Small CNC mill for super-fine detail (Newbie Q's)

[Eulercircles]

I am new to CNC, but have been reading up on it for quite a while now (started about a year ago). I need a small CNC that can mill very fine detail. What I want to do with it is take model kit parts I have, which I will redesign in CAD, and mill pieces that are either half the (linear) size or twice. I build Star Wars studio scale replicas, and am interested in making models that are either half studio scale or twice - need a machine that can allow me to replicate the detail parts.

Has a machine like this been built before?

I figure with a small machine, I should be able to control the accuracy/precision. Is this incorrect?

I can tell that for some parts, more than 3 axes would be best...

Please give me your input!

[Geof]

What do you consider fine detail? Plus or minus 0.001" or plus or minus 0.0001"? You can't go better than 0.0001" unless you start talking about temperature controlled rooms.

Or are you a fine woodworker where plus or minus 0.01" is fine detail?

You need to put numbers on things and you might find that a small low cost machine simply cannot do what you need.

[Eulercircles]

Originally Posted by Geof What do you consider fine detail? Plus or minus 0.001" or plus or minus 0.0001"? You can't go better than 0.0001" unless you start talking about temperature controlled rooms. Or are you a fine woodworker where plus or minus 0.01" is fine detail? You need to put numbers on things and you might find that a small low cost machine simply cannot do what you need.

I want to build the machine myself. I don't see why I would need to go finer than 0.01" because I could always sacrifice detail when I scale down. However, 0.001" would be nicer. They don't make end mills smaller than 0.01", do they?

The materials I plan on using are ABS or Delrin, to make a master, from which a silicone mold would be cast. Alternatively, I could use machinable wax to mill the part, or to mill the negative mold directly.

[Andre' B]

Originally Posted by Eulercircles They don't make end mills smaller than 0.01", do they?

Yes they do, smallest end mills I have found for sale were 0.0002" diameter, and yes that is the right number of zeros.
But as could be read between the lines of Geof's post you do not just put such a tool in any old machine and expect to do anything useful with it.

Repeatability of 0.001" should be fairly easy to get even if the absolute accuracy over the machines full travel is not as good. The repeatability would seem to be more important for your use then accuracy.

[TOTALLYRC]

Something along the lines of a cnc ready Taig and a G540 with a sherline 4th axis would probably get you going in the right direction.

Mike

[LeeWay]

I was able to build a small mill with better than .001" accuracy. I was fortunate to win a few great auctions on Ebay for very reasonable prices. Preloaded ground ball screws and nice THK linear ways that were new. I found a ready made cast iron IKO slide for the Z axis.
It has 12" x 9" x 9" travels.
I probably have $5000 in the machine including computer and software, though I already had the software.
I think a decent mill would start at about that price. Smaller mill can be had and built, but some may need upgrading to get .001" accuracy. It doesn't sound like you will be cutting any tough material, so a Taig is worth taking a look at.

[mike-acg]

I have a Roland MDX-20 and they claim the following resolutions:
Software Resolution - 0.000984 in./step (0.025 mm/step)
Mechanical Resolution - 0.000246 in./step (0.00625 mm/step)
It lists for about $4,695.00 including software and probe but I know I paid under $3,000 for it. It was easy to learn and might be a good way to start if you are new to milling. What size will you need? The MDX-20 is 8 inches (X) x 6 inches (Y) x 2 3/8 inches (Z) and the MDX-15 is 6 inches (X) x 4 inches (Y) x 2 3/8 inches (Z).
Mike

[BobF]

look at the widgetmasters mills.