Stell frame cnc 1500X1000. Adjustable table your opinion please

[Boyan Silyavski]

First of all thanks everybody for the participation to the thread.
Next i would like to introduce some of my conclusions and ask some things about all these that i have already read

1. I beam will not be used
2. For the rails support beams I am between these profiles
80X80 4 mm
80X80 5 mm
100X100 4 mm
100X100 5 mm
and for the table structure
80X80 4 mm or
80X80 5 mm
i want your advice

Look from what you started and where you jumped- 100x100x4 and 100x100x5

Read again what Dean /jazzcnc/ told you, first be sure for what you use it mainly and then decide on the thickness. Go to your local metal shop and check for your self about the 100x100x5 and 80x80x5. This is way too much. Ok, people use them but for builds that intend to cut mainly aluminum and so.

My main concern of using epoxy is the aging and the temperature effect to the table. I am talking about contraction expansion. The machine will be placed at my basement where i have temperatures from 8 ( winter ) to 26 ( summer ). Would that be a problem? What will happen if one day i decide to move the machine to another place. The truth is that epoxy look a good and easy solution, on the other hand i don’t fell good if i don’t have the ability to adjust. Also do we know how epoxy reacts. It is more than sure that epoxy doesn’t have the same contraction expansion ratio as steel. I have heard that pro builders that use cast iron, leave the metal for aging for 10 years...
Thanks again everybody. If anyone has something to suggest i am anxious to hear

Don,t get me wrong, but your main concern should be squaring the rails in one plane. And choosing square supported rails, not roundish.
I assume you don't have even a straight edge and you worry about contraction and expansion. First think do you need such an accuracy, then do you have the actual means to measure it, then how much is the cost of the tools to measure it...
For wood and plastic and occasional aluminum you need much lower accuracy than you are contemplating.

I mean relax, and be careful not to make some obvious mistake. Like making a cnc for another kind of job. remember the old saying: " The machine is strong as its weakest part". I constantly meditate on this when i catch myself overbuilding

[EddyCurrent]

Just grabbed these out of a video I saw if any use



details are here 3D Model of CNC Router c4d, obj, 3ds, fbx, dxf, skp, iges
and it looks like they had to add some triangulation to the legs after these photos

[ba99297]

So far thanks everybody for your answers
Your advices keep me away from mistakes that i think could cost me money time and poor final result
After all these answers, i decide

to use part of Silyavskis' table plan ( for part of the table that the X rails rest on) .
Not to use the I beams
Not to use adjustable beams for the X axis rails and go on with the epoxy solution.
This choice means that the table is solid as rock. So before i go on with the 3d design i want your advice about the table diagonal reinforcing.
Here are some autocad plans. They represent side view of X axis. I design 4 solutions ( A,B,C,D )
The upper yellow line represents profiled rails, and the green color is adjustable legs
Tell me your opinion.
I haven’t decide yet if i will go with 80X80 or 100X100 box section. It depends from the cost. The following plans are made with 80X80 box section
Thanks for your time

[EddyCurrent]

I like B but not everyone will

[Boyan Silyavski]

I like A but if i were you, would turn the 4 diagonals 180 degree/ mirror them upside. That will separate on smaller sections and support even further the X rails support + when pushed from upside will make a stretching force to the lower beam, not pushing, as it is now.
I mean instead of MM WW

If full height is desired, as Eddy says B is best, simple and strong + the diagonals will stretch again the lower beam, if pushed from above. And we all know steel can not be stretched

[ba99297]

Silyavski before i check for any new post at my thread i design in autocad this



and then i read your post
I think that we are thinking in the same way
To be honest you inspire me for my table plan ( especialy for the rail support beams ) thank you.
Aslo thanks everybody else like Eddycurrent and of course Dean for their ideas
Day after day, thread after thread post after post i feel that the knowledge and the experience of people that willing to help, give me the ability to make a solid machine. You know it is very important to make a step and have no question to be answered. That is what i almost fell now about the table plan. May be some small changes will be done, but the basic consept i think is this.
I will post 3d plans soon
PS A machine that is having rail height at 70 cm from the ground, has any disadvantage compared to a machine that is having rail height at 90-100 cm from the ground?
I will be happy to hear any other advice.
The only question that is waiting for answer is the beam dimensions 80X80 or 100X100 and of cource the thickness
And here i have some 3d plans.
I will come back with another plan a little bit different

[Boyan Silyavski]

It will work both with 100x100x3 and 80x80x 3 or 4mm. Depends on how strong would be your gantry, what spindle you will like to mount and how further you will like to push it.
I suggest you make your gantry from 2 pieces of the same profile you will use soldered together, hence 200x100 or 160x80 or do it from aluminum, the way Dean makes his machines, with a ball screw hidden in the gantry, depends what means you have.

The drawings look very good. Now if you aim at certain weight or to be able to pass through normal 1m wide door, don't make it higher . if you want to make it higher and at the same time light, just make the legs longer. Also if length, weight is a problem, you can lift the 4 lower beams to the middle of the M , and remove the middle leg below this point, this will not compromise the strength.

If you aim aluminum and hard stuff mainly, maybe a gantry like Jonathans will be better, look at his exemplary build