Can we make a 1/2 inch bumper
If you are referring to the thickness of the wood, then no. The rules state specifically 3/4 inch.
Go through the bumper rules, one by one if you have to. Failure to follow them will at the very least result in a lot of time spend fixing them, let alone the hassle/missed matches.
If you have a question about whether something with the bumpers you have is legal, don’t hesitate to post it–it’s better to be safe than sorry. Also, some of us are inspectors–we can tell you whether they’re likely to pass or not.
Note that you do not have to bag the bumpers with the robot, so you’ve got some time to spend making sure your bumpers look good and are legal.