please check my design. also screw position ?

[max_imum2000]

hello
as i am still new to this ,
i gut 6 thk slides 20W (115cm long)
and 2 thk ballscrew for x and y (80cm long)

i also have 7cm x 7cm , 2mm thick steel square shaped sections

from where i live it is so hard to get any other materials. or cast aluminum and finish it with presion at all.

so i decided to build a simple machine from what i have and use it to build another better machines

i have a 200oz steppers for this one.


now i dont know where should i place my ballscrew and how can i make it move the x-axis ?
can i put it on one side or at the center is better ?
must it be at the center line of the thk slide ? or up/down a little bit will be ok ?
is it better to place the thk slide in the x-axis as it shows in the pic or i can put it on the sides and it will be fine as well?

i am open to any suggestion . please give me your advice before i start making big mistakes

thank you

[mxtras]

My first impression is to lay the X rails on the side and then extend the gantry straight down to tie back across, under the machine to hook to the ballscrew.

Maybe others will chime in with their opinions.

Scott

[max_imum2000]

but will the thk slides be as good on the sides as in the top ?
i mean in handling loads ?

[mxtras]

Shooting from the hip, I would say yes - since you have two bearings on each side. Look up the THK bearing number to determine permissible loading and expected deflection and consider the weight of your gantry, etc. Spread the block out as far as reasonably possible on each side without sacrificing working envelope to maximize stability - standard procedure.

Scott

[max_imum2000]

how about something like this ?

[mxtras]

That's pretty clean and simple - can you show how the table would be supported?

Scott

[max_imum2000]

i was thinking of something like this.
and whole machine will be welded to a very normal steel constructed table .

[mxtras]

Looks like you are on to something. There are a hundred different ways to do this - yours is one way and probably a pretty good way to do it in my opinion. It's simple, compact and relatively easy to construct.

I would spread those bearings out a bit to help prevent skew and racking. Typically, you space them equal to 1/3 of the spanning distance to eliminate skew. In this case it would consume too much of your X stroke, though. There's a happy medium in there somewhere.

Scott

[max_imum2000]

thank you for your help.
i guess ur talking about spreading the bearing the y axis,
that sure i will do .

will it be better to place one bearing on top of the gantry and another on the side of it , instead of putting them both on the same side ?

[mxtras]

Actually, the "rule" applies to any linear bearing arrangement, but I was mainly refering to the X bearing trucks. If the distance between the rails (across the table) is, say, 1 meter then you would be served well to spread the X axis bearings at least 330MM apart from eachother (along the X axis) on the same rail to minimize or possibly eliminate the potential for skew. In stark contrast, I am looking at a commercial router that has a beam of 2 meters and the bearings are only 300MM apart on the X rails, but I have also seen this machine skew pretty easily. I would spread them out (if you can afford to w/o losing too much of your envelope) to the 1/3 rule.

On the Y axis - placing one on the top and one on the front would really help with rigidity but it would also make them much more difficult to align. Placing them on opposite sides would probably work OK but it would be a real pain to construct a structure stout enough to realize the benefit from the slightly unusual arrangement. I would suggest placing them on the front surface as they are shown, but spreading the rails out as far as you can. Same for the trucks on those rails - distance is your best friend for rigid guiding.

Scott

[max_imum2000]

this is turning into a very strange looking machine

anyway i hope it works fine.

about the x axis bearing the best space i could do it about 200mm as the distance between them is about 90cm.

what do u think so far ?

thanks

[BobWarfield]

A lot of folks put the gantry cross piece for the ballscrew underneath the square tubing that supports the linear rails instead of running it between the rails. This allows your table to be supported by cross pieces instead of just at the ends.

Another thought is whether you want those rails mounted on top of the square tubing or on the outer sides. Having it on the outer sides gives it a little more protection from the mayhem happening in the middle although it is theoretically a little weaker for the rail. It also makes the top edges very clear in case you need to drag heavy sheets of material over them and don't want to damage the material or your rails.

Now you can imagine the gantry being a hollow box that wraps all the way around your support frame, slides along rails in the middle. It looks a little less strange, you get to use a single uninterrupted piece on either side which is simpler, and the table is better supported.

Just a few thoughts for your consideration. Make sense?

Best,

BW