A great level to grind this out on is "Rise and Swine" Level 1 (2-1).
Put the two red wheels at the bottom, place the metal box and engine on top of the left wheel, place a wooden box and pig above the right wheel. Then press go.
Rinse and Repeat 50 times and you'll have the achievement.
As a bonus this will also get you desserts for the king and three stars on the level.