Driving the gantry on Z axis?

[Boyan Silyavski]

Maybe all comes from fact that he holds the spindle with only 1 bracket and is not using water cooled spindle with steel body. But you could definitely hear on second video that when digs in material, something vibrates. Or if he is using short hiwin blocks the overhang of all is a bit too much, or mixed effect of all this.

See below, i try to illustrate what i was talking about, using a drawing i am still working on:
-if there is a second spindle bracket the spindle itself strengthens the Z
-weak spot is in yellow, where spindle pushes at first, its so short and in between 2 pairs of long bearing blocks so its irrelevant, so all force transmits to the upper bearing pair, instead of the plate itself.
I also have a feeling that the initial push at that short yellow distance eats all vibrations instead transmitting them to gantry

- then spacing of gantry rails must be same as when spindle is at its lowest point, so it balances the arm of force, see black line

So seemingly very simple thing could be very strong if well designed. Somebody could say it needs further bracing, but not. This design is tested by me in first build and works like a charm routing aluminum fully extended without problem. See video at end of first build where 0.8kw spindle makes 1.5mm pass fully extended without a glitch. See that there is a moment of scream when digging downwards, that because the lack at that moment of sturdy table bed

[Skipsoaring]

Aaahhh... pictures are 1000 words etc!
I'll check out the vids again, how does that design cope with lateral loads (gantry side to gantry side)?
Would you consider Stainless steel with that fully extended?
My gut feel is that you wouldn't?
I did read your 1st build and was very impressed (I'm sure I have watched the video). I'm sure I'll read it again (along with many others).

[Skipsoaring]

The only drawings I am going to be contributing at the moment will be on paper and a mobile pic taken. My computer died earlier this week, these things are meant to test us!

[Boyan Silyavski]

Stainless steel with moving gantry , may be , if the gantry was 2 tons, the spindle 20HP BT50 , ballscrews were 30 size and bearing blocks 35 size roller bearing.


These computers were testing me too. First broke my main one before 3 weeks. Changed disc to SSD. Great upgrade in speed and all. Then the one at the workshop learned and it also broke. Yesterday fitted it also with SSD . Good that my laptop has already SSD. Needless to say that after previous crashes learned my lessons so all CNC drawings are on mirrored discs + cloud storage

[Skipsoaring]

Stainless steel with moving gantry , may be , if the gantry was 2 tons, the spindle 20HP BT50 , ballscrews were 30 size and bearing blocks 35 size........

Okeydokey!! Aluminium it is then!

I'll also be using cloud storage. Just gotta get a new computer

[Skipsoaring]

...Just gotta get a new computer

Got a new computer today, went out to get a cheapy and came home with a mac, ooopps!

Before I get too carried away thinking about my second machine, I need to start my first machine (hot wire) so that I can get the money for the second machine (and somewhere to build it)

[Skipsoaring]

Just had a read of this thread and found some of the fog lifting: http://www.mycncuk.com/threads/7112-...nium-etc/page1
I will be trying to build an extremely rigid machine, just won't be considering stainless as I feel it would be too restrictive.

[toomast]

Hi,
I had similar "vertical fixy" idea.
http://www.mycncuk.com/threads/7321-...x500x180-RIGID
Did not finished it though :( I also go with Silyavskis design.
Good luck!

[Skipsoaring]

Thanks for that Toomast.
Fixed gantry looks an idea.
When I think of a fixed gantry, I automatically 'see' the gantry fixed across the narrowest axis requiring a very long bed travel, 4m in my case! If built correctly am I right in thinking that there is no reason I can't have the gantry spanning the longest axis? This way my machine would be a smidge over 2x2m allowing for a cutting area of 2x1 or thereabouts with the bed moving across the shorter axis.
It was thinking about the size of the machine which got me thinking about having the gantry move as the z axis (as per the video in your thread).