Re: VMC no older than ??
- From: D Murphy <spamto154@xxxxxxxxxxx>
- Date: 13 Dec 2008 06:18:14 GMT
grumtac@xxxxxxxxxxxxx wrote in
news:30c66f26-ff0d-41f3-a69c-ae496546216c@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:
On Dec 10, 11:18 pm, D Murphy <spamto...@xxxxxxxxxxx> wrote:
The surplus record is a good place to start doing research. Here is
their VMC page -http://www.surplusrecord.com/srg/209093.htm
If you have some idea of the size range and price range you are
considering we might be able to narrow it down some.
Dan, thanks for the replies. I figure this is a tuff thing.... its not
like you can tug on an axis and determine if the machine is good or
not. All one can do is attempt to trust the seller and the sellers
claims.
Is there any guidance for what "low hours" really means ? What is the
life expectancy in hours for your typical VF-1, VM-1 type machine ?
All comments appreciated,
Figure 2,000 hours per year per shift. VMC's generally have horrible
spindle utilization or "uptime" so figure actual running time will be 30
to 60% of available production time.
Run hour meters are worthless as they can all be reset. Even the
"odometer" types that measure power on time.
Best bet is to hire a qualified uninterested service tech to examine the
machine. A $500.00-$1,000.00 bill is cheap insurance in the long run.
Plus it can give you negotiating leverage if there are some issues you
are willing to accept.
Check the spindle for noise, heat rise, run out, end play, and taper
damage. Check the drawbar pulling pressure. Check axes for noise,
backlash, and positioning error. If it's really important, a ball bar
test can tell you a lot.
Check axes for squareness, perpendicularity, pitch, roll, and yaw.
Make sure you and whomever you hire to check it out agree up front what
will be checked, documented, and what the fee will be.
Make sure your expectations are realistic. If it's used there will be
issues.
There was some nut job posting some years ago that bought a used Haas.
From everything he posted, plus his nut job web site dedicated todenigrating the poor broker who sold him the machine, he got a fair deal.
The machine had some minor issues. It was, after all, a used machine. One
of his favorite rants was about the dings in the table. If he was looking
for flawless he should have bought new.
I run across guys like this out in the wild from time to time.
As for the life of the machine, it's difficult to say. Poor maintenance
decreases the life of any machine. The materials being cut also affect
the life. Cast iron and graphite for example can do some damage. Crashing
a machine damages it far more than people realize. A machine that gets
crashed on a near daily basis might look real pretty, but could be a near
basket case underneath the fresh coat of WD40 making everything shine.
Measuring, listening, and testing are the best preventative to getting
screwed. There is nothing wrong with buying a machine that needs work
either. Just so long as you don't pay too much for the machine.
One of our customers bought a used CNC Swiss. He had it checked out
before he bought it. The machine had been crashed hard, probably more
than once. The sub spindle needed bearings, the backwork tool post and
X2/Y2 axes needed to be aligned. Otherwise the machine was in very good
shape. So he negotiated accordingly and hired us to repair the machine.
Even with the extra expense, he got a screaming deal on the machine.
Of all the scenarios I laid out in the other post, my preference is to
buy high end/less popular brands when it comes to used. Here's why; A
machine like a Haas is cheap new. A lot of Bozos buy them and there's no
shortage of Bozos running them. Your odds of getting a machine that has
been abused are higher and the odds of the machine being damaged from
crashes is also a lot higher as they are not as robust as a higher end
machine.
I needed a toolmaker's microscope for our office a while back. They
didn't give me much of a budget, so new I could buy a Mitutoyo measuring
scope with micrometer barrels. I started looking around for used and
ended up finding an older Gaertner toolmaker's universal microscope with
a DRO, lenses, reticles, external light source, and loads of other
accesories on Ebay. I got it for $500.00 because most people never heard
of the brand and I was the only bidder. This scope was probably
$12,000.00-$15,000.00 new 20 years ago. It came out of an aerospace
company auction where it led a peaceful life and was calibrated and
maintained regularly.
At 20 years old it's still better than anything Mitutoyo makes new and
far more useful due to its superior design, capabilities, and the box
loads of accesories that came with it. Meanwhile if you watch the
auctions for Mitutoyo scopes, used beat up ones with nothing extra
usually go for double what I paid for the Gaertner. Just because people
know the brand name and feel safe buying it. It's insane.
--
Dan
CNC Videos - <http://tinyurl.com/yzdt6d>
.
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