I built this drawing robot. It works great. I just started the work of adding the limit switches. I believe there are supposed to be 2 limit switches on the X axis but there is only one bumper on the lower clam shell to trigger one of the switches. I created this object which can be glued to the lower clam shell to create the other limit switch bumper. If you already have a printed clam shell print the addition otherwise print the whole bottom clam shell with both bumpers. I'm doing a remix of this whole printer which will include this bumper as part of the lower clam shell.

https://www.thingiverse.com/thing:1517211

Use Acetone to glue ABS and Krazy Glue (CA) for PLA. The limit switches should tuck into the pockets where the belt runs through on each end of the X axis.