[drogo81]

Hello everyone, I´ve been gathering all the elements I need to build a diy 4´x8´ cnc router.
so far this is what I got: 500, 1500, 2500mm hgr20s, (2 on the ¨Y¨axis), sfu2005 which are my biggest concern because started watching at this forum the recommendations of getting 10mm pitch on ballscrews. I have nema34s 4.5 Nm, and planning to get a 3.5kw air cooled spindle (8kg of weight). If somebody could give an orientation on where am I at right now to get the most optimal out of what i have, or any recommendations on changing something would be very appreciated. Also need advice on what size of aluminum extruded is needed for a good estructure. thanks a lot and got bless you¡

[Bad Wolf]

Hello everyone, I´ve been gathering all the elements I need to build a diy 4´x8´ cnc router.
so far this is what I got: 500, 1500, 2500mm hgr20s, (2 on the ¨Y¨axis), sfu2005 which are my biggest concern because started watching at this forum the recommendations of getting 10mm pitch on ballscrews. I have nema34s 4.5 Nm, and planning to get a 3.5kw air cooled spindle (8kg of weight). If somebody could give an orientation on where am I at right now to get the most optimal out of what i have, or any recommendations on changing something would be very appreciated. Also need advice on what size of aluminum extruded is needed for a good estructure. thanks a lot and got bless you¡

a 4' x 8' CNC is no toy, so you don't want to half do it. Everything starts and ends with the frame, as it will be the thing that limits you the most out of everything. Trying to think of an analogy... A top fuel drag car. 10,000+ HP, transmission, clutch and diff to suit. Put it in the right chassis and it will run 3's, put that same combo in your street car and it won't go anywhere near that. While a top fuel car relies on flex, a CNC wants none of it to perform at its optimal performance.

Get the CNC chassis wrong and everything else right doesn't matter because it will be limited by the frame. For a 4' x 8' frame you don't want to be looking at extrusion for the frame (I do use it on my gantry though). Said it several times before but box and triangulate the heck out of it, that is what will provide you with a CNC that can cut more than MDF.

Motors... I started off with NEMA 23's but currently upgrading to a single NEMA 34, so I think you are in the right ball park there. For the long axis (X or Y depending on your country) I am using 3210 to stop the whip.
Spindle... I would recommend water cooled over air cooled.
If you plan to have a 4' x 8' cut area you need to make the CNC much bigger than the size of the sheet.

FYI if I was to remake my frame I would make a few alterations to it. Hindsight is 20 / 20. I can cut steel slowly with this CNC.

[peteeng]

Hi Drogo - To take full advantage of a 3.5kW spindle you will require a VERY stiff machine. Do not underestimate how stiff it will need to be. 5mm pitch screws will give you heaps of force (at 4.5Nm and 5mm you will get 500kgf so thats 1000kgf on the double axis !!!), again needing a very rigid machine to take advantage of this force. I recommend a high rail design such as Bad Wolfs. Very stiff naturally as long as your happy sliding sheets in and out the end. If you want to side load then this needs to be thought about quite a bit.... If you are considering using aluminium construction extrusions I think you will be disappointed in their performance with such a machine., Look at AVID CNC machines of same size to guage dims of members... You may have to put a whip preventer on the long screw... this stops the screw sagging in the middle and starting the vibration, there's a few designs in the forum....Peter

[dazp1976]

If you want the most out of that nema 34 get a driver such as a DM860T that can take up to 110vdc.
I've just gone to 80v on one and the difference over a 60v is great.
If you put it on 90vdc supply you will be very happy. This will give you great velocity.
As for ballscrews you should get DFU not SFU. You can tweek them to eliminate as much backlash as possible and get better accuracy.