[Fraesi1]

Hello all,

I'm very new to CNC and also 3D printing, but anyway building my own CNC Router at the moment... When I checked my aluminum profiles (80x160mm so quite rigid) I noticed, that all surfaces are always a bit bend towards the slots. So if you are not center the linear rail (in my case HGR20) very precise at the center above the slot it will be mounted with a slight slope... To be able to center them very accurate, I printed slot nuts like the one in the photos. I redesigned them until i got a very tight fit into the slot and also into the mounting holes of the rails.

This worked very well. I was able to slide (well not "slide", it took a rubber hammer, even every nut is sliding well) the rail onto the profile while attaching the nuts into the holes.Its only 3D printed plastic, but these are many and the rail is bend only a very tiny bit. So I could feel how the rail was gently forced onto the center of my slot cm by cm.

I already aligned the 2 profiles that are holding the rails as good as i could on the base bars. So now I could install the portal bar for the first time :-)

My plan was to:
* Install the portal bar and tighten it well
* Loosen the bolts on the base on one side to allow the bars to adjust to each other
* Tighten the bolts a bit
* Loosen the bots on one rail, where the gantry would stuck and try to adjust the rail as little as possible to not move it to far from the center of the slot
* Repeat until the gantry slides nice and even

My "Problem": when I had the gantry installed it was already gliding the full length with a low, smooth and even resistance.. So I'm quite happy about this and - obvious - I now don't want to loosen the bars or the rails now. But as I have never worked with linear rails, I'm a bit unsure if this is a valid solution.

You always read: install one side of the rail as straight as you can and then use the gantry to align the other side, while tightening the bolts more and more. I can not measure the force to move the gantry, but to the hand it feels completely even and i have now installed the ball screw on the left side and this is moving also very smooth (even with the right side ball screw still missing and a gantry wide of 104 cm). So my question is, if it feels ok, should it be ok? Or is there a chance, that I have too much pressure on the rails, that i can not feel, but that will wear out them fast?

[peteeng]

Hi Frae - If they feel good then they are good. But you do need to check they are straight with a straight edge. Peter

[Fraesi1]

Hello Peter,
thank you very much for your reply, it's good to know they will not break beeing installed like this, the rest I will figure out :-) For this project I bought a precision dial indicator and tested the distance to both sides of the profile while sliding the gantry. The maximum deviation is +- 40-50 µm and its always close for both sides in the same direction, so the sides and the slots of the profiles seem to be quite parallel. How straight they are, I don't know, but I have nothing that is 1.2 meters long, that I would consider more straight, than these profiles.. I will think about this.