Thread: Quite an Unusual one
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.
Nice work Boyan, figured you must have epoxied both axis. Time consuming buisness but must be satisfying to get it that precise!
At the end i managed to move further the build. Thanks to my new friend and fellow forum member Jeff Potter who helped me a lot with machining all aluminum pieces for me.
Now what happened:
-i bought some sound insulating stuff so i can make the garage quiet, so nobody bothers me in the future when i am working. I mean the tourists that come now in the summer and rent the houses around me
-tested this and that and at the end finished the prototype of the fog-less mister and tested it while milling the aluminum pieces for the Z
-tapped and started putting the Z box together , 5mm tap stem fits perfectly in the 6mm drill guide
-The rails were meant not to obstruct the back plate. the idea was to use the back plate as a guide to mount them perfectly flat and square
-mistake in the design. How the hell i was going to screw the ball screw nut supports. So i decided to cut a slot and at the end they will be screwed with 3 screws only.
-as everything was machined very precisely and as i helped Jeff make his machine work in 3D mode, all fit perfectly together
-the idea of the shortest front plate is if i lift and hide the spindle to its highest possible position inside the box, so i could reach and change tools without problems
-the Z looks like a bad ass missile warhead
Some more. I hope you like detailed photos of builds. /there is 10 image limit and i like taking photos :-)/
-The rotating ball nuts were press fitted and all worked fine. Though i have to change small things in the design, things that made me think a lot how to mount all of it together. And how it will be dismounted in near future if i decide to repair the belt...
By the way i decided to start making together with Jeff and selling the assembly in the near future, for forum members and other. Redesign it a bit for any specific case and machine it properly. It is a result of the fact that i spend too much time fiddling with that assembly and investigating. And trying to find who will do it for me, and worrying if they did it properly and repairing their mistakes...
So i would announce it at its proper place in the forum, hence will stop to brag here.
-tadaaaa, second mistake. The 30t pulley is too much in front so hits the Z back plate
-mistake repaired easily, thanks god
- dry test looking for mistakes
-ready to "surface" straight the side plates
-i knew the sound proofing of the garage will pay off. why this always happens at lunch time when all normal people rest. had to take the bigger "surface" hammer and "surface" the plates for about half an hour
-another dry test and squaring together
Wow, 3 posts, it seems i had a lot to show and say
-the Z again, 2 spot welds to hold the side plates in place
-thats why i did not bother before too much rectifying the back Z plate. No i pushed it flat to the whole straight assembly, so all fell in place. Then spot welded CAREFULLY
-I know Dean, OTT and too much but that cost me only 30euros more. I promise never to do that again.
-squaring the Z in both directions against the straight edge that lies flat on long rails. this took a couple of hours to do it properly until satisfied
-another consequence of the mistake i made here
- That must be the most bad ass DIY Z axis i have seen on single gantry machine , OTT but make me proud and smiling when i look at it, so i assume it was worth it , did i say it looks like a missile ready to launch ?
See that big, no - huge mill vice? Thats a gift from Jeff for the build. have to rethink this and that for the bed. I never imagined i will have some day such a beauty. On other hand its not fair some people to have 3 of them
Last edited by Boyan Silyavski; 01-04-2015 at 02:53 PM.
Well done sylyavski! That Z looks VERY strong, I like it a lot.
You sir are raising the bar for all of us :)
Don't get the point of 2 ballscrews on Z axis Boyan but it sure looks Cool.!. . . Mega OTT but very Cool.
I will explain. So people don't get over excited and start doing machine with double ball screw assemblies on the Z . As i said i will not do that again.
First i wanted to use a pneumatic hammer to shape the 1mm metal sheet. So i thought better 2 ball nut assemblies than just double ball screw nut, cause so the vibration will be spread on 4 fixed ball screw supports instead of 2.
Then as we spoke it became clear that 1 ball nut assembly is ok, especially if fit with double ball nut.It also became clear that maybe i will not use at all the hammer but make separate machine.
But i saw that because of the Z rail length /i had them already/ i will loose Z travel, don't remember exactly but instead of 200 it was to be 160. Or i had to change this and that and move the upper bearing blocks on the Z plate too much down, which would make pointless the so strong Z box
And as all was designed for 200mm travel i decided to live with the 2 ball screws
So yeah, it was a mistake , not a design wonder, just cost me 1 ball screw more. One year ago i had no idea how big can be 2505 screw, how angular contact bearings work, that i could have made custom end supports and so on. Slowly evolving...
There are also some other small mistakes on the gantry design that i would not repeat, most of them are OTT because of the hammer idea. Not that big mistakes but unnecessary waste of time and energy. I know now how to make all much simpler and faster. Same strong.
Last edited by Boyan Silyavski; 02-04-2015 at 05:16 AM.
Brings back memories...
Anyway. How have you ensured alignment of the Z-rails - both their spacing (parallel to Y) and parallelism? I can't see any features for alignment, so either you milled reference edges in after assembly, spent time with a DTI and straight edge, or (I doubt) didn't do it? It almost looks like the spindle is just clamped by the plates with the arc-section cutout? If so I'd be a bit concerned about maintaining the accuracy of the rail alignment.
Either way, as you implied, in general it's more economical to use a larger ballscrew (or larger rails) than multiples *unless* the spacing of the linear bearings is such that racking is an issue. I mentioned it here regarding rails and stiffness, but similar reasoning applies to ballscrews.
Last edited by Jonathan; 02-04-2015 at 10:05 AM.