For a system to be able to place fluid on a substrate, the system must know where the nozzle tip is located. Standard on all MAX Series and DS Series platforms is an automatic XYZ nozzle calibration station. The XYZ calibration station is made up of these main components:
1 - Purge area to capture fluid dispensed from nozzle during set up.
2 - Z Position pad that determines offset between surface sensor and nozzle tip.
3 - XY calibration area used to dispense a dot of fluid and present it to vision system for alignment.
The XYZ calibration routine consists of these steps:
- Surface Sensor locates Z pad
- Vision System calibrates itself
- Nozzle touches Z pad
- Surface Sensor locates calibration area
- System dispenses a dot
- Vision System locates center of the dispense, thereby locating nozzle center
The calibration area has a number of configurations depending on the fluid and application.
Backlit Needle XYZ Calibration Station
When a dot is dispensed in calibration area, the vision system is tasked with finding dot center. Traditional methods of alignment use a top-down light but some fluids are very shiny and reflect rings of light when illuminated from above. These rings of light can mislead the vision system and cause an inaccurate calibration. To eliminate reflected rings, we utilize our backlit XYZ calibration area to turn off top-side light and activate bottom-side illumination. By illuminating from below, the vision system sees only a dark outline of the dot, making the edge, and hence the blob center, easy to find - resulting in the best nozzle positioning available. Backlit XYZ calibration can also be combined with top-side lighting for additional alignment control.
Paper with Backlit
Some fluids are thin and messy. Dispensing these fluids directly on the ceramic of the backlit XYZ calibration station can result in excessive fluid flow and an eventual, messy clean-up. We have developed a moving paper roll that increments and eventually rolls up dispensed fluid after the vision system has located dot center. This is an automatic way to capture messy fluid and always have a clean dispense area available. Paper is pulled over the backlit area so you can still benefit from the backlit feature.
For fluids that are optically clear or not easily visible to the camera, we use an impression pad. During the XYZ calibration routine, the system gently presses nozzle into an impressionable surface leaving an outline of nozzle tip. The vision system, equipped with our FullView Illumination feature, locates the nozzle impression center. To use the dark field feature to reflect impression geometry, system should be equipped with FullView Illumination.