[Coco] Coco CNC

[Andrew]

George,

I am glad to hear you are coming along great with your project! The guys 
at your shop know what they are talking about - mass does rule the day. 
Ultimately, it is about keeping the precision up along with the speed in 
a production environment. In order to do this, deflection has to be kept 
at a minimum. In order to do that, it requires a lot of cast iron and/or 
solid steel (precision made and ground at that, too). The bigger the 
machine (and the size of materials it can handle), the greater this mass.

However, if you aren't doing production work (and thus can decrease your 
feed rate - though with the slow stepping you are getting from the CoCo, 
your feed rate might be slow enough!), you can get away with lighter 
materials - a favorite is 3/4" MDF or HDPE for homebrew CNC mills. Very 
easy to machine with accuracy using mostly hand tools, and few power and 
shop tools (table saw and drill press, mainly). This is version one of 
the mill.

You then use version one of the machine to help create version 2 in 
something heavier duty - say, alluminium. This version should be much 
more accurate and better running than the first version, and will 
probably be as much as you need (indeed, the first version may be enough).

If you want to go any further though (with accuracy, feed rates, or 
denser materials to machine, like steel), you are going to have to 
invest in a real "desktop" milling machine. Desktop CNC milling machines 
exist, but can be pricy. You can, however, buy a rebranded Sieg X1 or X2 
through Harbor Freight (http://www.harborfreight.com - item numbers 
47158 and 44991, respectively). Go ahead and compare them to the Sieg X1 
and X2:

   - http://www.siegind.com/Products/br-x1-lathe.htm
   - http://www.siegind.com/Products/br-x2-lathe.htm

These machines seem to have "high marks" from a lot of people - several 
places offer parts and such for these machines - a nice place:

   - http://www.littlemachineshop.com

There are even a few people selling conversion kits to convert these 
manually operated mills over to CNC usage (typically, you need to supply 
the NEMA steppers and everything else - the kits usually cover mounts 
and such, precision machined for your model mill).

I recently purchased the rebadged Harbor Freight "X1", and set it up on 
my workbench (I still need to clean the grease off). It is a heavy 
sucker (100+ pounds), but is very small. I am thinking about converting 
it to CNC once I learn how to operate it properly by hand (I still need 
to buy a ton of accessories - collets, chucks, end mills, measuring 
devices, vise, clamps - before I can even think about milling - so right 
now it is an overpriced drill press). I will probably use EMC for mine, 
and not my CoCo.

I am impressed that you have done what you have done, though. Do you 
have a complete machine yet (you kinda sounded like you did)? I would 
love to see pictures of it!

-- Andrew L. Ayers
    Glendale, Arizona