On Thursday 24 August 2017 21:33:17 Gene Heskett wrote: > 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. > >
It wasn't that cold when I was there for 6 months before turnkey, and a bout a year after as I was doing the portal door cctv maintenance after. High 60's estimated. And to around 90F when they had switched to generated power full time, a month or so before turnkey. Big 6 cylinder diesels, biggest IC engine piston I'd ever seen till then, nominally a 5 gallon bucket for a piston. Top had a hole in it, some AH had left a wrench inside when the head was bolted down at the makers site. I guess it started and ran with it hammering around in there for about 10 minutes. That triple head and triple cylinder casting were, shall we say, beyond a simple resleeving rebuild. No profit left in that bid. > > 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 > > >>> <albertson.ch...@gmail.com> 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 <bodge...@gmail.com> > > wrote: > > >>>>> On 23 August 2017 at 05:17, Dave Cole > > >>>>> <linuxcncro...@gmail.com> 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 > > >> Emc-users@lists.sourceforge.net > > >> 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 > > > Emc-users@lists.sourceforge.net > > > 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 > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > Cheers, Gene Heskett 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
