Talk me in or out of a 12z mill

So closed loop servos is good. Learned something new today!
 
Where possible a closed loop servo system is always the best. And in my opinion, feedback directly from the load (the table in the case of a mill) is the best way to go. Unless you are buying a 6 figure machine, relying on the encoder/leadscrew for positioning accuracy introduces too many variables into the equation. I use magnetic readers on my mill that replaced the original encoders.

Open loop stepper systems tend to loose pulses, especially at higher speeds and/or heavy loads. It is possible to close the loop with stepper systems by programming in on-the-fly error correction, if you have a feedback device on the axis.
 
Where possible a closed loop servo system is always the best. And in my opinion, feedback directly from the load (the table in the case of a mill) is the best way to go. Unless you are buying a 6 figure machine, relying on the encoder/leadscrew for positioning accuracy introduces too many variables into the equation. I use magnetic readers on my mill that replaced the original encoders.

Open loop stepper systems tend to loose pulses, especially at higher speeds and/or heavy loads. It is possible to close the loop with stepper systems by programming in on-the-fly error correction, if you have a feedback device on the axis.

I once designed a 6-DOF system for a Darpa project that used high precision linear motors and laser interferometers for absolute positional data. Don't remember precisely, but repeatability of this system was in the millionths of an inch. We had to have real-time meteorological data for our error correction algorithms.

I'm pretty sure that during that project was when I lost all my hair... :(

Bill
 
Hi
Is this mill made in the USA. It looks like the one from Grizzly

Both the Industrial Hobbies and the Grizzly mill are made in China. The UK mill you linked is probably made there too.

There is some variation between the mills, but they all started life as clones built following the pattern of the Rong Fu 45 (RF45) square column mill.

The Industrial Hobbies mill received quite a few upgrades over the last decade at the behest of IH, gaining larger table, larger base, thicker cooler on the head, etc.

I would look a little more carefully at the specs when you buy a mill; the UK mill comes with an MT4 taper, which I would rather not deal with in a mill. You should be able to look around and find an R8 RF45 square column mill from an importer in the UK. Try here:

http://www.axminster.co.uk/metal-working/milling
 
Hi
Is this mill made in the USA.

It looks like the one from Grizzly

http://www.grizzly.com/products/Heavy-Duty-Mill-Drill-with-Stand-and-Power-Feed/G0755

or the one in the UK

http://www.amadeal.co.uk/acatalog/AMA45A.html

what is the difference in the mills, they all look the same, just the specifications,
in the speeds & motors. Is this one any better ????

The one in the UK look nearly the same.

ps
is tooling for the NT30 Spindle inexpensive and easily obtained in the UK

No, the mill is made in China.

The Griz isn't even close to the same table size or travel. Head mount to column is different too. Same for the UK one. As for the NT30, I can't say. It's more expensive here, at least the ones I've priced, and for much larger tooling than what I will be running. Don't know about across the pond. :)

When I talked to Paul (Ops Mgr) about this he told me that they hired a British company to inspect the machines in various places during the build process. A statistic sample was done, and the machines that were inspected showed up here in good shape spec wise. The others though, were hit-and-miss on the quality. So, they (Charter) decided to have the Brits inspect every machine intended for Charter Oak. But the cost increased. Always tradeoffs...

Given the story and the fact that they use these machines for the basis for their CNC mills, I decided to buy in. The proof will be in machine that I get I guess. Good or bad, I will report my findings to those interested.

Bill
 
Both the Industrial Hobbies and the Grizzly mill are made in China. The UK mill you linked is probably made there too.

There is some variation between the mills, but they all started life as clones built following the pattern of the Rong Fu 45 (RF45) square column mill.

The Industrial Hobbies mill received quite a few upgrades over the last decade at the behest of IH, gaining larger table, larger base, thicker cooler on the head, etc.

I would look a little more carefully at the specs when you buy a mill; the UK mill comes with an MT4 taper, which I would rather not deal with in a mill. You should be able to look around and find an R8 RF45 square column mill from an importer in the UK. Try here:

http://www.axminster.co.uk/metal-working/milling

Hi
Thanks for the info, will get a mill next year, still looking around.
I think the the UK mill can be got with a R8, but up to now it is the best i have seen in specs & cost.

Are all the parts interchangeable between the makes.

I think it is made in China.
 
wrmiller19,
Can you post pictures of the Stand you received from IH/Charter Oak and comment on it, I'm on the fence about buying the one with wheels.

Thank you,
Grant
 
Reach out to Bill Miller of Coolidge as they both purchased 12Z's this year.
 
Brooks: Coolidge didn't buy a stand, he built his. And I think I've had mine for a year now. Time flies?

Here's a couple of pics of mine from when I was initially setting up the mill. Initial impressions were not great with regard to the appearance of the welds, but it's still standing and I've been up on the stand with the mill in place working on the top of the head (about an additional 300 lbs. at that time), and nothing broke so I would say it's strong enough. I don't have welding capability to make my own stand so I popped for theirs and had them add 4" to the height.

DSCN4234.jpg

DSCN4235.jpg

I did make one change since these pics. I put some aluminum blocks under the levers to get them further back into the stand. I didn't like the look of them sticking out so far.
 
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