Stell frame cnc 1500X1000. Adjustable table your opinion please

[Boyan Silyavski]

Dont be in a rush with it. better think it again. from various angles.


Now a couple of questions which are related:

-Why the 280mm height? Did you purchase already the rails for the Z at certain length?
-what is the width of the Z carriage plate that slides on the gantry?

Because i believe that it can be made narrower and that bearings with some thought to go behind the Z, not to eat of your Z travel left right/x axis/.

-what about the total weight of the gantry? you are not going with servos, right? this frontal plate will weight a lot. Actually i don't like it for that reason. You can strengthen the gantry in other ways. For example plan B and fit triangles inside where the vertical pieces are and no face plate. If the vertical pieces are spaced ~30cm or less there will be no need at all for face plate.


I was personally for plan B, but... Check again all the details, may be a mix of them all. Cause now looking at my drawings in fact i see B impossible as you draw it, cause you only need 40mm of the ball screw support to go inside so the ball screw housing barely shows, but in that case the rails should go inside the profile, which is impossible. So may be draw it first. To me it seems that C is closest of all to the measures . Just move back the middle piece so its 43mm back from the front.
You can reinforce it like this/ the middle profile in your case/ :





I cant remember if you have already bought the ball screws and the rails, if not-fit that motor inside as i told you at the beginning :-) and save some money for beer :-)

[ba99297]

Sylyavski i answer your questions to make things clear

The 280mm height is the result of the conevrsations that i had at this thread. They advice me to have minimum distance betwen the outer face of the carriages 250mm. So i make combinations wtih 120X60 and 80X80 tubes to get that height. So two tubes 120X60 at the top and bottom and two 80X80 give me the 280mm

The width of the z axis carriage plate is 370mm. Even if i narrow it as you suggested, i wont get more y axis travel as the spindle plate will conflict with the bottom steel plate ( where x axis carriages will be bolted.

The total weight of the gantry so far is nearly 140 kgr
I will use servos. 4 yaskawa sgmph 400 watt each ( two of them for x axis). 2010 ballscrews for x and y axis, 1605 for Z. 2:1 geat ratio for all axis ( 2 at the ballscrew 1 at the motor. Htd 15 with 5mm pitch aluminum pulleys.

Rails carriages, ballscrews, motors and spindle (2,2 kw) are in my hands. So no change can be made at these components.
If there is any suggestion i will be glad to hear

Vagelis

[Boyan Silyavski]

I get it now. Then maybe you could look at my last post in my next build and consider how I am making my gantry http://www.mycncuk.com/threads/6619-...0346#post60346
May be you would like some of mine ideas which i belive will lead to very strong gantry with no overhang and exclusively made from profiles, like the ones you have. That's the best I have come till now.

[ba99297]

Here is my progress the last two days.
Yesterday all the day pass drilling and taping the bed and the table for attaching the bed
Attachment 12913
Attachment 12914



And that is how i end up today



No time to write. It is too late... Sorry
Tomorrow

Thanks


Vagelis

[ba99297]

Today progress
I have to weld the upper 80X80 pieces ( where the rails will rest )
The lower pieces ( over the foots) make i little curve ( nearly 5-6mm ) at the middle as reult of the heating.
So i decided to weld 4 spacers at the corners. Put the upper pieces with spot welding after make everything square and parallel as possible
Here we are
Four spacers 120mm at the corners


Then i put the upper pieces and before i spot weld i try to make everything square. I use the 1160mm pieces (this is th excact distanse that the upper 80X80 pieces should have) that i will use for the gantry, and other parts of the cutting bed to make everything parallel



After having the tubes as parallel as possible i messure the excact distnace and cut the rest of the spacers. Then i spot weld from the middle to the corners. After everything was in place i start to full weld the table. In order to avoid too much heat i make 2-3 cm welds at a time from one spacer to the other and from the on side to the opposite. So i pass along the table 20-55 times( welding and cleaning the welds). In order to have better welding results i rise the table to have better angle

End of the day and after turning the table upside down to full weld all the sides, i think the result is more than acceptable

0.0-0.1 radius ( messured at different spots) the offset between the upper rails and the vertical pieces.
This offset will be zero after epoxy ( ...i hope so )


Next step is to make the tuning foots. That is why i weld a 80mm piece at every leg with a hole in the middle to pass the m18 bolt.

Then the epoxy method will take place

Till now i think it must be nearly 200 kgr. The winch save me from a lot of work
Thansk for your comments
P.s Do you think that the legs should be connected at the lower part of the table?

Vagelis

[EddyCurrent]

Looking good, I think the legs are okay as they are. Make sure you paint the frame before doing the epoxy, it's a lot easier, but leave just the top surface of the upper rails bare metal so the epoxy sticks good.

[Boyan Silyavski]

Starts to look very impressive. Nice job. I envy you for your big and nice looking workshop.


-In my opinion you don't need to adjust the table by bolts. The machine needs to be sturdy at earth level. I plan to buy for mine 6 hockey plucks. That's what my friend did and works like a charm. Not needed, but he is a maniac.


-if you follow what Eddy said and paint it, may be don't paint also where the ball screw end supports will be. When the gantry is mounted, then fix the ball screw, then go to one end and then tack solder the fixture for the end support, then go at the other end and repeat. Then remove the ball screw and then solder it carefully there. So when all is ready in the same manner you rectify the ball screws. Cause if you solder now, later may be there would be need to re drill the holes and waste a lot of effort. That's my way of course.