CNC router

[MhmRobot]

Hello,
This is my first post in this forum, and I really find it very useful.
I an trying to design a CNC router for wood and aluminum cutting .
I attached the first design of my CNC. I used 4040 and 4080 aluminum profiles in addition to aluminum plates.
kindly any advices or recommendations with the structure design.

components:
2pcs HGR20 - 400mm linear rail
2pcs HGR20 - 700mm linear rail
2pcs HGR20 - 1000mm linear rail
12pcs HGH20CA Carriage
1pc SFU1605 - 400mm ballscrew with ball nut
1pc SFU1605 - 700mm ballscrew with ball nut
1pc SFU1605 - 1000mm ballscrew with ball nut
(3pcs ballscrew according to BK12/BF12 end machined)
3sets BK/BF12 Support
3pcs 8*10mm coupling
3pcs 1605 Nut housing
spindle 2.2kw with water cooling.
nema 23 2.5Nm.
Mach3 controllers

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[ger21]

Unless you really need that much Z height, reduce the height of the gantry by half. And make the side plates thicker.

[MhmRobot]

thank you,
I tried to make it lower as possible,
Now the z travel is around 200 mm, which is fine with me.

Now I will try to change the right and left sides to aluminum profiles as well. but I want to check the local market if I can get them.

Hope the design is better now. isn't it?

Thanks

[routalot]

You might consider bolting a length of angle extrusion vertically to those side plates.It will be interesting to see the design evolve,maybe add the other steppers and a spoilboard next.

[MhmRobot]

Thanks,

I tried to add corner part in blue, if I understand you well.

now I have two different designs, A without side profiles, and with the side part are aluminum profiles.


In design A the left and right sides weight 1.3 kg each and made from aluminum.
In design B the the single profile weights 1.2 kg so the total 2.4kg per side. the mass is more but better rigidity I think. and more costs.
One concern for design B is that How Can I align the linear bearing blocks to the profile since I have to drill them then bolt them with the linear bearing blocks.
I feel the main challenge is how to get this machine calibrated and aligned with the spindle. any ideas please. and what you prefer more design A or B.


it took me too much time to draw it and still the design needs more modifications on the frame structure.

[jckstrthmghty]

Since you have some nice parts you might as well add another motor and ballscrew on Y. You won't need the bottom brace on the gantry and for the most part remove the racking effect.

[ihavenofish]

that looks broadly similar to an xzero machine.

i can tell you where the weak points in that configuration are, which should extend to yours.

1: make the uprights as wide as possible. put the bearings as far apart as you can. the xzero was 6" on the 24" wide machines (widths of frame, not travel), and 5" on the 18" machines. wider would have been so much better.
2: make the ganrty cross structurally stable on its own. the xzero used a plate, you have an extrusion, but the same applies to both, brace it across the top or bottom to make a box section. this will reduce racking dramatically.
3: brace the end frame with the fixed end of the ball screw. the whole end frame can bow out under load. george countered this by just using thicker plates, but adding an extrusion or angle or anything else will work too.
4: as ger mentioned, lower is better. make the height as low as you can and still fit the work you want to do.
5: as same as above, reduce spindle overhand as much as you can. if possible, try to get the spindle between the upright bearings. this and the above reduce the twisting moment on the gantry back plate, every mm has a big effect.
6: make the machine length as short as possible as well. especially with light extrusions, the machine will sag, twist, and deform under cutting loads.

[peteeng]

Hi MR - You are going down a well trodden path. You will need to define what you mean by machining aluminium. For plastic, foam, timber the current design is fine. Once you step into Al World the game changes. You need to research the site and find machines that are actually cutting aluminium well or doing similiar stuff to what you intend to do and then compare these to yours. Your columns need to be much stiffer and your Z will need attention as pointed out by many people. Having a reference machine is very useful... Peter

[hanermo]

As the other experienced members said.
You z axis cantilever is very much too high.

You ideally want 1:2, aka twice the width for the height, but You have about 3.5:1, 3 times plus for the height.
7x less than desired.
And it is NOT 7x less weak. It is length pwr 3 so about 343 times less rigid.

Su:
Make the side plate stiffeners of sheet steel.
It´s cheap.
Use about 15-20 mm thickness.
You dont need to cut it into any shape.
A rectangle will do fine.

[routalot]

Looking better,but I think it would be a good idea to add another stepper and ballscrew on the long axis-as has already been said.this would also free the space along the sides below the extrusion to add an extra section for more stiffness and less deflection under load.By using vertical extrusions to hold the gantry beam in place you have increased the resistance to bending but also will be transferring forces to the bearing cars which will only be separated by the width of the vertical extrusion.This will exert quite a lot of leverage which you could reduce by inserting a roughly triangular plate to carry the cars and then mount the vertical sections to.I hope my attempt to attach a couple of screenshots will work.

[ihavenofish]

i would not use dual screws, it causes so much pain configuring it to behave right. if its a huge 4 foot wide gantry that "needs" support in the middle, then you have no choice, but on a smaller machine, single screws and a better proportioned and stiffened frame is easier.

[MhmRobot]

Thank you all for your valuable advices and comments. I really appreciate all of them.
I will update the design according to your advices.

Thanks