开云体育

In a message dated 99-05-10 02:17:47 EDT, Gar writes:

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.

Encoders on the linear drivers?

Drive one end of the gantry with a linear driver riding on leadscrew and then
use a figure 8 loop of aircraft cable to drive the other end of the gantry.
With ball bearing pulleys and 3/16" cable tensioned to near its rated load
(300 lb-ish I think), this works pretty well. I've seen the cable loop trick
done on a torch cutting rig that was used to cut large shapes from steel
plate up to 6" thick.

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

After taking apart enough big dot matrix and impact printers for motors and
power supply parts it dawned on me that just maybe IBM engineers had a clue
about linear motion. Take the same concept and beef it up by a factor of ten
or even a hundred or so... hmm.. The cable translation scheme comes from
looking at some old HP plotters and doing the same kind of calculation.

I worked in the oilfield for a while and found that building things big is
often easier than building them small, if you know how to rig large
equipment. Up to a point, brute force is usually cheaper and easier to hack
than high tech.

Jon

In a message dated 99-05-10 13:34:38 EDT, Andrew Werby writes:

Andrew Werby wrote:

[I believe the "shopbot" system started with a cable system like this, but
abandoned it in favor of rack and pinion gearing, which is less subject to
stretch and more positive.]

If you've seen a ShopBot "in the flesh", you'll understand. I live in Atlanta
and have been going to the Internation Woodworking Shows here for the last
six years. ShopBot is definitely in the shallow end of the gene pool as far
as CNC routers go. Pretty flimsy stuff. So it stands to reason that their
implementation of a tensioned cable arrangement wouldn't work all that well.

Andrew wrote:
[This is something I've been wondering about as well. If these things are
always hanging out covered with lube, it seems like they would be magnets
for dust, which is abundant in machines like this.]

Exactly, if you can avoid exposed lubricants you have gained a large
advantage in a machine of this sort.

Jon wrote:
>>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...

Andrew wrote:
[Perhaps brushes could be mounted in advance of the wheels, to push chips
out of the way?]

Yeah, I've done this and it works to some extent. After the brushes wear a
bit you have to readjust them or dust starts to cake again.

I'm gonna try to take a few pictures of my little CNC router setup. I"ll put
'em on a website and link to it in a message "real soon now". All I have is a
grayscale quickcam so don't expect superb quality.

Jon

Hello everyone,

So far I have been only monitoring this dialog. Some really good stuff
here. I was at NAMES several weeks ago and heard the presentation on CNC.
Thought it was really good. I live near Houston, Texas and am a member of
the Houston Home Metal Shop Club. We have several members who have built
home brew CNC machines. One of our members uses his to turn out unique
articles such as knobs for an church organ restoration project.

Regarding the Nuts and Volts magazine, after seeing the reference to it in
one of the post here, I went to their website. They offer a free sample
copy before you subscribe. The web site is at <>

Keith Mitchell

At 09:40 PM 5/10/99 -0500, you wrote:

From: "Dennis Mino" <dmino@...>

Are those magazines available at Barnes and Noble, etc.?


----- Original Message -----
From: <WAnliker@...>
To: <CAD_CAM_EDM_DRO@...>
Sent: Monday, May 10, 1999 7:23 PM
Subject: Re: [CAD_CAM_EDM_DRO] [CAD_CAM_EDM_DRO Nuts and Volts Magazine.

From: WAnliker@...

I received my copy of the Nuts And Volts magazine today. I would like to
call attention to an article on page eight, of the May 1999 issue.
AT HOME WITH COMPUTER NUMERICAL CONTROL (CNC), part 1, by Dan Mauch
I have read and enjoyed the article, and look forward to reading the next
parts, as they come out. There are some nice pictures of the machines

built

by Dan.

We now have 119 members.
Bill


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_________________

Message: 1
Date: Mon, 10 May 1999 08:40:18 -0400
From: rmcilvaine@...
Subject: Re: Digest Number 2

Mac said:

#1

- Select said items.
- pick or type the "change" command and select "layer" as the thing to
change. enter the new desired layer.

Yup, after reading the other posts, this should have been "chprops" not
"change". Amazing how fast you forget.

_________________

Message: 4
Date: Mon, 10 May 1999 06:58:16 -0700
From: "Dan Mauch" <dmauch@...>
Subject: Re: Digest Number 3

I have just made two ISA PCB cards that use the US digitals
7266-R1 From:
Tom Kulaga <tkulaga@...> web site. I will let you know
how it works in
a day or so.

Dan,

Please let us know. Can you also keep track of how much time it took to
build and what the final parts total $'s are? It would be good to get a
comparison to the price of the US Digital board. It uses 4 of the 7266
chips.

Message: 19
Date: Mon, 10 May 1999 22:57:21 -0400
From: "Chris Ellacott" <footman@...>
Subject: laser scanning

maybe i'm being [very] naive here, but, is the idea of a low
cost laser scanner a pipe dream?? what i envision
would/could? contain a few basic parts:

Depends on the definition of low cost scanner is. You can buy hi-res
flatbeds for way under $100US.

1) laser source (? spinning laser pointer type device to
create a 'line' of light - aperture to focus light on
required surface)
2) video camera (? filtered to just 'see' the laser light and
set at an angle so as to see the surface contour 'curve')
3) screen grabber board on PC (would 'grab' the image of the
contour of the object (foot in my case) at preset intervals of time)
4) CAD software (to assemble these curves into a solid model
and then alter the image as required)

This is the tricky software part. The curves from a scanned image are
typically a series of unconnected dots that appear (to the human
eye/brain as a line when displayed) as a line. So the software has to
infer which line each dot belongs to. To the computer, the dots are just
a big bucket of dots, each of which has an x,y,z coordinate.

Companies like Kurtzweil have been working on this since the 60's.

I'm not saying it can't be done, just that it won't be cheap technology
for a few years.

Hi everyone, I recognize a few names here. This seems to be the resource for my current project needs! I appreciate any input.

I am automating a coil-winding machine via either steppers or servo motors. The machine consists of a spindle (holds the coil bobbin) and a leadscrew which is electronically "geared" to the spindle. In a nutshell, the wire is layed down similar to a threading operation on the lathe, with multiple layers. The ratio of spindle to leadscrew must be variable from roughly 6/1 to 20/1, laying down magnet wire on the order of 100 to 800 TPI.

Torque requirements are negligible. Spindle speed must be variable from 0 to 300 RPM, with a very gentle acceleration/deceleration to avoid snapping fine wire.

I considered a closed loop system, but the chance of losing steps is minimal due to the minute torque requirement, and lost steps really won't harm the coil. So unless a powerful argument is made for servos, I have decided upon 2 stepper motors to control the machine.

My main question lies in software. I am a very good Visual Basic programmer, and I want this system to work under windows 95. Most software requires DOS Basic or C, which I really want to avoid. I can write to the parallel port, etc. Can anyone point me to a manufacturer who sells reasonably priced hardware, and software libraries which will allow me to accomplish this task? Is programming a soft acceleration difficult with steppers? I'd like to keep the cost of the NC portion under $1,000. TIA, I hope one day to be able to contribute to this group!

Kurt Bjorn
pyroware@...

If not you can order a copy or a subscription for Nuts and Volts. Call
1-800-783-4624 for a subscrtion or 1-909-371-8497single issues.
I Have sent in three articles so far and there will be a fourth. The first
one was published this month. Besure to tell them you want the issue with
the article At home with CNC.
Dan

trying to teach myself how to use AutoCad in my spare time. I
haven't got very far with it, but can produce simple two
dimensional, dimensioned, drawings. I have what ought to be a
simple question, but I cannot seem to find the answer. How can you
copy items (lines, text, dimensions, etc.) from one layer to
another? All my attempts just duplicate the items on the original
layer! Can it be done? If so how?

If you just want a copy of what of some or all of the stuff one layer
over to another then...
Type "copy" and press enter
It will ask to to select what you want to copy.
Pick lines or whatever one at a time or type "c" (for crossing)
and draw a box (pick one corner then the other). Anything
this crosses over or is in side of will be selected.
When finished selecting hit enter. It will ask for the base
point to copy from. (if you want them to be copied right on top of
the original just pick the same spot twice). An easy way to to
that is type 0,0 and hit enter and then type 0,0 again and
hit enter. Now there is a copy of what you selected right
on top of the original....but they are on the same layer.
You will need to move one copy to another layer. To do
thay type chprop (short for changeproperty) and hit enter.
It asks you to select what you want to change and it would
now be hard to select just one of the copies by clicking.... so
type "p" which stands for previous and hit enter.... this selects
all of the entities you selected last time (the ones you copied).
Now type "la" which stands for layer and type in an existing
layer you want to move them to and press enter.

"Brett Gober" <bgober@...> wrote:
Subject: Re: Minimill spindle

I am researching a minimill setup for machining detailed plastic injection
dies in aluminum or magnesium. I have found answers to most of my questions,
but I'm stumped when it comes to spindles. I'm looking at a system from
Model Master but I would like
to find some options for the supplied spindle. The air spindle pictured on
their web site is no longer offered. I'm told that the spindle supplied is
made by them (???) and is powered by a flexshaft motor. The motor doesn't
seem to be so important but I would think that something as important as the
spindle would be better to be purchased from a company that specializes in
precise spindles. I was told that their option for a high speed air spindle
is $2700. Sounds high, but I really don't know anything about what spindles
go for. Sooo my question for the group is where can I go to learn about
spindles that would replace the stock spindle on this machine. What makes a
spindle good or bad? I would like it to be highly accurate and high speed
with a 1/8" collet. I don't think I care if it is motor driven or air. I
think the mounting hole for it is 1". Any info on small spindles is greatly
appreciated as I am totally ignorant on this subject.

Brett

[CNC Junior sells one as an option for their machines for a lot less ($545)
, but I don't know if it would fit the Modelmaster. It is rated at 30,000
RPM, which is medium fast- do you need more? I don't know a lot about it,
but if you're interested I could find out for you.]

Andrew Werby

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

hi Kurt,

the main reason that you find little or no systems to run under Visual Basic
on windows 95 is that the system can pause periodically for "higher priority"
tasks. this behaviour cannot be easily stopped and would cause severe
problems if machining a surface. in coil winding the loss of an occasional
coil may be tolerated but the incentive to provide the software is not there.

accomplishing the geared behaviour you want between the spindle and the wire
guide is easy, especially for simple ratios. i think it is obvious, but will
just state that you use count pulses for the spindle and if your ratio is
10 to 1 then for every tenth pulse to the spindle motor the wire guide gets
one pulse. ramping up and down is also conceptually simple, your software
uses a fixed reference clock and for starting at the lowest speed it counts
say 100 clock times and issues an output step to the spindle motor. the
increment of how many clock times to wait is decremented and after 99 clock
times then next step is output and so on until the number of clock times
corresponds to the step frequency of the final speed you want the spindle
to run. at this count, the decrement loop is turned off and the spindle
runs constantly at the highest speed. of course, since the wire guide is
just a ratio from the spindle motor, it's speed ramps up exactly with the
spindle speed.

hopefully someone else on the list will be able to point you to a solution
using your desired software within your budget. commercial products
are available that will run with a VB front-end and include interface
boards inside your computer and the driver boards and motors, but all i
am aware of are several times your budget.

-ron wickersham

On 11 May 1999 pyroware@... wrote:

My main question lies in software. I am a very good Visual Basic programmer, and I want this system to work under windows 95. Most software requires DOS Basic or C, which I really want to avoid. I can write to the parallel port, etc. Can anyone poin

t me to a manufacturer who sells reasonably priced hardware, and software libraries which will allow me to accomplish this task? Is programming a soft acceleration difficult with steppers? I'd like to keep the cost of the NC portion under $1,000. TIA,


I hope one day to be able to contribute to this group!

Kurt Bjorn

Jonty50@... wrote:

In a message dated 99-05-10 02:17:47 EDT, Gar writes:

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.

Encoders on the linear drivers?

Drive one end of the gantry with a linear driver riding on leadscrew and then
use a figure 8 loop of aircraft cable to drive the other end of the gantry.
With ball bearing pulleys and 3/16" cable tensioned to near its rated load
(300 lb-ish I think), this works pretty well. I've seen the cable loop trick
done on a torch cutting rig that was used to cut large shapes from steel
plate up to 6" thick.

On big gantry bed mills, VBMs and similar machines, they use what they call
a tandem servo. What this is, is two completely separate servo drives, with
encoders, limit switches, home switches, etc. The CNC control is set up
such that it keeps the two axes aligned at all times. They apparently use a
bearing joint at one end, and a bearing in a slot at the other end, so the
machine won't be damaged if the two servo get out of sync. After doing
a home operation, they should remain sync'ed at all times. The software
on my 1970's Allen Bradley 7320 control was set up for this on the Z
axis, which confused me for a while.

Jon

May 11, 1999 - 4:24PM - CDT

1) It's good to know that so many people are interested in this topic -
Hopefully I can get some help in the areas in which I am weak -

2) Re: CNC Router How-To - Gar mentioned the routers that I've built (2) -
However they didn't use rollers on tubes but instead used Thomson NYLINER
bearings which are a very low-cost sliding bearing - I used DOM tubing which
is relatively inexpensive and accurate - I've done a lot of work with
woodworking machinery and chose this method because the tubes can be
lubricated quite successfully with floor wax instead of oil or grease and it
doesn't attract and hold the dust - Also the sliding bearings are self
cleaning - Haven't had any problems and they have been in service for a long
time -

3) Re: High speed spindles - I've successfully used a 20,000 rpm electric
spindle made from a DUMORE die grinder - They are available with collets up
to 1/4 diameter and they are relatively inexpensive - About $300 as I recall
- I am currently working up an air turbine spindle of 40,000 rpm using a
turbine from AIR TURBINE TOOLS, Boca Raton, FL - It too has a collet nose
and will take tools of up to 1/4 dia - This one is also relatively
inexpensive at under $400 - While $300 or $400 is not "chicken feed" these
are the best prices I've been able to find for tools of this quality - For
the CNC Routers mentioned in item 2) above I used PORTER CABLE commercial
routers with collets up to 1/2 inch diameter - Can't remember the rpm but it
is probably in the 15,000 to 20,000 range - As I recall they were less
expensive at about $150 but don't have nearly the quality of the other two
units - Perfectly good for routing wood but not for more precision
applications -

4) Re: EDM users - I am using Ram and Wire EDM - However they are a sort of
mixture of commercial and homebuilt - What I did was find some distressed
commercial units and rigged them up with a combination of software and
hardware - I've been working on a homebuilt Wire EDM for quite a while but
it seems that there is never enough time to devote to it - Now that the
newer Wire EDM equipment is out it is sometimes possible to find some REALLY
GOOD DEALS on the outdated stuff - The problem is just like that with buying
outdated CNC Mills - The controllers are horrible to keep running - A
combination of some of the homebuilt EDM power supplies that have been
published recently along with homebuilt CNC controllers could put these old
EDM machines in the home shops in the near future -

5) Re: Laser cutter - Several years ago I designed a laser welding machine
as a consulting job - The company used a YAG laser - I'm not a laser expert
but have spent qute a bit of time around industrial CO2 lasers also - If
possible I would suggest going with CO2 because it is a LOT safer and easier
to provide protection against damage to the operators -

6) Re: Tool Changes and Tool Length Offsets - Several people have responded
to this query but a side comment may be of interest - One key to a good
workable multiple tool system is an easy and reliable way to remove and
reinstall tools so that they are always the same length relative to some
reference dimension - I use ERICKSON quick change tools and have also used
several other systems - The problem with them is they are horribly expensive
for the hobbyist - I've been working on a homebuilt quick change tooling
system and while it isn't as nice as the commercial ones it is more than
adequate for home shop use and can be easily built - Everything is still in
the sketch stage but the actual tooling has been built and tested - This
will be a HOME SHOP MACHINIST column in the near future - I'll see if they
have any objections to my posting it to this list before it is published in
the magazine -

7): Re: STEPSTER software - I have downloaded this software and taken a look
at it - Haven't had time to actually get it running - I was saddened to hear
that the author had died recently - My question is this - Who is
successfully running this software and has anybody made any improvements to
it - Does anyone know of other CNC software available in source code - Or
have any of you written your own - I don't want to reinvent the wheel if
it's not necessary -

Roland Friestad <cardinal.eng@...

Hi Ron, thanks for replying to my posting. I know the windows environment
is a poor second choice to DOS, especially with cheaper controllers without
on-board processing, but I am determined to write a detailed GUI interface
for the coil winder. I also plan on using a stand-alone computer with a
decent processor, and no other tasks will be running. This will help smooth
out the process a bit, and avoid intermittent motion and pauses.


Arrick Robotics has an inexpensive 2-axis system that I am leaning towards.
After scouring dozens of WWW sites until my head hurts, there are very few
that aren't either pure DOS, too specific (3 axis mill conversions), or too
expensive. I like the Microkinetics catalogue, but to do the simple task I
want would require lathe turning software, full drivers, etc, at a high
price.

The flexibility of VB will allow me to greatly refine and easily modify the
interface.

Your description of acceleration and deceleration is simple and
enlightening. Thank you!

Kurt

The cover feature this month in _Computer-Aided Engineering_ page 56 May issue
is titled "Scanning Product Designs".

A laser scanner is on the cover and a large arm scanner is pictured inside.
This is just an overview of applications, how different types of scanners
work, post processing and the future of digitizing. there are also side-bars
with software vendors and hardware vendors. this won't tell you how to
build one but it is a useful resource to stretch your brain and see what
is being done in the field.

the article is not on the web site so far as i can tell (www.caenet.com)
but there are forms to subscribe. this is one of the free industry mags
so you have to fill in suitable information in their subscription form to
get on the list. (but Don Lancaster has told you how to do it, right?)

a note to Dr. Foot. -- they say there will be a feature article next month
on medical scanning.

-ron wickersham

What kind of costs are we looking at for one of these older EDM
machines,
perhaps with a dead controller? I have wanted to do some parts from time
to time that EDM would be good at, but could never justify the expense
of
having a "real" shop do them.

Bill Martin


Roland Friestad wrote:

ron wickersham wrote:
they say there will be a feature article next month
on medical scanning.

can't wait till next month!! thanks for the link...

Chris Ellacott

Looking for HobMaster, but please READ THIS FIRST! PLEASE, any responses
directly to me. I'm signed up for the Digest but so far I can't read it,
something about the formatting I think.

I'm looking for a version of HobMaster Lisp that I can run on AutoCAD R12c1
or R13c3. The "H" and "G" versions need R14, I know because I've been in
contact with Len Miller, the author of the program. Apparently he tries
always to be functional in the latest release of AutoCAD and seems to not
have saved any of the earlier versions of HobMaster.

If anybody can supply me with an earlier version of HobMaster which they
believe might run on earlier versions of AutoCAD, or can direct me to a site
wher I can download any version before Hbmstr_g.lsp, your assistance will be
greatly appreciated. (For any of you that are not familiar with HobMaster
Lisp, it draws a spur gear by simulating the hobbing process. It can be
downloaded from Len Miller's web site or
from .)

Remember, PLEASE, all responses directly to
Anthony
anthrhodes@...

Roland Friestad wrote:

From: Roland Friestad <cardinal.eng@...>

May 11, 1999 - 4:24PM - CDT

1) It's good to know that so many people are interested in this topic -
Hopefully I can get some help in the areas in which I am weak -

2) Re: CNC Router How-To - Gar mentioned the routers that I've built (2) -
However they didn't use rollers on tubes but instead used Thomson NYLINER
bearings which are a very low-cost sliding bearing - I used DOM tubing which
is relatively inexpensive and accurate - I've done a lot of work with
woodworking machinery and chose this method because the tubes can be
lubricated quite successfully with floor wax instead of oil or grease and it
doesn't attract and hold the dust - Also the sliding bearings are self
cleaning - Haven't had any problems and they have been in service for a long
time -

3) Re: High speed spindles - I've successfully used a 20,000 rpm electric
spindle made from a DUMORE die grinder - They are available with collets up
to 1/4 diameter and they are relatively inexpensive - About $300 as I recall
- I am currently working up an air turbine spindle of 40,000 rpm using a
turbine from AIR TURBINE TOOLS, Boca Raton, FL - It too has a collet nose
and will take tools of up to 1/4 dia - This one is also relatively
inexpensive at under $400 - While $300 or $400 is not "chicken feed" these
are the best prices I've been able to find for tools of this quality - For
the CNC Routers mentioned in item 2) above I used PORTER CABLE commercial
routers with collets up to 1/2 inch diameter - Can't remember the rpm but it
is probably in the 15,000 to 20,000 range - As I recall they were less
expensive at about $150 but don't have nearly the quality of the other two
units - Perfectly good for routing wood but not for more precision
applications -

4) Re: EDM users - I am using Ram and Wire EDM - However they are a sort of
mixture of commercial and homebuilt - What I did was find some distressed
commercial units and rigged them up with a combination of software and
hardware - I've been working on a homebuilt Wire EDM for quite a while but
it seems that there is never enough time to devote to it - Now that the
newer Wire EDM equipment is out it is sometimes possible to find some REALLY
GOOD DEALS on the outdated stuff - The problem is just like that with buying
outdated CNC Mills - The controllers are horrible to keep running - A
combination of some of the homebuilt EDM power supplies that have been
published recently along with homebuilt CNC controllers could put these old
EDM machines in the home shops in the near future -

5) Re: Laser cutter - Several years ago I designed a laser welding machine
as a consulting job - The company used a YAG laser - I'm not a laser expert
but have spent qute a bit of time around industrial CO2 lasers also - If
possible I would suggest going with CO2 because it is a LOT safer and easier
to provide protection against damage to the operators -

This is the project that I will be constructing for myself Roland, so if
at all possible I will have many questions for you as to the laser head
setup and the setting of the mirrors. Any insight as to the best way to
mount the laser? Stationary or on the gantry???. From the research I
have done so far, the linear movement of the gantry/optics is the least
of my worries. It appears that the laser setup and cutting control of
the laser is going to be the challenge. Any help is greatly appreciated
in advance from all our members during my project.

Don Hughes

6) Re: Tool Changes and Tool Length Offsets - Several people have responded
to this query but a side comment may be of interest - One key to a good
workable multiple tool system is an easy and reliable way to remove and
reinstall tools so that they are always the same length relative to some
reference dimension - I use ERICKSON quick change tools and have also used
several other systems - The problem with them is they are horribly expensive
for the hobbyist - I've been working on a homebuilt quick change tooling
system and while it isn't as nice as the commercial ones it is more than
adequate for home shop use and can be easily built - Everything is still in
the sketch stage but the actual tooling has been built and tested - This
will be a HOME SHOP MACHINIST column in the near future - I'll see if they
have any objections to my posting it to this list before it is published in
the magazine -

7): Re: STEPSTER software - I have downloaded this software and taken a look
at it - Haven't had time to actually get it running - I was saddened to hear
that the author had died recently - My question is this - Who is
successfully running this software and has anybody made any improvements to
it - Does anyone know of other CNC software available in source code - Or
have any of you written your own - I don't want to reinvent the wheel if
it's not necessary -

Roland Friestad <cardinal.eng@...

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welcome to CAD/CAM/EDM/DRO@..., an unmodulated list for the discussion of shop built systems in the above catagories.

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.

The way you describe it, it only uses 4 encoders? That shouldn't
be too difficult to do, I'd think. Using 2000cpr encoders you
could probably get pretty darn accurate too. It would be direct
drive to the encoders, so no backlash to worry about either. The
only critical thing would be to get the dimensions of the arms
dead accurate or your readings will be off. Using the index pulse
off the encoders would also be a must, and the initial dialing in
to determine where each arm is in space is also very critical.
Luckily, this is all one-time work, and once it was done, you
could just get down to using it.

As far as the software goes, I could handle something like that
pretty well I think. Well, let me get a little specific on that
one: gathering the point cloud would be really easy, but what do
I do with it then? Output into some kind of CAD program or
something? You'd need to stitch all those points together into
surfaces or you wouldn't be able to do much with it.

Give me a few ideas about how to use the output data, and we could
really go somewhere with this. I've got a few rotary encoders
sitting around here, and I could probably lash up something that
would be really inaccurate but good enough to test the concept.

-Tom Kulaga

On Tue, 11 May 1999 21:17:6 -0700, Tom Kulaga <tkulaga@...> wrote:

The way you describe it, it only uses 4 encoders? That shouldn't
be too difficult to do, I'd think. Using 2000cpr encoders you
could probably get pretty darn accurate too.

Not sure; did you check my short math doodle I posted recently. Looks
like with 2048 cpr X 4 in quad, with even a short 10" single arm (just
for purposes of illustration), the resolution per count is about 0.007",
and that's just for the first joint. Course, that's resolution, not
accuracy. Still, I DO think even with whatever res we could muster with
inexpendo rotaries, such a simple device would have lots of valuable
uses.

...gathering the point cloud would be really easy, but what do
I do with it then? Output into some kind of CAD program or
something? You'd need to stitch all those points together into
surfaces or you wouldn't be able to do much with it.

Think Rhino ... presto, done deal. If you look on the Rhino3D site
(www.rhino3d.com), under the topic of 3D-digitization, you'll see that
Rhino provides the model creation poof, from the point cloud. That's why
I suggested earlier that I'm sure them guys would provide the necessary
info to make such a DIY gizmo compatible with say their Microscribe
driver, or some such.

Give me a few ideas about how to use the output data, and we could
really go somewhere with this. I've got a few rotary encoders
sitting around here, and I could probably lash up something that
would be really inaccurate but good enough to test the concept.

Sounds GREAT. An intrepid experimenter! Goodie. I trust the factoids I
mentioned above regarding Rhino3D providing the surface model creation,
are sufficient to stimulate your cerebral cortex further? B)

Gar

Hello all,
I've not had the time to go back on your previous posts. I may be
rehashing a well worn thread but will ask again anyway. Has anybody used the
Microkinetics package with the encoder feedback? Any good? I have the same
comment on how "quirky" the MicroKinetics software can be. Is the Flash Cut
software any better? Substantially better? Worse? I've used a few servo
equiped machines and may now be expecting too much from my stepper based
machine? Thank You all in advance.
Peter