kan@dg-rtp.dg.com (Victor Kan) (01/14/90)
Did anyone watch "This Old House" this week? They toured a stairway factory with a curious mix of automation. A three-headed router used to cut spiral stair steps was controlled by a huge computer (the size of a Vax 11/780 at least) with a paper tape reader for program input. I think there was even a hex keypad on the front. Where do you think these paper tape control programs were generated? An MS-DOS machine (AT class) was running a high resolution, color CAD application which spit out paper tape descriptions of the image on the CAD screen. The MS-DOS machine also generated drafts on a high speed rolling plotter (for lack of a better word, not flat-bed). When the hardcopy of the design was finished, it was transferred to a large electronic drafting table controlled by a Compaq 386. Attached to this table is a special mouse which included a numeric keypad and a magnifying glass with cross hairs. This was used to transfer the hardcopy image to another computer. This was perhaps the strangest arrangement of computers and data transfer methods I have ever seen. The question I must ask is "Why?". The factory has been in business for decades so I can understand that they started with automation early, when paper tape was a common data medium. If the three-headed router is tied to the old computer, I can understand their use of the PC to generate paper tapes from CAD screens. But why use the electronic drafting table to transfer the image to a modern computer (the 386 was next to the table so I assume it was the host device), rather than just swap diskettes? It can't be that hard to write a data conversion program between their CAD program and their manufacturing program. | Victor Kan | I speak only for myself. | *** | Data General Corporation | Edito cum Emacs, ergo sum. | **** | 62 T.W. Alexander Drive | Columbia Lions Win, 9 October 1988 for | **** %%%% | RTP, NC 27709 | a record of 1-44. Way to go, Lions! | *** %%%
jim@aob.aob.mn.org (Jim Anderson) (01/15/90)
In article <2201@xyzzy.UUCP> kan@tom.dg.com () writes: >They toured a stairway factory with a curious mix of automation. [Victor Kan goes on to describe a AT running a CAD application generating a paper tape for a computer router and plots, which were transferred via an electronic drafting table to another computer.] >The question I must ask is "Why?". The factory has been in business >for decades so I can understand that they started with automation >early, when paper tape was a common data medium. If the three-headed >router is tied to the old computer, I can understand their use of >the PC to generate paper tapes from CAD screens. As a person intimately involved in the machine shop automation, the collection of equipment described is typical of many machine shops. The tradition of using paper tape to transfer programs to a CNC (Computerized Numerical Control) started many years ago when computers were very rare. (The original NC machines used relays and step switches...). Many years later, when computers were getting common enough to show up in manufacturing environments (initially only as the machine controller), they needed to maintain compatibility with the old machines for program transfer. The most common means of producing programs for machine tools during this time (60s, early 70s) was with Flexowriters or Teletypes, both of which used paper tape. Later, as computers became more common on the programming side, the compatibility issue came up again. The only way the programming systems could get the data to all the machines on the shop floor was with paper tape. Many of the machines produced, even into the 80s, didn't have bidirectional RS-232 ports. Even now, the RS-232 communications to the machines rarely use anything more than parity checking for data integrity (Checksums? CRC? what's that? :-). As we go into the 90s, machine tool communications is finally starting to improve. Machine shops (at least the forward thinking ones) are starting to connect the machine tools to their CAD systems (if they ever bothered to get one), thus finally getting rid of paper tape. I do have one remark about the advantage of paper tape. Because many of the computers installed as CAD systems are PCs running DOS, they are inherently single-user. If the computer operator is in the middle of working on a CAD drawing, and the machine tool needs a program to run the next part, either the machine tool has to sit idle until the computer is available (and at $50-$500 per hour operating cost, this ain't cheap), or the computer operator has to be repeatedly interrupted to send the next program to the machine. With paper tape, the tape can be punched when the programmer is done, put on a shelf, and when the machine is ready for it, the machine operator can go get it without interrupting the programmer. This can be worked around by getting multiple computers, but many machine shops don't want to spend the additional money for another computer, just because the first one might not be available for a few minutes. >But why use the electronic drafting table to transfer the image to a >modern computer (the 386 was next to the table so I assume it was >the host device), rather than just swap diskettes? It can't be that >hard to write a data conversion program between their CAD program and >their manufacturing program. In many cases, especially with the PC types of CAD systems, the CAD vendors don't supply a compatible output format. I have run into (sometimes expensive) CAD packages that can't output anything except their internal part file format, and the CAD vendor doesn't document that. It is also not uncommon for a manufacturing program to be very picky about the data that they accept. In the case of the manufacturing program, the vendor may not provide any way except drafting table input. This may sound silly, but there are those packages available. In the case of some of these packages, they may be in an early release, and a CAD interface hasn't been written yet. -- Jim Anderson (612) 636-2869 Anderson O'Brien, Inc New mail:jim@aob.mn.org 2575 N. Fairview Ave. Old mail:{rutgers,amdahl}!bungia!aob!jim St. Paul, MN 55113 Lucifer designed MS-DOS to try men's souls. Jim Anderson (612) 636-2869 Anderson O'Brien, Inc New mail:jim@aob.mn.org 2575 N. Fairview Ave. Old mail:{rutgers,amdahl}!bungia!aob!jim St. Paul, MN 55113 Lucifer designed MS-DOS to try men's souls.
xanthian@saturn.ADS.COM (Metafont Consultant Account) (01/18/90)
In addition to other problems keeping paper tape in use in machine shops, (vice rs232 links to transfer data), machine shops are incredible noisy electronic/emf environments. Most communications must be at least coax quality to avoid large data hit rates. Similar noise pervades the power lines. Keeping the PC quality machines in otherr rooms/buildings (better) with isolated power supplies and no wiring into the machine shop is frequently just good sense. Think about the start/stop currents to get all those tons of metal moving! Every workstation a radio transmitter. ;-) (Former Newport News Shipbuilding Employee...) -- Again, my opinions, not the account furnishers'. xanthian@well.sf.ca.us xanthian@ads.com (Kent Paul Dolan) Kent, the (bionic) man from xanth, now available as a build-a-xanthian kit at better toy stores near you. Warning - some parts proven fragile. -> METAFONT, TeX, graphics programming done on spec -- (415) 964-4486 <-