[Kitty]

Well , that's what my father always said and so did an artist friend of mine a few days back.
In order to do that i need to step away from the obvious way of buying stuff especialy for building a router, since on that path it will take years before anything gets built at all because of the finances.
So it's back to basics, i spent a few days working out a design for a CNC-router that i can build entirely from commonly and localy available material, like 100x50x5mm rectangular tube and 40x40x4mm square tube.
Something that is widely available over here, some of it even at the local metal recycling facility.
If i can get it there it's durtcheap, otherwise it's still quite affordable.
It has to be a gantry type thing because i want to be able to add a rotation along the X-axis or a rotational table in the middle in the future
I don't have a 3D CAD program like Solidedge , but i do have access to lightwave , a 3D modeling and rendering program, which will do just fine for this.
So here's what i came up with so far:

only a few parts need to be machined on my small milling machine the rest is a matter of a metal saw and a drilling.
The milling motor is going to be a Kress FME 1050.
I'll use 25mm supported rails with linear ballbearings for guideance and TR24x5 trapezium screws for motion, which will be replaced with 25 mm ballscrews in time.
No running support needed since the screws will be shorter than 1000mm between the bearings.
The Horizontal Beam, it's support, the legs of the Gantry and the bridge are 100x50x5 mm rectangular alluminnium tube.






The 90 degree angles i basicaly achieve by putting in 90mm long pieces of 40x40x4 mm square alluminnium tube.
This will also neatly close the ends of the tubes.
At least that's the plan.
I am not an engineer, but i think this will do the job, if not , i can replace the 40x40x4mm Tube with solid alluminium.










Obviously any help and/or suggestions will be appreciated at this stage.
Especial concerning construction (like i said, i'm not an engineer).

[FandZ]

So your proposing to drop your whole Y axis instead of having just a z axis that comes down? I'm hoping I'm interpreting your design right. I don't know, that'll add to the cost of your build and doesn't do much to strengthen your machine. Also, you'll have to be more carefull with the way you secure your stock. It would be easier to knock into something when you have the whole Y axis dropping.

Then there are the 90 degree connections, that will be some precise work that'll need to be done to get everything to square up.

I'm posting an idea you may want to look at. It would be easier and cheaper to make. Probably a little stronger. I'm not knocking your design but there are a lot of variables that would have to be considered on it.

[Kitty]

indeed i'm proposing to drop the whole y axis, because i can't machine parts for a sturdy z-axis that comes down with 15-40cm between the lowest point of the carriage and the collett.
the space between the vertical leg pais is exactly 1 meter which will allow for approx 70 cm movement of the collett on the y-axis. to give an idea of the dimensions.
For starters im gonna use that kress (that thing weighs 1.7 KG) and have at least 15 cm between the lowest part of the y-carriage and the collett at al times and not much wider than the motor itself, i can't do that with a moving z-axis on the Y-carriage.
with a moving Z-axis that distance would have vary to from 15-40 cm to mill 25 cm deep (no way that is gonna be stable (unless you use a massive y-carriage)
that would mean a massive assembly running across the Y axis to carry a z-axis with a carriage and that would mean even more forces and weight on the y-axis carriage than with a y-axis dropping thus a more massive support for the Y-axis.
Its a lot cheaper to use those 4 linear supported rods on the Z-axis than to make an assembly with a sturdy Z-axis that sticks out at least 15 com below the Y-cariage.
A Z-axis on the y-carriage also means a lot of machined parts and that is a problem.
This way i can use stock material that can be sawn and drilled except for the bracket that holds the milling motor.
That i can do myself.
Milling and turning is an entirely different matter.
Also i have some additions in mind, like automaticaly changing tools and a rotating x-asis (lathe).
that would require a locked position on the y-axis and a locked position on the z-axis.
I just can't machine complicated parts and i don't know any metalworker localy who is willing to machine them for me, which means i would have to have it made by a company and that would involve a small fortune in hours making them + shipping costs that would be rather excessive.
I'm on disability so that is out of the question.
I can get alluminnium tubes and bars and sheet up to 20mm thick quite easily, but i don't have access to machines to work on it, except a small lathe, a small milling machine,which are no good for the parts i would need and a circular saw to cut lengrhs of tubes.
It would also mean more planning and saving more money and that usualy means nothing gets done, because something more important will always come up.
Room is not an issue, i could make it 2 meters wide and long if i wanted, it's the machined parts that i can't make and the costs and availability of the linear guiding and screws.
btw that design is for the y-axis and z-axis, just assume that those 4 vertical legs are straigth, rigid and exactly vertical, so its up to acurate placement of the stationary horizontal beam(which could even be smaller, since it's only an extra adittion to prevent the construction from slanting sideways, it's just simplest to use 100x50x5mm stock for that as well).

[Khalid]

good design.. keep it up man..

[Arbo]

Definitely a cool design.

[dertsap]

do you see any potential trouble in keeping the gantry 100% parallel to the table ? will you be using servos or steppers

[Kitty]

Not realy, if those tubes are cut with a circular saw the ends will be exactly 90 degrees which means that a tube that is bolted to them with braces inside should be at a 90 degree angle too because it will get pulled tightly against those ends.
provided the holes for the bolts are drilled accurately ofcourse and if those 4 vertical legs are exactly the same length and perpendicular to the table.
I"ll use steppers and microstep drivers to drive the screws, which i colored lightblue in the isometric drawing.
1 screw opposite the motor on the bridge to drive the y-carriage and the 2 outmost bars in the drawing are the z-axis screws for the bridge.
That way i can put the bearings for the z-axis inside the 100x50 mm tubes and the screw for the y-carriage will be on top of the bridge, out of the path of any debree that might not be sucked up by the vacuum to keep it clean.
I think 6.4 Nm NEMA 34 steppers should suffice, but i'm not sure, i'm not an engineer, so i cannot calculate the forces needed.

[ger21]

Someone posted a finished machine with a similar design a few months ago, and said it worked very well. Unfortunately, I have no idea how to find the thread.