Aluminium Profile Type Router - Initial questions

[CNCRY]

What you are doing when squaring the gantry is setting it perpendicular to the MASTER RAIL and NOT the frame. Infact forget the frame because unless you have built it perfectly square and aligned the Master rail perfectly parallel to it then you CANNOT measure from it. The MASTER rail is the ONLY reference point you work from.

So the ball-screw must also be perfectly parallel to the MASTER rail. Likewise, the Ball-NUT is set parallel to the gantry side.

So if you have set your ball-screws perfectly parallel to the MASTER rail, which you should have done. Then any angular adjustment on the gantry in respect to the MASTER rail means there must be an angular twist between the Ball-NUT and Ball-SCREW and this will cause excess wear and binding.

The goal is to get the gantry perpendicular in respect to the MASTER RAIL and the ball-SCREW perfectly parallel to the MASTER rail. This will then put the Ball-NUT perfectly parallel to the ball-SCREW.

When all this is done then this will show you how much Shimming and spacing is needed at various places around the machine in relation to the Frame. If you have built a perfectly square frame then it should be easy.!!

You may find the best place to shim to get square without impacting the screws/nut relationship too much is between the Gantry plates and profile at each side.
This is where building in lots of adjustment points comes into play and helps with setup and fine tuning, don't be surprised if this takes you many weeks to get right with lots of strip downs.

Edit: I've just done a quick sketch in SW to show how much just 1deg of misalignment translates across the length of a gantry or machine.
The measurement show the numbers except one and that is the twist of the ballnut in relation to the ball screw but the number is 0.70mm of twist which would wear a ballnut out in no time and cause lots of binding.

The Rubber is BAD idea, your basicly building in Back-Lash. The rubber will allow it to float even under compression. Don't underestimate the forces and the amount of inertia that will be applied to ballnut which transfers to the ballscrew which pushes on the Endbearings which will be sat basicly on rubber engine mounts.!!

OK so full honestly, in terms of the rail and ball-nut alignment, what I've done is to set the master rail using the thickness of the extrusion as a gauge and then use a fixed size block offset from the edge to ensure the rail runs parallel to the edge of the extrusion.
Then the "slave" rail is firstly set it the same way with not fully tight bolts, then run the gantry along it to ensure it runs smoothly along the rail and moves the rail very slightly to a final adjustment. (but in theory its the same offset from extrusion as master rail)
The axis runs smoothly with no ball-nuts attached at least!
Then the ballscrews were attached to extrusion using tooling plate spacer so in theory are fully parallel to the extrusion.
So yes clearly its not fine precision, and a fair amount is riding on the aluminium profile being to good tolerances which I guess is much harder on box steel build, but to see where I'm coming from I didn't know what a DTI even was was a couple of months ago!
So with that said, I'm hoping I can tweak things without any major changes to the machine.

The rubber part is only on the dual Y (formally known as X :) axis) ballnut. As per below in red. The bolts are still coupled into the ballnut mount, but I can easily replace that with 1mm aluminium shim.


I've attached the motor mounts now so am going to run it tomorrow and see how it moves. Is it obvious it its binding , does it judder etc?
Then if shimming is needed use this on the gantry and Ball screw mounts.

How should you align the ballscrews vertically - I tried using a DTI on the rail touching the ballscrew but hard to where on the thread it sat. Or use a small block sat on the screw..?
Do people use the 3, 4, 5 triangle method to check square then adjust and set limits? As there are various ideas out there..

Will report back after running it - wish my luck