Sturdy and Fast all Steel CNC , my first build

[toomast]

Actually I meant X-axis then.
I understand that you ensure with epoxy that the rails are parallel. But how did you adjust HIWIN bearing blocks to match the rails?
Surely you did not weld the laser-cut parts so precisely?

[Boyan Silyavski]

Actually I meant X-axis then.
I understand that you ensure with epoxy that the rails are parallel. But how did you adjust HIWIN bearing blocks to match the rails?
Surely you did not weld the laser-cut parts so precisely?

The machine when long rails epoxy is poured must be glued to the floor so you will not bump it later. Then long rails mounted. Then first i poured epoxy on the gantry top , the gantry in normal position as near as it would be in final setup. Then flipped the gantry 180 degrees and the leveled top epoxy now down resting on the already leveled long Y rails. Then i poured epoxy on the low gantry rail and on the legs. So now we had everuthing parallel, gantry legs, low rail and upper rail.

Then i squared the gantry top rail as described bellow. In short i squared a straight edge on the long rails. Then using 2 equal sized aluminum bars and checking them square against the straight edge i squared the top rail. Then additionally using only one piece at both sides i carefully finished the job feeling the scratching . Drilled and mounted the same way. See first picture
Now i had 1 top rail ready and square.

The bottom gantry rail.
I mounted the plates on both rails. The plates that screw to the bearing blocks. The Z was still only pieces, not soldered. Then via 2 clamps i mounted the lower rail more or less. But clamps not tightened very much. Then using the front Z plate that will be later soldered to the both plates that screw to the bearing blocks i checked and aligned perpendicularity to the squared straight edge resting on the long rails , picture below.

Note should be taken here that when i bolted the 2 plates from the Z i pushed them from behind till they touched the screws, so i know they are alligned to the bearing blockes, as the holes are laser cut. I mean because of this i am sure that their edges are parallel with the corresponding rails. Later i will have some additional opportunity to align them on one plane/the z face plate/ as i can move one of them a bit back


So i mounted the lower rail. Z was carefully spot weld fixed while all was bolted on its place. No paint anywhere on the machine where bearing blocks contact with frame, metal only.

4. Bolting the gantry to the frame and aligning the gantry rails.

Needless to say - a lot of problems.

a/ First to say i have dry bolted the gantry before painting all. It was ok. So what was my surprise when everything was painted, the machine fixed on the welding jigs for comfort and the gantry will not fit. So i called a friend that helped me and 3 times i had to lift the gantry and lower it, mean while widening the holes. The reason. This is crazy- the machine is outside, the sun heats the frame and it widens. cause i made the machine in the winter...
So basically now i cover all the time it so it could not heat . My garage is small i mean to work inside.

So at the end i squared perfectly the gantry and bolted it


b/ Now next unsuspected problem. How do i fit the rails on the gantry to be perfectly square with the long rails on the frame? I knew i could do it somehow but in reality it was a big challenge.
I know how to do it if say i make 10 same machines, a fixture and no problem. But how to do it on the cheap. Cause this machine really ate a lot of money spend on little things.
After a lot of thought i fixed the straight edge perpendicular to the base rails and decided to start with the upper rail first.
Once the upper rail was square, there came the problem with the lower rail. A friend of mine says we have all necessary stuff always at hand. So i was in no rush, thought it a whole weekend and just have done it.
Another difficulty was that i do all alone at home with no help, so first i more or less squared it using clamps and then drilled and tapped 2 holes only. Then aligned and bolted until happy. Then drilled the rest of the holes directly on place and bolted. Photos speak better than words how all of this was done.

Of course i managed to chip the paint here and there so it seems when everything is working i have to retouch it at the end. No big deal.


2 equal pieces of aluminum square bar were used to fix more or less the correct distance to the upper rail.




Both were precisely squared to the straight edge which was squared to the base rails. 2 pieces of rail were used to support them, a kind of parallels . Not seen on the pictures at the end only one was used at both sides so to make sure the fit is perfect and is really squared.




Holes were marked, 6mm drill used to clean the epoxy so it will not unglue or raise during drilling the beam, then 4.2mm drill to make the holes and then tapped. With the help of the nice little block i have.




On all drilling and tapping the gantry was clamped so it will not move around. here is the fixture which helped me align the lower gantry rail. Dont laugh at my square, had to clamp a rule to make it longer. I said we have all we need at home, just some imagination is needed.
Used thickness gauge though to align it perfectly /yes i love that word/.

Note should be taken here that when i bolted the 2 plates from the Z i pushed them from behind till they touched the screws, so i know they are alligned to the bearing blockes, as the holes are laser cut. I mean because of this i am sure that their edges are parallel with the corresponding rails. Later i will have some additional opportunity to align them on one plane/the z face plate/ as i can move one of them a bit back.

[toomast]

I swear I read this section many times before! But could not understand...
I guess my brain refused to believe that it is possible to fix the bearing blocks and then weld the parts together and end up with perfect alignment...
Even hammering some 10mm steel plate to perfect plane seems unbelievable. Guess it depends who is holding the hammer or welding torch :)
Sorry you had to copy hole page from your thread!

All the best,
Toomas

[Boyan Silyavski]

The key there is to leave possibility for alignment.

I mounted the plates so all bolts touched the holes from one side, and as they were laser drilled they were more or less straight. But later i drilled the holes 1-1.5mm wider. So at the moment of mounting i had not only the margin of the hole itself , but of the widened hole. So its easy to adjust cause there is space that allows it.

The other key is to have 2 precision squares and 1 straight edge. So at all times you can check and assure perfect fit. You can not measure how perfect, but if you insist and try that no visible gap is left at any place, you will finish with very precise machine. And not be lazy, cause you need sometimes to check a simple thing 10 times untill you are definitely sure its straight.

And when i say check, i mean check with strong led torch

[toomast]

Silyavski, do you think 10mm steel is minimum for Z axis?
I hink that I will at least try to build my Z axis from steel. If I dont succeed that I will go for aluminium :)

[Boyan Silyavski]

Steel is cheaper, faster and easier if you don't have a mill or other cnc. 10mm steel and that having in mind the way i did it, where the rails and the rectangular bars that the rails lay on, play the role of ribs that strengthen all. You will be surprised how flexible is 10mm of steel if not strengthened by bracing plates that provide strength in contrary direction.

I managed to mill with that Z/180mm fully extended/an aluminum plate- 1.5mm deep pass, and lack of cooling and proper bed fixture was the problem to go deeper per pass.