affordable CNC with decent tolerances and speed

I would like to CNC vertical mill some 2024-T3 aluminum parts from stock approximately 12"X12"X2". The parts are about 6"X6"x2" and have a general profile tolerance of +/-.001. The parts will require full 3 axis machining.

What are my basic options for a fairly affordable CNC but one that has decent enough speed and rigidity to make these parts in an average/reasonable amount of time? For instance I would be happy if I could make them in half the time that say a $50,000 used Haas or Fadal VMC could make them in. The machine would only run about 10 hours a week so it doesn't need to be too hell-for-stout.

A small machining center? A retrofit/conversion? A benchtop? Import vs domestic? Other options?

I would like to keep the price down under about $7k if possible. Am I dreaming?

Thanks folks.

Joe

Reply to
joe_d_builder
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+/-.001, 3 axis profiling,
Reply to
skuke

= For instance I would be happy if I

think you mean twice the time

The machine would only run about 10 hours a

Look for bridgeport rigid ram cnc , 7k all day, I prefer heidenhain, but the very late BOSS [with a crt for instance] are ok from what I hear, the the bridgeport factory pc controls seem to get mixed reviews.

get as new as you can afford.

buy nothing prior to about 1985, preferably 1990

if this is a money making proposition, don't be afraid to borrow money, those HAAS toolroom mils start around 20, so a 4 year lease is something in the 4 hundreds a month, do the math.

Reply to
yourname

Dreaming. A new VMC with those specs will cost $30K-$40K. You might find something used for 2/3 that price. Don't bother with benchtop stuff unless you're certain you'll never be running larger parts. Consider adding an automatic tool changer to your features list.

Profiling requires servos and a decent (i.e. modern vintage) controller that can run all 3 axes simultaneously with look-ahead. Beware of low-cost older machines with decent iron but have stepper drives or a controller box Marconi would recognize.

We bought a couple of these VMCs last year, and they've worked out well > I would like to CNC vertical mill some 2024-T3 aluminum parts from

Reply to
Tim Killian

Look at:

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as an example of used machines. Keep looking, they are everywhere!

Reply to
Tom Gardner

Reply to
Tim Killian

Good info, thanks all.

Yaa, I meant *twice* the machining time of the 50k machines :)

I would be fine with a used machine but don't want something that will require a lot of maintenance costs of course.

Does the ALLIANT CNC VERTICAL MILL W/ANILAM CRUSADER M EQUIPPED WITH:

9" X 42" fit the bill as far as ability to hold this tolerance and also the run time?

I might be pursuaded to go with an enclosed machining center for a little more money since it may work better down the road. What are my price options for the smaller units and also for the less expensive (I'm assuming import) units? Used prices but not for worn out stuff. What are the top places to watch for these as they become available?

Thanks again guys.

Joe

Reply to
joe_d_builder

I've programmed and run several Alliant w/ Anilam Crusader (circa 1985-90) as well as well as later Fadals (1993+) and Bridgeport EZ Track (1998). Did R&D, as well a 3 axis Aluminum molds. Neither of the knee mills could hold

+/-.001 without a lot of work and very careful setups. You needed to consider ALL aspects of the problem if you really wanted to hold your required tolerances. The Fadal could hold .001" on 3 axis w/o *too* much trouble.

I'm sure you could find a used 3 axis knee mill in the $7k range, but that machine would probably have been "ridden hard and put away wet." It won't hold the tolerance you request (without a lot of extra work, and then only just maybe).

Spend more money and you'll be happier in the long run. JMHO. Also, please consider if you *really* need +/-.001" Are you making matched dies? ...duh, I guess not if they're aluminum. But my point is that .001" is pretty tight to hold day in, day out with any kind of efficient speed.

Reply to
skuke

That was what I was wondering. I would recommend to the OP to find out how the 3d contour will be measured, and go from there...

Regards,

Robin

Reply to
Robin S.

I have a Wells Index CNC knee mill. The mill itself weighs 6000 lbs. So it's bigger than your typical bridgeport type knee mill which weigh about a ton. The control on the mill failed a few years ago and I bought a new control from AJAX. Even though about 20 years old and plenty used the machine is quite accurate. So holding .0005" location when boring holes is a breeze. I can get closer by changing the program to compensate for position error because the machine repeats to .0002". So an older machine can be checked for error in both positioning, flatness, and squareness and if good enough then it might fill the bill. I bought my Index mill mainly for complex shapes, not for production. My next mill will be enclosed, the Index is not. Being enclosed will keep the chips and coolant in the machine and allow higher speeds and feeds without throwing chips and coolant all over the place. ERS

Reply to
Eric R Snow

I agree with you that one can program out (minimize) positional errors by approaching from the same direction to eliminate back lash issues, center drill, drill... With all due respect, true hole position is much easier to hold and measure than the 3 axis contouring the original poster wanted.

My experience with the knee mills (and even the Fadal to a much lesser extent) is that to interpolate a round circle is pretty gosh darn difficult. You wind up with some "egg" shaped hole with dwell marks at the axis' when the ball screw must actually come to a complete stop for a moment to turn the other direction.

Please try it: Interpolate a ~3-4" circle in a rigid piece of aluminum with a good rigid endmill of your choice. Take a few finish passes. Then, without removing the part from the vise (to eliminate other problems like stress/tension relief), measure TIR with a test indicator. I'm pretty sure you'll have at least .001" TIR.

So I think trying to hold 3 axis timing on a cheaper, less rigid machine will be all but impossible.

...just based on my experiences. ...your results may differ.

Reply to
skuke

skuke wrote in news:12ejv15bq6owk$.1oehahivela0c$. snipped-for-privacy@40tude.net:

Try holding +/- 0.001 mm (1 micron) all day, day in, day out. 0.001" is like having a ballfield to play in by comparison.

Reply to
Anthony

Nothing wrong with using customers for R & D, at least according to microsoft. jk

Reply to
jk

Ok, let's put it another way.... what small enclosed VMCs are available and what do they usually run used (for one that hasn't been beat to death)? I figure if there is a machining center with a toolchanger and everything it will probably do what I'm after. I don't need to hold .001" on the whole part but definitely need to for certain areas of it.

JOe

Reply to
joe_d_builder

You need to identity what you need at this point. After reading this group for several years, and selling tools for several years, knowing what you

*need* is paramount.

If you spend $7K on a machine that cannot do what you want it to, you have wasted that money, and the time required to buy (and perhaps sell) that machine.

So... Be specific...

Regards,

Robin

Reply to
Robin S.

Is it research if they aren't interested in the results?

Regards,

Robin

Reply to
Robin S.

Doh! The OP would have just spent his entire budget (and then some) on temperature controlled coolant and enviromental controlled shop and inspection!

Reply to
skuke

You need a 6"-12" cube work envelope? Look at some of the newer Haas and Fadal "tool room" mills. Haas even has a new line called the Office Mill(?). I'm not sure that has enough power and space for your needs, but check it out.

I think you basically need to stay away from knee mills if you *really* need .001" on any significant parts of your job. Yeah, you could do it, but it's just way more work. Look into bed mills with or without enclosures. Maybe a Milltronics, Hurco or Prototrak (bed mill version). Even with the last three mills, look for a head/quill design that will be sufficiently rigid for your needs. I don't know the prices for any of the above, but they are all well over $25k new.

Maybe you should just job out the contouring part you can't currently do??

Reply to
skuke

skuke wrote in news:gp8g5i8m5jmu$.1kacz6ey0d9hw.dlg@

40tude.net:

Hehe...and that doesn't include the automatic temperature adjustment for the machine tool either.

I will agree, a knee mill type situation for the OP is not going to hold his tolerances. The OP would be better off with a used, but good condition bed mill. OP: check out some used Mazak mills, ought to be fairly reasonable in price, and they are good machines.

Reply to
Anthony

Which demonstrates a critical differnence between the machine tool and software industries.

--RC "Sometimes history doesn't repeat itself. It just yells 'can't you remember anything I've told you?' and lets fly with a club. -- John W. Cambell Jr.

Reply to
rcook5

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