5 months ago

Important Considerations for laser marking an identifier on die-casting

This white paper covers the impact of contrast, Data Matrix Size and optical power of the laser on the time required to mark a DMC. It also discusses laser safety for open-air enclosures and for a closed laser safety enclosure with rotary table. But why stop at that. We also discuss the impact of post treatment process on the legibility of DMC and strategies to make the DMC legible even after shot blasting. Have a look, you'll be glad you did. Feel free to contact us at: Browse our website at: Get in touch on our social media channel: Facebook: LinkedIn: Twitter: Google+: YouTube: Xing: Instagram: Viadeo: Learn more on our laser marking & traceability, laser cleaning and safety standards blog Blog:

Figure 8- Sealed

Figure 8- Sealed enclosure with rotary loading table The sealed enclosure designed ong>anong>d presented in this section includes a rotary loading table that allows the robot or operator to load ong>anong>d unload the part in the machine while the ong>laserong> is ong>markingong> the part. Figure 8 shows the principle of operation of this enclosure design. The part is first loaded on a piece holder designed specifically ong>forong> the part geometry. Then the table turns, locating the part within the enclosure. While this part is being ong>laserong> marked, the robot cong>anong> continue to work on the rest of the sequence; moving through quenching, trimming, placing the part on exit conveyor, grabbing the next part, ong>anong>d verification of the mark’s integrity. Safety sensors are used to ensure the door remains closed during the ong>laserong> ong>markingong> process. To be a valid Class 1 ong>laserong> machine, this type of enclosure must have no holes or gaps that would allow a direct or specularly reflected beam to emerge. This type of enclosure is especially interesting ong>forong> mong>anong>ufacturers because the table cong>anong> be loaded ong>anong>d unloaded while ong>markingong> occurs. That makes the time ong>forong> the table to revolve the only time to consider as a non hidden-time process, provided the ong>markingong> time is less thong>anong> the rest of the cycle time to mark two parts. This type of enclosure thus makes it possible to use much longer ong>markingong> times, such as those required ong>forong> deep shot blast resistong>anong>t marks, presented in the next section about post treatments. Comparison between the two enclosure types Although the two enclosure types presented above cong>anong> be well suited ong>forong> a die casting environment, they have their own advong>anong>tages ong>anong>d disadvong>anong>tages. Table 3 below summarizes the pros ong>anong>d cons of these two types of industrial enclosures. Table 3- Pros ong>anong>d cons of the two enclosure types proposed: The open air enclosure ong>anong>d the rotary table enclosure OPEN AIR ROTARY TABLE Pros Cons Pros Cons • Lower cost • Smaller footprint • No moving parts • Marking time is not hidden time • Required engineering meong>anong>s to prevent humong>anong> access to get to Class 1 • Intrinsically Class 1 • Marking time is hidden time • Allow use of lower power ong>laserong> since ong>markingong> time is hidden • Allow to do deeper marks • Higher cost • Bigger footprint • Moving part • Time ong>forong> the table to revolve is not hidden time

POST TREATMENT RESISTANCE STUDY A Laserax LXQ-100 (100W) fiber ong>laserong> was used to mark 2D Data Matrix code on a Mercury Marine aluminum part made of a 362 alloy (a low iron, high silicon alloy). This ong>laserong> operates at a wavelength of 1.06μm ong>anong>d emits pulses of 100 ns duration at a frequency of 100 kHz, ong>forong> ong>anong> average power of 100W. The readability is then studied after having undergone several post-treatments: E coating only, shot blasting only, ong>anong>d shot blasting ong>anong>d E-coating. The study focuses on the influence of ong>laserong> parameters on the robustness of these ong>markingong>s to determine the optimal parameters ong>forong> each process. For shot blasting, the technique of deep ong>markingong> is used [1]. It consists in protecting the mark from the shot blast process by lowering the surface on which the black is marked. To do so, multiple passes are done with the ong>laserong> to remove material beong>forong>e doing the blackening. If the cells are small enough, shot will not be able to reach the black ong>markingong> ong>anong>d it will remain intact. Surface ong>markingong>s will also be tested ong>anong>d compared to deep ones. Those ones would be advong>anong>tageous compared to the previous method since it is much faster to mark without the deep etching step. Although a multitude of parameters cong>anong> affect the results, this study focuses on the following: CELL SIZE For the deep-marked 2D barcode, two different code sizes were used, approximately 13 mm ong>anong>d 16 mm ong>anong>d three cell sizes were tested: 0.4 mm, 0.6 mm ong>anong>d 0.8 mm. The number of cells was adjusted so that the total size was approximately 13 mm or 16 mm. Smaller cells allowed encoding more inong>forong>mation ong>anong>d thus increased the redundong>anong>cy in the encoding of the 2D code inong>forong>mation. On the other hong>anong>d, larger cells are easier to read. It was thereong>forong>e necessary to find the right balong>anong>ce between the size of the cells ong>anong>d the amount of redundong>anong>cy. The table below summarizes the dimensions of the ong>markingong> samples. Table 4-Summary of the dimensions (side lengths of each square) of the deep ong>markingong>s. Cell size 2D code dimension 2D code size 0.4 mm 32 x 32 12.8 mm 40 x 40 16.0 mm 0.6 mm 22 x 22 13.2 mm 26 x 26 15.6 mm 0.8 mm 16 x 16 12.8 mm 20 x 20 16.0 mm To mark deep into the material, it was necessary to make several passes with the ong>laserong> beong>forong>e ong>markingong> the code itself. Material was etched so that the ong>markingong> that was in the bottom was then protected by the surface around it. The depth ong>anong>d the time of ong>markingong> was increased with the number of passes. For surface ong>markingong>s, the number of passes is one. For surface marked 2D code (no deep etching step), a larger dimension of 20mm x 20mm was used since these “stong>anong>dard” marks are much faster to make. Cell sizes from 0.5mm to 1.25mm were tested. The corresponding Data Matrix dimensions is presented in the following table. Table 5-Summary of the dimensions of the surface ong>markingong>s. Cell size 2D code dimension 2D code size 0.5 mm 40 x 40 20 mm 0.75 mm 26 x 26 19.5 mm 1.0 mm 20 x 20 20 mm 1.25 mm 16 x 16 20 mm For stong>anong>dard applications, a white background provides better contrast ong>anong>d better readability. Since the post-processes we studied modified the surface, it was not obvious if this was needed. For the resistong>anong>ce to shot blast, white background will not be tested because it has been shown in a previous study that it was erased by the process. For e-coating, all samples were done twice, both with ong>anong>d without white backgrounds, to study the effect of backgrounds on readability. RESULTS The results are divided in three sections: Painting only, shot blasting only, shot blasting ong>anong>d painting. The data was collected with a Cognex Datamong>anong> 8050 reader. Each sample was read six times, with different orientations. It then collected the value of the contrast ong>anong>d the unused error. The contrast was a value between 0 ong>anong>d 1 defining the brightness difference between the

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