We have created a 3dprintable frame building jig to help establish adequate spacing for the Z axis it can be found here if you decide to print this we recommend you check its marked measurements before use. The Important measurements here are the 6mm and 40mm these will ensure the spacing is correct. If you have ordered extrusions from a supplier please verify the length prior to using this jig. the jig uses the (stacked dimension for assembly and wrong cut lengths will effect the outcome. The Z axis kit is ZM(length)+6MM for each Z size.