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Re: Digest Number 56
Jon Elson
From: "Fox, Dan" <dfox@...>well, sometimes you do research and development projects not truly knowing where they will lead. Apparently, much of the heart of EMC is in the motion control and motion planning sections, and the interpreter that takes RS-274D (G-code) and converts it into the planned motion. These pieces were originally created for robotic applications, and may be the heart of some other projects. Another factor that pushed this development was the OMAC committee, which was originally composed of large users of robots and machine tools, who were interested in bringing down the cost (both purchase and maintenance) of these machines. I think the OMAC is dead, nothing new has shown up on their web pages in years. I believe it was originally hoped that EMC would lead to machine tool manufacturers basing their controls on open systems, and delivering a much cheaper product to the workplace. That certainly hasn't happened (yet). And, there's no obvious rush to do so, either. Small shops may well be willing to pay extra to get the conversational features that many proprietary controls offer. So, I don't know if there are projects in the private sector that are using EMC, or some of the components, and paying back to the economy. I think there are some small projects at NIST or other labs that are using EMC or some of the components in reasearch or facilities. I know that NIST is setting up a mill in their own machine shop to use EMC. That's because it is there, and it gives NIST some local, machinist-type feedback on what is good, and what needs to be made better. It is hard to know where this is all going. EMC may be one of those blind alleys that never really provide much payback for all the work that went into it. On the other hand, the guys who wrote the original RS-274 standard in the 1960's would be STUNNED to see how widely and broadly their little design has become integrated into manufacturing. Not only mills and lathes, but robots, pick-and-place machines for circuit board assembly, CNC drilling of printed circuit boards, laser photoplotting of master artwork for PCB photoetching and the making of micromachined components, etc. all use some version, variant or dialect of RS-274! There are entire industrial sectors dedicated to turning RS-274 commands into precise motion. We wrote the book (in the US) and it is used all over the world, now in its' fourth decade. Jon |
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Pic servos
Andrew Werby
"Dan Mauch" <dmauch@...>wrote:
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Subject: Re: List question see www.jrkerr.com It is a programmable controller chip call the PIC servo that does the intelligence for a low cost servo system. Dan -----Original Message-----
From: TADGUNINC@... m <TADGUNINC@...> To: CAD_CAM_EDM_DRO@... <CAD_CAM_EDM_DRO@...> Date: Thursday, June 17, 1999 6:40 AM Subject: Re: [CAD_CAM_EDM_DRO] List question From: TADGUNINC@...[This looks interesting, Dan. Have you ever tried these out for controlling servos? Has anybody here? I assume the $175 is per axis, but still, it doesn't look that bad if that's all I'll need to retrofit my old mill to accept unlimited g-code file sizes. Could it be that simple? Are these the kind of boards that have their own chips onboard, so they can buffer the input from the computer and real-timeness isn't an issue? Or is there something I'm not taking into consideration here? I wonder how well the control software that goes with these things really works...] Andrew Werby Andrew Werby Andrew Werby - United Artworks Sculpture, Jewelry, and Other Art Stuff |
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Re: newbie question
Jon Elson
"Fox, Dan" wrote:
This might qualify for the eventual FAQ, except I've never seen itYes, ball nut is the proper term. Yes, there are inner 'works'. The works are ball bearings. So, the nut does not slide on the screw, the rolling balls make it a rolling action, thereby reducing friction (and wear) to minute levels. There is a rounded track in the nut, and the balls roll to one end of the track, so a recirculating tube of some sort is provided to return the balls back to the other end of the track. If you put two separate circuits of balls in one nut, and either make the two tracks slightly off the screw pitch, or put springs between the two nut sections, you can preload the two nuts against each other. This makes an anti-backlash screw. Depending on design, you can get screws that will deliver thousands of pounds of linear force, with backlash on the order of .0001" or so. Obviously, for a precision machine, or a CNC where smooth, complex motions are required, removing backlash is a very desirable thing. The reduction in wear and friction is an added benefit. Jon |
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Re: bills thoughts and comments.
Jon Elson
From: Leslie Watts <leswatts@...>This sounds very interesting. I had a strong interest in the LM628/629 chips. I got samples, lots of documentation, etc. from National Semi. The one thing I couldn't figure out was how to keep 2 (or more) of them synchronized, especially on 'chained' moves, where 2 axes are making many very small moves, as in circular interpolation, etc. I called Nat semi, they told me they'd just been bought by Fairchild, and were real busy at the moment. But, anyway, they had no info on synchronizing multiple axes. For plain linear moves, you just give the 'go' command as close to simultaneously as possible, and it should do fine. But, on a multi-axis chained move, if one axis gets a bit ahead of the other, you want the slow axis to speed up, or the fast axis to slow down, just a little. But, you don't want the faster axis to go into 'ramp down to stop' mode, or it will really muck up the motion. So, I never built a system with the LM629 chips, because I couldn't be sure this problem wouldn't come to haunt me. I am concerned with interrupt latency and the lack of feedforwardYes, it really seems to work quite well. You can get graphs out of the system to help in tuning the parameters. - making 7' machine ways to .001" with only a level, 12x18 surfaceThat sounds like QUITE a trick! - designing and building preloaded ball screw support bearingsI need to replace a preloaded pillow block on my X axis, because it is just too light for the job it is now being required to do. I have some angular contact bearings, but I'd like to hear your ideas. - Surplus sources for linear motion components (Chicago area)Always interested in where to get good parts from. Thanks, Jon |
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Re: Digest Number 56
Patrick Huss
NIST doesn't allow access to archives of its mailing list to anyone outside
NIST. Unless you were with that list from the very begining, you probably missed some important discussions. On the contrary, Onelist, as you all know, lets us all access the list archives. Seems pretty unambiquous, really. If it ain't broke, et cetera, et cetera Patrick Message: 13discussion of shop built systems in the above catagories. To Unsubscribe: |
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Re: Still lurking
In a message dated 6/17/99 0:51:30 AM EST, rhj-rbj@... writes:
<< By all means have some other threads going afterall I want to know about guideways rods ballscrews and etc to decide what to use. Any recommendations for starters (routing sheet metals brass, aluminium and plastics abs,acrylics and styrene mostly for model components in 1:72 and 1:24 scales). Keep up the terrific work everyone. >> I like the Bishop Wisecarver "Dual V" grooved bearings running on 1/4" diameter hardened rod. If you route or saw a groove just over 1/8" deep and just under 1/4" wide in heavy aluminum bar or rectangular tube you can press the rod into the aluminum. I've made several sets of linear bearings this way now and it works quite nicely.. Jon Croad jonty50@... |
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Linux for Beginners
Bob Bachman
I have been struggling to learn enough Linux to setup EMC. This is not a
learning curve - more like a long uphill climb!! I have installed RH 5.2 on a dedicated machine but don't seem to be able to get an isp connection to work. Need the connection to download RTLinux and EMC. Also don't have a clue of how to install patches, compiling, etc. The quest continues. I ran across a linux version called DRAGONLINUX which can be installed on a DOS or Windows machine and only takes ~20mg of disk space. I'm certain it won't run EMC but it may help to learn the basics of running linux. The url is: Take a look. It may be something to putter with until you make a commitment to a dedicated linux box. Don't split the list - I don't understand most of what I read - but I read it anyway! My goal is to retrofit a bp clone cnc I have that is equipped with servos, amps, and linear scales, but is missing the control console. Bob |
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Re: Digest Number 56
Fox, Dan
Actually, I subbed to the EMC list over at nist.gov about a week before this
one took off. There's really no activity on that one to speak of; just a message every other day or so. I gotta ask an ugly question: Does Uncle Sugar have 2 FTE's or thereabouts cranking on an open-architecture CNC software system/product just so that 3 dozen galoots can have lots of fun in their garages? From what I can tell, there's 2-maybe-3 of us that are using EMC to make a profit. The NIST site mentions some GM involvement, and it does seem reasonable to think that this stuff would enhance American competitiveness etc., but ......? What does this EMC project do that makes it worth $1/4M/yr +/- to you and me? Enquiring minds want to know. --dan fox, who meant the question in the spirit of open inquiry but is sending his best asbestos suit out to be cleaned in the expectation of needing it real soon anyways Message: 13 Date: Wed, 16 Jun 1999 23:58:24 -0700 From: garfield@... (Gar Willis) Subject: Re: List question On Thu, 17 Jun 1999 00:37:52 -0600, "Tim Goldstein" <timg@...> wrote: Actually, Fred Proctor (the honcho that is in charge of EMC over at theGood heavens, now WHY would he do a thing like that?? Oh well, I guess it works both ways, eh? But IF that's the case, that's perhaps mutha naicha's way of suggesting that the focus of a purely EMC list is sub-optimally narrow? But geez, how can that be?; EMC alone is no smallish puppy, in itself. Guess I dunno. It's a problem similar to evolution maybe, that shows just how much diversity or focus is the best balance. A successful organism is a flexible one. Heh. Gar |
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newbie question
Fox, Dan
Hello, All!
Boy, I've never been on a list before where the lurkers got so much attention! Makes me feel wanted. :-) I haven't contributed because I don't have a whole lot to say as yet. I'd love to do some of this stuff, but I have so many other things in the queue ahead of it that I'll be happy if I get to it before retirement. :-) To keep my metalworking jones fed, I'm working my way through the Gingery series. (See the Lindsay Books website) This might qualify for the eventual FAQ, except I've never seen it addressed. What in the heck is so great about ball screws, that make them worth so much? Why are they so much better than Acme or regular, triangular-profile screw threads? Do they "work" differently from other threaded screws? And are there some kind of inner "works" to a ball nut (is that a proper term?)? Thanks in advance - --dan fox |
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Re: List question
Dan Mauch
see www.jrkerr.com
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It is a programmable controller chip call the PIC servo that does the intelligence for a low cost servo system. Dan -----Original Message-----
From: TADGUNINC@... m <TADGUNINC@...> To: CAD_CAM_EDM_DRO@... <CAD_CAM_EDM_DRO@...> Date: Thursday, June 17, 1999 6:40 AM Subject: Re: [CAD_CAM_EDM_DRO] List question From: TADGUNINC@...discussion of shop built systems in the above catagories. To Unsubscribe: |
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Re: Still lurking
Tim Goldstein
I put all of the links you have collected on a web page at
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I have also added a link from my main machining page to this new page. Tim [Denver, CO] ----- Original Message -----
From: <TADGUNINC@...> To: <CAD_CAM_EDM_DRO@...> Sent: Thursday, June 17, 1999 7:48 AM Subject: Re: [CAD_CAM_EDM_DRO] Still lurking From: TADGUNINC@...but here are a bunch I've got so far...(Thay're named so I know what theymean, but if you see a subject that sounds interesting click on it. Also Iare very helpful!)supplier san diego motionCorporation manufacturer of bearings and related precision productsgingers pagecodes</A> <A href=">more cad manufactureres</A>Machinery Corp. Inventory Price Listdiscussion of shop built systems in the above catagories. To Unsubscribe: |
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Re: bills thoughts and comments.
Leslie Watts
Well, I guess it's time for me to delurk. This is my first post to
the list. I am in the final assembly stage of a 5'x5'x2' gantry mill of my own design. This 2500 lb machine throws a 750 lb moving gantry and in most places has a design structural stiffness of 100 lb/.001". The intended control system is LM628 based (Tech80 5638). I have written c control programs for this many times in the past and it has worked ok. Motor update is 250 microseconds and trajectory commands can be sent at 1 khz if you pull some tricks. I am concerned with interrupt latency and the lack of feedforward in the LM628/pc though. The hard realtime capability of rtlinux EMC looks very appealing as does the first and second order feedforward algorithm. The high feedrates and and low following error requirements I have demand a high performance control. Buying an expensive manufactured control is not an option. I'm not a linux or unix guy but this group has me about to take the plunge. (big mistake? :^) ) It looks like this list is going to be a major resource for me if I decide to try EMC. Mabye I can share some of the problem solutions I have found if others are interested and we can all learn something in one diversified list. Some of the problems I have been working on are: - making 7' machine ways to .001" with only a level, 12x18 surface plate, and hand angle grinder - Welded tube space frame design using finite element analysis - active and passive structural damping - designing and building preloaded ball screw support bearings - Surplus sources for linear motion components (Chicago area) My project is for small side business rather than hobby but I think we might share the need to make cnc machines on a shoestring budget. Leslie M. Watts ITW Advanced Technology Group (847)657-4559 |
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Re: List question
Dan Mauch
The pic handles the encoders and had the PID filter. You need the PIC step
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with the servo board and the rs serial board. You need to d/l the setup info via a serial port to set the PID filter and the other parameters. Then you can switch to the pic step and run your dos based parallel port programs from there. I experimented with the PIC Servo and found that under serial operations it was blazing fast. Under the pic step is was incredibly slow where I was unable to get 250 RPMS out oif it. But I see that he is coming out with a rate multiplier which should speed it up significantly. I was going to design a servo system around the pic servo chip because it was so low cost. JRKerr even gave me the gerbers but the top layer gerber file was corrupted. For some strange reason he would not send me another copy of the top layer gerbers. I also don't have the time to reverse design the top layer. Other wise I could make a low cost servo system kit available . -----Original Message-----
From: Tim Goldstein <timg@...> To: CAD_CAM_EDM_DRO@... <CAD_CAM_EDM_DRO@...> Date: Wednesday, June 16, 1999 9:04 PM Subject: Re: [CAD_CAM_EDM_DRO] List question From: "Tim Goldstein" <timg@...>to use for your servo motors?boards discussion of shop built systems in the above catagories.from www.jrkerr.com that I am intending to use to move my table. To Unsubscribe: |
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Re: What would we read????
In a message dated 6/16/99 10:29:46 PM Pacific Daylight Time,
mfraser@... writes: Right now if we split the list and everybody continued to lurk on other subjects, what postings would we have to read?????? The EMC/Lunex thread is within our subject headings, the vacuum forming is not, but I want to encourage lurkers to speak up, and will endure some noise now to get more people posting. As more threads on the list topics are going then we can discourage the "noise". It is my humble opinion that most are not too unhappy, they are still subscribed, and I assume reading the postings, I will always encourage those that want a different thread going to speak up, and get it started. Control from this seat is going to be as minimal as possible. bill List Manager (Whose EE dates to '68, when they STILL taught us vaccuum tubes....) And my technician level, and 2nd class FCC goes back to 56....... grin(old Fart) |
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Re: List question
Dan Mauch
You may run into a problem using the pic servo stuff with a step and
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direction software. They have the pic step but it executes rather slowly even on a 486-33 whereas on the serial port it screams. You may also run into a problem with having enough power. You may need external amps. Dan -----Original Message-----
From: Andy Olney <aolney@...> To: CAD_CAM_EDM_DRO@... <CAD_CAM_EDM_DRO@...> Date: Wednesday, June 16, 1999 8:00 PM Subject: Re: [CAD_CAM_EDM_DRO] List question From: "Andy Olney" <aolney@...>discussion of shop built systems in the above catagories. To Unsubscribe: |
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Re: programs to write G-code
James Eckman
From: Jon Elson <jmelson@...>They were there this time, I'll take a look at them this weekend. Thanks! Jim |
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Re: DYNA 2400
Dan Mauch
Yes I have one. They have are a really nice machine , heavy duty and about the best desktop mill I have seen. My dyna runs but it uses conversational G code. I am working on a way to remove their electronics and add mine. Basically, I want to take their drivers, remove the MCU and replace it with a modern translator.
If you have a chance to pick up one of these machines for under $400 then do so. Dan A few months ago I had a chance to bid on a bench-top CNC machine, the Dyna Myte 2400c, sold by Dyna Mechtronics of Sunnyvale, CA. Although I ended up not bidding on this machine, it seemed like a much better package than all the Sherline conversions I had seen advertised. And it was a rather expensive machine if you bought one new. However, this machine has been out of production for 7 years and there is little factory support available. Is anybody familiar with this machine or the larger machines Dyna Mechtronics sells. I still wonder if I made a mistake not bidding on this machine. One of the problems with this group is that a few of you guys don't appear to get any sleep; this is an incredibly active discussion group. Even a lurker has a hard time just keeping up with the postings. But please keep in mind that some of the audience to these discussions are not up to speed on this subject. Let the members be responsible for their own editing of the list's threads. Regards, Stephen Barmash Rockville, MD |
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Re: List question
Fred Proctor
There is an EMC mailing list proper that I set up a few months ago to
alert EMC users of new releases, etc. To subscribe to this, send mail to: listproc@... with subscribe emc in the body of the message. To unsubscribe, do the same, with "unsubscribe emc" instead. The list itself is "emc@...". Anyone can post; only subscribers will get the postings. The problem with emc@... is that you already need to know about the EMC to benefit from it. That's why the EMC postings started popping up on the CAD_CAM_EDM_DRO mail list. I was surprised at the amount of EMC postings, which dwarf those on the emc@... list. Of course, if you aren't interested in the EMC, it's a pain to have to hop through all the related messages. One way to reduce traffic on this list is for EMC users to post most of the discussion to the emc@... list, especially if it's something that's not likely to elicit new interest from anyone on the CAD/CAM list. I myself sort email by subject, and then trash anything in a subject I don't have the time to read. You can also filter messages by subject, so if [CAD_CAM_EDM_DRO] and EMC appear in the subject line, you can trash it or move it to a folder that you may only read and trash periodically. --Fred |
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bills thoughts and comments.
The following is the invitation sent when you were asked to subscribe:
Hello, Welcome to the list. Please take a moment to review this message. This list is for discussion of CAD_CAM_EDM_DRO. The list is aimed at the construction and use of this equipment in a Home Shop Machinist environment. I would hope that the discussion will consist of Links, sources, progress reports, and things of this nature. It is not aimed at the commercial professional systems, and there users. However there comments will be welcome with regard to our projected uses of the systems. The list is a direct result of the discussions on the above subject at NAMES, 1999. Hopping that it helps all of us interested in this phase of our hobby. I feel that all postings should be done the same fashion as in the Modeleng-list, with all attachments sent direct to whoever asks for them, rather than posting to the entire group. I set the list up for over 17, due to the safety aspects of the electric's, and mechanic's involved. The list is unmoderated and hope that we can keep it that way. Any comments or suggestions will be greatly appreciated. Looking forward to sharing information with all. Bill To unsubscribe from this list, go to the ONELIST web site, at www.onelist.com, and select the User Center link from the menu bar on the left. This menu will also let you change your subscription between digest and normal mode. Thanks, Bill The List Owner I feel that the list is doing what it set out to do, I have not felt the need to split the list, as I think that most of the postings have been within the concept of the list, Helping all of us in the shop, on the list subjects. To get more on the subjects you are interested in, you must help to push them and get the threads you want started, and you must also help feed and nurture them, if you don't see what you want, then bring up the subject. Because this is an unmoderated list you have more freedom in what you post, hopefully within the constraints of the subject of the list. If the noise gets excessive on a subject, then we will address toning it down, steam engines etc. If anyone disagrees with me, I would encourage them to open a dialog on the subject. Also anyone is free to start a list on ONELINE if they so desire. We have 203 on the list today, and only about 20 or so posting, so there are a lot out there that are lurking, and I would ask them to start threads that they are interested in, if there needs are not being met with the current threads. These are my thoughts as of now, and you are encouraged to accept, or oppose them. bill List Manager PS, I do understand the desire of some to split the list subjects. |
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Re: List question
Pete Jarman
As a lurker I would say keep the list as one. I have a home workshop with a
Taiwanese mill/drill which I am slowly improving as time allows. I also have a cupboard with some steppers and driver boxes which I rescued from the scrap bin about 10 years ago and one of these days I will have enough of my other projects out of the way to start fitting the steppers to the mill drill and thinking about a control system. Till then I'm lurking and watching developments so that when the time does come to start I will be some way up the learning curve. Pete Jarman IMLEC 99 at Northampton North of Bedford, England 3-4th July 1999 |
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