Quite an Unusual one

[Boyan Silyavski]

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



-that's better



-another dry test and squaring together

[Boyan Silyavski]

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

[mitchejc]

Well done sylyavski! That Z looks VERY strong, I like it a lot.

[toomast]

EPIC.
You sir are raising the bar for all of us :)

[JAZZCNC]

Don't get the point of 2 ballscrews on Z axis Boyan but it sure looks Cool.!. . . Mega OTT but very Cool.

[Boyan Silyavski]

Thanks guys!

Don't get the point of 2 ballscrews on Z axis Boyan but it sure looks Cool.!. . . Mega OTT but very Cool.

Thanks Dean,

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.

[Jonathan]

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.

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.

I've probably mentioned this before, but I'm not convinced that a double not would actually work better than 1 nut here. In a double nut system the nuts are preloaded against each other, so a force is applied the load on one nut decreases whilst the force on the other nut increases. For any force above the preload force, all the force will be transferred to one nut.

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.