Re: Digest Number 220

If the incoder is Mounted to the motor you will be able to turn up the
gain further before the system starts to oscillate. Any springiness
between the motor and the encoder will introduce a phase lag that is bad.

CAD_CAM_EDM_DRO@onelist.com wrote:

> > Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the discussion of shop built systems in the above catagories.
> To Unsubscribe, read archives, change to or from digest.
> Go to: http://www.onelist.com/isregistered.cgi
> Log on, and you will go to Member Center, and you can make changes there.
> For the FAQ, go to http://www.ktmarketing.com/faq.html
> bill,
> List Manager
> ------------------------------------------------------------------------
>
> There are 25 messages in this issue.
>
> Topics in today's digest:
>
> 1. Re: EMC-head
> From: batwings@...
> 2. Re: edm
> From: batwings@...
> 3. Re: These servo motors worth a darn?
> From: batwings@...
> 4. Re: Model Engineers are here
> From: "Marshall Pharoah" <pharoahm@...>
> 5. Re: Re: What do we want?
> From: "Marshall Pharoah" <pharoahm@...>
> 6. Frustrated !
> From: "Arne Chr. Jorgensen" <instel@...>
> 7. Re: Model Engineers are here
> From: Bertho Boman <boman@...>
> 8. Re: Model Engineers are here
> From: Jon Anderson <janders@...>
> 9. Re: These servo motors worth a darn?
> From: Jon Anderson <janders@...>
> 10. Re: Model Engineers are here
> From: batwings@...
> 11. Re: These servo motors worth a darn?
> From: batwings@...
> 12. Re: These servo motors worth a darn?
> From: Jon Anderson <janders@...>
> 13. Re: These servo motors worth a darn?
> From: stratton@...
> 14. Re: These servo motors worth a darn?
> From: Jon Anderson <janders@...>
> 15. Re: These servo motors worth a darn?
> From: "Marshall Pharoah" <pharoahm@...>
> 16. Re: These servo motors worth a darn?
> From: stratton@...
> 17. Re: These servo motors worth a darn?
> From: "Marshall Pharoah" <pharoahm@...>
> 18. Re: What do we want?
> From: "Ian Wright" <Ian@...>
> 19. Re: Re: What do we want?
> From: "Ian Wright" <Ian@...>
> 20. Re: Re: What do we want?
> From: "Ian Wright" <Ian@...>
> 21. Re: What do we want?
> From: Andrew Werby <drewid@...>
> 22. Re: These servo motors worth a darn?
> From: stratton@...
> 23. More Software
> From: "Arne Chr. Jorgensen" <instel@...>
> 24. Re: Re: What do we want?
> From: stratton@...
> 25. Rhino and CAM
> From: Andrew Werby <drewid@...>
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 1
> Date: Tue, 19 Oct 1999 18:50:09
> From: batwings@...
> Subject: Re: EMC-head
>
> At 08:51 PM 10/19/99 -0500, you wrote:
> >Hoyt,
> >I saw your comments on alt.machines.cnc tonight. I'm one of the lunatics
> >who likes the pain of installing Linux/EMC , but I'm making thousands of
> >dollars in the process.
>
> That's very nice. And you're being polite too! Nothing wrong with being an
> emc head, just to clear that point up. How are you making so much money?
>
> >We (the EMC cult members) are addicted to the free updates and good quality
> >software ; )
>
> I can appreciate that. Whatever floats your boat. I didn't mean for my
> opinions to start a war in here, but tell me, how do you avoid it?
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 2
> Date: Tue, 19 Oct 1999 18:50:34
> From: batwings@...
> Subject: Re: edm
>
> At 10:52 PM 10/19/99 -0500, you wrote:
> >GASP! DON'T look at that page! This guy is NUTS! He has hooked
> >directly from the power mains to his workpiece and electrode, with a few
> >lightbulbs and a rectifier diode in series! This is so dangerous, I just
> can't
> >believe he really did this. (Maybe it is a troll, or he's trying to kill
> us!)
>
> It sez so right on the site that this is not very safe, and it gives
> recomendations for making it safer. Believe me I wouldn't want anyone
> killed, even my two fave trolls. I only wanted to show how simple it is in
> principle.
>
> >I'm leaving the above URL unobliterated so that you can see what NOT to do.
>
> A much more positive thing to do is provide advice on how it should be done
> instead, no? Maybe you can describe your home-built edm? I haven't tried
> making anything toward that purpose yet but do have projects in mind.
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 3
> Date: Tue, 19 Oct 1999 18:51:50
> From: batwings@...
> Subject: Re: These servo motors worth a darn?
>
> At 10:08 PM 10/19/99 -0700, you wrote:
> > Can I put the encoders on the end of the screws or
> >would that introduce some sort of servo error?
>
> That should be the most accurate way to use them; connected directly to
> screws the only errors you'll get would be in screws themselves.
>
> I've seen comments on belts being subject to error. Many or most 'real'
> machine tools use a timing belt drive to the screws and that doesn't seem
> to be a problem. The precision of the belt follows the molds and the molds
> can be made to very close tolerances. You do need to have a tensioner
> arrangement; I just hang a ball bng on the mount for the motor and let it
> impinge the backside of belt. By using a bng with a bigger bore than the
> fastener and with two large OD washers to span the bore, you can make it
> adjust very simply, IE by pushing it by hand onto belt and then clamping
> the fastener. Works for me.
>
> Best wishes,
>
> Hoyt McKagen
>
> Belfab CNC - http://www.freeyellow.com/members/belfab/belfab.html
> Best MC Repair - http://www.freeyellow.com/members/batwings/best.html
> Camping/Caving - http://www.freeyellow.com/members/batwings/caving.html
> I'm ordinarily hairy but I sing like a canary
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 4
> Date: Wed, 20 Oct 1999 08:45:32 -0400
> From: "Marshall Pharoah" <pharoahm@...>
> Subject: Re: Model Engineers are here
>
> OK. You can add me to the list of Model Engineers, I guess.
> My interest right now is stationary steam. I also end up creating odd parts
> for
> ancient farm machinery.
>
> I subscribed to this list when it started because the homegrown DRO was
> exactly what I was looking for. Now you all have me thinking I might
> want to replace my mini mill with a large machine (actually, I've wanted to
> do that for years)
> with some form of controller (that's the new part).
>
> Marshall Pharoah
> Software Engineer
> Adirondac Software
> PIC/6805/6811/68000
> Asm/C/C++
>
> -----Original Message-----
> From: Paul Devey <pdevey@...>
> To: CAD_CAM_EDM_DRO@onelist.com <CAD_CAM_EDM_DRO@onelist.com>
> Date: Tuesday, October 19, 1999 11:04 PM
> Subject: Re: [CAD_CAM_EDM_DRO] Model Engineers are here
>
> >From: "Paul Devey" <pdevey@...>
> >
> >Hi Ian,
> >
> >In understand what you are saying. Their are a few companies here in North
> >America that are servicing the Model Engineer market. It still costs a few
> >thousand C$ to implement. Dan Mauch does provide a low cost solution to the
> >DIY types.
> >
> >From my own experience I see the Model Engineer having some large steps to
> >overcome in getting their systems running:
> >
> >Learning a CAD system;
> >Familiarising themselves with gCode;
> >Learning to setup their machines for program execution (setups are not
> >entirely the same for CNC as they are for a manual system); and
> >Becomming comfortable with the CAM portion of the equation.
> >
> >I think some regular contributers are MEs but have not come out of the
> >closet.
> >
> >Paul
> >-----Original Message-----
> >From: Ian Wright <Ian@...>
> >To: CAD_CAM_EDM_DRO@onelist.com <CAD_CAM_EDM_DRO@onelist.com>
> >Date: Tuesday, October 19, 1999 7:20 PM
> >Subject: Re: [CAD_CAM_EDM_DRO] Model Engineers are here
> >
> >
> >>From: "Ian Wright" <Ian@...>
> >>
> >>Hi Paul,
> >>
> >>I realised that there are a few MEs on the list but they tend to be a bit
> >>reticent and I wondered if this is because they feel overpowered by the
> >>professionals who ooze experience. The point I was trying to make -
> >probably
> >>badly, is that there is a 'market' for good but inexpensive software and
> >>electronics. Many of the MEs I know would, like me, be unable to persuade
> >>the keeper of the domestic purse strings, of the need to expend hundreds
> of
> >>pounds (or dollars) on a piece of software which, in an essentially hobby
> >>situation, is unlikely to ever repay its cost and, more importantly, is of
> >>no direct benefit to her! Neverthless, these same people would love to try
> >>their hands at computerising equipment they already have or could make and
> >>would, with the lateral thought processes which seem to afflict most MEs,
> >>soon be able to inject a lot of useful ideas and tips into the forum. This
> >>is where the inevitable 'them and us' situation of professionals who can
> >>repay the cost of a suite of software on one job and the penniless but
> very
> >>enthusiastic HSM causes difficulties in understanding. Fortunately, some
> >>software houses are now realising this situation exists and are making
> >>programs available free or at very reduced costs for 'private,
> >>non-commercial users' but this concept doesn't yet seem to have percolated
> >>into the realms of the types of program in which we are interested and the
> >>software producers don't seem to realise that, if they allow users to
> >become
> >>'addicted' to their programs, they are likely to have a regular future
> >>income from purchases of updates which may make up for the initial lost
> >>income.
> >>
> >>Ian
> >>--
> >>Ian W. Wright
> >>Sheffield UK
> >>
> >>
> >>----- Original Message -----
> >>From: Paul Devey <pdevey@...>
> >>To: <CAD_CAM_EDM_DRO@onelist.com>
> >>Sent: 19 October 1999 21:19
> >>Subject: [CAD_CAM_EDM_DRO] Model Engineers are here
> >>
> >>
> >>> From: "Paul Devey" <pdevey@...>
> >>>
> >>> Ian,
> >>>
> >>> Their are some model engineers on this list. Maybe we are a bit quite.
> It
> >>> takes some effort to juggle carreer, family and workshop.
> >>>
> >>> I am working towards producing tangable products with a CNC lathe and
> >>mill.
> >>> I am surprised at the efforts that are involved. I am finding that their
> >>is
> >>> alot to learn for the casual player. My hats off to the professionals.
> >>>
> >>> Paul Devey
> >>>
> >>>
> >>> -----Original Message-----
> >>> From: Ian Wright <Ian@...>
> >>> To: CAD_CAM_EDM_DRO@onelist.com <CAD_CAM_EDM_DRO@onelist.com>
> >>> Date: Tuesday, October 19, 1999 2:22 PM
> >>> Subject: Re: [CAD_CAM_EDM_DRO] What do we want?
> >>>
> >>>
> >>> >From: "Ian Wright" <Ian@...>
> >>> >
> >>> >Hi gang,
> >>> >
> >>> >The one thing we are desperately missing at the moment is a Linux based
> >>> >program to produce the g-code files from a drawing. We have the machine
> >>> >control in EMC and we have one or two potentially useful CAD programs
> >>(I'm
> >>> >playing with Varkon at the moment and, with perseverance I reckon I
> >>should
> >>> >have mastered it by the next millennium!!! ;o) in the meantime, there
> >are
> >>> >others well under way in development and, for anyone who gets really
> >>> >desperate, there are commercial programs which are very comprehensive
> >>but,
> >>> >it seems to me, we are still dependant on Windows based conversion
> >>> programs.
> >>> >As I am retired and thus quite cash-limited I would have difficulty
> >>> >justifying the cost of many of the commercial programs and therefore
> see
> >>> >linux and GPL programs as an ideal way forward. Any time penalties in
> >>> >swapping between applications are of little consequence to me as the
> one
> >>> >thing I have in plenty now is time! I'm surprised that we have not, so
> >>far,
> >>> >attracted many of the model engineering fraternity and wonder if this
> is
> >>> due
> >>> >to the high cost of commercial programs - if so it is a shame as people
> >>of
> >>> >that ilk often have a wealth of very useful information and expertise
> >>which
> >>> >they are only too willing to share.
> >>> >
> >>> >Ian
> >>> >--
> >>> >Ian W. Wright
> >>> >Sheffield UK
> >>> >
> >>> >
> >>> >----- Original Message -----
> >>> >From: Bertho Boman <boman@...>
> >>> >>
> >>> >> Any suggestions for converting programs?
> >>> >>
> >>> >> Any suggestions for plugins in AutoCad?
> >>> >
> >>> >>Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the
> >>> discussion of shop built systems in the above catagories.
> >>> >To Unsubscribe, read archives, change to or from digest.
> >>> >Go to: http://www.onelist.com/isregistered.cgi
> >>> >Log on, and you will go to Member Center, and you can make changes
> >there.
> >>> >For the FAQ, go to http://www.ktmarketing.com/faq.html
> >>> >bill,
> >>> >List Manager
> >>>
> >>> > Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the
> >>discussion of shop built systems in the above catagories.
> >>> To Unsubscribe, read archives, change to or from digest.
> >>> Go to: http://www.onelist.com/isregistered.cgi
> >>> Log on, and you will go to Member Center, and you can make changes
> there.
> >>> For the FAQ, go to http://www.ktmarketing.com/faq.html
> >>> bill,
> >>> List Manager
> >>>
> >>
> >>>Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the
> >discussion of shop built systems in the above catagories.
> >>To Unsubscribe, read archives, change to or from digest.
> >>Go to: http://www.onelist.com/isregistered.cgi
> >>Log on, and you will go to Member Center, and you can make changes there.
> >>For the FAQ, go to http://www.ktmarketing.com/faq.html
> >>bill,
> >>List Manager
> >
> >>Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the
> discussion of shop built systems in the above catagories.
> >To Unsubscribe, read archives, change to or from digest.
> >Go to: http://www.onelist.com/isregistered.cgi
> >Log on, and you will go to Member Center, and you can make changes there.
> >For the FAQ, go to http://www.ktmarketing.com/faq.html
> >bill,
> >List Manager
> >
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 5
> Date: Wed, 20 Oct 1999 08:46:55 -0400
> From: "Marshall Pharoah" <pharoahm@...>
> Subject: Re: Re: What do we want?
>
> I have been collecting links for a short while. I am just starting to
> organize them. I could make this available, probably next week some time.
>
> Marshall Pharoah
> Software Engineer
> Adirondac Software
> PIC/6805/6811/68000
> Asm/C/C++
>
> -----Original Message-----
> From: Bertho Boman <boman@...>
> To: CAD_CAM_EDM_DRO@onelist.com <CAD_CAM_EDM_DRO@onelist.com>
> Date: Tuesday, October 19, 1999 11:42 PM
> Subject: [CAD_CAM_EDM_DRO] Re: What do we want?
>
> >From: Bertho Boman <boman@...>
> >
> >Thanks Andrew for your detailed info.
> >
> >Hopefully, it is collected and eventually will go into a FAQ. It would be
> great if there was a mini-listing of different
> >software and what they do. As new ones are found, they could be added to
> the listing.
> >Bertho
> >
> >>Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the
> discussion of shop built systems in the above catagories.
> >To Unsubscribe, read archives, change to or from digest.
> >Go to: http://www.onelist.com/isregistered.cgi
> >Log on, and you will go to Member Center, and you can make changes there.
> >For the FAQ, go to http://www.ktmarketing.com/faq.html
> >bill,
> >List Manager
> >
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 6
> Date: Wed, 20 Oct 1999 16:47:07 +0200
> From: "Arne Chr. Jorgensen" <instel@...>
> Subject: Frustrated !
>
> Hi folks,
>
> You are all come with interesting inputs, - the problem is for me to
> follow you. I don't know what has happen, but onelist seems to
> send mail at different hours than before. I am a bit out of sync.
> And I never received digest #217 at all. ( Had to look for it at the
> archives, and the printout cuts away a lot of what you have written,
> because onelist has used a wider margin. Then again when I don't
> have it in the mailbox, - even more complicated )
>
> I have prepared a new list for software topics, but have not made it
> official yet. ( and I am not sure if I should at all )
>
> CAD: There is 4-5 projects under Linux for this.
> CAM: We may define this differently.
>
> G-codes: There is no big problem to make such a program. It looks
> like there is enough people that could help out on the work.
> The big problem is to manage it, to form a constructive team, and
> define everything. This is what I am most concern about at the
> moment. The GPL stuff add to this, because the reward is "happy
> faces", and that is much more difficult to master, than just pay
> someone a salary.
>
> I did write a sort of automated package once, - and had to do all
> kind of tricks to make a background program, work on data from the
> geometric data base in AutoCad. I was a nightmare, but I got
> something working, and it would output data to the machine control.
>
> Because I gained some ideas, how things could work, - some of my
> comments may seem "out of the ordinary". But here is some of the
> root to why I did like Varkon, and other packages, that is made
> modular, and you have access to the data base. ( This was not
> written in order to sound smart, - just to explain why I sometimes
> raise strange questions )
>
> Bertho wrote:
>
> > It would be great if there was a mini-listing of different
> software and what they do.
> > As new ones are found, they could be added to the listing.
>
> YES !
>
> The thing is, we are not going to reinvent the wheel. But in order
> to sort out what we would like, what others have made available,
> - this would be very helpful.
>
> Several have already defined a lot of "how they" work, - and they
> have already split it up into "phases". This is making it easier
> to see how to define the tasks.
>
> I noticed a remark from Jon Elson: he had 18 years of ..... Good,
> I don't argue. But it is very clear that others tend to do strange
> things, and want to do them. They also have some weird machines,
> etc. Here is where I like the concept of something modular in a CAM
> application, but it may be too difficult. I don't know. And I
> also have something in the back of my mind: Many new things have
> come from people doing stuff - that none of the smart guys thought
> were possible. My point here is that some seems to hold back a bit,
> because they feel that they don't have the knowledge.
>
> I have never, and will never even think of what I write as a
> competition of who is smart. And no one should be afraid to raise
> any stupid question, or topic.
>
> If I am out of line here, then forgive me. I am a bit confused, -
> because I fell out of sync, and it is too much work to patch
> everything into place again.
>
> As a last remark: We will have nice applications to go along with
> what we like to do. It all takes a bit of time, but there is several
> groups that work on these things. But Bertho has come up with
> several good things, and the thing I quoted him on, is something I
> have tried to point out earlier. We are not up to date on what the
> Linux community is doing, - and some of what we look for, may
> already be there.
>
> //ARNE
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 7
> Date: Wed, 20 Oct 1999 09:44:02 -0400
> From: Bertho Boman <boman@...>
> Subject: Re: Model Engineers are here
>
> I am curious. I know what electronic, electric and mechanical engineers are. What is a Model Engineer? Is it actually a
> professional title or a person building small models?
> Bertho Boman
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 8
> Date: Wed, 20 Oct 1999 07:23:40 -0700
> From: Jon Anderson <janders@...>
> Subject: Re: Model Engineers are here
>
> Bertho Boman wrote:
>
> > What is a Model Engineer? Is it actually a
> > professional title or a person building small models?
>
> It's a collectively self-applied label. In it's strictest sense,
> someone buying kits, machining according to blueprints, and assembling
> an engine or model wouldn't qualify.
> The work of some model engineers however, truely rivals anything
> from the "official" engineering diciplines, and are often accomplishd by
> folks with no formal engineering background.
> An example would be the fellow that built a scale running model of a
> Roll Royce Merlin V-12, with no formal training as a machinist,
> engineer, or designer.
>
> Jon
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 9
> Date: Wed, 20 Oct 1999 07:30:46 -0700
> From: Jon Anderson <janders@...>
> Subject: Re: These servo motors worth a darn?
>
> batwings@... wrote:
>
> > That should be the most accurate way to use them; connected
> > directly to screws the only errors you'll get would be in screws
> > themselves.
>
> I'm not concerned with physical accuracy here. Surely having the encoder
> directly attached to the screw is optimimum for accurate measurement of
> what the screw is doing. What I am not sure of is if having the motor
> and the encoder separated by a timing belt might introduce any sort of
> servo error. If there is even the slightest wrapup or lag between the
> belt and screw (most noticable when accelerating a heavy load from a
> stop) will the controller see no motion for the given output and start
> ramping in more current than really required. This is a big difference
> between stepper and servo systems. The encoder tracks motor velocity as
> well as position.
>
> Jon
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 10
> Date: Tue, 19 Oct 1999 22:28:59
> From: batwings@...
> Subject: Re: Model Engineers are here
>
> >Bertho Boman wrote:
> >
> >> What is a Model Engineer? Is it actually a
> >> professional title or a person building small models?
>
> It's a real job description in some places. I was hired once as 'lab
> assistant/model maker' and I used manual machines to produce stuff for
> civil engineering soil testing. One of those proj was a rather big shear
> box, suitable for railroad track ballest. It stood 8' tall, 10' square, was
> boxed up with 10" I-beams and was driven by a 15 Hp hydraulic power supply.
> Developed 14 tons shear and 7 in vertical load, was fully instrumented and
> was controlled and had data taken by an HP scientific computer. I was
> responsible for 100% of specification, design, procuring and the entire
> build, setup and calibration. And that was with no formal training in engg
> or for that matter in shop practice. We had no CAD/CAM either, so a good
> bit of the design was sketches and out of head; try it, you'll like it.
> Later I was promoted to 'instrument maker', about the same thing as far as
> duties but a bit more $$$ and a bit more time spent sitting on ass.
>
> Best wishes,
>
> Hoyt McKagen
>
> Belfab CNC - http://www.freeyellow.com/members/belfab/belfab.html
> Best MC Repair - http://www.freeyellow.com/members/batwings/best.html
> Camping/Caving - http://www.freeyellow.com/members/batwings/caving.html
> I'm ordinarily hairy but I sing like a canary
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 11
> Date: Tue, 19 Oct 1999 22:34:16
> From: batwings@...
> Subject: Re: These servo motors worth a darn?
>
> At 07:30 AM 10/20/99 -0700, you wrote:
> >what the screw is doing. What I am not sure of is if having the motor
> >and the encoder separated by a timing belt might introduce any sort of
> >servo error. If there is even the slightest wrapup or lag between the
> >belt and screw (most noticable when accelerating a heavy load from a
> >stop)
>
> If your drive is designed for those loads to begin with it would not be a
> problem.
>
> I've used a Chevalier mill with belt drive and linear scales on the axes.
> Same difficulty arises in principle there. The machine never displayed any
> signs of being out of step between motor and motion. This is a very typical
> setup in modern machine tools. I don't think it would be so popular if it
> had that sort of error associated with it.
>
> Best wishes,
>
> Hoyt McKagen
>
> Belfab CNC - http://www.freeyellow.com/members/belfab/belfab.html
> Best MC Repair - http://www.freeyellow.com/members/batwings/best.html
> Camping/Caving - http://www.freeyellow.com/members/batwings/caving.html
> I'm ordinarily hairy but I sing like a canary
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 12
> Date: Wed, 20 Oct 1999 07:52:07 -0700
> From: Jon Anderson <janders@...>
> Subject: Re: These servo motors worth a darn?
>
> batwings@... wrote:
>
> > I've used a Chevalier mill with belt drive and linear scales on
> > the axes.
>
> This machine has some sort of feedback from the motor. Has to (unless
> it's a stepper system). The purpose of the linear encoder is to track
> actual postiion regardless of backlash or lead screw pitch error.
> While I understand drives and motors should matched to the loads, my
> concern has nothing to do with that issue. My question has to do with
> introducing a potentially flexible link between the motor and the
> encoder that is tracking the motor. Yes, I understand modern belts flex
> very little, but there is some. Does this pose a problem, is the
> question.
>
> Jon
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 13
> Date: Wed, 20 Oct 1999 11:00:52 -0400 (EDT)
> From: stratton@...
> Subject: Re: These servo motors worth a darn?
>
> > This machine has some sort of feedback from the motor. Has to (unless
> > it's a stepper system). The purpose of the linear encoder is to track
> > actual postiion regardless of backlash or lead screw pitch error.
> > While I understand drives and motors should matched to the loads, my
> > concern has nothing to do with that issue. My question has to do with
> > introducing a potentially flexible link between the motor and the
> > encoder that is tracking the motor. Yes, I understand modern belts flex
> > very little, but there is some. Does this pose a problem, is the
> > question.
>
> Well it should be possible to somehow design a servo system that would
> look at two encoders, one on the screw (or a linear) and one on the
> motor. Or put an encoder on the screw and the tachometer (which is
> often seperate rather than numerically dervied from the encoder) on
> the motor.
>
> Chris
>
> --
> Christopher C. Stratton, stratton@...
> Engineer, Instrument Maker & Horn Player
> (978)538-5179 work, (617)492-3358 home
> 30 Griswold Street Cambridge, MA 02138
> http://www.mdc.net/~stratton
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 14
> Date: Wed, 20 Oct 1999 08:25:03 -0700
> From: Jon Anderson <janders@...>
> Subject: Re: These servo motors worth a darn?
>
> stratton@... wrote:
>
> > Well it should be possible to somehow design a servo system that
> > would look at two encoders, one on the screw (or a linear) and
> > one on the motor.
>
> Chris,
>
> I know there are boards available that can track both inputs, but I'm
> working at the low end with scrounged stuff.
> The motors I have, should they even prove up to the task, have encoders
> that don't have the resolution I want. I've been looking around for
> encoders, and it seems they all would be easier to mount to a plate and
> couple to the screw. Attaching them directly to the motors would be more
> work.
>
> Jon
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 15
> Date: Wed, 20 Oct 1999 12:53:40 -0400
> From: "Marshall Pharoah" <pharoahm@...>
> Subject: Re: These servo motors worth a darn?
>
> I've been looking at building the DRO using Digital Research mylar strips,
> with an eye towards later on adding either steppers or servos. Am I
> heading down the wrong route?
>
> Marshall Pharoah
> Software Engineer
> Adirondac Software
> PIC/6805/6811/68000
> Asm/C/C++
>
> -----Original Message-----
> From: Jon Anderson <janders@...>
> To: CAD_CAM_EDM_DRO@onelist.com <CAD_CAM_EDM_DRO@onelist.com>
> Date: Wednesday, October 20, 1999 11:30 AM
> Subject: Re: [CAD_CAM_EDM_DRO] These servo motors worth a darn?
>
> >From: Jon Anderson <janders@...>
> >
> >stratton@... wrote:
> >
> >> Well it should be possible to somehow design a servo system that
> >> would look at two encoders, one on the screw (or a linear) and
> >> one on the motor.
> >
> >Chris,
> >
> >I know there are boards available that can track both inputs, but I'm
> >working at the low end with scrounged stuff.
> >The motors I have, should they even prove up to the task, have encoders
> >that don't have the resolution I want. I've been looking around for
> >encoders, and it seems they all would be easier to mount to a plate and
> >couple to the screw. Attaching them directly to the motors would be more
> >work.
> >
> >Jon
> >
> >>Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the
> discussion of shop built systems in the above catagories.
> >To Unsubscribe, read archives, change to or from digest.
> >Go to: http://www.onelist.com/isregistered.cgi
> >Log on, and you will go to Member Center, and you can make changes there.
> >For the FAQ, go to http://www.ktmarketing.com/faq.html
> >bill,
> >List Manager
> >
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 16
> Date: Wed, 20 Oct 1999 13:14:10 -0400 (EDT)
> From: stratton@...
> Subject: Re: These servo motors worth a darn?
>
> > From: "Marshall Pharoah" <pharoahm@...>
> >
> > I've been looking at building the DRO using Digital Research mylar strips,
> > with an eye towards later on adding either steppers or servos. Am I
> > heading down the wrong route?
>
> It may not be the most efficient road, but I wouldn't call it wrong.
> First, having the DRO itself is a big plus for computer 'assisted'
> machining. I've done things using the computer for guidance and my
> hands as the servos that would have required a tracer attachment to do
> otherwise.
>
> You may not be able to run a full closed-loop servo system using the
> linear encoders, however if supported by software they could provide a
> great 'missing step' detector for an otherwise open-loop stepper
> system. And even in a servo system with rotary encoders, I could see
> them being beneficial as a secondary confidence check. But again that
> requires software support.
>
> The biggest reason I think you should go ahead though is the
> experience you will gain by figuring out how to mount the scales, wire
> up the encoders, interface them to the computer, find or write
> software, etc. All of that should come in usefull when you go for
> full CNC.
>
> Chris
>
> PS - do you perhaps mean "US Digital" instead of "Digital Research"?
> The former manufacture mylar strips for use with HP reader heads, I'm
> not aware of the later being in the DRO business.
>
> --
> Christopher C. Stratton, stratton@...
> Engineer, Instrument Maker & Horn Player
> (978)538-5179 work, (617)492-3358 home
> 30 Griswold Street Cambridge, MA 02138
> http://www.mdc.net/~stratton
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 17
> Date: Wed, 20 Oct 1999 14:06:53 -0400
> From: "Marshall Pharoah" <pharoahm@...>
> Subject: Re: These servo motors worth a darn?
>
> Yup, that would be US Digital.
>
> I just trashed an old Digital Research computer. Must have been hanging on
> my mind.
>
> On the mylar strips, do I just go ahead and order a total number of inches,
> or does it need ot be pre-cut.
>
> When I mount it, should it be spring loaded at one end?
>
> Is there a certain amount of tension it should be under?
>
> Marshall Pharoah
> Software Engineer
> Adirondac Software
> PIC/6805/6811/68000
> Asm/C/C++
>
> -----Original Message-----
> From: stratton@... <stratton@...>
> To: CAD_CAM_EDM_DRO@onelist.com <CAD_CAM_EDM_DRO@onelist.com>
> Date: Wednesday, October 20, 1999 1:16 PM
> Subject: Re: [CAD_CAM_EDM_DRO] These servo motors worth a darn?
>
> >From: stratton@...
> >
> >> From: "Marshall Pharoah" <pharoahm@...>
> >>
> >> I've been looking at building the DRO using Digital Research mylar
> strips,
> >> with an eye towards later on adding either steppers or servos. Am I
> >> heading down the wrong route?
> >
> >It may not be the most efficient road, but I wouldn't call it wrong.
> >First, having the DRO itself is a big plus for computer 'assisted'
> >machining. I've done things using the computer for guidance and my
> >hands as the servos that would have required a tracer attachment to do
> >otherwise.
> >
> >You may not be able to run a full closed-loop servo system using the
> >linear encoders, however if supported by software they could provide a
> >great 'missing step' detector for an otherwise open-loop stepper
> >system. And even in a servo system with rotary encoders, I could see
> >them being beneficial as a secondary confidence check. But again that
> >requires software support.
> >
> >The biggest reason I think you should go ahead though is the
> >experience you will gain by figuring out how to mount the scales, wire
> >up the encoders, interface them to the computer, find or write
> >software, etc. All of that should come in usefull when you go for
> >full CNC.
> >
> >Chris
> >
> >PS - do you perhaps mean "US Digital" instead of "Digital Research"?
> >The former manufacture mylar strips for use with HP reader heads, I'm
> >not aware of the later being in the DRO business.
> >
> >--
> >Christopher C. Stratton, stratton@...
> >Engineer, Instrument Maker & Horn Player
> >(978)538-5179 work, (617)492-3358 home
> >30 Griswold Street Cambridge, MA 02138
> >http://www.mdc.net/~stratton
> >
> >>Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the
> discussion of shop built systems in the above catagories.
> >To Unsubscribe, read archives, change to or from digest.
> >Go to: http://www.onelist.com/isregistered.cgi
> >Log on, and you will go to Member Center, and you can make changes there.
> >For the FAQ, go to http://www.ktmarketing.com/faq.html
> >bill,
> >List Manager
> >
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 18
> Date: Wed, 20 Oct 1999 11:43:42 +0100
> From: "Ian Wright" <Ian@...>
> Subject: Re: What do we want?
>
> Robert,
>
> Look at FlashcutNC. It's a commercial program but they have a demo available
> which works all but saving files. However, you can get around this by doing
> the conversion and then copying and pasting the resulting g-code into a word
> processor / notepad and saving it from there. Works in Windows, don't think
> they have a linux version.
>
> Ian
> --
> Ian W. Wright
> Sheffield UK
>
> ----- Original Message -----
> From: Robert N Ash <esccmail@...>
> >
> > Does anyone have more insight on 2D or 3D DXF
> > conversion to G-code.
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 19
> Date: Wed, 20 Oct 1999 11:48:45 +0100
> From: "Ian Wright" <Ian@...>
> Subject: Re: Re: What do we want?
>
> Hi Lon,
>
> Don't you worry about twist in a helical coupling under load especially on
> direction changes etc.?
>
> Ian
> --
> Ian W. Wright
> Sheffield UK
>
> ----- Original Message -----
> From: Jon Elson <jmelson@...>
> > This is actually quite small, on typical sprockets with even 10 teeth or
> so.
> > The big problem is power-grade roller chain starts out with mediocre
> > range of pitch error, and it gets a LOT worse as the chain ages. One of
> the
> > components is eccentricity in the rollers. There is a precision grade of
> roller
> > chain, which would help. But, I won't use a toothed belt, gears or
> anything
> > between the encoder and the leadscrew - only a helical coupling.
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 20
> Date: Wed, 20 Oct 1999 11:34:08 +0100
> From: "Ian Wright" <Ian@...>
> Subject: Re: Re: What do we want?
>
> I tried to think this one out when I was designing my machine and I came to
> the conclusion that, if the toothed belt is wrapped around the pulleys to
> any significant degree - that is with more than 3 or 4 teeth in contact at
> any one time, then slight pitch irregularities will have no effect. What
> would be more significant would be the closeness of fit of the belt teeth
> into the pulley recesses. Unless you use (or make) pulleys with close to
> 100% match between tooth and recess size, there is the possibility of slip
> between belt and pulley which would give inaccuracy. You actually need to do
> quite close selection as there appear to be large variations in different
> products. When I was looking for an economical system to use I decided on a
> 5mm pitch belt and checked several possible belts and pulleys. I got a
> couple of industrial (very expensive) belts from engineering suppliers and a
> couple of different lawn mower drive belts, I als had two or three old belts
> out of photocopiers etc - about 7 in all. Only two of these were the same!
> All the others had different width teeth/spaces and their respective pulleys
> were designed for different amounts of freedom on the recesses. Predictably,
> the lawnmowers were the sloppiest fit on their pulleys although the belts
> seem to be made to quite close tolerances on pitch but I was surprised to
> find the amount of variation on the industrial and commercial belts. Prices
> for the small belts I bought ranged from 2.36UKP (lawnmower) to 10.87UKP
> (industrial). The cheaper belts also had reinforcing cords of some type of
> synthetic material whils the industrial ones have stainless steel wire
> reinforcement which is wound as a spiral and sticks out of the edges of the
> belt as sharp spikes! The worst case of pitch error would occur if one of
> the teeth on the belt was wider than the slots in the pulley when the belt
> would ride up and effectively follow a larger radius for the partial
> revolution whilst that tooth is in contact with the pulley.
>
> Ian
> --
> Ian W. Wright
> Sheffield UK
>
> > From: PTENGIN@...
> >
> >Cog belt drives do not
> > have this error to any significant degree and are used almost exclusively
> for
> > this type of drive. Think of a flat belt with smooth round pulleys and
> then
> > cut notches for projections cast onto the belt
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 21
> Date: Wed, 20 Oct 1999 11:22:37 +0100
> From: Andrew Werby <drewid@...>
> Subject: Re: What do we want?
>
> >Message: 2
> > Date: Tue, 19 Oct 1999 23:50:01 +0100
> > From: "Ian Wright" <Ian@...>
> >Subject: Re: Re: What do we want?
> >
> [Actually, I mis-spoke (or mis-wrote) The drive on my mill's screws isn't a
> steel roller-chain, like on a bicycle- it's a toothed rubber belt which
> engages a corrugated pulley. This would be closer to the "pure curve" you
> mention, but I'm not sure if they are accurate over long distances. It does
> seem fairly positive over the short (6" between centers) distance. Has
> anybody seen or heard of a router driven with one of these- not using it to
> drive a ball-screw, but actually attaching the sliding stage to one (or
> more) of these toothed rubber belts?]
>
> Andrew Werby
>
> >Hi Andrew,
> >
> >In theory, a chain drive should be less accurate than a cable as movement
> >round the sprockets is not continuous. That is, the links of the chain go
> >round the sprocket as a series of straight lines rather than a pure curve.
> >Whether the resulting (small) error is significant in your application would
> >have to be a part of your considerations.
> >
> >Ian
> >--
> >Ian W. Wright
> >Sheffield UK
> >
> >
> >----- Original Message -----
> >From: Andrew Werby <drewid@...>
> >I heard Shopbot, which originally used
> >> a cable drive, has discarded it in their later models in favor of a
> >> roller-chain and sprocket drive system. I was considering this myself, for
> >> the router I'm assembling from scratch. Has anybody tried it on any of
> >> their machines?
> >
>
> Andrew Werby - United Artworks
> Sculpture, Jewelry, and Other Art Stuff
> http://unitedartworks.com
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 22
> Date: Wed, 20 Oct 1999 14:29:53 -0400 (EDT)
> From: stratton@...
> Subject: Re: These servo motors worth a darn?
>
> > On the mylar strips, do I just go ahead and order a total number of inches,
> > or does it need ot be pre-cut.
>
> You can cut it, but their maximum length is someting like 34 inches.
> The price per inch is constant for all pieces over 7" so you might
> as well order the lengths you want.
>
> > When I mount it, should it be spring loaded at one end?
> >
> > Is there a certain amount of tension it should be under?
>
> Dan Mauch glued his (epoxy I think) to a strip of aluminum and put the
> whole thing including pushrod-driven read head inside a rectangular
> extruded tube. I clamped mine between two pieces of .5" Al U channel
> that form guide rails and mounted it in a relatively shielded location
> behind the lathe. The reader head is sticks up from below and is
> carried by a J shaped bracket. Dan's enclosed method is superior if
> you have the room for it - I didn't.
>
> Chris
>
> --
> Christopher C. Stratton, stratton@...
> Engineer, Instrument Maker & Horn Player
> (978)538-5179 work, (617)492-3358 home
> 30 Griswold Street Cambridge, MA 02138
> http://www.mdc.net/~stratton
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 23
> Date: Wed, 20 Oct 1999 21:26:10 +0200
> From: "Arne Chr. Jorgensen" <instel@...>
> Subject: More Software
>
> Hi folks,
>
> I don't remember quit what I wrote previously, ( hope I didn't say
> any thing stupid :) , but as you all know, there is zillions of
> links and stuff on the web, and I am sure that among those, we will
> find a lot of useful stuff. So before trying to code anything, - I
> think it would be worth the effort to look around. And as Bertho
> said, we should organize the stuff a bit. The thing is that there
> is so much, - and the map is changing everyday. We may follow in
> each others footstep, and just waste time on something others are
> familiar with already.
>
> I guess I am doing that now: I have just looked at BRL-CAD,
> something I guess some of you already have opinions about.
> What kind of output formats does it have ?
> Is it nice ?
>
> ( I wonder if one of the developers has written some stuff I had in
> school once upon a time )
>
> Then I found a NC/CNC/CAM package for Autocad. I have not unzipped
> the software yet.
> Papers on NC toolpath generation and modeling.
> Just to name a few items.
>
> ( I don't want to mess up everything, but some of us would like
> CAD/CAM under Linux and related stuff )
>
> //ARNE
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 24
> Date: Wed, 20 Oct 1999 14:38:32 -0400 (EDT)
> From: stratton@...
> Subject: Re: Re: What do we want?
>
> > [Actually, I mis-spoke (or mis-wrote) The drive on my mill's screws isn't a
> > steel roller-chain, like on a bicycle- it's a toothed rubber belt which
> > engages a corrugated pulley. This would be closer to the "pure curve" you
> > mention, but I'm not sure if they are accurate over long distances. It does
> > seem fairly positive over the short (6" between centers) distance. Has
> > anybody seen or heard of a router driven with one of these- not using it to
> > drive a ball-screw, but actually attaching the sliding stage to one (or
> > more) of these toothed rubber belts?]
>
> I dissasembled a wang dot matrix printer that had a carriage driven
> that way. Still kicking myself for throwing away the servo - saved it
> for many years, then tossed it only about a year before learning how I
> could have used it.
>
> Chris
>
> --
> Christopher C. Stratton, stratton@...
> Engineer, Instrument Maker & Horn Player
> (978)538-5179 work, (617)492-3358 home
> 30 Griswold Street Cambridge, MA 02138
> http://www.mdc.net/~stratton
>
> _______________________________________________________________________________
> _______________________________________________________________________________
>
> Message: 25
> Date: Wed, 20 Oct 1999 11:49:36 +0100
> From: Andrew Werby <drewid@...>
> Subject: Rhino and CAM
>
> On Mon, 18 Oct 1999 18:30:14 -0400, "Clint Bach"
> <clintbach@...> wrote:
>
> I dunno about the metric on "amount of conversion" but have you looked
> at Rhino3D as a modeling environment where you can "doodle", create a 3D
> solid model of your creation, and then output directly CAM-compatible
> G-code?
>
> [Sorry- Rhino's an excellent modeler, but it doesn't output g-code. The
> closest it comes is the STL format, which can be used for the basis of a
> conversion to g-code, (by another program, like DeskProto), or it can be
> used directly by some rapid prototyping machines.]
>
> Andrew Werby
>
> Andrew Werby - United Artworks
> Sculpture, Jewelry, and Other Art Stuff
> http://unitedartworks.com
>
> _______________________________________________________________________________
> _______________________________________________________________________________