emboss-today
Rapid manufacturing of embossing tooling for permanently marking thin plastic.
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:
The coupons were punched out but the letters were left in place for electrochemical deburring in 14M H3PO4, ~1 minute, 3 VDC:
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:
The tool was cleaned with IPA and attached to a desktop rack-and-pinion-style press using double-sided tape:
A piece of silicone rubber was similarly attached opposite the tool to prevent bottoming out on the metal platen:
The press was tested 100 times on a scrap of 0.5 mm PETG:
The 101st test was performed on a scrap of 0.75 mm polycarbonate:
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:
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:
Embossing was also performed on stock with both layers of protective film still in place; prior to film removal, the URL was legible:
However, legibility was reduced once the film was removed, suggesting film should be selectively removed from shields prior to stamping:
