Sounds like you have a budget and if you are willing to put up a tilt up
building and temperature control it, you have some money to spend.
There was money to spend on the system I was quoting about 9 years ago
until the DOD budget was slashed, then it all went away. I got Siemens
involved and they had no issues tying a laser tracker into their CNC
system. The router was a 5 axis design. We were using standard
Siemens servo drives connected via Ethernet/Profinet on Fiber optic
cable. The actual control system will not be the big cost for your
system. The drives and mechanical system/gantry and building will be
much more costly. The laser tracker was some serious cash as well, but
not much compared to the building and gantry and framework. Siemens had
all of the CAM software required as well.
It can be done. All of the technology existed 9 years ago. But there
is nothing cheap about it.
If you are really going to do this, you might want to make sure you have
flexibility designed into the system so you can do multiple processes
with your system. Welding, cutting, routing, etc. Being close to a
waterway might be a good idea as well. Huge things don't fit on semi
trailers very well.
Dave
On 8/23/2017 12:19 PM, Rick Gresham wrote:
The building will likely typical concrete tilt-up or something similar. The
system will have to track/control position in real time. Collisions will be
very expensive so redundant systems are easily justified. It may need some
sort of collision avoidance system as a back up, too. If the crosses some
boundary, everything stops. Stoppages are not a big problem, bumps in the dark
are.
I've wondered about redundant control systems but haven't come across any
information yet. Anyone remember the triple Tandem non-stop systems NASA used?
Three fault-tolerant systems running in parallel. If they came up with
different results, it was odd-man-out. Probably don't need to go that far for
this application unless something available off the shelf affordably.
On Aug 23, 2017, at 8:56 AM, Chris Albertson <[email protected]> wrote:
There are many ways to measure position. With something this big and
expensive I would suggest some redundancy. The cost of measuring is tiny
computer t the cost of a 100f gantry.
One of the bigger problems I see is flex in the system and thermal
expansion. If the goal is 1/8th inch over a 100 foot run then their needs
to be some design margin so you'd be designing for something like 1/16th
inches.
I doubt that simply measuring how for you are along a steel bed will work.
Yes you could try but the beam itself will bend and change it's length.
You would have to measure absolute position relative to fixed locations on
the floor.
I don't think I've ever seen a building made to close tolerances either.
The sports are not going to be square to each other or level or vertical.
I't not hard to compensate for the not-perfect mechanics. You can also
continuously calibrate the sensors from know references inthewtork space
On Wed, Aug 23, 2017 at 2:21 AM, andy pugh <[email protected]> wrote:
On 23 August 2017 at 05:17, Dave Cole <[email protected]> wrote:
A 3D laser tracker was part of the control scheme to track the actual
tool
head location.
That way standard rack could be used for the positioning mechanism and
the
position could be corrected on the fly via the laser tracker.
That might still be a good idea, because it seems that such a machine
might need to be modular, so units that are friction-drive on standard
rolled steel sections seems like a likely solution.
There will be some tyre-creep, but the laser (or acoustic) feedback
could correct it.
I heard of a system where you have a microphone in each corner of the
room and a "clicker" that is localised in space by clever acoustic
processing.
The application was measuring accelerometer positions when
instrumenting a car or van body. If you have ever "walked" a Faro arm
round a van body you would know why the system seemed attractive.
--
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916
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