Assuming the spindles are ok, re-angling the wiper (Like Frank said) usually helps. If you tried it and it didn't work try going the other way. Ford dealers used to have a special tool to ensure the blade contacted the screen at the right angle!
Also check the spring in the wiper arm, they can weaken and snap and check the metal sections of the blade are flexing freely.
Finally, try greasing the ball ends of the linkage. Easily done if you have stripped it to grease the spindles.