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Matt Shaver wrote:

[There are other documents like the NCMS (National Center for Manufacturing
Sciences) Next Generation Controller Part programming Functional
Specification (RS274/NGC), which, unfortunately, only exist as paper
documents. This one is 127 pages and I have a Xerox which also has Tom
Kramer's handwritten notes in the margins regarding the inconsistencies in
the document. I'd scan it and html it if I had the time. I can't imagine how
long it would take to OCR it and then as slow as I type, we'll all be dead
before I could finish, plus, what do I do with Tom's handwritten notes?
Footnotes? Appendix?]

I have this document, too. I could scan it, but it would have to be published
as an image. There is so much henscratching all over it, no OCR could
read the original printed text (which is wrong in many places, hence the
henscratches).

Paraphrasing NCMS:

G09 Exact Stop (Non-Modal) Causes an exact stop before the next move begins.
G61 Exact Stop Mode (Modal) Same as G09, except it doesn't affect rapid
moves.
G64 Contouring Mode (Modal) Default mode where the next move begins when the
previous move has reached a position within the "tolerance band" specified by
the machine builder. (I wonder where this tolerance is in the EMC, and how to
change it?)

Unfortunately, they don't seem to work.

Right, I was pretty sure from some email with Fred that this was a permanently
active feature, right now. There is no 'tolerance'. The next move starts as
soon as the deceleration of the current move begins. Since the deceleration
is a linear ramp at a fixed rate, if you slow the feedrate, the decel begins closer
to the end point. So, if this is a problem, you can program or override the
feedrate at these points to prevent rounded corners (or crashes!) where it
matters.

Unfortunately, they don't seem to work. The reason for the blending in the
first place (as explained to me by Fred, and which I hope I remember
correctly) is that the heritage of the EMC is the robotics family, not the
machine tool control family. There are three variables involved in motion
control:

1. Desired Velocity (feed rate)
2. Maximum Acceleration Rate
3. Path Geometry

<snip>

The immediate problem with all this is that the stepper guys (and that will
be me soon as well) have acceleration limits low enough that they are getting
blending at machining feed rates. This could cause there to be radiuses where
none are expected! Either they will need to hop up the hardware to allow
faster acceleration (higher supply voltage Tim?), or G61 needs to work, or
you need a dwell between every move (the other alternative of limiting the
feed rate isn't a good answer).

Well, I see it on my fairly responsive servo system, especially when I have
some non-cutting moves above 45 IPM.

Jon

Tim Goldstein wrote:

I finally have made my first item using EMC!!!

I meant to say congratulations, and welcome to the (small) club
of us EMC users!

What are the scripts I should be looking at for the simulation version?
While it is not perfect it will be faster than going through a 500 line
program a bunch of times at a MAX_VELOCITY of 20 ipm!!!

There should be scripts with names like run.sim that include a motor
simulator instead of the real-time module that drives the physical
motors. But, Matt's fix sounds a lot easier (I didn't think of setting
the run pointer to the end)!

P.S. Don't you or Matt sleep?

Sure - I think he is a night owl like me. I do my sleeping in the
morning. I burn the midnight oil because it is the only time I
can get somthing done without interruptions.

Jon

Tim Goldstein wrote:

Jon,

Thanks for the write up on your mini EDM project.

I think I follow everything except for what you are using as an EDM
capacitor? What do you mean by a 6uf 250V paper?

There is a type of capacitor called a paper or oiled paper capacitor.
Many non-electrolytic caps of 250 V or more, and of large values,
are made this way. They have quite low series inductance, which
is the desired quality. A mylar or polypropylene film capacitor
would also work fine, but cost a lot more.

Jon

I got an e-mail from Dan Chamberlain and he was asking if EMC would work on
a system with 20 mb RAM? He is looking to put it on a laptop and that is the
memory he has in it. I did caution him that Linux is pretty particular about
hardware and that may keep him from using his laptop.

He also wanted to know if the stepper version supported 4 axis's? My guess
is no considering we only have pin out connections for 3 axis's. Does the
servo version support 4?


Tim
[Denver, CO]

Hello All,
Welcome to the new members. We have 189 members today.
I would like to encourage all members that are lurking to jump in and talk
about the topics of your choice. I am happy with the EMC/LINUX thread, but I
am also sure that there are other threads waiting in the wings, PLEASE all
jump in and post. (how else can I learn?) We all will get more from the list
as more people post there thoughts, questions, successes, failures and
desires to the list.

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bill anliker
list manager

Would it be possible for one of our more knowledgeable people on EMC/LINIX to
write up a short discourse from step one on how, where etc. to get this
system going.
1. Where to find the programs, and what to download.
2. How to install it in our computer, pitfalls.
3. A bit more basic information on how to get started for us raw recruits to
your war zone.
4. Help get more of us beginners into your world.

Thank you in advance,

bill
List manager

Message: 17

Date: Sun, 6 Jun 1999 02:42:39 -0400
From: "Matt Shaver" <mshaver@...>

More interpreter information is in the file:

ftp://ftp.isd.cme.nist.gov/pub/emc/emcsoft/RS274NGC_22.doc

I am about halfway through turning this document into html which will improve
its accessibility. The raw .doc file doesn't have the table of contents,
illustrations, tables, etc.

Looked at the raw DOC using Wordpad. Looking forward to seeing that in
HTML,
EMC looks great so far! At the bare minimum it will serve as a starter
for
so many variations! I'll have to check out the source code some more.

Jim Eckman

I have been in contact with them, too, about a 250 line/inch scale and they
said no dice. Does anybody know why not? Sure seems to me that this would be
a better unit than 200 or 360!

Thanks -

Mark

Sorry about that Guys. Must be old age.
Ray

I checked out your web site. You are doing some really interesting things.
I noticed that you are making printed circuit boards. I have been using the
Datak positive PC boards for years using a low cost vacccum IR exposure
system.
Until recently I was using Dancam to take the excellon drill files and I
have a program that optimizes and converts the excellon file to tool path
for Dancam. Alas, the tool path files are not compatible with G code
interpreters. How are you converting your artwork to drill your PC boards.
Dan

Dean
Its not that hard to do. Put in a new condenser. One of the easiest fixes.
While you are at it clean and adjust the points. In my meager lifetime I
have solved many problems that seem to be carb related by changing condenser
and adjust points. However, If you haven't ran the proper sized drill bit
through the passages especially the idle passage it just wont run for beans.
Ray
Auburn
Do you plan to be at the Roy show? I will be up in the tower again. Our
club has bought its own progressive sled but have rented the fancy one in
Oregon for this year.

Skimming through the documentation, I couldn't find this- how do you use
the home switches in the code? Maxnc uses a G61 switch sense command and
commercial CNCs use different proceedures.
What do you do to home the machine? My switches aren't hooked up yet, but I
would like to know before long.

Thanks,
Dan

From: "Tim Goldstein" <timg@...>
P.S. Don't you or Matt sleep?

No.

',)
zzz...zzz...zzz

From: Jon Elson <jmelson@...>
This is the blending of moves. It can be a problem when you make an X
move, then a Y move, as the Y move will start to ramp up when the X move
just begins to ramp down. But, for a string of short continuous moves

describing

a fluid curve, you need this, or the machine will absolutely CREEP. (My
antique AB suffered from this.)
Maybe we should ask Fred Proctor for some sort of switch (either in
the RS-274 program (G-code) or on the user interface) to turn this
on and off.

[There are other documents like the NCMS (National Center for Manufacturing
Sciences) Next Generation Controller Part programming Functional
Specification (RS274/NGC), which, unfortunately, only exist as paper
documents. This one is 127 pages and I have a Xerox which also has Tom
Kramer's handwritten notes in the margins regarding the inconsistencies in
the document. I'd scan it and html it if I had the time. I can't imagine how
long it would take to OCR it and then as slow as I type, we'll all be dead
before I could finish, plus, what do I do with Tom's handwritten notes?
Footnotes? Appendix?]

Paraphrasing NCMS:

G09 Exact Stop (Non-Modal) Causes an exact stop before the next move begins.
G61 Exact Stop Mode (Modal) Same as G09, except it doesn't affect rapid
moves.
G64 Contouring Mode (Modal) Default mode where the next move begins when the
previous move has reached a position within the "tolerance band" specified by
the machine builder. (I wonder where this tolerance is in the EMC, and how to
change it?)

Unfortunately, they don't seem to work. The reason for the blending in the
first place (as explained to me by Fred, and which I hope I remember
correctly) is that the heritage of the EMC is the robotics family, not the
machine tool control family. There are three variables involved in motion
control:

1. Desired Velocity (feed rate)
2. Maximum Acceleration Rate
3. Path Geometry

Imagine a tool path that goes along the X axis for a while, and then gently
radiuses into a Y axis move. In the servo systems I've worked on so far, at
machining feed rates it's no problem for the control to follow this toolpath
while keeping below the maximum acceleration limit. Now imagine the situation
that occurs at the end of a drilling cycle where we are rapidly pulling up
the Z axis to get the drill clear of the hole, and then we rapid in X and Y
to the next hole location. At the top of the Z travel we have to make a 90
degree corner at the rapid traverse rate. This move is definitely going to
exceed the maximum allowable acceleration rate. In robotics applications the
typical practice is to blend these motions together with a large enough
radius to limit the acceleration to an allowable rate while maintaining the
programmed feed rate. This is "exact velocity" mode. That's how the EMC works
now. As Jon points out, if you have a long series of short moves describing a
fluid curve, this is exactly what you want, because if you run in "exact
path" mode and come to a full stop before beginning the next move you will
gouge the surface and your mold or whatever will look like hell as well as
take forever to machine! However, I have experienced the problem of having a
drill broken off in a hole because X and Y started moving before the Z axis
had dragged the drill clear of the hole. This is definitely an "exact path"
operation! I believe Jon programs his drilling cycles by hand (or with one of
his nifty programs) without using the G8x series of canned cycles. I believe
his retract move is done as a feed move. What I have done to get around this
problem with rapid moves is to insert a dwell (G04) between the rapid moves
as shown in the skeleton program template at the end of this post. Another
workaround is to specify a retract level high enough off the top of the part
so that the drill is clear before blending occurs.

The immediate problem with all this is that the stepper guys (and that will
be me soon as well) have acceleration limits low enough that they are getting
blending at machining feed rates. This could cause there to be radiuses where
none are expected! Either they will need to hop up the hardware to allow
faster acceleration (higher supply voltage Tim?), or G61 needs to work, or
you need a dwell between every move (the other alternative of limiting the
feed rate isn't a good answer).

N5(SKELETON 00-00-00 1 filename, date, etc...)
(set up modal operators)
N10G17G20G40G49(XY plane select, inch mode, cancel diameter comp, cancel
length offset)
N15G54G80G94G98(coordinate system 1, cancel motion, feed/minute mode, initial
level return)
N20M48
(The next 3 lines probably aren't needed anymore, they fixed an old bug)
N25G91
N30G0X0Y0Z0
N35G90
N40G53G0Z0(retract quill)
N45X0.Y0.(move X and Y to the tool change position, change as required)
N50M05M09(spindle and coolant OFF!)
(display a message for the operator)
N55(MSG,LOAD TOOL #1)
N60M00(don't move until the operator presses the S key)
(clear the message line)
N65(MSG, )
N70T1M06G43H1(change to tool 1 and get its length from the tool table)
(start G0 lines with a .001 second pause to avoid motion blending problems)
N75G04P.001G0X1.0Y1.0S1000M3M8(rapid to the starting XY, spindle CW, coolant
ON, change as required)
N80G04P.001G0Z0.25(rapid to .25" above the part, change as required)
( )
(the program goes here, don't have blank lines)
( )
(PROGRAM END)
N980G0Z0.25(rapid to .25" above the part, change as required)
N985M05M09(spindle and coolant OFF!)
N990G53G0Z0(retract quill)
N995X0.Y0.(move X and Y to the tool change position, change as required)
N1000M2(end program)

From: "Tim Goldstein" <timg@...>
I am confused on this one. What do you mean by "open the file for editing"?
The only ay I have been opening files in Xecm is by pressing the open

button

when in program mode. Is there another way to open them where they are
editable?

The way I am doing it now I don't see a "Set Run Mark" button.

In auto mode, select File from the top menu, and then Edit (or just press E
on the keyboard) and you can open the currently loaded program file for
editing. This allows editing and setting a "run mark" on the line where the
cursor is.

Matt

hi Jon & Tim,

suggest making the deceleration override a G-code instruction as you want
to turn it on for the many short moves of an interpolated spline as you point
out, but on a square feature on the same part you want the motion completing
in one axis before starting in the other.

an even better approach is found in a commercial control i use at work
which has a parameter set in G-code which they call "Tangency factor" that
automatically controls the overlapping accelerations between blocks based
on the angle. (how it works i don't know -- not open source -- mfg Thermwood)

-ron

On Sun, 6 Jun 1999, Jon Elson wrote:

Tim Goldstein wrote:

---snip---

kept running it lower and lower just to try it out. At
Acceleration set to
.05 it does this lazy motion thing. At .15 it looks ok. When I cut parts
I will check it for sure.

This is the blending of moves. It can be a problem when you make an X
move, then a Y move, as the Y move will start to ramp up when the X move
just begins to ramp down. But, for a string of short continuous moves describing
a fluid curve, you need this, or the machine will absolutely CREEP. (My
antique AB suffered from this.)
Maybe we should ask Fred Proctor for some sort of switch (either in
the RS-274 program (G-code) or on the user interface) to turn this
on and off.

Jon,

Thanks for the write up on your mini EDM project.

I think I follow everything except for what you are using as an EDM
capacitor? What do you mean by a 6uf 250V paper?


Tim
[Denver, CO]