Accurate Strong Gantry

[JAZZCNC]

And IMHO after playing a lot and rethinking all designs and reinventing the wheel, my conclusion is that if all things taken into account we must not forget that we usually use only 2.2 -3kw spindle, using only 6-12mm bits, so we should not forget the strongest point of each design and choose it when needed, cause at the end they will all work if made properly.

Now your getting what I've been trying to tell you for nearly last 2yrs. . . . . . . It gets even more stupid than just the spindle because half the time these massively over engineeered machines only ever cut wood or foam.!!! CRAZY

This design and the over hang are no problem what so ever.! . . Milling machines and Many large commercial horizontal designs use much much larger overhangs but rest of the machine is built to match.
Like Boyan rightly points out your design is weak where it matters most and not very well thoughtout in other areas. This why I would support and brace the uprights on 2 planes and support the gantry on 2 sides with rails.
The over hanging spindle wouldn't bother me in the slightest with correctly sized and spaced bearings. But if you want the best layout which is slightly more complex and costly then have the Axis which the spindle travels on supported both sides so effectively having a Box in Box arrangement.

Personally like Boyan says don't re-invent the wheel just make it fit your purpose.!!

[Ross77]

Well to be fair the first post did say 1000N cutting force so guessing big cutters will be used and with 0.05mm accuracy that's not much error budget within the whole machine.

Without getting in to complex design calcs the quickest and most economical solution is to over engineer the frame. The extra weight can be benificial and also a problem with regard to acel-decel and dynamic loading but this design stops all the loading being transferred to the x axis like a moving gantry. So wont be as much of a problem.

The natural progression of a diy machine is to upgrade so having a strong sturdy frame means you get bigger steppers or higher powered spindle at a later date.

I know that the machine will be limited by its spindle power and cutter diameter and in fact tool deflection will be the ultimate limiting factor to cutting and feed speeds but this isn't a commercial machine.

I always believe that the machine should be designed from the cutting tool back through the spindle and the rest of the machine. Maybe It would be better to start again with the design spec to confirm what spindle and cutters will be used and go from there. :0)

[vargai]

Maybe It would be better to start again with the design spec to confirm what spindle and cutters will be used and go from there. :0)

I have changed the design and want to include the spindle being important( and heavy) part so the parameters:
3 kW motor + belt driven spindle with a later ATC option
Cutters "anything" that the motor can drive ( in plastic I can use 50 mm face mill :)
100-10000 rpm( so conventional machining range)
one option is AC motor +VFD -only the motor is 25 kg I know
other:s cheaper type servo motor or similar- designed for this purpose
I need some help in this subject to choose.
I made some searching but still have not find too much here.
Something I found on Blakburn's post but its reading is not aloud for small children.
So pls point it to if any is here
Thanks

[Boyan Silyavski]

Now your getting what I've been trying to tell you for nearly last 2yrs. . . . . . . It gets even more stupid than just the spindle because half the time these massively over engineeered machines only ever cut wood or foam.!!! CRAZY

This design and the over hang are no problem what so ever.! . . Milling machines and Many large commercial horizontal designs use much much larger overhangs but rest of the machine is built to match.
Like Boyan rightly points out your design is weak where it matters most and not very well thoughtout in other areas. This why I would support and brace the uprights on 2 planes and support the gantry on 2 sides with rails.
The over hanging spindle wouldn't bother me in the slightest with correctly sized and spaced bearings. But if you want the best layout which is slightly more complex and costly then have the Axis which the spindle travels on supported both sides so effectively having a Box in Box arrangement.

Personally like Boyan says don't re-invent the wheel just make it fit your purpose.!!

Yeah Dean, i hear you now. Just needed to spend my first 1000kg of steel so i could understand you better . You know, new toys, new experience...