In mold cleaning, laser cleaning has the characteristics of high efficiency, low cost, low wear and tear, high cleanliness, etc. With the development of laser technology, more laser equipment is used in the field of mold cleaning.
Laser cleaning is a fine cleaning process, according to different contaminants and different substrate materials to choose the appropriate parameters, in order to achieve the perfect cleaning of contaminants while not harming the substrate material. Therefore, laser cleaning mold in the laser parameters are very important to set. Only completely understand each laser parameters will have what kind of impact on the cleaning effect, in order to be able to set the precise parameters, only set the right suitable parameters to achieve the perfect cleaning effect.
Laser cleaning mold principle is the interaction between the laser and pollutants, light energy into heat, in a very short period of time to vaporize pollutants to achieve the purpose of cleaning. Laser cleaning is based on the absorption of laser energy, to absorb laser energy, you need to choose a different laser wavelength, different substances on different wavelength absorption rate is different, you should choose the highest absorption rate of laser wavelength. But this is only theoretical, the actual status quo from the perfect ideal gap is still very large. For example, the domestic laser leading Rike, Chuangxin, Jepte and other laser manufacturers, can choose no more than three kinds of laser wavelength, such as Chuangxin laser only wavelength of 1064nm fiber laser, so the domestic laser equipment mostly use the wavelength of 1064nm fiber laser. But it does not mean that there is only this one wavelength laser, nor does it mean that this wavelength laser has the highest effect, it is just the most widely used in the field of laser processing, because it is relatively easy to maintain, cost-effective and long life. This is like having only one kitchen knife at home, all the places where the knife is used are solved with this kitchen knife, which is also a special period in the development of laser, later more wavelengths of lasers will be applied to the processing field.
In the context of such a status quo, and then to understand the laser parameters set, since the laser wavelength selectivity is not much, then on its cleaning principle has changed. Theoretically is the pollutant absorption of laser energy instantaneous vaporization to achieve the purpose of cleaning, but the actual mold cleaning is the mold itself to absorb laser energy to generate thermal stress, thermal stress is greater than the adhesion force to achieve the purpose of cleaning. Under the guidance of such a theory, laser cleaning mold in the need to pay attention to the following parameters:
1. Laser energy density. Laser energy density is the most important parameter in laser processing, laser energy density must be in between the cleaning threshold and damage threshold. Just can achieve the cleaning effect of the laser energy density value called cleaning threshold, just damage to the substrate material laser energy density value called the damage threshold, between the cleaning threshold to the damage threshold is a very narrow range, laser energy density below the cleaning threshold, no matter how long the scan, no matter how many times the scan can not achieve the purpose of cleaning, if the laser energy density is higher than the damage threshold, it will cause mold material irrecoverable damage. Laser energy density in the actual operation is not calculated, but through experiments, so before cleaning the mold must first find a piece of scrap mold test parameters, the parameters are appropriate before being used in formal cleaning.
2. Laser repetition frequency. Laser pulse width and repetition frequency with each other affect the laser energy density. When the laser repetition frequency increases, the peak power will be reduced, the energy of a single pulse will be reduced, the peak power seriously affect the laser energy density, but also seriously affect the cleaning effect. So the final laser parameters is the balance between pulse width, laser power, repetition frequency of the three. In the actual operation of the pulse width as low as possible, laser power according to different machines is to determine the value of the repetition frequency to take as small as possible, but appropriate.
3. Beam quality. In the mold cleaning process is often used in the fiber optic line transmission laser, in the transmission process will be the laser beam "shaping", adjust the laser divergence angle and spot diameter. The smaller the divergence angle, the longer the depth of focus, the scanning head farther away from the mold. The smaller the spot diameter, the greater the energy density, and the spot diameter also closely affects the laser energy density.
4. The number of pulses. The number of pulses will affect the cleaning threshold and damage threshold, they are different at different pulse numbers.
In short, laser cleaning mold, laser energy density is one of the most important parameters, laser wavelength, laser repetition frequency, laser beam quality, the number of pulses are in different angles affect the laser energy density, and finally in the balance of the four sides to form a stable laser output. Many parameters can not be tested by calculation, through simulation experiments can be easily derived, so before the laser cleaning mold, the experiment becomes very important.
