[Harmonyof4]

I am starting a build on my table and I was hoping some kind souls might Lend me some of their experience.

The cutting area will be 2000mm by 4000mm the table will be made of steel and use rack and pinion on the x and y axis and the x will be a ball screw. The machine will be driven by servos.
I desire the ability to cut wood, aluminum, and also possibly steel on the machine

Is this possible and are their any glaring problems I don’t see?
I will post my ideas for a frame but I wonder if I should be using 4x6s instead of 2x2s for the frame?

[joeavaerage]

Hi,

I desire the ability to cut wood, aluminum, and also possibly steel on the machine

I think you're being over ambitious. You will get away with wood, and if you build heavy maybe aluminum, but steel....forget it.
Machining steel requires HUGE RIGIDITY....and you'l just not be able to get it with a machine of your size (2m x 4m) unless you
use many tons of steel in the frame and gantry.

Lets say your require rigidity R to do wood, then you'll need 5R minimum to do aluminum, even slowly and gently, but you'll need
50R to do steel. There is a reason that mills capable of machining steel weigh many tons despite having travels of less than a meter.

Craig

[pippin88]

Commercial machine to machine ('cut') steel with travels of 4x2m would weigh many tons, about 30 tons.

Wood + aluminium + steel is just not realistic for almost any machine. Requirements are too different.

Steel requires high torque, high rigidity.

Wood requires high rpm, high speed.

[peteeng]

Hi Harmony - Your list is Ok but the steel needs to be removed as others say. Steel is in disharmony with the size and requirements of the other materials. For a 2m wide gantry you will require very very rigid beam to cut aluminium. But the rest timber, plastic etc will be easy. The devil is in the details. My advice is do not start the build or buy anything until you have drawn it in CAD & costed it. Everything is connected and its easy to blow the budget or do something poorly if you do it in pieces.... Peter

The frame 4x6 or 2x2 depends on how many you use and its thickness. You need to draw it up to see how it goes. A steel frame that size will be very heavy. I expect you will need to make it in modules to keep them manageable, unless you have a crane available...

[joeavaerage]

Hi,
the capability to cut steel, certainly in the size you are talking about I think is impossible within a hobby budget.

If you relax the steel requirement, even then you will need to make a heavy steel frame and gantry to cut aluminum.
One way to make it much MUCH easier is to build smaller. I know everyone wants to make a big machine to do this, that and the other
thing....but do you have the budget for it?

Just ballpark figures here, and the may be some dispute over them but if you spent $10,000 to build a 2m x 4m machine of rigidity R,
then you could build a 1m x 2m machine of the same rigidity R but for $2,000. Making a smaller machine as a huge impact on cost,
or another way of looking at it is that for the same cost you could make a much more rigid machine which improves accuracy, vibration and
may mean that you can cut aluminum well, and maybe even steel, whereas a big machine would be restricted to wood and plastic.

Craig

[pippin88]

Also, what do you need 2x4m for?
Does your stock come in that size?

Most machines are sized to take common sheet sizes, for good reason.

[Harmonyof4]

Also, what do you need 2x4m for?
Does your stock come in that size?

Most machines are sized to take common sheet sizes, for good reason.

Round numbers mostly and that it’s the size the rail and guides came in without cutting them.
I have been going back and forth over it.
4x8 would be more manageable for sure but I also wanted to cut larger doors out of solid wood and do whole cabinet runs quickly
I’m not super worried about the price of the steel etc but maybe I should be

[Harmonyof4]

Hi,
the capability to cut steel, certainly in the size you are talking about I think is impossible within a hobby budget.

If you relax the steel requirement, even then you will need to make a heavy steel frame and gantry to cut aluminum.
One way to make it much MUCH easier is to build smaller. I know everyone wants to make a big machine to do this, that and the other
thing....but do you have the budget for it?

Just ballpark figures here, and the may be some dispute over them but if you spent $10,000 to build a 2m x 4m machine of rigidity R,
then you could build a 1m x 2m machine of the same rigidity R but for $2,000. Making a smaller machine as a huge impact on cost,
or another way of looking at it is that for the same cost you could make a much more rigid machine which improves accuracy, vibration and
may mean that you can cut aluminum well, and maybe even steel, whereas a big machine would be restricted to wood and plastic.

Craig

Thanks Craig,
So if I dropped it down to 4x8, how thick of steel do you think I will need to make it stiff enough to cut the aluminum?
Cutting the 16ga steel sheet was more of a dream than a requirement.

[joeavaerage]

Hi,

So if I dropped it down to 4x8, how thick of steel do you think I will need to make it stiff enough to cut the aluminum?
Cutting the 16ga steel sheet was more of a dream than a requirement.

OK, that is a more achievable result.

Make the steel as big sectioned and thick walled as you can find. The stiffer the machine is the better. There is no such thing as a 'limit
to stiffness', you may end up at a place of 'diminishing returns' as far as design goes but you'll never end up with a machine that is too stiff.

As peteeng has already suggested you should draw what you have in mind up and then subject it to rigorous FEA analysis. I have a paid
subscription to Fusion 360 and the FEA module gets a workout when I'm designing a new structure, it illuminates poor design which
otherwise passes your 'seat of the pants' test. It can also point out that your spending way too much time and effort on assembly A when in fact the
dominant source of flexure s assembly B.

Craig

[peteeng]

Hi Harmony - You need to find a commercial machine that does what you want (or a build in this forum) and use it as a benchmark. This will give you an idea of how big things need to be. Designing a machine from scratch and first principles is a mission for the non-technical. It will take 3 or 4 machines before you have a feel for what's needed and you probably don't want to build 3 machines so an existing benchmark is very useful. Peter