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From: Jon Elson <jmelson@...>
Maybe, someday, we'll even have
conversational programming, but I'm making parts, and loving every
minute of it!

Actually, if we made a button or menu item in xemc that would call your
little gcode generators (maybe even put a GUI dialog box in front of yours),
we'd have it now! Sure, there's no graphical toolpath display...

Matt

From: Bob Bachman <bobach@...>

Jon,

Thanks for the response. How do you connect the two boxes? Serial? Network
cards?
I have some WD network cards which are supported by Linux.

Yes, I got PCI Ethernet cards for most of the machines, but the CNC
machine has an ISA card. I chose thinwire ethernet (10-base-5) over
twisted pair (10-base-T) because it didn't require a hub, and I knew
the technology well. Actually, I have at least 6 machines that could,
potentially, be hooked up.

I liked Linux so much, I decided to set up another Linux system and
migrate a whole bunch of stuff I do for the home, and my business,
to it.

Jon

"Leighton M. Reed-Nickerson" wrote:

From: "Leighton M. Reed-Nickerson" <w2hie@...>
I've seen references to Max-NC and Ah-ha, but no mention of Microkinetics...
is that because Microkinetics is. In the opinions of the group, good or bad,
or too expensive. Or, is it that this group is getting a lot of enjoyment
and gratification out of home-brew CNC, where I'm into CNC to make parts
fast and efficiently.

Please don't take that as a criticism, If I had the time I would love to
home brew a CNC controller.

Well, no question about it, us bleeding edge guys really went through the
wringer on this. I even had an antique commercial CNC control first,
but it was slow and a bit unreliable. Now that the trail has been blazed,
the pain should be a LOT less. And, although I have not actually run
a machine with the competing products, I have run their demos, and
looked at what they can, and CAN'T do. I feel quite happy with EMC,
and wouldn't want anything else. Maybe, someday, we'll even have
conversational programming, but I'm making parts, and loving every
minute of it!

Jon

Ron Ginger wrote:

From: Ron Ginger <ginger@...>

Well, I sure drew out the lurkers with that one :-)

and it seems to have opened up a couple new threads as well, so great,
lets forget splitting and keep talking.

The question of coordinating 2 (or even 3) PIC servos- or for that
matter any servo is one that has bothered me. There are several servo
boards Ive sen that are single axis, with serial port control. Can these
be used for coordinated movements? I notice the PIC has a command to set
the time of a movement, so I asume you could calculate the longest time
and program both boards to that time.

I would really like to hear from someone that has done this

Well, I really haven't DONE it, but I've worked with several systems
that do it, and I have picked some of the intricate code apart.
Clearly, one processor that can do it all makes it easiest.
That's what EMC does now. Since a single routine generates
all waypoints on the toolpath, and then passes the positions it
expects all axes to be at, at every tick of the trajectory generator's
clock, the axes should stay well in sync under normal conditions.
Anything where the separate axes have their own system clocks
could get out of sync, and at least could be 1/2 a tick out at any
moment. If the servo loop runs fast enough, this error will be small.
HP makes a real neat servo chip, not too different from the LM628,
but much cheaper. BUT, it doesn't have fractions in the velocity,
meaning that, say, X can move at 1/2, 1/3, 1/4, etc. the speed of
Y. But, X can't move at .53725 times the speed of Y! Well,
that's unusable for multi-axis work. You couldn't even do a decent
circle with it. Most of these things don't use time, they use velocity.
So, the main program computes velocity such that all the moves
take the same time. An easy computation, although you also need
to scale the acceleration, so all axes accelerate for the same time
before coming to their respective constant velocities.

Jon

I have no experience or expertise to say whether your idea would work, but
off the cuff it sounds like it would be more work than it is to just load
Linux and get EMC running. I think with the help and support of this group
someone could get Linux and EMC set up and running in a couple of evenings
and from that point on the Linux portion becomes pretty transparent and you
just deal with EMC.


Tim
[Denver, CO]

I guess I'm one of the one hundred ninety that are saying nothing, so to change that I'd like to say, NO don't split the list. I
enjoy learning about all the topics discussed here.

I currently have a Grizzly bed mill that I'm converting to CNC using AHHA software and PacSci motors. I am ordering ballscrews
from Nook Industries (precision rolled) and have put a 3 HP DC motor on the spindle. I plan to pick up Linux 5.2 this weekend
and try to get EMC going also and compare the two (AHHA and EMC).

I also have a couple of really big BostonMatic CNC mills (about 13,000 LBS each) to upgrade the controls on. I'm sure that what
I learn from the discussions on this list will help me decide which software and hardware to use in this project also.

Thanks, everyone !!

Ward M.


WAnliker@... wrote:

rtr@...
maybe I'm missing something, but integrating the movements of a couple of
axes is what Bresham's Algorithms in linear and circular motion is about.
It breaks down the motion into a lot of very small motions and steps the
control through these small motions. It never allows the axes to loose
synchronization by more than the resoplution of the machine, if you choose
to limit the small motions to that size.

Ted Robbins

----------

From: Ron Ginger <ginger@...>
To: CAD_CAM_EDM_DRO@...
Subject: Re: [CAD_CAM_EDM_DRO] List question
Date: Thursday, June 17, 1999 6:52 PM

From: Ron Ginger <ginger@...>

Well, I sure drew out the lurkers with that one :-)

and it seems to have opened up a couple new threads as well, so great,
lets forget splitting and keep talking.


The question of coordinating 2 (or even 3) PIC servos- or for that
matter any servo is one that has bothered me. There are several servo
boards Ive sen that are single axis, with serial port control. Can these
be used for coordinated movements? I notice the PIC has a command to set
the time of a movement, so I asume you could calculate the longest time
and program both boards to that time.

I would really like to hear from someone that has done this


ron

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bill, List Manager

Linc,

If you are working with cnc routers as a business, I would recommend the cnc
controller from Microsystems of Buckhannon in Buckhannon WV.

I have been using a copy now for about three years on my homebuilt cnc
router. It works great and is very easy to use. The cnc controller was
originally developed as a follow-on product for the Digital Tools cnc
router.

Bob Campbell
Euless, Texas

rcamp@...

Hi,

I've been lurking for a while, and learning...

I've seen references to Max-NC and Ah-ha, but no mention of Microkinetics...
is that because Microkinetics is. In the opinions of the group, good or bad,
or too expensive. Or, is it that this group is getting a lot of enjoyment
and gratification out of home-brew CNC, where I'm into CNC to make parts
fast and efficiently.

Please don't take that as a criticism, If I had the time I would love to
home brew a CNC controller.

Linc

Leighton M. (Linc) Reed-Nickerson
Broadcast Technology US
Phone: 360-834-1862
Fax: 360-834-6061
Web www.broadcasttechnology.com

I have been reading all the EMC for Unix stuff with great interest. But
I really don't want to go through the pain of converting my home CNC
over to Unix. My experience with Unix is that it is a catch 22 of
sorts: it is a really cool operating system because it is an open
standard; it is also a real pain in the ass because its an open
standard. But I have been thinking about something ever since I read
that the decision to go Unix was for real time determinism. Wouldn't it
be fairly simple to create a FIFO memory buffer between the computer and
motor controller such that it buffers motion commands from a
non-realtime computer and issues them in real time? The FIFO would not
even need to be very deep if you had a feedback to the computer to tell
it "I'm full now, stop transmitting". I don't know the EMC program
structure, so I don't know how hard this would be to implement in code.
But it seems simple, and would open the door to using any operating
system.

Mike

I have used this chipset in the past also (at least the 629 version). I
never knew you could update the trajectory at 1khz though. As far as
multi axis chipsets go, a real nice one is the PMD chip. Their sales
guy bugs me every 6 months or so. Lately he has been telling me they
have a 4 axis chipset with feedforward velocity and accel. It goes for
about $150.
But given how fast and cheap the 16 and 32 bit microcontrollers are
getting now-a-days, I have come to believe closing the loop in firmware
on a processor is the way to go for a ground up system.

Mike

Well, I sure drew out the lurkers with that one :-)

and it seems to have opened up a couple new threads as well, so great,
lets forget splitting and keep talking.


The question of coordinating 2 (or even 3) PIC servos- or for that
matter any servo is one that has bothered me. There are several servo
boards Ive sen that are single axis, with serial port control. Can these
be used for coordinated movements? I notice the PIC has a command to set
the time of a movement, so I asume you could calculate the longest time
and program both boards to that time.

I would really like to hear from someone that has done this


ron

Hi Folks,
Yep, Finally! I have an Alpha version of Stepster ready - Warning it is
almost definitely broken somewhere, as I've done a serious re-write, and I
probably broke one or more things.

Anyway, if you wish to test it, let me know, and I will e-mail it to you.

Charlie

PGP Key Avalible upon request

From: Jon Elson <jmelson@...>



Bob Bachman wrote:

From: Bob Bachman <bobach@...>

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.

Yes, the network is one of the difficult things. I got enough networking
going to connect my machines. I have the modem on a Windows 95
PC, so I do all my net surfing and downloading on that. Once I have the
.tar or .tgz files on the Windows machine, it only takes 5 seconds (literally)
to send the complete EMC file to the Linux machine with an FTP
utility.

That may actually be a relatively safe way of handling the situation.
Getting PPP up and configured on Linux (or any Unix) system is not
altogether obvious. With the side effect that you may end up with
an insecure system attached to the Internet. For some reason, systems
as shipped are almost never configured to be secure. At the very
least, you might find your system hijacked to relay pornographic spam
if sendmail is running and improperly configured. Or worse yet, _you_
might not find out about it. At least until your system logs fill up
all available disk space.

For help with almost any aspect of setting up Linux, but especially network
and video hardware/software, the how-to and mini-how-to files
(which are on the RedHat CD, as well as on the net) are essential.
I would NEVER have gotten networking up without those guides
open in front of me.

Jon

Also check out



--
Paul Amaranth | Rochester MI, USA
Aurora Group, Inc. | Software Development
paul@... | Unix / C / Tcl-Tk

Bob Bachman wrote:

From: Bob Bachman <bobach@...>

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.

Yes, the network is one of the difficult things. I got enough networking
going to connect my machines. I have the modem on a Windows 95
PC, so I do all my net surfing and downloading on that. Once I have the
.tar or .tgz files on the Windows machine, it only takes 5 seconds (literally)
to send the complete EMC file to the Linux machine with an FTP
utility.

For help with almost any aspect of setting up Linux, but especially network
and video hardware/software, the how-to and mini-how-to files
(which are on the RedHat CD, as well as on the net) are essential.
I would NEVER have gotten networking up without those guides
open in front of me.

Jon

Tim,
Did you every manage to pin down where the interference was coming from
or what made the most difference?
are all cables now shielded?
What was the "more shielding" that smoothed out the motor and did you find
the victim to be the parallel port cabling?
Mo

I don't know if your problem is the same, but I had the same thing happen

to

me as I increased the amps I started getting problems with lost steps on
curves. It was particularly bad with about a 1/2" radius and moving around

7

ipm. The step loss was quite consistent on the parts with curves, but I
could do slow or rapid moves along an axis all day long and the moves were
perfect with no steps lost. It ended up being a shielding problem. I

thought

the interference was coming from the mosfets & heatsinks, but Jon made a
post and thinks it is from the circuit board (with his knowledge and
understanding I don't have much reason to disagree). Dan Falck posted

about

having a similar problem as he upped the juice on his system also.

The fact that your loss of steps increased as you upped the amps makes me
think you are experiencing the same type of thing. When I was lossing

steps

I also would notice that the motor was running very ragged. More shielding
caused my step loss to go away and the motor started sounding much

smoother

running.

Paul,

Thanks for the url. Good stuff there.

Also check out

Bob "Also a Michigander" Bachman

Jon,

Thanks for the response. How do you connect the two boxes? Serial? Network
cards?
I have some WD network cards which are supported by Linux.

Yes, the network is one of the difficult things. I got enough networking
going to connect my machines. I have the modem on a Windows 95
PC, so I do all my net surfing and downloading on that. Once I have the
.tar or .tgz files on the Windows machine, it only takes 5 seconds

(literally)

to send the complete EMC file to the Linux machine with an FTP
utility.

I just moved the 4 .pdf ebooks from the RH cdrom onto my laptop so I can
reference
them while trying to get things to work.

For help with almost any aspect of setting up Linux, but especially network
and video hardware/software, the how-to and mini-how-to files
(which are on the RedHat CD, as well as on the net) are essential.
I would NEVER have gotten networking up without those guides
open in front of me.

Bob

Jon Elson wrote:

This sounds very interesting. I had a strong interest in the LM628/629

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.

Well, the board I have has 3 628 chips and the buss decoding, timers,
and host interrupt support hardware.

Tech80 seems to know more about the chip than National does! It is true
that you can't change accel on the fly, but you can issue a coast
command then as soon as the busy bit goes low you can change all motion
parameters. They (Tech80) recommend running in velmode and going to
coast at a breakpoint for maximum multi-axis interpolation performance.
They also suggest not waiting for their interrupt parser to figure out
that the busy bit is low (100 microseconds after a write) and just shove
the data with careful timing. Min command update time is about 1000
microseconds using this method.

Position mode will keep axes synchronized within one read cycle but as
you say results in choppy motion. I do observe that it is smoother than
one might think with proper filter tuning however.

Well, the microseconds add up and you can see why I am interested in
the potentially higher performance of EMC.

As for the generation of long straight edges or ways it is just using
the principles of hand scraping but using a hand grinder instead of a
scraper. One can easily take off fractional thousandths with a power
grinder. The process is neither easy nor quick but it is cheap and very
accurate.

Sounds like you are familiar with bearing design but if anyone else
is not I have an autocad drawing of a preloaded duplex angular contact
bearing block for 25 mm ballscrews that costs about $30. These cost
$300+ from ballscrew manufacturers. I decided a big box full of these
would really cut into the beer money so I sentenced myself to stand at
the mill and surface grinder for a few saturdays. I don't want to send
the drawings as attached files but might mail.

Oh, I bought about 11 meters of new THK 45 mm linear rail with 13
Bearings for $1100 from Mann-made Enterprises in Addison ,Il. I'll post
the number when I can find it.

--
Leslie M. Watts
ITW Advanced Technology Group
(847)657-4559

I vote to keep the list intact. Yes, there are things I don't
understand, and am not interested in, but if I filtered everything
I _thought_ I didn't need, I probably would never have considered
either Linux or EMC, and I'd still be dreading Big Bad Bill's
copyrighted "Blue Screen." Linux/EMC looks like a better bet. I
imagine there will be other topics that seem boring at first,
but become interesting with a bit of effort.

Geoff