After placing the linear guide blocks on the X rails, I placed the gantry on top of them and proceeded to align everything. I spent a lot of time aligning the X axis rails. This included making sure they were parallel with each other and also that they were perpendicular to the Y axis rails on the gantry. I clamped together a few 24” squares to get the rails parallel and then placed some 1-2-3 blocks on top of them to check that the Y axis rails were perpendicular. I clamped the rails in place as I went to keep the alignment correct. Once I was happy with everything, I marked out where the linear bearings should be mounted to the gantry. I drilled the gantry and mounted the linear bearings, then installed the gantry on the rails again. I forgot to mention that I had previously found the balance point of the gantry using a thin piece of wood running the long way under the gantry. I marked that balance point on the base of the gantry on both ends and that became the center point between the two linear bearings.
The alignment was double and triple checked prior to bonding the rails in place with the System Three adhesive epoxy. I still have some adjustment available in the rails to make fine adjustments with a dial indicator. I had previously used a chemical etch on these pieces of bar stock, but the epoxy should be applied very soon after the etching to get a good bond. I had let too much time pass and since I am experimenting and learning here, I decided to use the “wipe down with acetone” method for this to evaluate how the bond holds up compared to the other axes where I used the etching and sanding methods.