Is there a machine that buffs the surface?

Is there a machine that corrects the following problem.

We laid travertine stone tiles and when they dried the levels we not good on some of the times .  Not sure if there was settling going on in the mortor or what but you can not run a finger from one tile to the next with out encountering ridges.  Is there a machine that buffs the surface and can rectify this problem.  and then what kind of sealer should be used?

 

thanks

Jennifer Rodrigues