DIY Marble - Metal Machining 3 axis CNC Router

[Halbmond]

Greetings gentleman,

Here I would like to post my new welded construction 3 axis cnc router design.
X axis : 3.000 mm
Y axis : 2.200 mm
Z axis : 600 mm

It is now on design stage.
Material to be machined will be marble and carbon steels.
First post will be about Bridge - Saddle - Ram Design.

Center of gravity for total bridge assembly along with saddle and ram, is behind the Y axis Saddle which is pretty nice.

At first i started with one linear rail on each side of bridge (X axis) and one ball screw.(1st design)
Afterwards I increased the linear rails on each side to 2 in second and thirth designs.
Difference is,linear carriage mounted bridge supports on each side is 300 mm for second 200 mm for thirth and 140 mm for first.
Center distances of linear carriages is 200 mm for both second and thirth design.

Total 3 designs. I would like to hear what is your choosing among these 3.

Linear rails are roller bearing type for higher load capacity.

X axis
Linear guide rail Size : 35 mm
Quantity on right side : 2
Quantitiy on left side : 2
Ball screw size : 40x8 mm

For Y axis 3 linear guides . One of the linear guide rail is located on top with a different direction.
This will improve the strength of the bridge %20 higher according to the studies.
Linear guid rail size : 35 mm.
Ball screw size : 32x5 mm

For Z axis; there are 4 linear guide rails. 2 at rear 2 at sides.
Linear guide rail size : 28 mm
Ball Screw Size : 32x4 mm (may be this size will get smaller)
There is also possibility to change Z axis drive from ball screw to rack - pinion.
Rack and pinion will have less space therefore ram mass center will get closer to bridge.

There will be 2 counter weight pneumatic or hydraulic cylinders located on Z axis saddle for balancing the Z axis Ram.
This will improve Z axis servo performance.

Mass :

Ram : 240 kg Saddle : 240 kg Bridge : 1.200 kg

Y and Z axiss will have 1 kW servo motor - 3000 rpm drive, directly assembled to ball screw via coupling.
X axiss will have 2 piece of 1 kW servo motor directly assembled to ball screw.

[Halbmond]

Well i cant see attachments with my cellphone, uploaded from my pc!?

[routercnc]

Well i cant see attachments with my cellphone, uploaded from my pc!?

Pictures are OK on my phone.

Looks like an interesting project. On the Y axis will you be able to weld all those pieces and get flat and parallel surfaces for the carriages which connect to the Z axis?

[Halbmond]

Pictures are OK on my phone.

Looks like an interesting project. On the Y axis will you be able to weld all those pieces and get flat and parallel surfaces for the carriages which connect to the Z axis?

Indeed it is interesting project and very good static and dynamic properties the bridge structure has.
We have plenty of machining centers which is capable of machining this big structures. After stress relieving we will machine all of the rail bottom plates, carriage connection plates, bearing block connection plates.
We are going to machine 4 surfaces of the bridge , one by one at a horizontal bohrwerk cnc .It will make the surface flat and paralell to the corresponding surface within tolerance of (+- 0.05)

I would be glad to get any recommendation or comment /critics, especially for the bed frame.
I can reduce the footing quantity from 4 to 3 on each side of bed frame and place triangle support plates between footing and linear rail profile.

[Halbmond]

You may see rail lock and carriage lock units at every axis.

[pippin88]

Regarding two rails per side, or three on the Y axis:
Have you seen any commercial machines do this?
Just go with bigger rails if you need the load rating capacity.
A second rail adds a lot of cost and hassle machining and aligning. (Though it appears you have access to machines for doing this).

What are the cutting forces in marble machining? How do they compare to metals?

[Halbmond]

Here are self leveling chock and my standard leveling blocks for bed frame foots.

[Halbmond]

Regarding two rails per side, or three on the Y axis:
Have you seen any commercial machines do this?
Just go with bigger rails if you need the load rating capacity.
A second rail adds a lot of cost and hassle machining and aligning. (Though it appears you have access to machines for doing this).

What are the cutting forces in marble machining? How do they compare to metals?

For cutting marble you need higher speed spindle than required for metal and less kW.
Max spindle kW for marble in the market is 15-18 kW with minimum 12.000 rpm
Actually for marble machining 9-12 kW is just fine, 15 kW is required if you gonna use 800 mm diameter saw.
If you are going to have 5 axis, each axis must have min 500 Nm torque capacity.

Min spindle kW for metal machining in the market is 15-20 kW - 6.000 rpm


I have seen lots of commercial cnc machines having 2 linear rails on each side. Paralel or different directions.
We are going to buy a new gantry style machining center. I have seen lots of catalogs.

For marble 1 linear rail is enough, for steel it depends on your y axis length.

Actually I think 1 linear rail will do fine, because my y axis is not wide much.
Expanding the rail size is better option. At the moment X axis linear carriage model : RGW35HC (Width: 100 mm) I will replace it with RGW45CC (Width: 120 mm,same length)

In our workshop we have 2 8 meters Z axis capacity horizontal and vertical CNC. You can machine 100 tons of any piece.
I will need much smaller CNC.

This CNC is for my friend and will be started to welding a couple of weeks later.

[pippin88]

I read this on my phone and did not really get the scale / size of the machine you are building (very large!).

Thank you for the interesting pictures of those very large CNC machines.

[Halbmond]

This was another design of mine for 6 axis machining of marble.
Both Bridge and Z axis is symetric construction.

My friend showed me some catalogues for same purpose CNC machines, mostly italian.
I came up with this design and project will start whenever they change their workshop to a bigger workshop.


I will share project technical drawings when this construction finishes.
There will be total 2 CNC with this type. Only difference that the other one will have concrete block X axis just like the one at attached pict. X Axis is not mobile

Base Foundation of this machine will be separated from workshop foundation by 5 cm.
There will be pits for anchor bolts below x axis footings. Those pits will be filled with grouting epoxy.

[Halbmond]

After pippin recommendation I changed X axis design.
After changing double linear on each X axis to one linear rail, mass of bed frame and bridge are changed.
Double linear rail type : RGW35CC - 35 mm width rail - 100 mm width linear carriage block
One linear rail type : RGW45CC - 45 mm width rail - 100 mm width linear carriage block

6 linear carriage bearings canceled, 2 piece of 4m length linear rail canceled.
With the reduction of steel profiles, there is approximately total 1.500 - 2.000 USD cost reduction due to one rail design.

Old Mass :

Bridge : 1.200 kg
Bed Frame : 4.800 kg

New Mass :

Bridge : 1.100 kg
Bed Frame : 3.950 kg

I need help about X axis drive. I think both X axis and Z axis should be rack&pinion design instead of ball screw.
At X axis ball screw is way above linear rail I didnt like it, and rack&inion will get the ram closer to the saddle for Z axis.
Any ideas.