I want to construct electromagnetic dot pin stylus for use on aluminium shhets.Can any body sggest me the design in principle?

Why reinvent the wheel? contact these companies:

Technifor
http://www.technifor.com/index.php

Schmidt Marking Systems
www.gtschmidt.com/stylus/index.html

Matthews Marking
www.matthewsmarking.com/products/tech/propoint.php

Dapra Marking
http://dapramarking.com/dot-peen-marking.htm