BigAl's 4x8 CNC machine...

[mikeschn]

Point taken. I guess we all made the same assumption based upon the commercial nature of it's regular use.

Given the chance to just cut stuff out with a CNC, of course I would!

I'm so nuts about CNC that I built my own desktop CNCto do just that and plan a 8'x4' sheet version within the next year or so.

I think you and your friend might try something a little more adventurous though. Maybe the mythical Roswell or that little folding Probert?

How about a photo/video of the beast in action?

I'd love to see more information on your 4x8 cnc...

Mike...

[IASCOTT]

Mike

Here's a good place to start I been looking this over and might build one even though I really have know practical use for one.

http://buildyourcnc.com/default.aspx

Scott

[mikeschn]

That looks like a desktop CNC. Do you have any links to the 4x8 you are thinking about building?

Mike...

[BigAl]

Hi guys, Since Mike has called my bluff ;) here are the outline requirements I have for my 8x4 CNC Mill.

* Must be able to cut a full 8x4 sheet with minimal margins. I will only cut 2D shapes from the sheet material, so no fancy 3D modelling.

* Must be able to run from a domestic power source.

* Must be something I could store on its side, inside my newly built 12x10 workshop. Actually I have been fantasising about something, permanently at a 70 ish degree angle. Kind of like those saws they cut up your sheet materials with at Home Depot, but with a mill instead of a saw.

* Must use either my 1200w router and/or my 710w trim router as the cutting bit and my 400mw laser for laser etching.

* Parts must be readily available. i.e no special access required.

* Parts and overall project must not cost a small fortune.

Here is one design challenge I am currently facing:

The table top CNC mill I already built moves the XYand Z axis by means of a threaded rod running through a permanently fixed bolt on the axis. It will be very difficult to find an 8+ foot long threaded rod. I'm thinking pulleys or chain and sprocket?

Any suggestions will be appreciated. I am already the member of CNCZone, but I know you guys are also very innovative.

[IASCOTT]

If you look at the kits and their pictures you can get a real good idea of how to enlarge the smaller ones. With a 4x8 table one I would go with chain drive on the on the x and y axis and threaded rod for the z axis. I would also use v grove bearings for all the movements.

Scott

[mikeschn]

Have you checked out the Blackfoot 4x8 4.0 yet?

http://buildyourcnc.com/blackFoot48v40.aspx

Mike...

[BigAl]

Thanks for the link, Mike. I hadn't seen that before. It contains some useful information...

The x and y axes are helped by roller chain mechanisms at a pitch of .25". The chain and sprocket combinations are ANSI #25 specification. The z-axis uses lead screw at 1/2"-10 TPI @ 5 starts for a travel of inch with 2 turns. Accuracy and smooth operation is maintained using an anti-backlash nut on the z-axis.

...

2 NEMA 24 motors and 2 3.0 amp drivers, 1 NEMA 34 motor 1 high current driver

[BigAl]

Interesting that the Blackfoot rides along on a single length of chain.




A great video of it in action here.

[mikeschn]

The chain has to be a whole lot cheaper than an 8 foot (or longer) lead screw.

Gotta mull that one over though...

Mike...

[BigAl]

Been busy on SketchUp...

Here is a concept for the X-Axis of a 9 x 3 device.

The linear bearings are shown in orange. All construction is in 1 inch MDF.

[BigAl]

Just has an idea of how to be able to cut a full 8x4 sheet whilst still having a table with a small footprint for my workshop.

I am thinking of making a 4x4 table where I cut half the sheet, rotate it 180 degrees and cut the other half. I will maintain alignment of the sheet by either guide rails, and or dowels on the table that will fit into drilled holes on the sheet.

[IASCOTT]

For your linear bearings I would go with the V-grove bearings. It cuts down on the milling of parts to create your linear bearings. They are the second bearing shown on this page.

http://buildyourcnc.com/bearingsproducts.aspx

Scott

[BigAl]

Hi Scott, It was my original intention, but at $128 for 16 it's the champagne option for my lemonade budget.

[mikeschn]

CNC Joe has some good ideas for a larger CNC machine...

http://www.youtube.com/watch?v=WwEkrQo6740

Mike...

[mikeschn]

Here's his thread on cnczone...

http://www.cnczone.com/forums/joes_cnc_ ... ybrid.html

Mike...