A requirement to mount a dual laser device just off the coater pan of a roofing line put our design engineers to work to see how a device could be made to exist and to work in those extreme conditions.
- The high temperature and the IR energy being radiated from the pan and the sheet requires cooling. Not so much to protect the sensors, but to keep the structures holding the sensors from warping and throwing off the measurement. The sensors are capable of 0.0001 in accuracy thus any warping of the structuree is unacceptable
- Since the devices will eventually control the squeeze roll gap at the pan then the accuracy must be verified often. We propose a ‘temperature compensated standard sample’ at the start and end of each scan.
- The ‘C’ frame scanner is designed with massive side beams which by design fights the inherent expansion effects. This in addition to the cooling keeps the sensors where they need to be for accurate measurement. The cooling also maintains an appropiate environment for the laser sensors mounted at the tips of the ‘C’ frame.
- The standard samples are mounted just beyond the edges of the widest sheet and the scanner scans over them at the start and at the end of each scan
- In this location any piece of equipment is prone to get hot filled asphalt splashed on it. To prevent the corruption of the measurement due to this event we use the measurement itself to determine if and when the sheet is starting to fall too close. We then trigger a fast acting shutter which closes over the sensor to protect it.
- A ‘C’ frame design is used to maintain the correlation between the sensors. Even if the scanner is moved up and down due to ‘clinkers’ getting into the support guides. Both sensors will move together and thus maintain the differential measurement without error.
- In addition to this early warning of the sheet coming too close we suggest that the shutter be connected into the line speed as well as the E-Stop circuit for the same reasons
The above items were just some of the criteria rolled into the design study for this application.