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Date
Re: ballscrews

[email protected]
 

thanx for the PICS Dan, I understand visual sooooo much better than words
Tracey
Re: Installing rotary encoders

[email protected]
 

OK, at the risk of beating a dead horse, If you have access to .0001" DRO
scales, wouldn't they provide a more accurate method of locating the table,
than indirectly with encoders?
If not I'll be installing encoders on my mill, if so can the programs you
guys are running be set up to read from scales?
Finally, does anybody have info about how well the BOBCAD program works? And
can it be used with the Linux programs for a source of the G codes?
Re: attaching to leadscrew

Jon Anderson
 

Bill,

BS&A is Ball Screws and Actuators. The ActiveCam nut is a self adjusting
polymer nut available in acme and V-thread configurations. The big
difference with the ActiveCam nut is the method of adjustment. Every
self adjusting nut I've seen is spring loaded in some fashion, often by
keying the two nuts axially and providing a collar that is threaded to
one nut and torsionally loaded against the other nut. Under light loads
they are pretty much backlash free but under heavier loads there is the
backlash in the self-adjusting thread that can be taken up, creating
backlash in the nut. The ActiveCam has a cast SS sleeve with a 3 lobed
cam at one end that mates with a similar cam profile on one half of the
nut. It's torsionally loaded such that it rides up the cam faces and
takes up the slack between the two nut halves (which are keyed by a
hex). This arrangement removes the freeplay entirely since the SS sleeve
cannot be compressed. In practice, I found that the stock tension of the
torsion spring won't remove all backlash, I gave the SS sleeve a bit of
an added twist and am down to .0004-.0006 backlash.
BS&A can be reached at or 1-800-882-8857.

Jon

WAnliker@... wrote:


From: WAnliker@...

In a message dated 6/15/99 10:46:24 AM Pacific Daylight Time,
drewid@... writes:

BS&A ActiveCam nuts
Could you elaborate on just what these are. And possibly the source, in case
they are needed.
My problem is connecting to the lead screws, when the handle I am replacing
is the device taking the back lash out of the screw/nut. How is the best way
to do this??
bill
List Manager

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Problems with linux 2.2.10 + beta5 + emc-14-Jun-1999 - anyone ?

Max Heise <[email protected]
 

Hi, I'm new to the list. Let me first introduce myself.
I'm student at the department of mechatronics/automation at the university
of applied sciences in Esslingen/Germany.
This is probably kind of offtopic, but is anyone using emc with linux-2.2.x
and the rtlinux patches for new kernels from ftp.rtlinux.org ?
The kernel and the rtl examples are running fine, but I get lots of errors
when building the emc-14-Jun-1999 package - as anyone tried this this yet
with success?

An other thing for the FAQ:
A month ago, i've spend two nights to figure out that emc and the shared
memory is quite sensitive to ipfilters like ipchains and ipfwadm. If you
get problems with these, flush input/output/firewall rules.

If anyone needs the exact error message, send me an email.

Max

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Max Heise, mahe@... &#92;&#92;|//
mahe@... /----&#92;|/--&#92;
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| / |
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(___/
Re: FAQ etc

[email protected]
 

Kudos to Patrick!!!!
re vac forming

Chris Ellacott
 

[This message contained attachments]
Re: attaching to leadscrew

[email protected]
 

In a message dated 6/15/99 4:05:47 PM Pacific Daylight Time,
janders@... writes:


BS&A is Ball Screws and Actuators. The ActiveCam nut is a self adjusting
polymer nut available in acme and V-thread configurations.
Thank you Jon for the excellant explanation, and the link.
bill
List Manager
re vacuum forming

Chris Ellacott
 

[This message contained attachments]
Re: Installing rotary encoders

Ted
 

rtr@...
Jon,
I have no disagreement with anything you have said except for the method of
measuring axial displacement. When an axis is quickly stopped after
traversing under load, even heavily built cast iron milling machines
exhibit more than the static displacement measured by pushing and pulling
the axis. That's why I suggest a shock (Gentle, of course) method of
measuring axial displacement.

I have often used helical cut couplers and find them satisfactory. I
suggested the surgical tubing as a low cost alternative for encoders in the
50 to 200 cycle range. When you get to very high resolution encoders, you
run out of error budget with surgical tubing. The shrink tubing and a
small metal tubing sleeve might help keep oil off the rubber.

Ted
----------
From: Jon Elson <jmelson@...>
To: CAD_CAM_EDM_DRO@...
Subject: Re: [CAD_CAM_EDM_DRO] Installing rotary encoders
Date: Tuesday, June 15, 1999 12:01 AM

From: Jon Elson <jmelson@...>



From: "Ted" <rtr@...>

This procedure isn't difficult, but must be understood to successfully
install a rotary encoder where none have been before.


Then drill and tap for a couple of set screws at 90 degrees to allow
you to
indicate it in. Put the indicator near the end of the pin, because
that's
where the coupling will fit. The pin doesn't needto stick out more
that an
inch when you finish. You can cut it off and file the end when you
have it
in place, indicated, and clamped with the set screws. Do thiswork on
the
pin gently then indicate it again. Encoders don't like a lot of
vibration
so bring it within 3 thousandths or better. I'm always happier if it
comes within one and a half thousandths.
Most encoder warranties are voided by NOT using an appropriate coupling.
I use couplings made from a single piece of metal, slotted helically to
provide
radial and axial compliance, but no torsional compliance.


You can connect it with an oldham coupler or similar low inertia
couplers.
Surprisingly, if you mount it so the shaft pin and the encoder pin
come
within a few thousandths beyond the slop in the system, you can use a
piece
of surgical tubing for the coupling. You can add an outer layer of
heat
shrink tubing if you think the surgical tubing is too compliant, but
I've
never had to. The extra stiffness will transmit more vibration to the
encoder, a bad trade off. There is little friction in good encoder
bearings so the surgical tubing wall thickness is adaquate for a
coupling.
Obviously, you can't do this if you need to drive the screw or brake it
through the encoder shaft, a bad idea in any case.
Actually, many good encoders have a fair amount of drag in their
bearings. They use a pair of angular contact bearings with preload, to
stiffly constrain the shaft from any radial movement, which would
show up incorrectly as rotation. They also have at least one, usually
two shaft seals, to keep crud out of the bearings, and grease out
of the optics. That all adds up to inch-ounces of static drag.
I'm using 1000 line encoders, counting all transitions, so that is
4000 counts/rev, or more than a count for every tenth of a degree.
It would be foolish to waste that accuracy with a homemade coupling
that allowed twist to develop. Also, the metal coupling is good for
many years, what if the surgical rubber turned to gum? Do you know
what OIL does to LATEX? Yucck!


Besides eccentricity in the rotation of the encoder coupling pin, the
error
that kills the most encoders is failure to allow enough room between
the
ends of these two shafts. All sorts of distortions occur when an axis
is
stopped after a rapid movement. Ten thousandths of longitudional slop
is
not unusual in a ball screw, more in an acme screw.
I don't know how a precision machine could possibly keep any accuracy
if there is .010" longitudinal movement of the screw! I have a total of
.001" of slack in my mill, and I'd like to find the sources, and reduce
it.
But, that is the sum of ALL the sources of slack, like torsion of the
leadscrew, shaft couplings, bowing of the screw, slack in the angular
contact bearings, slop in the anti-backlash ballnut, etc. etc.

Jon


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Re: EMC stepper & misc fixes

Jon Elson
 

From: "Tim Goldstein" <timg@...>

I found a problem in the new jun-14 build. When in manual mode the first
time you do a jog on an axis it moves at about .5 ipm. After the first move
all subsequent moves are at the rate indicated in the feed rate box. If you
go into another mode and then return to manual the S L O W move returns
for the first move.
Yes, I believe I've seen this behavior in the servo version, too. I usually
change the jog rate first, and then (maybe) it does it correctly.

Jon
Re: ball screws Backlash

John Grant
 

Dan Mauch wrote:
The regular rolled cut ball screws can get down to about
.002 and save about $20 per axis if that is acceptable. Otherwise the
additional expense is sure worth it.
Dan
I thought that ground screws cost much than an extra $20.

John Grant
Re: Vaccum Forming

Tim Goldstein
 

Mario,

I would almost swear that in one of Don Ross's model airplane books he lists
a company that makes a low cost high quality home vacuum forming machine. I
will try to remember to check tonight when I get home.

Tim
[Denver, CO]

----- Original Message -----
From: <MIADsgns@...>
To: <CAD_CAM_EDM_DRO@...>
Sent: Tuesday, June 15, 1999 8:59 AM
Subject: Re: [CAD_CAM_EDM_DRO] Vaccum Forming


From: MIADsgns@...

Anyone has done a vaccum forming machine for home use?

Mario

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Re: Vac Forming

Matt Shaver
 

From: MIADsgns@...

Hi Folks:

I am looking for someone to do some vaccum forming of RC micro heli
canopies.
Looking for 10 units at the moment. I provide the plug (s). Please call me
or write to me direct. I do not want to go with a large company because of
the high cost involved for such short order. I am looking for someone that
knows how to vac form and has descent equipment. Someone that does this
from
home perhaps? I am pressed for time, otherwise I would vac form the
canopies
myself. Material has to be lightest available, styrene or similar clear.
One possibility is to find a shop in your area that makes orthopedic braces
or prosthetic limbs. Most of these devices have vacuum formed parts that are
custom made to fit the user, so a lot of ten will be mass production to these
folks! You may have to supply both the forms and material since they may not
stock what you need.

Good Luck,

Matt
Re: re vacuum forming

[email protected]
 

In a message dated 6/15/99 5:39:57 PM SA Eastern Standard Time,
footman@... writes:

<<
I run a small company that manufactures foot orthotics (supports) - these
are vacuum formed over plaster casts of peoples' feet - sounds like you want
something that ends up with a flawlessly clear finish - with my equipment
(home made), my plastic (or carbon graphite & plastic) ends up with an opaque
finish that is fine for orthotics, but would likely be lacking for your
purposes - let me know if you want more info . . .

Christopher Ellacott, D.Ch.
Chiropodist >>


Interested in your home equipment. I made a desktop vac former that works
well with thin plastic and uses a shop vac. but I need more succion to form
with heavier plastic and finer detail. Any clues as to how to modify such ?

Mario
Re: attaching to leadscrew

[email protected]
 

In a message dated 6/15/99 10:46:24 AM Pacific Daylight Time,
drewid@... writes:

BS&A ActiveCam nuts
Could you elaborate on just what these are. And possibly the source, in case
they are needed.
My problem is connecting to the lead screws, when the handle I am replacing
is the device taking the back lash out of the screw/nut. How is the best way
to do this??
bill
List Manager
Re: EMC stepper & misc fixes

Matt Shaver
 

From: "Tim Goldstein" <timg@...>

I found a problem in the new jun-14 build. When in manual mode the first
time you do a jog on an axis it moves at about .5 ipm. After the first move
all subsequent moves are at the rate indicated in the feed rate box. If you
go into another mode and then return to manual the S L O W move returns
for the first move.

I am not quite sure on this one, but I think it occurred. I will try it
again next chance I have at the machine.
Fred has been trying to find the cause of this elusive bug for a long time.
You are correct that upon entering manual mode, the first jog move is slow. I
forget whether you have to reverse direction to get the normal jog speed back
or whether it's just the second move regardless of direction. I also can't
remember if it's just the first move that's slow, or if the first move for
each axis is slow. Once you clear this condition, and jog speeds are normal,
you can "reset" the bug by switching to AUTO or MDI mode and then returning
to MANUAL mode.

Matt
Re: ball screws Backlash

Dan Mauch
 

Am very familiar with the antibacklash double ball nuts. I have them on my
full size mill. The regular rolled cut ball screws can get down to about
.002 and save about $20 per axis if that is acceptable. Otherwise the
additional expense is sure worth it.
Dan

-----Original Message-----
From: TADGUNINC@... <TADGUNINC@...>
To: CAD_CAM_EDM_DRO@... <CAD_CAM_EDM_DRO@...>
Date: Tuesday, June 15, 1999 7:07 AM
Subject: Re: [CAD_CAM_EDM_DRO] ball screws Backlash


From: TADGUNINC@...

Dan,
I'm not sure how to reply without getting a bunch of the old mail
included
sorry.
But about your lead screws, how do I contact Thompson? As far as the
backlash error, if you preload two ballscrews against each other couldn't
you
effectively eliminate the backlash? I know the more expensive mills used
backlash eliminators (see page 97 of "Machine Shop Practice" Vol. 2, if I
ever get a scanner I'll send PICS instead of references) with two nuts and
adj. preload on the nuts with acme lead screws. It not only nearly
eliminated
backlash but also prevented damage to the cutters servos, etc., when climb
milling with heavy feeds. This was the approach I was going to take with my
mill, however the ball screw setup seems to be a better way to go to cut
down
on the drag and size of the servos required.
Tracey DeChambeau

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Re: FAQ etc

Patrick Huss
 

Hello, my name is Patrick and I'm a lurker.
Wow, what a list!
I've just purchased an EMCO F1 mill, and I'm determined to run this machine
with the EMC software. I have an old Compaq that I need to replace the ROM
in to get it to recognize harddrives over 500M, as soon as I get the part
I'll be loading LINUX and adding a larger drive(not neccesarily in that
order).
I find this list extraordinarily useful, mostly because, although I'm
confident when it comes to software and computers, I have a lot to learn
about electronics. There really seems to be some very experienced and
intelligent people on this list who are more than generous with their
knowlege. I'm not even the first Sculptor on the list, as the ubiquitous
Andrew Werby has preceeded me in membership : ) Resources such as this list
are invaluable to artists, who may not have the steady income to justify
spending gads of money on software and machinery, but do have the insight to
recognize how important an asset technology can be.
I'm looking forward to utilizing this list as an important resource, and
hope maybe someday to contribute as much as I have gained.


Patrick Huss

-----Original Message-----
From: WAnliker@... <WAnliker@...>
To: CAD_CAM_EDM_DRO@... <CAD_CAM_EDM_DRO@...>
Date: Tuesday, June 15, 1999 11:30 AM
Subject: Re: [CAD_CAM_EDM_DRO] FAQ etc


From: WAnliker@...

In a message dated 6/15/99 3:45:25 AM Pacific Daylight Time,
rhj-rbj@... writes:

So come on you lot express yourselves as I am sure I am not the only one.
cheers
There are 201 members on the list this morning, and that means a lot of
lurkers. I hereby give you guys (gals?) permission to join in on the
discussions....... grin.
bill
List Manager

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Sign up for the ONElist Weekly Survey. Go to homepage for details.
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welcome to CAD_CAM_EDM_DRO@..., an unmodulated list for the
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Follow up on 14-jun build EMC

Tim Goldstein
 

Fred,

I spent a few minutes this morning verifying the Verify function and it is
as I thought last night. The following code goes through the verify function
with no errors, but if I try actually running this code I get the arc
mismatch problem on line 153.

N10 F8
N11 G40
(begin finish)
N151 G00 X0.170863 Y-1.712010
N152 G01 X0.170863 Y-1.712010
N153 G02 X0.164990 Y-1.712225 I0.167665 J-1.704943
N154 G01 X0.151577 Y-1.707299
N155 G02 X0.124092 Y-1.599349 R0.261777
N156 G01 X0.070711 Y-0.070711
N150 M2

So, I like the way the verify function works, but would like it better if it
errored on the code <bg>


Tim
[Denver, CO]
Re: 10 amps to drive steppers

Dan Mauch
 

One of my customer's student disconnected a 4.6 amp stepper and it blew the
sense resistor and two mosfets.
Dan

-----Original Message-----
From: Tim Goldstein <timg@...>
To: CAD_CAM_EDM_DRO@... <CAD_CAM_EDM_DRO@...>
Date: Monday, June 14, 1999 9:51 PM
Subject: Re: [CAD_CAM_EDM_DRO] 10 amps to drive steppers


From: "Tim Goldstein" <timg@...>

Mo or Jon,

Would love to have a schematic of this setup and would definitely be happy
to get it posted.

Regarding disconnecting a motor on a Camtronics board while it is powered
and running, I inadvertently did this once and the board survived with no
harmful side effects. I may have been lucky as I only had some small NEMA
23
motors set up at about 1 amp.

Tim
[Denver, CO]

-----Original Message-----
From: Mo [mailto:mo@...]
Sent: Monday, June 14, 1999 7:50 PM
To: CAD_CAM_EDM_DRO@...
Subject: Re: [CAD_CAM_EDM_DRO] 10 amps to drive steppers


From: "Mo" <mo@...>


From: Jon Elson <jmelson@...>
A properly designed stepper driver shouldn't be troubled by operating
with no load. Unplugging or plugging in the motor while the driver is
active could cause some arcing that might cause damage, but just
running
the driver with no motor connected shouldn't be a problem.
Jon, unfortunately both types of board I have here warn that this is a
certainty
and I believe the Camtronics boards are the same. I have inadvertantly
killed one that way.
It must be in the design, as you say. Where a manufacurer warn
specifically
that their design
will be seriously damaged by this - it is good to take the precaution.





Here's what I did, although it is on a servo system, but the
problems are
similar. The E-stop signal on my system releases a pair of relays (one
a signal size, the other a power contactor). When these relays are
released, they connect a power resistor to the servo amps power
input, discharging the power supplies. When the relays are engaged,
first the signal relay closes, connecting the same power resistor in
series with the DC supply and the servo amps. Another contact on
this relay connects power through to a time delay circuit. After
a 1 second delay, giving time for the resistor to ramp up the
voltage in the servo amps, the power contactor closes, delivering
direct
power to the servo amps. When this relay closes, it also connects
the enable input to the servo amps to +12, turning them on.
This gets rid of all the high DV/DT transients when powering things
up and down, and makes sure that whenever there is a fault, everything
is powered down in a controlled manner.
Perfect power up and enable sequencing. The power bleed resistors are the
absolute
minimum needed for those that do not have a similar set-up and
are still in
the process of playing around with their assembly.
Jon do you have a schematic for that set-up - if not I could
knock something
up and put it on Tim's site for members who would like to go that route.


Mo




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