In order to reduce
In order to reduce ong>markingong> time, we also tested the resistong>anong>ce of surface ong>markingong> to shot blasting. Codes with 0.75 mm, 1.0 mm ong>anong>d 1.25 mm cell size were tested. Since shot blasting is ong>anong> abrasive process, the surface marks will be affected ong>anong>d thereong>forong>e their contrast ong>anong>d readability will be different. As with deep ong>markingong>, the cell size influenced the results: Similar to the mark submitted to E-coating, cells of 0.75 mm were not readable. For the 1 mm ong>anong>d 1.25 mm cell sizes, the best ong>anong>d average results over six measurements are presented in table 6. The average contrast value beong>forong>e the post process was 0.72. The quality of the mark was sufficient ong>forong> the reader to read it from the 6 different ong>anong>gles tested. But, as we expected, the contrast was low because the code was not protected unlike the one with the “deep” mark. If less contrast is acceptable, this method may be a good alternative to deep ong>markingong> if a shorter cycle time is necessary. Note that the images showing the results after shot blast were accidentally not saved correctly ong>anong>d we could not re-photograph them because the painting was already done, so we unong>forong>tunately cong>anong>not show them in this paper. Table 6- Results ong>forong> the surface ong>markingong>. Cell size 1.0 mm 1.25 mm Best contrast 0.392 0,388 Best unused error 88 100 Average contrast 0.363 0.362 Average unused error 77 53 SHOT BLAST AND PAINTING After being shot blasted, the shot blasted samples undergo the E-coating process. The paint chong>anong>ged the appearong>anong>ce of the mark, so the readability was different. Figure 13 shows the evolution of the contrast through the sequence of post processes, ong>forong> the optimal 0.6 mm cell size. Note the drop in contrast after shot blasting. However, the application of E-coat paint on the sample increased the contrast to even higher levels thong>anong> beong>forong>e either post process. E-coating then, is a way to considerably increase the contrast of ong>markingong> after shot blast. Figure 13- Best contrast of 6 readings after shot blast ong>anong>d e-coat painting with cell size of 0.6 mm in function of the number of passes. Figure 14 presents pictures of the 2D codes ong>anong>d shows the number of passes ong>anong>d required ong>markingong> time ong>forong> each.
Figure 14- Influence of the depth on the contrast after shot blast ong>anong>d paint. Table 7 presents a summary of the best results ong>forong> deep ong>markingong> ong>anong>d surface ong>markingong>, ong>forong> the process of shot blast only ong>anong>d shot blast + painted. CONCLUSION Table 7- Best results ong>forong> resistong>anong>ce to shot blasting only (1) ong>anong>d shot blasting ong>anong>d painting (2). Deep ong>markingong> Surface ong>markingong> Marking time 37 s 2 s Cell size 0.6 mm 1.0 mm Code size 13.2 mm 20 mm Number of passes 12 1 Best contrast/unused error 1 0.616/90 0.392/88 Average contrast/unused error 1 0.563/67 0.363/77 Best contrast/unused error 2 0.694/60 0.671/100 Average contrast/unused error 2 0.669/35 0.642/70 Laser ong>markingong> is the most viable, ong>anong>d sometimes the only possible technology ong>forong> permong>anong>ently ong>markingong> die castings to ensure traceability of the component from casting to final assembly ong>anong>d even in the use phase. While there are mong>anong>y off the shelf ong>laserong> markers on the market, it requires a significong>anong>t amount of know-how to select the right technology, adjust all the parameters, determine the exact ong>markingong> procedure ong>anong>d ong>markingong> type as well as the integration of a ong>laserong> marker into a die casting cell in a way that Class 1 ong>laserong> safety cong>anong> be guarong>anong>teed. The ong>laserong> type ong>anong>d ong>markingong> parameters need to be adjusted to provide the required ong>markingong> in the given cycle time ong>anong>d setup/environment, ong>anong>d often the ong>markingong> needs to be adjusted to guarong>anong>tee proper readability after surface treatment processes – ong>anong>d often the right compromise needs to be found between cycle time, required contrast ong>anong>d size of the ong>markingong>. Even ong>forong> shot blasting ong>anong>d e-coating, certainly the two most demong>anong>ding surface treatments ong>forong> die casting, solutions cong>anong> be found so that the ong>markingong>s will remain readable ong>anong>d a second ong>markingong> step or possible loss of traceability cong>anong> be avoided. If the part positioning is not perfectly repeatable, a 3D head cong>anong> identify the position ong>anong>d adjust the ong>laserong> accordingly. A subsequent immediate verification of the ong>markingong> with a camera cong>anong> in some cases be a useful addition. Compared to other ong>markingong> technologies, ong>laserong> ong>markingong> is often considered as rather dong>anong>gerous, but it was shown that there are several possible ways of building ong>anong>d integrating a ong>laserong> marker into ong>anong>y kind of die casting cell (or ong>anong>y other mong>anong>ufacturing environment) in a very safe way that guarong>anong>tees Class 1 ong>laserong> safety ong>anong>d will ensure that no operator will be put at ong>anong>y kind of unreasonable safety risk. With this paper we hope to have addressed some of the major concerns of die casters when it comes to ong>laserong> ong>markingong>. We have been working on providing solutions ong>forong> this industry ong>forong> several years ong>anong>d feel that we are now in a position to help die casters mong>anong>age the challenges of their processes ong>anong>d environment ong>anong>d enable perfect traceability that will help them with quality assurong>anong>ce, improve their processes, ong>anong>d satisfy customer requirements. REFERENCES 1. Fraser, A., Maltais, J., Hartlieb, M., Frayssinous, C., Vallée, R., Godmaire, X., “Review of technologies ong>forong> identification of die casting parts,” NADCA Trong>anong>sactions 2016