Mill 480x500x180 RIGID

[toomast]

Very interesting design. Have not seen this approach yet.
What do you exactly mean by counterbalance?
First thing that pops into my mind is to add 2x rails for Z-axiz to other side of the gantry(cost and alignment issue). And maybe move spindle closer to center line of the gantry. But maybe move Z rails on the sides of the gantry at all...
I will put it on the canvas.

[JAZZCNC]

What do you exactly mean by counterbalance?

Well the name says it all really but how you go about achieving it depends on design.! You can use Gas struts or simple counter weight on rails like you mention.
Last year I nearly bought a large-ish Industrial 5axis VMC overhead gantry machine that had a long heavy Z axis which used simple counter weight on round type linear rails running down the back with a pulleys at the top, just like the Old sash windows.!! Simple an affective with very little setup, aliagnment wasn't critcal.

And maybe move spindle closer to center line of the gantry.

Not understanding you here.? Spindle Nose will determine it's location on Gantry or Plate it fastens on, you won't want the collet nut any higher than the lower edge of the mounting plate.!

But maybe move Z rails on the sides of the gantry at all

Again not understanding.? Why move the rails on the gantry.? Nothing to be gained doing this.!

[toomast]

And almost a hole year later I am back. Despite not posting I have frequently visited forum and learned a lot more. Mean time some fantastic build logs have completed which have sent my mind wondering...

This is my fixed gantry next revision. Frame design is more clear and simpler now. Z is counterbalanced with gas struts. I decided not to limit my design with the random components I have. In near future I have possible projects for this machine - so then I can review the hole design and make needed changes in workarea or something else.

[JAZZCNC]

Thats looking excellent and will be a very strong capable machine. Only thing I see that you dont show is any scope for adjustment between the moving table rails and the gantry upright rails.? (Or is that why the moving table frame is blue.?) They need to be perfectly perpendicular to each other.!

You wont easily achive this welding the frame so you need some form of adjustment building into the machine. !! PLENTY OF ADJUSTMENT IS THE KEY TO GOOD DIY BUILD.!! . . . I say this in CAPITALS because it's often missed and then regreted later.

[toomast]

The blue frame is separate from main frame and therefore adjustable. For now I`m not sure how the adjustment and rigid fixating of the bed frame will look like...

Welding the big frame together will take some time but. Wonder if there is any point creating subassemblys and bolt them together?...there is not any adjustment needed if I epoxy level gantry upright rails and bed frame is adjustable. It will be heavy fo sure.

[toomast]

In search of a better/simpler/cheaper design I have come up with these versions. As pictures illustrate I did not succeed.





For the time being this fixed gantry design will come to a halt. As I have a need for larger work area and more general machine. Probably will go with something similar to Syliavski`s design.
This project is published in https://grabcad.com/library/fixed-ga...nc-460x500mm-1
Thanks for listnening!

[Robin Hewitt]

It still looks a tadge wrong to me...

I thought the big advantage of the fixed gantry was that you could localise the support for the bed where it was needed. You put your rails on the bottom of the bed and your linear blocks under the gantry. There is no point in supporting the bed anywhere but under the gantry, you are just introducing unnecessary overhangs

The machine should appear as a gantry with a bed sliding through it