On Wednesday 13 February 2008 15:40, Stephen Wille Padnos wrote: > >I'm starting to suspect that EMC is a project that started out, not to > > emulate the commercial equivalents, but built bit by bit to do various > > things on the cheap, I'm starting to suspect that EMC is not a realtime > > machine control system, but rather an offline (non realtime) simulator > > that relies on assumption (I sent signals to move X 1.01 mm, therefore I > > shall assume it has moved 1.01 mm) > > Actually, you have it backwards. Many of the commercial controls are > based on EMC2 code. EMC was originally developed at NIST and was public > domain. It was part of a standardization project for machining > languages, and was written as the reference implementation of the > newly-developed RS274NGC standard.
Really ???? http://www.isd.mel.nist.gov/personnel/kramer/pubs/RS274NGC_3.web/RS274NGC_3TOC.html Section 1.2.2 "RS274 is a programming language for numerically controlled (NC) machine tools, which has been used for many years. The most recent standard version of RS274 is RS274-D, which was completed in 1979." Section 1.2.3 "The NGC architecture has many independent parts, one of which is a specification for the RS274/NGC language, a numerical control code language for machining and turning centers. The specification was originally given in an August 24, 1992 report "RS274/NGC for the LOW END CONTROLLER - First Draft" [Allen-Bradley] prepared by the Allen-Bradley company." Section 1.2.4 "In 1995 the EMC project collaborated with several industrial partners in an open-architecture machine tool controller project known as VGER (a name, not an acronym). This project retrofitted an SNK 5-axis machining center with an open architecture controller. NIST provided the RS274 interpreter for this project [Kramer4]. It was intended to be able to interpret some existing programs for the SNK machine which were written for its former Fanuc controller [Fanuc]. Thus, the RS274/VGER Interpreter took Fanuc flavored RS274/NGC code as input." >From that, and other references (both in assorted documentation and original source code), I would conclude that the EMC interpreter does NOT conform to any ratified "stansard" - It *may* be based on documented behaviour of a common (in 1990-4) control system that *might* be compliant in part with a recognised "standard". The current "extended" interpreter certainly does NOT conform to any published standard (i.e. as issued by DIN, ISO, EIA, or any other official body) - A subset of instructions may be compliant, but that is all. As for the claim that "Many of the commercial controls are based on EMC2 code", that is stretching things a bit - Mach1/2/3/4 may have it's roots in the original EMC interpreter, and there *may* be a few other hobby level controls out there that appear to be similar. > Although there is a simulator mode (something you won't find on any > commercial control You really should look at the current offerings from the likes of Heidenhain and Seimens - I'm sure even the top end Fanuc controls would offer simulation and/or preview modes. > - why bother, nobody would buy one just to stick it > on their desk), EMC2 is very much realtime - to the limits of the PC > it's installed on. Parts of the core code run in a realtime environment - For example, trajectory planning, PID, and IO. Parsing of assorted files is non-realtime, done in user space (unless someone has been screwing around with the code). > It is used on machines from tabletop lathes to 20-ton machining centers. I have EMC running on a desktop mill, but not emc2. > There is no "hobby-class" controller that uses feedback. None. I fear you will lose a bet - Last I heard Mach3 can use feedback with a suitable IO card. > The least expensive commercial controller I know of with feedback is in the > $5000 range. With the value of the US dollar being so low, $5K would be close. Certainly, there are a number of commercial controls available on the market under $10K. > Heh - "the emc coder". EMC was developed by a few PhDs at NIST, then > added to by about 20-30 developers over the last 10 years. Odd that... There are over sixty names listed on the Sourceforge site. Perhaps you would be so kind as to tell us who currently has access to the repository (including anyone not listed at Sourceforge). ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
