On Thursday 24 August 2017 19:06:13 dave wrote: > Only half kidding; the power room of a Titan I missile site would just > about do. 55 F year around. IIRC the measuring system needs about 4X > the resolution of the tolerance you need to hold. Concrete and steel > have approx the same thermal coeff of expansion. > > I like the idea of access to a major waterway. I really could not > believe it when the contractor for the new sections of the Narrows > bridge opted to ship by truck. ( I90 Chicago to Tacoma) Got held up > for quite a while at the WA border while everyone fought of regs and > paperwork. My thought was the they had decent waterway all the way and > basically could have lifted them off the ship ... or off a barge into > place. But then what do I know. Politics and logic are rarely in the > same room. ;-) > > Most interesting project. > > Dave > But Dave, that would need someone in power to have common sense!
I don't have it handy, but I am dead certain there is a Murphy's Law about that which absolutely prevents it. :) > On 08/23/2017 09:59 AM, Dave Cole wrote: > > 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 > >>>> > >>>> ------------------------------------------------------------ > >>>> ------------- > >> > >> ------------------------------------------------------------------- > >>----------- > >> > >> Check out the vibrant tech community on one of the world's most > >> engaging tech sites, Slashdot.org! http://sdm.link/slashdot > >> _______________________________________________ > >> Emc-users mailing list > >> [email protected] > >> https://lists.sourceforge.net/lists/listinfo/emc-users > > > > -------------------------------------------------------------------- > >---------- > > > > Check out the vibrant tech community on one of the world's most > > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > ---------------------------------------------------------------------- >-------- Check out the vibrant tech community on one of the world's > most engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
