This design should be more effective than the credit card I was using, but it hasn't yet been road tested (or printed) in its current form.. The previous version was printed and tested and modified with a sharp tool to resemble this one.. It did manage to clear ice well after modification. This is the largest size I can print on my 3d printer with 155mmx155mm bed...

mini_ice_craper.stl was made with Tinkercad. Edit it online https://www.tinkercad.com/things/0CWjb7JBg1U

ice-scraper.stl was made with autodesk fusion 360