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Talking of lightweight machines that are 100 N/um stiff.

It will NEVER be a gantry design because with a gantry design you have to spread your wide geometry all over the place. You are taking the...

Thanks
And if you put the design into FEA what is its stiffness?

Got the bearing stiffness data, see attached.

So it turns out the 35mm bearings are more than good enough for 173 N/um, according to that paper, number of axis plus connected objects, in my case a...

OK finally got past rails and bearings level design and onto screws.

The total weight of my x and y axis is only 155Kg minus the weight of the screws and motors.

If I could realistically get...

You will be fine, you will be able to extend the boom fully because you are lifting less than 500kg. This means you wont have to get the feet far under the bench if at all.
What I should have said...

That will depend on the power of the spindle motor I choose and the actual stiffness I achieve.

I want to use this machine to make a much larger outdoor gantry CNC for welding/3D printing boats,...

I now have both x and y over 200 N/um

Now to find some suitable screws.

I am now confident that what ever bearings and screws I purchase, I will be utilising their maximum stiffness.

Which I...

Refined it further, the mesh and the dimensions.

Spaced my rails another 100mm apart on the Y axis which improved the X-axis results by 50 N/um.

I think it would have been up to 100N/um but I...

Be careful if you get an engine hoist and have not used one before, they are stable when the load is over the long feet that stick out, but if you try to use them to put something on a bench then...

Sorted out the Y axis deflection problem.

Y axis is now 250 N/um. So I only gained 10N/um from doubling the thickness of the spindle column to 20mm. But I get 40N/um from spacing the tracks...

Beefed up the spindle.

Then simplified my x and y axis to the more traditional setup.

Wow the previous unconventional setup is a lot stiffer than the conventional.

This time even though the...

Did my first full simulation using HWIN 35mm rails.
Optimised the rails and cars first.
Then attached them to the frame.
Reduced the steel and size.

I wanted to see what total stiffness I would...

Yes most of the Haas machines are under 5000 kg and these figures are the shipping crate figures so the actual weight of the machine must be a few hundred Kg less.

CM-1 950 kg
DT-1 2336 kg...

Added the bolts, it is still 500N/um because when you add the force to the 3 faces you effectively constrain them together.

The thermal analysis was excellent because all the distortion is on the...

Well I seem to have cracked it

This is the torus with 2 steel plates either side.

Simulated as just stuck to the concrete using regular adhesion giving 500N/um Stiffness.

I know from my...

Well surely the correct approach would be to carry out thermal and vibration analysis compare the max deflections to the max deflections caused by machine forces, and if they are less then it wont be...

I'm confused as to your statements on vibration and thermal issues with machine. What is it about a Hobby machine that makes these effects insignificant? Do you have any data or one of your thousands...

That's interesting, would love to see one of your 150N/um designs, what sort of machines were they, C shaped? Gantry? How did the FEA predicted stiffness vary from the actual stiffness? how much did...

Refined and checked the mesh, the 1 cubic meter of concrete shaped as a Torus is actually 125N/um stiff.

I've attached the step file for anyone who wants to check the simulation in their FEA.
...

I think if you did some research you will find that concrete is 20 > 25 GPa in bending and if you treat it like any other material and work with it's actual properties and not the properties you...

Here's a concrete only frame, no steel that can do 100N/um and is only 1 cubic meter of concrete for a cost of $108.

The inside circle diameter is 800mm so if your spindle post is 300mm you would...

If I had to machine accurate parts in an apartment I would go the EDM route, especially for gears.
You don't require any stiffness, basically a 3D printer in a fish tank.
You can get or make your...

Here I discovered the best way to attatch rails to the concrete.

If you constrain both sides of the concrete with through bolts, then the force constraining opposite sides will be equal, so you...

This video was posted by Jack on my thread about using concrete in machines.
What he says about keeping symmetry works, if you keep the same amount of steel both sides of the concrete then there is...

In case anyone is thinking of going down the 300x300x28mm box section of aluminium with 35mm steel rails rabbit hole then you might want to reconsider as you will get deflections of up to 0.2mm on...

I have been doing FEA analysis on this same design. Looking at thermal distortions from using steel on concrete.

I would recommend you do the same, simulations like the machine is warm from...

Did thermal analysis of shapes.

Made a simulation that simulated the concrete being at the max possible temp where I live, then the air temp around it drops to the minimum possible temp where I...

The concrete on steel was giving distortions that would stop you achieving the accuracy of a 100N/m machine, I predict the heat distortion from aluminum on steel would be more than the distortion...

No it doesn't, see attached pics it costs $130 cubic metre there and here it costs $108 a cubic metre

Don't make me waste any more time checking your error prone calculations, like the time you...

This is just arguing over semantics, they were using weaved mats before, it's obvious, to sane people, that they just cut out some steps from the existing process. I think everyone here has wrapped...