Cheapest CNC that will accurately cut 1/4 inch 6061 aluminum?

Doing LOTS of preliminary shopping. Besides motor power, apparently the CNC device sturdiness is an important concern when cutting harder materials. When the cutter changes
directions, apparently a week structure will cause it to move out of line.
The merchant makes a lot of difference. When dealing with Chinese junk, you can get all sorts of different things, including different configurations and accessories, under the same model number.
A $10,000 unit is fine, too. No doubt it's amazing.
Thanks.
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-0000 (UTC) typed in rec.crafts.metalworking the following:

    First, define "accurately"?     Assuming repeatability (the notion that the second, fortieth, N+! part are "with in spec" of the first.) and that the first one is not out more than +/- 30 thou? +/- 10 thou?     Over what lengths?
    Sorry, I don't have any answers. It's been too long since I was actively a machinist, but I do know the questions.
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pyotr filipivich
"With Age comes Wisdom. Although far too often, Age travels alone."
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On 4/18/2020 7:20 PM, John Doe wrote:

LOL. You know when it speeds up that is speeded up video right? The machine is still running at the slow speed shown at the beginning.
AS long as the machine is not "sloppy" it can usually cut accurate enough parts for many applications even having some flex in it if you use appropriate cut strategies. Modest cuts for roughing over size (under size) with roughing clearance, and then much lighter cuts to bring it to final dimension so the machine flexes less.
The machine in that video is likely not very rigid. One give-away is the plastic printed spindle mount. A wood bed is also not often associated with a stiff rigid machine.
The parts they are cutting in the video don't require any high degree of accuracy so its fine for the job.
Even on somewhat heavier machines in my shop that can do heavier work I take similar strategies. Fast heavy roughing over sized, then slower lighter cuts to bring to within specification.
Now comes the big deal. Can you take strategies with the machine to get you within your specification. Often you may see machining prints that say +/- 0.005 inches. (0.127 mm) I didn't know that was also the standard for many industries if a lower tolerance was not specified. I freaked out trying to get everything I made within 0.001 inches. (0.0254 mm) I wasted thousands of hours chasing a spec that was unnecessary for many things. Sure a tool holder or a slip fit bushing should be much closer, but amazingly many things don't need to be all that accurate.
What you need to do is decide how accurate (and repeatable) you need to be for the projects you plan to do.
My first el cheapo (only a few hundred dollars) was easily able to make aluminum parts within +/- 0.005 inches if I used well planned cutting strategies... well after I fixed a few stupid things that were causing excessive backlash in the lead screws (SLOP). I even used it to make parts for some of my other machines in a pinch. I mostly bought it for wood carving and making wood plaques.
The answer is to decide what your tolerance is (specifications for tolerance) and buy the best machine you can that can be made to exceed those tolerances.
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-0000 (UTC) typed in rec.crafts.metalworking the following:

    Sorry about the snark.
    OTOH
from last summer when I was asking about small scale cnc.
^c ^v
http://lcamtuf.coredump.cx/gcnc/
"Guerrilla guide to CNC machining, mold making, and resin casting"
It's long, but broken up into chapters, and chapter 2 "Setting up a CNC mill" "Pointers for selecting a low-cost, hobbyist-friendly CNC mill, stocking up on tools, and keeping the whole setup in great condition for many years to come." may be useful. Looks a couple of years old, so specific models might not be current.
The author's interest is in making molds for casting small precision plastic parts for robot building.
==recommendations from that thread:
"A small CNC mill like a Taig, Sherline, or Ximotion/MaxNC would be good for this sort of thing.
I V-lead Taig can be adjusted to hold better than .001. A ballscrew Taig is around the same, and is much faster, but wear can not be adjusted out.
A MaxNC may need to be adjusted. I totally changed the one I had so.... It held better than .001.
I know little about Sherline, but there are plenty of Sherline users around. Some of the better built CNC gantry mills (CNC routers) like the Velox machines might also produce satisfactory results.
Cutters are readily available, at least in the USA."
=    Those are commercial options.
    Anyway, the video doesn't show the "important part" (to me) which is the controllers and the rigidity of the framework / moving parts. You can probably assemble a rigid enough setup "using things found around the shop" (depending on your shop.), it will be the controllers which will be "the problem". Which in turn depends on your sources and skills in adapting, installing.
    Good luck.
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