Being invented in the 1960s, A laser is a device that emits light through a process of optical amplification. The laser’s ability to read, cut, mark and bind tough materials and etc. is widely used in many industries.
What can lasers do?
- In consumer industry, since year 1974, laser scanners for reading universal product codes (UPC), or bar codes, have become common in retail stores.
- In manufacturing, lasers are a universal tool for engraving, drilling and marking a broad range of materials.
- In medical industry, the lasers can be used to a surgical removal of tissue, eye surgery, laser beauty, and etc.
Why do a laser needs thermal management?
- Poor-product. The process of operating an industrial laser involves the use of auxiliary gases (a mixture of nitrogen, carbon monoxide, and helium) to convert electrical energy into light of the same wavelength and phase. This process generates a lot of heat, which may be harmful to the manufacturing process using laser beams. If thermal conditions are not properly adjusted, it will lead to poor products.
- Waste heat. Heat is the biggest cause of field failures, especially for higher power laser diodes. The waste heat must be removed quickly and efficiently, otherwise the laser will suffer catastrophic damage, or at least shorten its service life.
- Diminish the accuracy of the laser beam.
How to apply thermal management for a laser?
- For those lasers heating up quickly like CO2, disk, diode, and fiber lasers: they all need reliable and efficient cooling method for their resonators, optics, and laser heads, even during load fluctuations, to provide consistently high performance.
- Effective solutions to control the heat generated by lasers include the use of industrial chillers. A chiller should always keep the temperature at a stable value and fluctuate preferably as little as possible when the laser both is at full load or partial load. The higher temperature control accuracy, the better the laser performs. Nowadays, the industrial chiller is a universal way to help manage the heat produced by lasers.
How to choose a chiller to cool the lasers?
The chiller provides coolant at a consistent temperature and flow rate to the laser’s resonators, optics, and laser heads. So it’s essential for a chiller to accurately control temperature and water pressure. The waste heat must be removed from a laser which is also called heat load. Usually expressed in unit of watts or BTU/hr. The heat load is the minimum capacity of a chiller to cool a laser.
Every chiller has a cooling capacity curve. Nominal cooling capacity is given at 25℃ coolant output temperature and 25℃ ambient air temperature. For example, when the ambient air temperature is 20℃, the liquid temperature is 20℃, the nominal cooling capacity is 550W. See the picture below:
Coolant is the key part for the chiller running process. And not every laser uses the same coolant. We need to choose the appropriate coolant based on different conditions. The main coolants are tap water, water glycol, and deionized water. The most coolant is ordinary distilled or tap water. It is often treated with additives which include algaecide to prevent algae growth, and/or ethylene glycol to prevent corrosion and lower the freezing point of the fluid. Some lasers require deionized water, which can be very corrosive to many materials. If this is the case, the chiller must have only DI compatible materials in contact with the coolant, and it should be equipped with a deionization box to maintain the required resistivity level.
The proper pump is also an important factor for the chiller, which can control the coolant flow rate and pressure. A positive displacement pump provides same flow rate regardless of the recirculating system pressure drop or increase.
- Communication features. It allows the chiller to be connected with a computer. Interfaces such as RS-485 enables remote operation of a chiller from a computer. With this kind of interface, the chiller can be remotely monitored and set. Including set temperature, actual coolant temperature, coolant pressure, fault conditions, and etc.
- High/low temperature alarms help prevent damage from coolant that is too hot or too cold.
- Low-flow alarms protects both chiller and laser from frozen coolant.
- Coolant filters protect the laser and the pump from harmful particles.