AndyUK's Build - 1.2x1.0m Gantry

[AndyUK]

I promised an update on the frame - here she is in all her badly painted glory!!

Since the last photos, I've

• Faired the edge of the epoxy into the frame and repainted the box sections.
• Filed off the meniscus along the edges and at the ends.
• Marked drilled and tapped the epoxy for the rails.
• Roughly aligned the rails for parallelism
• Checked the levelling with a precision straight edge - more details below.
• Thrown the gantry on the rails - it glides super smooth (and made me very happy!)
• After getting happy about that, I then got very sad. Turns out my steel frame is a bit of a rhombus! When I bring the gantry to one edge, it hits the end of one rail about 3-5mm before the end of the other, and the opposite occurs at the other end. I don' t think this will actually affect anything, except perhaps my pride...
• I then did some more milling, making my Z and Y nema 23 motor mounts. That was fun. :)
• Did a rough assembly - All I need now to make the Z and Y axis move under their own power are the belts which are on order. It was nice to be able to measure the distances between pulley centres physically rather than just in CAD.

The rails both show the same trend, they're high at the ends and low in the middle with an error of about 0.05mm - I'm sure this could be better, the epoxy still set relatively quickly, so I'm sure there are improvements to make. It could be that I just haven't filed down the ends of the epoxy enough and they're slightly propped up at the ends, but its 'close enough' for me at this stage. The other consideration is that this value is the stated accuracy of my straight edge, so optimising it now seems counter productive. I will probably come back and shim the rails, but I'm keen to do a 'proof of concept' and am aiming to have the machine cut something by Christmas.

I've noticed that the Z axis isn't as smooth as the others; I think it might be the alignment of the ballscrew vs the rails, I've discovered that my design is a bit of a nightmare to try and measure the alignment between the two, because the rails and the screw are attached to different parts. The other thing it might be is that the Z axis is the only one thats had a load of EP2 applied - does that typically increase the resistance on the screw? I can turn the pully by hand no problem, but you can feel that it has more and less resistance at different ends of the travel, which is something I don't feel on the Y. Any hints or tips?

The other problem I'm now considering is how to check the axis are perpendicular... can anyone point me in the right direction? I think Boyan mentioned needing two precision squares to align properly... I can see why you'd need one, but two?

Thanks!