difficult to make it exactly perpendicular to the surface so by moving the camera up/down on Z axis the image crosshair can shift which is compromising the positioning precision. I played a lot to adjust the camera and with the time I achieved quite good vertical alignment but it's a slow process.
At the end I found one elegant solution of the problem - if a laser is mounted on 45 angle to the camera (on 70-100mm distance away) and if the laser spot is hitting the center of cross hair when focused on the surface then we can guarantee that the camera distance to the surface is always constant and the perpendicularity of the camera to surface is not so important. See attached a picture describing how the method works and a short video showing how the laser and camera perform together:
https://www.youtube.com/watch?v=50kZa79QLbA
There is one benefit of using the laser - now we can measure distances in Z direction with precision around 0.05..0.1mm. If we focus the camera/laser on one surface and if we set this Z level to zero then if moving the camera/laser to a new position(and focusing the laser spot on the new position) we can see the new Z level.
The design of the laser mount allows to tilt the laser in two directions to get the spot exactly under the camera crosshair (or slightly on one side to avoid covering from both lines of the crosshair) . See video how laser tilting works:
https://www.youtube.com/watch?v=vujrtNEpsyM
Once the laser spot is on the exact place we can fix the position with the screws.