strange noises when starting up

I'm starting to get a loud ratcheting sound on either the X or Y axes when the printer homes. The print head either wobbles and makes the sound until I tap it, or the bed does that. In both cases, I tap them and they home.... Then while printing, it's getting louder and louder.

any suggestions?

Eek. Are you sure you have nothing attached to the lower extremity of the up/down axis? At one point, I thought it would be a good idea to attach a bit of rubber to the lip at the bottom of the travel area, but it made that sound every time I homed the axes.

no,nothing attached. it happens with both the X and Y, but not all the time. It's either one or the other. and it's really loud printing now.