[FoRK] The other CMM -- personal coordinate measuring machines now available....

Ken Meltsner meltsner at gmail.com
Sat May 21 13:11:25 PDT 2005


CMM to a mechanical engineer usually refers to really expensive
computerized devices that move a hard point around in space to measure
the exact coordinates of surfaces.  They're the equivalent of a
pantograph (for old-timers that remember mechanical drawing aids), but
3-D and computerized because they generate a lot of points.  3-D
modelers use digitizing devices to enter in sculptures and such, but
they aren't nearly as precise as a real CMM.

I was reading one of my favorite lists -- old tools -- and a google ad
showed a link to a site claiming personal (i.e. cheap) CMMs.  These
are not the sort of words that ever get used together in my
experience, so I went to the site.

Faro, indeed, has a low-end CMM arm that could be considered
"personal" -- it doesn't require a clean room or a massive
vibration-free table, and it doesn't have the 0.1 mil precision (2-3
micrometers) that a "real" CMM has, but it is computerized and can
digitize anything within a 4 foot distance.  I can't find a price, but
it's probably under $10K since the next model up, a low-end real CMM,
is $20K.  $10K is a magic barrier for corporate purchases in many
cases, so that's my guess.

This is a game-changing device.  Take the mundance problem of
installing kitchen counter tops.  If you have to fit an existing
space, you would traditionally make a template from hardboard or thin
plywood that fit the not-square walls, the sink,moldings, etc. by
scribing an offset line and cutting the plywood to match the existing
boundaries perfectly.  Then, you'd just put the template on top of the
countertop and use a router (or a grinder for granite) to trim
everything to match.

Lots of people do this every day; there's a little back and forth
fixing to get a good template, but it's a reliable way to make things
that fit -- measurements are never as accurate as the real thing, or a
template taken from the real thing.  We did this in the high tech
world of aircraft engine design -- a CAD system was used to create the
surface of a highly twisted fan blade, but the CAM system cut
cross-sections that were mounted in a frame, filled with plaster of
paris between the sections, smoothed, and used to drive a milling
machine that had a ball that matched the mill size and a 3-D
pantograph mechanism so that the die material was cut to match the
form.

[Except now we would send die surfaces to a 3-D CNCmilling machine, of
course, but that's for incredibly high tech applications.  Maybe --
there's still a lot of low tech manufacturing involved in high-tech
products. ]

The part that intrigues me is that a major kitchen installation
company now uses a CMM to measure the countertop space instead of
making templates. and then dumps the data into a CNC router that cuts
the exact shape automatically.  Faro claims huge savings this way, but
the amazing part is that the CMM is out of the clean room and into the
job site.

This sort of thing is huge.  Drop the price of a CMM to $5K and you'll
have all sorts of applications that used to require skill, specialized
measuring devices, or trial-and-error --  good precision measuring
devices of the traditional sort might start at a couple of hundred
dollars and go up into the thousands any way. and they aren't nearly
as flexible or multipurpose as a CMM.

Big changes, guys.  Who knows?  Some day, we might even have a
workable standard for 3-D model exchange...

Ken

At Last! The Personal CMM

The FARO Gage Plus™, along with the FARO Gage™, are the industry's
first personal line of Coordinate Measuring Machines (CMMs). With
their 48" working volume, they are the "mount it to where you make
it", truly portable, cost-effective, 3-Dimensional, no-training gages
for machinists. Complete with graphical and tabular reporting with
SPC, the FARO Gages replace all conventional gaging devices with an
expandable library of gaging tools. Save time and money by replacing
your cluttered inspection area with the one tool that can do it all.

Setting up in seconds, the FARO Gage allows anyone, anywhere to
measure parts and assemblies directly on the machinery producing them
or on your surface plate. Made specifically to be used by shop floor
personnel, it is accurate and powerful enough for advanced measurement
including statistical analysis such as GD&T and SPC. Even better, it
records all of the user's measurements automatically and creates
comprehensive reports.

-- 
Absolute power corrupts absolutely, but model train sets do a pretty
good job as well

-- 2/28/05, in a odd dream


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