Stell frame cnc 1500X1000. Adjustable table your opinion please

[Boyan Silyavski]

But I am wondering if the ballscrew sould be placed between the two 80X80 beams of the gantry, in front of Y axis (near z axis ) or in the back of Y axis. I also wonder about the best way to connect Y axis with X axis carriages.
Any idea will be helpful

Vagelis

Hi,
many different schools of thought here. Basically depends on what you aim to achieve, what rigidity you aim for, the overall weight of gantry you will finish with, and how you intend to move this weight, how fast and not at last the money that you can spend on the structure, the motors and the drivers.

To resume it all for the gantry sides: 1 side plate like at the drawings could be ok if you keep the gantry not raised, directly on the sliding plates, if you raise the gantry you will have to do a profile like structure to make it stiff and strong in all directions/ possibly from 10mm thick steel sheet will be best/. There is a calculator in the sticky post for that purpose.

Now to the gantry drawing itself. Have in mind that this is not the voice of experience, i am like you building now my 2 first machines, however i gave it a lot of thought:

The typical:

-Screw at the back will work, many make their machines that way, combined with the rails on top and bottom of the gantry. That is how i designed my first build.
Points to consider: more complicated Z design, rails need more time to be aligned, care should be taken for the Z strength in all directions.

-Screw in the middle. Great design, but most do it from aluminum-plate at the back and plate at the front with channel in the middle. While i like it i did not choose it due to expensive material, my inability to process it at home precisely-cutting, drilling tapping...etc., Beautiful but quite costly. Of course it could be done from steel plate, but then the combined weight. Or ribs here and there at the back, but still without a front plate will not be strong enough to my liking. Plus the plates will protect the ball screw.

-The typical commercial router, rails on the front plate, screw inside, raised gantry. I could not help but post the picture of the Techno, which is a typical example


If into woodworking and sheet material ok. But not a multitask one. Man, how i hate that design . The z could go left right further, so the table could be not so wide, but then the gantry raisers should be strong enough, then the Z travel is very small, so if we want travel of 200mm then the weight, then the motors...etc.

Other:
There are other designs but as they are very purpose specific i would not recommend them.
You could take a look also of my design of gantry on the second machine i am starting to build.I hope will be successful. Its meant for strength and precision for the long gantry, also an ease of implementing, especially epoxy leveling the rails . Just as an idea that you could further develop if you like it http://www.mycncuk.com/forums/router...html#post52573, though more soldering, various sizes profile, heavier.


At the end the design is choosing between the various trade offs for the purpose of what will suite you most.