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    # emboss-today
    
    
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    Rapid manufacturing of embossing tooling for permanently marking thin plastic.
    
    
    ![101st_impression](img/url_multitest.jpg)
    
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    ![mfg_tool](img/url_tool.jpg)
    
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    ## need
    As part of our covid-19 face shield production efforts, we need to permanently mark units that end up in hospitals with a few basic identifiers: a manufacturing batch number and a shortened URL for assembly instructions. The Zund needs to spend its time cutting rather than marking, and doctors have complained about the smell of laser-engraved text.
    
    ## rapid embossing tool manufacturing
    Several letters were cut out of 0.5 mm Cu stock using our nanosecond laser micromachining system:
    
    ![oxfording](img/oxfording.mp4)
    
    ![tool_in_oxford](img/tool_in_oxford.jpg)
    
    The coupons were punched out but the letters were left in place for electrochemical deburring in 14M H3PO4, ~1 minute, 3 VDC:
    
    ![tool_deburr](img/tool_deburr.jpg)
    
    Letters were then carefully punched out using a sharp probe under the Lynx Evo inspection microscope. Each 6 mm letter was sanded on two opposing sides to remove remaining cut debris in preparation for soldering. A piece of 0.02 mm Cu sheet was cut with sheet metal snips, fluxed, and the letters carefully soldered on using SAC305 solder:
    
    ![tool_soldered](img/tool_soldered.jpg)
    
    The tool was cleaned with IPA and attached to a desktop rack-and-pinion-style press using double-sided tape:
    
    ![mfg_tool](img/mfg_tool.jpg)
    
    A piece of silicone rubber was similarly attached opposite the tool to prevent bottoming out on the metal platen:
    
    ![mfg_press](img/mfg_press.jpg)
    
    The press was tested 100 times on a scrap of 0.5 mm PETG:
    
    ![mfg_100_tests](img/mfg_100_tests.jpg)
    
    The 101st test was performed on a scrap of 0.75 mm polycarbonate:
    
    ![101st_impression](img/emboss-today_101st.jpg)
    
    
    Later tests updated this process as follows:
    - 0.25 mm Cu
    - 5 mm letter height
    - no electrochemical deburr
    - sanding bottom rather than sides of letters
    - reflowing solder under letters rather than tacking sides
    
    This updated process was used to fabricate a tool with the Project Manus face shield URL, minus dots (as these were lost). Laser micromachining took 40 minutes, while manual assembly took roughly 30 minutes:
    
    ![url_tool](img/url_tool.jpg)
    
    The tool was mounted with double-sided tape on a cold rolled mild steel bar, which was held to the press using NdFeB magnets (flipped sideways above for visibility). The tool produced acceptable results in 0.020" PETG:
    
    ![url_multitest](img/url_multitest.jpg)
    
    Embossing was also performed on stock with both layers of protective film still in place; prior to film removal, the URL was legible:
    
    ![url_protectivefilm1](img/url_protectivefilm1.jpg)
    
    However, legibility was reduced once the film was removed, suggesting film should be selectively removed from shields prior to stamping:
    
    ![url_protectivefilm2](img/url_protectivefilm2.jpg)