Process laser cutting

Laser cutting, welding, and hot working leave a discolored oxidized layer or scale on the surface of the worked steel. This must be removed in order to perform many of the surface finishing processes. The acid pickling process is used to remove the oxide or scale of metals and corrosion products, in which acids or acid mixtures are used. 

Laser cutting tools are commercially available, so there is no need for individual development. The device should be equipped with a two axes-driven laser head and possess the ability to adjust the laser power in order to permit also surface treatment such as laser ablation (Figure 4.110). For a continuous process, also enough space must be supplied for the continuous inlet and outlet of the foil. Further, a means to position the laser head with respect to the foil is necessary. This part of the process has only been tested using individual short foils and was still not integrated in the continuous process. However, continuous laser cutting of foils is a known commercial process and it is expected that the amount of future development in this part of the process will be limited. 

A molecular fluorine excimer laser (157 nm) was also used to ablate PMMA chips to a depth of 500 pm [197], It was also reported that acrylic (or PMMA) plates were processed using a laser-cutting machine [198],... 

Laser cutting is a fast growing process. The laser can act as a materials eliminator. Concentrating its energy on a small spot, it literally vaporizes the material in its path. If the workpiece is held stationary, the laser drills a hole. If the piece is moved, it slits the material. The induced heat is so intense and the action of the laser is so fast that only little heating of the adjacent areas of the piece takes place. 

The calibration technique used makes trimming of the sensor possible at the end of the fabrication process (including housing of the sensor). Furthermore only electrical signals are required (no laser cutting is needed). The calibration data are stored permanently on the chip. 

Nevertheless, during recent years, an increasing number of potential commercial applications of femtosecond laser treatment have been demonstrated, e.g., the fabrication of injection nozzles and medical implants (stents) [72]. Some femtosecond laser systems have already been installed particularly for mask repair in industry [73, 74]. In particular, biological tissue (cornea, tooth, bone) can be treated successfully [11, 75, 76]. Even transparent human chromosomes were laser-cut (170 fs, 800 nm, minimum FWHM cut size -100 nm) by a multiphoton-mediated process [77]. But, a killer application is incalculable. 

Processing of ceramic inserts traditionally has taken one of the paths shown in Fig. 7. Table 2 summarizes typical processing conditions. Figure 8 shows a hot-pressed alumina-SiCw billet laser cut to circular insert shape. 

Laser cutting allows for almost free design of the microfluidic channels in the tape gasket. Figure 5 shows laser-cut double-sided adhesive tapes with microfluidic channels. The tape adhesive is still protected by its liners. The tape cutting can also be depth sensitive, i.e., kiss-cuts down to the carrier liner can be done if the tape roll is used in further automated roll-to-chip or manual tape-to-chip bonding processes. 

The laser-cutting process for silicone gasket membranes and double-sided adhesive tape gaskets will be developed further. Ultrashort pulse lasers are becoming commercially viable allowing direct microchannel ablation even in transparent thermoplastics like PMMA, COC, or... 

Temper rolling has been paired with roller leveling in some new heavy-coil processing lines. There is evidence that, in fact, the result is a more stable, and flat, plate. This stability is particularly important if the resulting product is going to be used for precision fabricating or laser cutting, for example. 

Laser cutting is a thermal process converting photon energy, condensed into a very small spot, into heat. To clarify the scope of this chapter, detailed descriptions of all the components of a laser system cannot be given in here. Furthermore, all the statements refer to the CO2 gas laser representing the vast majority of the applications in metal cutting. However, most of the general descriptions also apply to solid-state lasers. 

Figure 6 illustrates the basic laser cutting process. The beam is applied directly to the material at a predetermined focal height. Coaxial with the beam flow, the assist gas passes through an aerodynamically shaped nozzle. This assist gas jet supports the heating (burning with O2) of the material and removes the... 

---