Y axis assembly

Use M4 x 14mm socket head screws to attach one HGR15 linear guide to flat surface of the C beam:

Then use M3 x 14mm and post-insertion T nuts to attach the other HGR15 linear guide to the flat surface of the C beam:

Then use M3 x 12mm and post-insertion T nuts to attach the rack to the flat surface of the C beam – at the side where the last linear guide was installed (the one with the M3x14mm screws with post-insertion T nuts) – but pay attention to respecting a 10mm space between the rack and the linear guide: this can be done by putting on regular distances a precision shim or a 3mm spacer between the linear guide and the rack:

Notice the use of a 3mm spacer as a guide to respect the 10mm distance between the rack and one linear guide: this is very important and is necessary to let the linear bearings run without resistance – do this at regular intervals:

Optional: if you want to reinforce the structure, you can use 2040 rails to insert into the space of the C beam: give it a good push so that they then fit together:

And then you can add the linear bearings (2 per linear guide), and then attach the corner plates – you can use M5 x 12 or M5 x 15mm screws: