开云体育

Brian, I think it's www.teachcnc.com
try that.........

May 9, 1999

From: Roland Friestad

I have great hopes for this forum and the future of Low-Cost CNC/CAD/EDM/DRO
etc - Although one of the things I've found is that the definition of
Low-Cost varies a lot depending on who's doing the defining -

To introduce myself: I'm a professional engineer and tool & die-maker with
a background in Aeronautical and Mechanical Engineering. That means I can
use P.E. after my name, something that combined with anything from $0.50 to
$1.00 will get a cup of coffee in anything but the most expensive restaurants.

I was on the design staff of Piper Aircraft and was Chief Engineer of
Bellanca Aircraft - I also spent some time at UNIVAC working on the
computers used on the first moon landing craft - That's where I first became
aware of the use of computers for actually moving and controlling real-life
equpment - I've been hooked ever since

I dropped out of the corporate rat-race over 25 years ago and started a
small manufacturing company specializing in short-run metal stamping, making
parts for other companies - I have come to prefer to work for smaller
companies rather than the "big boys" who generally expect you to be suitably
respectful of their size - I could write a book about those experiences -

I got into CNC as soon as I could afford to buy my first Bridgeport CNC mill
about 20 years ago - It revolutionized my thinking about building dies and
tooling - The local Technical School talked me into teaching CNC programming
since I had the first equipment in the area - I taught for about 20 years on
evenings and weekends -

The classes were held at my shop and the students needed to get into my CNC
mills to run their projects and "smoke test" their programs - It seemed that
a die building project was always in the mills when they wanted to run their
own projects - That's when I searched for a small CNC machine to use for
teaching - What I found was equipment that appeared to be terribly
over-priced for their capabilities and size - So, fancying myself a designer
I built my own retrofits, using commercial mills and lathes as the basic
frames -

I know enough electronics to be dangerous and the assembly language computer
programming I was taught at UNIVAC is so hopelessly out of date that I
needed to find a company to provide the CNC motion - I located a small
outfit run by two guys working out of their basement and contracted with
them to build the first CNC controller for me - They have since grown into
what is now CENTROID -

The first CNC machines were successful as teaching tools and other teachers
wanted similar machines so I started building them - The project got out of
hand and what started as a sort of "hobby project" has become a fairly large
part of my small business with approximately 400 machines done up to now -
These include CNC lathes, mills, routers, laser welders, rotary tables, and
some very special custom machines -

In 1989 I started writing a series of articles for HOME SHOP MACHINIST
magazine on retrofitting these machines, providing drawings and resources
for those who wanted to get into CNC in a low-cost way - This continued for
several years but I've been sort of inactive with the articles for the last
few years - I'm working on a whole new series to be published, the first of
which is a home-built DRO for small mills -

Don Fergle and myself have presented the CNC Seminars at N.A.M.E.S. for the
last two years - It is satisfying to see the standing-room-only crowds at
these seminars - I"ve been talking to the N.A.M.E.S. directors about an
expanded program for the next year's exhibition - Will advise when they let
me know if it is going to happen -

I'm pleased to see the growing interest in these areas and will try to
contribute as much as possible - I see various areas that need work and
would hope that we can all progress together by combining efforts and
sharing information -

I feel that my own expertise is in the areas of mechanical design and
machining rather than that of programming and electronics - Consequently I
would be more than willing to coordinate and share with those who have
complementary capabilities -

One thing that I have been thinking about for a couple of years is the
possibility of hosting some sort of get-together for those who want to build
or retrofit milling machines or lathes -

I've got a fairly complete machine shop and lots of space - While I build
and sell systems to schools for training of CNC operators and programmers,
the hobbyist movement is where my personal sympathies lie -

Those of you who might want to participate in such a get together at my shop
can let me know via this forum -

I am thinking of about a week long project where you could bring your
machines along and spend time making parts and sharing ideas using my shop
and equipment -

A lot of these projects would probably be of interest also to the readers of
HOME SHOP MACHINIST and I could write them up for publication if everyone
agreed -

I apologize to be so long-winded about this - I'll try to keep it shorter in
the future but it's kind of nice to know that I'm not the only one out there
with these kinds of interests -

Roland Friestad <cardinal.eng@...>

Pardon e'moi, I tweaked the subject to help follow-on's.

On Sun, 9 May 1999 13:25:41 EDT, Jonty50@... wrote:

Yeah, the thing is outtahand.

Hee hee, yeah, unlike the hobby itself, eh? :)

The parts aren't really such a problem. The Bishop Wisecarver V wheels, wheel
mountings and track were around $600 for the lot.
...
The V bearings run around $20 each, it basically takes 4 per axis. I've found
that the B-W track is not necessary, the wheels do very nicely riding on 1/4"
diameter hardened steel rod ( I use music wire) that can be just pressed into
a 1/8" deep slot milled in an aluminum bar or rectangular tube. Very smooth
motion, even smoother than the B-W track.

Huh, neat trick! This is actually wunnerful news on the pricing front,
too, specially for guys that wanna route stuff where they're not
necessarily looking for Bridgeport resolution.

Jonathan (do you go by that, or is Jon OK?), lets peel the next layer
off the onion if yer willin? What are you using for axis translation:
rackNpinion, lead-screws, what? And WHERE on earth did you source the 8'
dimension on the Y axis trans. from?

Also, given your structure and your axis hardware, roughly what
resolution are you hoping for?

One of the other nice attributes about this type of guide is that it
doesn't require surface friction lube'ing like shafting or ways, eh?
That can be a problem when routing things like wood and especially foam
or plaster. This fact was brought to my attention somewhat "late" in my
own project plans, by a fellow who sent me some in-progress plans for a
big router table he had built outta "rollers on tubing". I'll get his
reference out if anyone's interested (actually be surprised if he wasn't
in the group already, but I've forgotten his name, and his plans are in
storage, sigh). He mentioned his design goals were to avoid having to
continually worry about cleaning linear bearings and keep the
shafts/ways wet with lube. I thot that was a pretty important point I
had missed when planning me own, so I mention it to "the wise". B)

[SpeakinOplaster and milling/routing/machining it, I got a cool lil
dollop I'll dribble out in a separate post about a new USG product y'all
might be interested in.]

BTW, I saw a V-guide based system for CNC plasma cutter positioning in
some pix somewhere, and was pretty impressed with how robust that 2-D
system was, especially in such a harsh environment (plasma cutters
product TONS of fine particulate dust, donchaknow). Of course, there the
resolutions allowed using steel angle for the guides, so I mention it
just as a 'similar' example (if the guides don't have to be lube'd, you
can SWEEP the guide clean with a brush arrangement on either side of the
roller). The availability of nonspendy precision V-bearings, and also an
even lower cost way to build arbitrary length guides with that neat
trick of Jon's sure sounds like a nice way to get started experimenting
with these systems. Oh well, I guess if I'd waited, I coulda changed
horses in the middle of the stream, but hey, that's science, eh?

Gar

On Sun, 09 May 1999 13:04:21 -0500, Roland Friestad
<cardinal.eng@...> wrote:

I apologize to be so long-winded about this - I'll try to keep it shorter in
the future but it's kind of nice to know that I'm not the only one out there
with these kinds of interests -

Roland Friestad <cardinal.eng@...>

Hey! Speak of the guy, and poof, he appears! This is the machine
designer I mentioned in a previous post that had alerted me to the
issues of routing on wood/plaster/foam in a "lube'd ways environment".

Welcome, Roland. Excellent to have you aboard. Looks like Obie Wanliker
has created a barn-burner. B)

BTW, I think I misspoke a tad too diminutive of your router design. I
said it was "in progress". What I shoulda said was the *plans/drawings*
were in progress; the actual machine design had been deployed at a
couple of schools already, when we last talked over a year ago, IIRC.

Gar

On Sun, 09 May 1999 18:09:27 +0100, you wrote:

From: "Ian W. Wright" <Ian@...>

Hello group,

With a bit of luck, this list will be the best thing in my life (sad
eh?)

As some of you know already I repair and restore high class watches and
small clocks and I am wanting to find a way of making small parts easily
and accurately. A typical problem might be that a complicated
chronograph may come in, having suffered the attentions of an 'expert',
with one or more of its internal operating levers missing. At the moment
the only way I can reliably make a new part is to cut and fit it
gradually bit-by-bit using the remains of the movement as a guide - a
very hit-and-miss affair. I have worked out that, by taking digital
photos, importing them into Autocad and drawing over them, I can design
the required new part to a high degree of accuracy and confirm that it
will work OK before I cut any metal BUT I then have the major problem of
transferring the designed shape onto the metal and cutting it
accurately - a scribed line in my scale of things can be half the width
of the finished part!
So, I have been playing about for some time with ideas to make a wire
EDM and a miniature CNC miller - each with a table size of only about 6"
x 6". However, I have continually fallen at the first fence as I don't
seem to be able to get a stepper interface working properly. The
steppers I have are marked 'Step-Syn' type 103G770-0344, 24 volt, 0.22
Amp, 1.8 deg/step, 5 wire. I have tried a number of published stepper
driver circuits but these are mainly for low voltage motors and seem to
give up when I try to hang a power darlington output stage on them to
handle the higher voltage. I must admit to not having tried Dan's
circuit yet but, after so much wasted time and expense, I'm a little
sceptical of paying out for 24 transistors on a maybe! (Sorry but I am
the archetypal Yorkshireman - deep pockets and short arms!) I tried
running an emulation of this circuit on an electronics workbench program
and it seemed to work, although with apparently jittery outputs - then I
moved and reconnected a wire I had connected to the wrong place and it
stopped working!
Can anyone advise me on the practical solutions they have found and,
also, can anyone tell me how the feedback circuits of a wire EDM work -
I'm sure this is really the machine I need for most of the work I want
to do.
Some of the watches etc. I have been working on recently are on my
web site at

Best wishes

Ian,
Have a look at
They do a stepper board 30v dc, 2 A max for 28.17 Pounds UK
They also publish data sheets on stepper driver circuits under data sheet number
232-5345.
These are 'pdf files and can be read with Acrobat
They also carry stepper motors in 17,23 and 34 frame sizes.


Regards,
John Stevenson
Nottingham, England

A few links people might find usefull.
Please feel free to add to:-


Ahha Controller web site.
What is usefull on this site is the demo software.
if you ignore the nag screen saying that you haven't got a card fitted this
works as a very good simulator. The program will not allow you to edit any files
but these can be edited out of the program with DOS edit and then re-run.

Look for a file called Manedit.txt this is a good file to learn the basics of
CNC as is the help on F1


Bobcads web site
Cheap CAD / CAM package that will do some 3D work.
Not without faults but good for the money. I believe the demo is the full
version but limited to either so many lines or so many days.


Discriminator web site
A CNC simulation program with full editing facilities like renumbering,
different codes in different colours and a graphical display of the tool path.
Demo version virtually uncrippled but full version only $30.00


Dolphin web site
Good and cheap 2 1/2D CAD / CAM package for mill, lathe and wire EDM plus
involute and coms package all in at one price, no extra to pay.
Old DOS program but very user customiseable and unlimited support.

Regards,
John Stevenson
Nottingham, England

On Sun, 09 May 1999 09:28:32 -0700, garfield@... (Gar Willis)
wrote:

BTW, Rhino, especially for what the program does, is actually NOT
terribly expensive. I think I saw one early adopter vendor selling
copies for around $400 IIRC. Not cheapo, to be sure, but not like a
license for a full copy of Autocad, neither.

Geez, Looeeze, I'm havin to backtrack up the filetOfoot menu ad nauseum
here! Sheesh. IF ONLY I'd read the archives of previous posts before I
started blathering.

Turns out Andrew Werby, who is IN this group, was the guy I was thinkin
of in me post above, and at least THAT part of me pea brain that stored
the *price* was working aright. His "early adopter vendor" offer for
Rhino3d is at:


Sheesh, me whada Maroon, eh?

Garputz

type it is www.teachcnc.com

As previously promised, here's a blurb on a unique US Gypsum
castable/machinable medium that's plaster-like (read, inexpensive), BUT
instead of machining off in a dust/powder as you'd expect with plaster,
it forms actual/real CHIPS/swarf and can be cleaned up easily. It also
gives nice sharp feature definition post-cut and is easy on cutters,
unlike ordinary plaster.

I see the supplier I got my sample from isn't there anymore, so I have
to track down another for a price. I'll get back to ya on that.

*Rayite 100*

"This gypsum product offers an efficient
means of producing prototypes,
moulds and models. Easy
water:powder mixing and close 'cast to
size' aspects makes less waste than
other methods. High edge definition,
non-hazardous shavings, low cutter
wear. Mix it, Cast it, Machine it."

[note the last sentence, eh?]


Rayite MDM (the "MDM" stands for "model duplicating media")
which is highly touted by the professor emeritus corporation of auto
body styling and contour modelling, Chavant, Inc. :

and take a look at the articles on model and pattern making with Rayite.

Although based on the same chemistry, Rayite 100 and the "MDM" product
are distinctly different materials targeted for diff. usage, but I
figured BOTH might be of interest to the group.

Gar

Hello everyone! I'd like to send a thank you to Bill for starting
this list, and for dropping me a note to check it out. Looks like
there's a *ton* of talent here, and some real potential for a good
new source of info on this topic.

A little bit about me: I'm the guy who setup the DRO+ page at
. It's a homebuilt encoder
interface that's very similar to the US Digital interface card
that some members of this list own. It's very much a work in
progress, but I'm happy to note that at least one user has had
success in building it. There may be more, but they haven't said
anything to me yet.

By trade I'm a mechanical engineer, but my hobbies range all over
the map. I've got a good amount of experience with motion control
and robotics, and built one semi-autonomous robot and one fully
autonomous, both while in college. I also did a ground-up CNC
conversion of a 10" South Bend lathe, including the software and
G-code interpreter. Got me an easy 'A' in my Senior Design class :)

Past projects have found me working with automation and control
schemes ranging from small, self-contained microcontrollers and PLCs
up to multiple-CPU, PC-based designs incorporating machine vision,
radar, and laser rangefinding systems. The mobile robot I entered
in the 1998 AUVS competition was probably the coolest thing I ever
did, and took 6th place overall. If it wasn't built around a huge
industrial style golf cart, it woulda taken first I bet. <G>

I don't have a home shop set up yet, since I just moved into this
house 4 months ago, and there's a list of honey-do's a mile long.
So, until the wife is out of chores (never will be, it seems) and I
get the time, I'm just an idea guy. I'll try to chime in where I
can be helpful, and I'll keep polishing the DRO page so even total
beginners can make use of it.

I have plans to expand the web page to include primers on steppers
and servos, instructions to build a 4-axis motion controller,
servo amplifiers and power supplies, and more. I'm really stuck
on PC control of machines. Robots, machine tools, whatever. As I
get brilliant and not-so-brilliant ideas for homebuilt control
hardware, I'm just going to add them to the webpage. At the rate
I'm going it might take me forever, but I hope not. :)

One last note to those of you who own the US Digital encoder
interface board: The DRO software at my webpage should work great
with it. My card and the USD card are both based on the LS7266R1
interface chip. Right now the software is a little lame, but I can
add backlash compensation, 3rd and 4th axis support, and feedrate
displays if you want them. Not much work involved either. If you
want something more, drop me an email and we'll talk it over.

I'm really looking forward to participating in this list. Looks
like you brought together one heck of a bunch here, Bill.

-Tom Kulaga

Don Fergle and myself have presented the CNC Seminars at N.A.M.E.S. for the
last two years - It is satisfying to see the standing-room-only crowds at
these seminars - I"ve been talking to the N.A.M.E.S. directors about an
expanded program for the next year's exhibition - Will advise when they let
me know if it is going to happen -

Consider something for Friday before the show - likely some of the
Yack arena would be available and you'd get most of a day. I'd love
something with some hands-on - making a decoder card or a display
(although a PC is likely a better deal on the latter).

I guess I should intro as well - I'm Russ Kepler. I am the list
admin for the modeleng-list (as well as some others) and do the odd
bit of machining in my shop. I've got a Lagun FT-2 vertical mill, a
newish Atlas 12x36 lathe, Atlas 7" shaper and am in the process of
rebuilding an Atlas horizontal mill. I have most of the additional
tooling I need - TIG, OA, stick welding capability, heat treat (I
also make my own bullet swaging dies) and such. I make mostly small
stationary steam engines and tools - I am in the middle of making a
small tool & cutter grinder from castings obtained from the UK.

Bill asked me here, even though I have expressed a lack of interest
in placing yet more computers in my home. I get enough of computers
at work (I design DNA and protein analysis systems) and with another
4-5 systems here (Linux on this system running as a usenet node) I
get enough exposure. That doesn't stop me from having a DRO in the
shop - I placed on one the mill some time ago, and someday would like
to do the same with the lathe.

Anyway, it's good to see some of the names here, and I'm sure that
it'll be a productive group.

--
Russ Kepler russ@...

Please Don't Feed the Engineers

That would be a great idea, I think we could come up with a design for an arm using some inexpensive encoders but the software
might be a bit tricky. Anybody got any ideas??

Gar Willis wrote:

I agree, Rhino is a stellar goodie (I was lurking on the beta testers
list during it's development, and I must say the developer guys are also
a bunch of nice chaps, no fat-heads, ifyagetmedrift).

The reason for chiming in was to mention something that is IN Rhino
already, and that is: interface drivers for a couple of the high-end 3-D
measurement tools, ya know, them gimbled arm thingies you use to
digitize in 3-D. Now, THERES a grand other possible group project, eh?
Develop a low-cost, workable resolution 3-D digitizing arm. Woooheee,
you are about to enter the "dream and drool zone".

---------------------------------------------------------------------

James P Crombie
Summerside PEI Canada

My Astronomy stuff
RhinoCad 3D Stuff

---------------------------------------------------------------------

In a message dated 99-05-09 14:06:02 EDT, you write:

<< From: garfield@... (Gar Willis)

Pardon e'moi, I tweaked the subject to help follow-on's.

On Sun, 9 May 1999 13:25:41 EDT, Jonty50@... wrote:

Hee hee, yeah, unlike the hobby itself, eh? :)

Umm.. I have more hobbies than time or money unfortunately. It's kind of
strange how they all seem to be coming together synergistically lately. I'm
into (in no particular order) astronomy, computers, heavy duty machinery,
electronics, R/C planes, hard SF (the kind with rivets) and amateur science
pursuits ranging from meteor trail observation by reflected radio waves to
building my own seismograph many years ago.

>The V bearings run around $20 each, it basically takes 4 per axis. I've
found
>that the B-W track is not necessary, the wheels do very nicely riding on
1/4"
>diameter hardened steel rod ( I use music wire) that can be just pressed
into
>a 1/8" deep slot milled in an aluminum bar or rectangular tube. Very smooth
>motion, even smoother than the B-W track.

[ Huh, neat trick! This is actually wunnerful news on the pricing front,
[too, specially for guys that wanna route stuff where they're not
[ necessarily looking for Bridgeport resolution.

Thank you.. I got the idea from playing around with sliding glass door
rollers for a really low cost/precision router table (let's face it; for
routing wood 1/64" is more than adequate). The sliding glass door roller run
just fine on 1/4" rod. If you polish the rollers and the rod a bit they are
surprisingly smooth too.. I was gonna use birch ply for the whole thing,
table, gantry and so forth and just rout some grooves for the rod to lie in.
Another promising project that has not yet come to much beyond a few
preliminary experiments.

[ Jonathan (do you go by that, or is Jon OK?), lets peel the next layer
[ off the onion if yer willin? What are you using for axis translation:
[ rackNpinion, lead-screws, what? And WHERE on earth did you source the 8'
[ dimension on the Y axis trans. from?

Jon is fine.. I saw there was already another Jon here so used the
untruncated moniker to try and avoid confusion. BTW, you're one of the few to
spell Jonathan correctly.

I've been mulling several different translation options. There are linear
driver steppers that have a built in lead nut and ride on a lead screw. I had
thought to place a lead screw on either side of the table for the 96" axis
and just allow a linear stepper on either end of the gantry to carry it. This
plan avoids the whipping problem associated with turning long lead screws at
high RPM.

Another option would be a belt drive using a toothed belt and gearwheels. I
have all the parts for this option and am currently designing the gearboxes
required to allow a 0.0005"/step cog belt system. Belt drive is nice because
it has inherent dampening and cushioning properties and also doesn't mind a
some dirt and grit much. Use the larger size belts (I'm using 1" wide "L"
belting) and they are remarkably strong.

Another idea which I'm getting from my Astronomical interests is a form of
friction drive. Before you think I'm completely whacked out, let me tell you
that large telescopes around the world are gradually moving from a worm and
gear style drive to friction drive to track the stars (rotation of the earth
actually) in order to perform long duration astrophotography. Friction drive
is both more accurate and more easily machined than a worm and gear. Yeah, it
surprised me too...

Anyway, I envision an aircraft type cable stretched the length of the axis
with a friction type drive working its way back and forth down the length of
the cable. The cable will describe a path in much the shape of the greek
letter omega as it wraps around two passive pulleys at the left and right
bottom of the omega and a somewhat larger driven pulley that will form the
upper loop of the omega. I've done a couple of quick and dirty experiments
that have made me fairly confident that I could produce such a system that
would work to my requirements.

] Also, given your structure and your axis hardware, roughly what
] resolution are you hoping for?

For my purposes,. I'll be delerious if I get 0.002" repeatability, 0.010"
wouldn't be unusable.


[One of the other nice attributes about this type of guide is that it
[ doesn't require surface friction lube'ing like shafting or ways, eh?
[ That can be a problem when routing things like wood and especially foam
[ or plaster. This fact was brought to my attention somewhat "late" in my
[ own project plans, by a fellow who sent me some in-progress plans for a
[ big router table he had built outta "rollers on tubing". I'll get his
[ reference out if anyone's interested (actually be surprised if he wasn't
[ in the group already, but I've forgotten his name, and his plans are in
[ storage, sigh). He mentioned his design goals were to avoid having to
[ continually worry about cleaning linear bearings and keep the
[shafts/ways wet with lube. I thot that was a pretty important point I
[ had missed when planning me own, so I mention it to "the wise". B)

I've tried the "rollers on tubing". It works fine until you get dust under
the rollers and then the dust cakes under the intense pressure. The nice
thing about the BW wheels riding on hardened rod is that the contact area is
so small and hard that it just cuts right through most crap that gets on the
rods.. BW touts the "wiping action" of their wheels on their V track and it
does seem to work reasonably well that way too...

Well, I've run on at the fingertips for long enough.. Have fun folks...

Jon Croad...

Hello list, we now have 110 listees.

I would like to place a question for the list that has been bugging me.
In most of what I have read, a tool is changed automatically in the
professional machining centers, CAM.
How are tool changes handled in the smaller equipment like the Sherline, and
the modified manual machines?
I realize that it has to be done by hand, but how is the programing handled,
so that machine can be powered down, and restarted when tool is changed.
Also in the programs I have looked at, commercial, the characteristic's of
the tool are placed into the program.
How is this done in the small programs for the Sherline's , etc.? Also how
is the tool position and the program synchronized at the start of machining?
And after a tool change?
bill

Gar Willis wrote:

I even had a chat with one HP 'marketing droid' type about this, and
couldn't seem to get across to him the value of a 250 (X 4 = 1000 in
quadrature) cpi sensor. Since they make a 200 and a 360 cpi model
presently, there's no reason they couldn't build a 250! And NO,
unhappily, their engineering guy told me (hope springs eternal) you
couldn't USE a 250 cpi optical strip with a 200 cpi sensor to get 0.001"
native resolution. The sensor arrays are specific to almost exactly the
optical resolution, so they need to MAKE the bloody thing!! 8(

actually, you can make the whole works yourself, if you can get the
grating. What you do is use another piece of the grating as an analyzer.
To obtain the 90 degree quadrature shift, you TILT the analyzer grating
such that the spots you pick for your photocells are skewed 1/4 of a
grating pitch with respect to itself. The only limitation on this is that
the grating needs to be wide enough so the 2 photocells can be placed
a short distance apart (1/4 to 1/2 inch) and when the analyzer grating is
tilted, both photocells can see through both the analyzer and the
measuring grating. A 1/4" wide grating would be about the minimum
width. If this isn't the case with whatever strip you plan to use, then
you need to make 2 analyzer pieces, and give one of them a position
adjustment, so you can set up the quadrature phasing. It really isn't
that hard. I was working with a .000005" version of a dial test
indicator that used the tilted analyzer grating trick. Even setting
that one up wasn't very hard, and that was a VERY precise set
of gratings.

Jon

On Sun, 09 May 1999 23:56:22 -0500, Jon Elson <jmelson@...>
wrote:

actually, you can make the whole works yourself, if you can get the
grating.

Yeah, but honestly, I don't have time nor patience to be making sensors
and adapting optics. Fine if it's my avocation, but it's not. I DO
appreciate the rundown on the basic simplicity of 'quad' via optics, but
I wanna make parts, not develop sensors and so-forth. It's just sad that
HP doesn't see the value of a 250 X 4 sensor array. If they did, then US
Digital would make the optics post-haste, and it'd be a done deal.

Me, I got other fish to fry. Sad (maybe) but true, life is short. B)

Gar

On Mon, 10 May 1999 01:40:30 EDT, Jonty50@... wrote:

Umm.. I have more hobbies than time or money unfortunately.

Gee, HOW unusual. -not- Heh.

Jon is fine.. I saw there was already another Jon here so used the
untruncated moniker to try and avoid confusion.

Ahh, yup, gotcha.

I've been mulling several different translation options. There are linear
driver steppers that have a built in lead nut and ride on a lead screw. I had
thought to place a lead screw on either side of the table for the 96" axis
and just allow a linear stepper on either end of the gantry to carry it. This
plan avoids the whipping problem associated with turning long lead screws at
high RPM.

Yeah, and it's used on several largish gantry systems I've seen on the
Web. Me bein paranoid, I worry about losing a count, and racking the
gantry, rather than the racking forces of possible imbalance on the
guides. Guess we all have our boogie-men to deal with.

Another option would be a belt drive using a toothed belt and gearwheels. I
have all the parts for this option and am currently designing the gearboxes
required to allow a 0.0005"/step cog belt system. Belt drive is nice because
it has inherent dampening and cushioning properties and also doesn't mind a
some dirt and grit much. Use the larger size belts (I'm using 1" wide "L"
belting) and they are remarkably strong.

Keep us posted; this sounds interesting for the "router-in-the-large".

For my purposes,. I'll be delerious if I get 0.002" repeatability, 0.010"
wouldn't be unusable.

Yeah, for my foam routing purposes too, 0.010" would also do OK.

The nice
thing about the BW wheels riding on hardened rod is that the contact area is
so small and hard that it just cuts right through most crap that gets on the
rods.. BW touts the "wiping action" of their wheels on their V track and it
does seem to work reasonably well that way too...

Ahh, I see, interesting; a place where concentrated force works to your
advantage.

Thanks for the feedback.

Gar

Hi list,
I hail from downunder, and like many of you have dabbled
a bit. My best fantasies involve building multi cylinder IC engines.
To this end over the past year have bought a small cnc Boxford
lathe 125TLC. and a small cnc mill. This 1985 lathe is about 50%
bigger than a Sherline and was origonally supplied to
schools as a cnc training lathe.
One of the catches was that it required a BBC Computer to
run it, and the one supplied was not well. To cut a long story
short it is up and running. In the back of my mind is a Microkinetics
conversion since a few years ago I bought the Microkinetics hardware
and software.
The mill is an American DynaMyte 4-axis (1987) with a 6"x6" usable work
envelope. I had difficulty useing the software system, and a knowledgable
friend converted it to run off the Microkinetics board and software.
I only have the g-code converter software as the cad part to convert
to g-codes is fairly dear. My adviser says I will
learn more about programming if I programme directly in G-code. I find the
Millmaster software a bit quirky, but I guess its like most learning curves.
So far I try and draw it up in Autocad, find all the co-ordinates,
and g-code them in. I haven't actually cut much metal yet, but drawn
a lot of circles and lines with a pen in the spindle.
Probably the most interesting project has been a motion control movie
camera system I built. This is a 16 axis system although up
to date I have not used more than 8. The card and software is from
Kuper Control and is specifically designed for the movie industry.
Kuper is in Albaquerkie USA. Their system was used in Titanic amongst
other films. The X axis is 8foot long, z axis is 5 ft high.
The tower runs on precision track with a wire control not unlike a
huge plotter with a winch drum at one end. the 2 stepper motors are
over 1000" oz with a planetry gear box on each motor. The cross member
carrying the 31 kilo camera and 40 kilo cross arm is counterbalanced with
70 kilos of weightlifters weights on a stainless steel cable running
over a pulley. (This cable broke on one memorable occasion that I
would rather forget) The other axis, all small stepper motors,
are pan, tilt, focus, zoom, turntable, and possibly iris.
There are a few upgrades planned. I acquired 2 10ft ball screws from
a huge map plotter that weighed over 3 tonnes and I hope to substitute
the wire system eventually.
The system is only really suitable for tabletop work. I have used this on
about 8 serious jobs, and it performed quite well.
I hope this is of interest.
Peter.

Peter Bailey
pbailey@...

James P Crombie <jpcrombie@...> wrote:
Subject: Re: Rhino Segue

That would be a great idea, I think we could come up with a design for an
arm using some inexpensive encoders but the software
might be a bit tricky. Anybody got any ideas??

[I've got an Immersion Microscribe digitizing arm, and although it was an
expensive piece of equipment ($3k) it doesn't seem very complex
mechanically. The whole thing swivels on its base, then rises about 10
inches and supports the main arm, which pivots in a plane perpendicular to
the table it sits on. At one end of this section is a counterweight, at the
other another pivot with a shorter section of arm with another joint from
which the stylus depends. All the joints, with the exception of the
swiveling base, are parallel, operating in the same plane of movement.
These are also very heavy-duty joints, in what appears to be die-cast
metal. If someone could figure out the angular encoders and software
interface, the rest could probably be done in a simpler manner if someone
had a reasonably well-equipped machine shop.]

Gar Willis wrote:

I agree, Rhino is a stellar goodie (I was lurking on the beta testers
list during it's development, and I must say the developer guys are also
a bunch of nice chaps, no fat-heads, ifyagetmedrift).

[I participated in that too, which is how I got involved in selling the
program when it came out. It was a rare privilege, as a user, to be
allowed to communicate directly with the writers of a program and to find
them so responsive to such various wishes and needs. I preserved and
categorized some of the most useful questions and answers we exchanged, and
have them archived on my site under "Rhinotes". ]

The reason for chiming in was to mention something that is IN Rhino
already, and that is: interface drivers for a couple of the high-end 3-D
measurement tools, ya know, them gimbled arm thingies you use to
digitize in 3-D. Now, THERES a grand other possible group project, eh?
Develop a low-cost, workable resolution 3-D digitizing arm. Woooheee,
you are about to enter the "dream and drool zone".

---------------------------------------------------------------------

James P Crombie
Summerside PEI Canada

My Astronomy stuff
RhinoCad 3D Stuff

[While these are handy devices, the thing I drool in my dreams about is a
home-made laser-scanner. It's basically a lot easier to catch 3d points by
shining a light at them than by physically touching each one. I heard about
a hand-held device some researchers at the V&A in London had cooked up,
which they were calling the "tricorder"- apparently it worked by casting a
grid over the target object, then comparing the distortions in the grid to
a flat one, and working out the location of the points from that. It
sounded good, but I haven't heard any more about it since last year, when
it was supposed to be coming on the market shortly. Perhaps it became mired
in a patent dispute.]

Andrew Werby

Andrew Werby - United Artworks
Sculpture, Jewelry, and Other Art Stuff