DIY CNC Milling Machine / Router

[yngndrw]

Hi,

I am building a CNC mill / router. (Can't decide what to call it.)

First a bit of background: I live at home with my parents, so I haven't got much space. I've got an 86x86 inch room to work with. Pretty small for a workshop, but It'll have to do.

I'm intending on getting a 7x14 sized lathe and an X2 sized mill. (Both converted to CNC.) I also intend on building a CNC router (I'll call it a router to save confusion with the converted mill.) which will be used for PCBs and larger parts that the mill can't take. I also intend to use it for cutting stock. (I need 1.5" diameter copper bar cut to length, as the lathe doesn't have a big enough through hole.)

The bed of the router was going to be about 200x150mm with 70-100mm of Z travel, but I think I'll change that to around 500x500mm. I also intend on building an A and B axis. (Rotary table for A, turning spindle for B.)

I have been talking through email to Paul from cncathome.

I started off by designing the spindle, for this I based mine off of what Paul had done:
http://www.cncathome.com/spindles.html#atc

He has given me a lot of help about the whole of the project, but I don't want to annoy him with so many questions.

I had also bought a 100mm travel C3 ground ballscrew, but the pitch was 1mm. I thought that this was good for the Z axis, but his advice was that I wouldn't get a high enough feed rate for drilling through PCB and would wear out the bits too quick. I'll sell that ballscrew when it arrives.

Anyhow, I was then advised to purchase one of these:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=330239614745
The seller is away right now so it will probably take a little while to arrive.

I intend to find another longer version for the Y axis, that's 1/2 of my job pre-done.

For the X axis, I will use linear slides and a ballscrew. I might slave two motors together, not decided yet.

Speaking of motors, here's what I have planned. I have bought two of 36Ncm stepper motors from here:
http://www.arceurotrade.co.uk/Catalogue/Stepper-Motors
This was initially going to be a 2 axis laser cutter, but as it's not a mill it needs atleast 3 axises. I'm unsure as to the motor requirements now in terms of torque, while still keeping the speed.

For the spindle I've found:
http://www.nesail.com/detail.php?productID=4177
The 1912 from there seems great, as long as I can cool it. I'll seal it into an aluminium block and will probably water cool it. I think that the 1912/1Y would be ideal for me.

I've attached the spindle design. My concerns are that the top bearing (Which takes the force of the pulley.) should be a roller bearing and also that the top part is too thin. (7mm with a 4mm hole through it.)

I'll be using two 19tooth pulleys with a 6mm wide 2.5mm pitch 180mm long belt. (Rated to 40000RPM.) The bottom bearings are proper spindle bearings. They are angular contact and are rated to 54,800rpm with grease lubrication, or 93,200rpm - with oil. I intend to run the spindle upto about 20000-30000RPM.

Pulley:
http://uk.rs-online.com/web/search/s...duct&R=2864531

Belt:
http://uk.rs-online.com/web/search/s...duct&R=4745038

Questions:
1) Should I use a roller bearing instead of the normal bearing for the top of the spindle ?
2) Should I pressureise the spindle housing, to keep dirt out ? (But would that remove the oil on the bottom bearings ?)
3) Is the top of the spindle too thin ? If so what can I do about it ? I've already bought the bottom bearings so it has to be 10mm diameter at the bottom.
4) Would that motor do ? I intend to mount a tachometer onto the output of the motor for Mach3.
5) How can I attach the pulleys to the shafts ? I don't want to grind a flat in the motor shaft and I don't want it to vibrate at high speed.
6) Any other suggestions ?

Thanks for any help,
-Andrew.

PS: The spindle bearings that I have are a matched pair of Fafnir 2MM200WICRDUL. (10mm ID, 30mm OD, 9mm Thick) It says on a site that the last three letters of the code mean "DUPLEX UNIVERSAL, LIGHT DELOAD" - I presume that means that the faces are ground for light preload. I probably won't need the 1mm spacer in my .pdf.

Link: http://www.ahrinternational.com/FAFN...nclature.shtml