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12-08-2017 #11
Thats how i did it on the gantry, my first build. gantry was flipped 180 degree and i poured gantry sides and lower beam epoxy. Then flipped and did upper rail. No problem.
But you will need a straight edge and 2 precision squares for later when mounting the rails and so...
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12-08-2017 #12
Dear Clive S,
My design dictates at least 2 idler pullys per ballscrew if i want to go single x axis nema 34 stepper... and have the whole bed space.
Or... i have to limit bed space and cross the bed...There is room in the design to do this though.
And 1 side is up against a wall anyways.
When going single stepper,
i think i would buy a wide stepper pully,
and shift the ballscrews a belt width and use 2 belts, 1 for every ballscrew.
For now a 2 stepper x setup looks more convenient from a mechanical point of view.
2 short belts.
lots of bed space
My Electronic pov is opposit.
For inertia it seems, in my mind, better too.
2 powerful 3+Nm steppers on high voltage digital drivers. Instead of a single bigger 8/12nm nema34. this is just a gut feeling , not based on any sound research.
Not sure what makes a 3, 3,1 or 4 Nm nema 23 stepper best choice.
Just high amps low inductance right?
Any thoughts?
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For now a 2 stepper x setup looks more convenient from a mechanical point of view.
2 short belts.
lots of bed space
with am882 drives from China
I do have a nema 23 4Nm on my mill but don't see a difference in them..Clive
The more you know, The better you know, How little you know
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13-08-2017 #14
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14-08-2017 #15
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09-09-2017 #16
Dear Boyan,
Not sure iam really clear what your preference is.
Do you mean use a single motor on 2 belts solution?
Mechanical advantage is :
- Y axis can not get out of alignment easy?
* disadvantage idler pullys
or
use 2 motors and solve alignment in the homing sequence by electronic controls...
- Y axis can be aligned easily that way.
* Some (cheaper) controls dont do gantry squaring sequence.
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09-09-2017 #17
Ok some progress.
In the summer months the build did not get a lot of attention.
I did manage to get some of the steelwork done.
Did any of you run wiring through the box section?
Verstuurd vanaf mijn SM-A320FL met TapatalkLast edited by driftspin; 09-09-2017 at 01:07 PM.
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09-09-2017 #18
Aren't you going to put brace at the bed, at the long axis?
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09-09-2017 #19
if you are experienced with belts, know how to tighten properly long belt, know how to align all components then go with 1 motor and belt system. If you dont have the space, have a suitable controller board, go with motor each side. At the end is a question of convenience.
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09-09-2017 #20
Frame bracing.
Well no...well not yet.
Span is 2x1650mm span 120x80x4 mm box section....
plenty stiff one would think...
In Theory,
At 400 pounds of moving gantry weight 0.0027 inches vertical deflection would occure ... but the bed would move also. so. well.
At a more realistic 100 pounds 0.00068 inches
This would only be a problem if the workpiece was stiffer than the box section right?
In my design there is no absolute movement between router bit and workpiece when vertical X axis flex would occure. So no accuracy problems there.
By now total weight is 190 kg with no gantry...
I do believe "ringing" might become a problem... the assembly has a +/- 1khz resonance frequency.
I might fill her up with something like sand or epoxy mix concrete or something need to look in to that.
For shaking appart there is something to be said though.
Bracing at the bottom should solve x axis flex.. some of it anyway. It felt plenty stiff  those diagonals are out of the way great.
Y/X direction flex / bracing... yes.. well.. erh there is going to be cabinets installed ..
And maybe a few bits like: compressor airbrush type , vacuum cleaner, dust removal cyclone, cooling for spindle,
electronics cabinet.
X-direction flex bracing
I cannot yet fill the under the bed space with diagonals... yet.
There will be bolt on triangles when stuff like that is sorted.
Y-direction flexbracing
There is a 3mm thick plate 1000mm x 200mm with curved edges between the legs.. bolted with 4xm10 threaded rod to the legs.. plenty long m10 rod +/- 100 mm for building up tension.
Diagonal cross frame flex.
At this time i have prepared 4 m12 screws at the bottom of the legs to level the frame
And help with aligning icw anker bolts to the concrete floor.
When it is level and all legs (set screws) are in contact with the floor.
It feels incredibly stiff.
When now a set screw is set out of alignment by a 1/4 turn (M12) the table is wobbly ... proof of stiffness...
Any thoughts?
I have no good idea what the shaking forces are like in real life.
Verstuurd vanaf mijn SM-A320FL met TapatalkLast edited by driftspin; 09-09-2017 at 03:17 PM.
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