Quote Originally Posted by JoeHarris View Post
How have you aligned the y axis rails? Apologies if this is explained elsewhere and I've missed it..?

OK, the squaring. It was the main challenge at this size and the precision i would like to have. There was no skipping there. I had it clear before soldering the machine and the design was affected by it. I will try to explain it below. Every detail counts and i will try to explain it step by step.
The key to my way of thinking, apart from no skipping, was hard stop mounting, means i don't measure anything/cause i don't have the means to, instead i rely on straight edge, square and touching without gap. On the first machine i have made i managed to achieve 0.01mm more or less in all directions. This one was quite bigger challenge.

Another point is that i always strive for absolute alignment and straightness, not relative, meaning i don't skip relations or directions. Knowing of course that's not achievable in real life at home. But when you strive for the impossible the result is more than acceptable




Y axis is my long axis . Epoxy leveled, then mounted left rail permanently, against straight edge. Now it was to square the right rail. Then using precision square and straight edge aligned both ends. Then clamped there. Aligned middle, then clamped, aligned other ends then clamped. Marked the holes, un-clamped everything. Then again repeated the process against straight edge clamping here and there. Now i had small level problem even after spending so much time on leveling, this due to a small leak. Other thing on such size was that even using straight edge and precision square, at such length everything seems square but is not , at the end its up to you to feel the squareness scraping them against each other. i could say that was the most difficult job on the machine, and most time consuming.

X is my gantry rails where Z moves left right. First of all i left the plate on which the gantry steps upon the bearing blocks to protrude 10mm at the back. I mounted the plates but not the gantry. The plates were still not soldered. And i made sure using straight edge that they are perfectly on one line and square.Then i mounted the gantry on top of them. Then i soldered carefully on place, just fixing tacks. Then i dismounted the gantry and plates and soldered on the ground. Then mounted again up. Checked if all is OK. Then dismounted the gantry and put the gantry on its back over the Y rails. See pictures above. #143
The idea was the Y rails are now leveled with earth, cause i did not move the machine, so perfectly horizontal. So when i lay down the gantry on its back, using shims i can perfectly square the said plates to the Y rails, 90 degrees. So now i poured epoxy Under the X rails. The result was later when mounted, the X rails are perfectly 90 degree to the Y rails. Now the thing that was left was to mount the X rails properly and square them in the other direction to Y/parallel, meaning when all mounted left and right height of X rails to be same distance to bed/ .
So with the gantry still laying on its back and gantry legs at 90 degree to the Y rails, epoxy poured and dry, i measured same distance from the lower X rail to the gantry legs plates/which were on same plane from before, when i mounted them on machine and soldered gantry on its place./ . Used verier then tightened the bolt, so all was hard stop mounted. I could have drilled and mounted the lower rail now, but i just clamped it, cause i had max permission of +1mm up or down or the ball screw would not fit in gantry and Z plate. So basically i had to mount the ball screw on its place, let it have some future play for adjustment, then mount other rail and the Z plate. Some fiddling with all that and i knew where all should lay. So marked, dismantled all and using the vernier again mounted the lower X rail. Checked against straight edge, marked, drilled, tapped and fixed.
Now having one rail mounted permanently i had to mount again the ball screw, the Z plate and so i mounted the second rail.

So at the end of it i lifted the gantry on its place and using straight edge, precision square and the protruding gantry leg plates for reference i squared the gantry.