开云体育

Jonty50@... wrote:
Subject: Re: CNC Router How-To's

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.

[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.]


[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)

[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.]

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...

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

Andrew Werby

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

Roger says:

______________________________________________________________
_________________

Message: 15
Date: Sat, 08 May 1999 14:52:10 +0800
From: Roger Mason <rogerd@...>
Subject: Introduction and CAD Question

<snip>

I notice that the heading of this list includes "CAD". I am
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?

<snip>

Roger,

Having been away from ACAD for a few months and not having a copy in
front of me I can't give you a step by step...but, experiment with
these:

#1

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

#2

- Select said items and save them as a block. Not just a local block but
save them to disk, the command to type would be "wblock".

- Change to the desired layer and insert this block. Then explode it.

- Check to see if the new entities are on the desired layer.

#3

- Get a AUTOLISP book or on an AUTOLISP page on the web. Both are
littered with AUTOLISP routines for this sort of stuff.

______________________________________________________________
_________________

Message: 4
Date: Sat, 8 May 1999 09:09:43 -0500
From: "Steve Lindsay" <slindsay@...>
Subject: Re: Digest Number 1 & homebrew DRO

I didn't know that US Digital had a PC inerface card. This would
be the way to go for a dro. Life is probably much similar
this way

<snip>

I would think an
interface card
would be faster
and US Digital is probably doing a lot of the work on the
hardware/interface
that
I was doing in code.

Steve,

This is correct. They buffer the incoming quadrature pulse train,
therefore it is very difficult to miss a pulse. I haven't been able to
out crank mine (the PC I'm using is a 16mhz 286!). They also do up to
(software selectable) 4x quadrature count on board.

______________________________________________________________
_________________

Message: 24
Date: Sat, 08 May 1999 23:52:42 -0700
From: garfield@... (Gar Willis)
Subject: Re: interface board

On Sat, 8 May 1999 20:10:15 -0500, "Steve Lindsay"
<slindsay@...> wrote:

If US Digital has encoders to read from a linear strip this
would cure the problem of slippage.

This is correct.

Well, they DO, but doggonit they (or you should really read
"HP") don't
have a linear resolution that in quadrature comes out to some nice
English (or even Metric) quantum.

It is quite simple to apply any multiplier you wish in software. You can
have it read in cubits per degree it you want.

In the code I wrote you specify the unit of measure multipier, the
quadrture multiplier, etc. in a setup file.

Use the G& M code M06 that is for tool changes. In your code simply add M06
before the move that requires it. In manxnc some versions the machine stops
the X-Y travel. You shut off the spindle unless you have a spindle
controlled solid state relay and then change the tool and press enter.
Desknc is similar.
See www.teachcnc.com
Dan

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

Message: 1
Date: Sun, 9 May 1999 07:05:26 EDT
From: PTENGIN@...
Subject: Re: I'm New here

In a message dated 5/8/99 8:22:10 PM Hawaiian Standard Time, pencad@...
writes:

<< Now, my project I want to do I to assemble a laser
cutter of approx. 40-50 watts, CO2 powered laser. >>

Hello folks. Peter Tsukamoto here. I have just joined and am most impressed
with the potential of this group. I look forward to reading the posts
everyday.

In regards to the laser project Don is attempting, my only input would be to
use extreme caution around a laser processing machine. If any of the laser
energy inadvertently got directed into a persons eyes, that would be the end
of that persons vision. I doubt the laser goggles sold by the laser makers
would be enough to prevent damage. At the very least, a visit to a metal shop
that has a metal cutting laser and observing the shielding techniques would
be warranted. Peter

I used to design, build, and service custom laser machining systems. If
you are inexperienced with such systems, I recommend finding out how the
commercial ones are internally arranged. At the bare minimum, all the
possible beam paths should terminate in non-reflective surfaces that can
stop the beam. We used to build our (YAG) laser heads into a well so
that if a mirror was misadjusted, it would be stopped by the wall. I
know that there are commercial suppliers of CO2 heads, perhaps their
catalogs can help a bit.

Jim Eckman

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

Gar Willis wrote:

From: garfield@... (Gar Willis)

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.

Well, I really don't think it would be that big of a project. But, knowing that,
I went with precision ballscrews and relatively cheap shaft encoders. You
can get a much greater resolution that way. A leadscrew with .200" lead
(5 TPI) and a 1000 line encoder (counting all transitions for 4000 counts/rev)
gives resolution of .00005" per count. If you can get a .100" lead screw
(I have one for the Z (quill) axis) you get .000025" per count - that's 25
micro inches. Great for EDM feed.

Jon

WAnliker@... wrote:

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.

Well, an M02 is a temporary stop in the program, not the end. So, the
control waits for a manual command to 'un-pause'. There are also
commands to stop the spindle, coolant, etc. I don't have the spindle
control hooked up yet, so I manually stop the motor, but the program
has to retract the quill, and maybe move the table so there is sufficient
clearance to pull the tool holder out of the spindle. I have gotten a selection
of end mill holders to mount all the different sizes of tools at repeatable
Z offsets. I made a thing that looks like a cylindrical parallel, but has an
R-8 taper socket in it. I can measure the length of a tool, and reference
it to some 'master' tool. I use a center drill for my 'master' reference.
You can see some bad pictures of this at :

Most CNC controls have a tool length offset feature for this purpose.
You set the 'master' tool so that Z=0.0 when the tool is touching the
top of the work (or the surface the work will be placed on, if you
have Z=0.0 for the bottom of the part). You then enter the offsets
(the difference between the master length and that tool's length)
into the tool length offset table. When the program selects the new
tool, it will add the offset to the requested Z position, to compute
the position to move the tool to.

Also in the programs I have looked at, commercial, the characteristic's of
the tool are placed into the program.

It is not necessarily in the program, but for the sake of remembering what
tool to use, it should at least be a comment. RS-274D comments look like
N0100 (Insert .500" end mill)

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?

Using a .200" edge finder near the lower left corner of a part, you would
touch it to the left side, and then enter in MDI mode G92 X-.1
because the edge finder's center is .1" left of the part. Then, touching
the edge finder to the bottom edge, you'd enter G92 Y-.1.

Then, for setting height/depth, I often use either a center drill or an
end mill for the first operation. So, I lower the tool until it almost
touches the top of the part, then I slip a piece of paper I know is
.005" thick under the cutting edge, and jog the tool at an extremely
slow feed rate until the paper drags under the cutting edge. Then, I
enter G92 Z.005 (because the tool is about the thickness of the
paper above the top surface of the part).

And after a tool change?

If the tool length is preset, and the program will call up the correct
tool length offset (by tool #) then you do nothing. Otherwise, you
need to do the 'touch off' thing above to reset the Z coord. The
X and Y will not be affected.

Jon

There are a couple of air spindle jig grinders that might fit you needs, we have one at work that can be put on a milling maching
or into the tool holder of a lathe, nice little tool. its about 3'' in dia and 3" long with 3/4 arbor about 2" long to mount it
with. Comes with a filter, regulator, oiler setup and runs at 60k rpm, will tap 1/4 or smaller tools
take a look at the following url

Brett Gober wrote:

From: "Brett Gober" <bgober@...>

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

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James P Crombie
Summerside PEI Canada

My Astronomy stuff
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Thanks all for the information on tool changes and positioning, made it sink
in finally.
Especially liked the concept of having tools preset in there holders.

Now the next question.
In looking for stepper motors, I often find only amps and volts given for a
stepper. Is there a relationship between the in/ounce rating of a motor to
the amps/volts specification of the motor?

I am looking for one stepper in the 400 in/oz. range, and two steppers in the
250-350 ranges, prefer low dollar as the retirement budget is somewhat
limited. Actually an understatement, very limited.
Bill

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

Hello,

I saw your note on the alt. machines. cnc newsgroup and decided to join.

I am a clockmaker who makes precision regulators, mostly half second mantle
regulators. I make my living repairing old clocks, mostly european 18th
and 19th century pieces.

Like most classically trained horologists, I was trained to work with
files, and hand gravers on watchmakers lathes, and all sorts of bizarre
techniques from the dark ages of metalworking. There are clockmakers who
think it is somehow cheating if you have a lead screw on your lathe.

I have slowly expanded my machine shop where I have a 10" south bend lathe,
a Bridgeport clone kneemill with DRO, both bought new, and two surface
grinders, the older of which I plan to rig up with polishing wheels and use
as a surface polisher. I have a bench top horizontal mill by Barker, which
I use as a dedicated wheel cutter, when accuracy is not of critical
importance, and an old potter lathe which I use for abrasive stuff which I
want to keep away from my good tools. That and a few of the aforementioned
jewelers lathes and a couple of polishing spindles make up my basic setup.

I suspect that there is no way to make a living at what I like to do unless
you do things in quantity, and hence my interest in CNC. I have been a
longtime lurker in alt. machines. cnc, but find it puzzling and ocasionaly
intimidating.

Anyone with an interest in my work can take a look at my (somewhat
outdated) web site at www.arcadianclock.com

I look forward to some interesting stuff.

David M. Munro

My intro: Roland inspired me to get into CNC through his Home Shop
Machinist column. He helped me over the phone too. I have a mill/drill
and Sherline mill that are converted. Dan Mauch has supplied me with a lot
of parts and a lot of help. Kevin Carroll helped me with his Ericsson
stepper drive design. I made a couple of controllers with them. I just
bought a pc board from Dan to make another one (I got tired of making the
pc boards). I have built a stepper controller at work to control a motion
control unit for a 3D UV curing oven.
Recently, I have been interested in the Nist EMC project. Jon Elson has
been very helpful with this. He has a servo amp kit that takes advantage
of this free and powerful CNC software.
My next project will be to set up the EMC controller on another computer.
It involves setting up Linux, which I have done before, but am not good at.
I really need some help getting this up and running. The last time I set
it up I ended up removing it because things were going wacky.

As you can see, this group is very integrated. Most of us have talked to
each other before. It's great that we have a forum ( I was getting tired
of "How do you get a chuck unstuck?" or "What's the best milling machine to
buy?" on rec.crafts.metalworking). We will come up with a lot of good
discussion.

Tool change question:
I have been using Maxnc software on my CNC mill/drill and have found that I
can make a tool change and touch off on the top of the part with little
problem. The biggest problem is the fact that it is a round column
mill/drill that makes moving the head up and down tricky. Most of the
time, I try to put the work in a vice and then I will jog the spindle away
from the part to get clearance. Jog back when finished and touch off. The
fabled RF-45 mill/drill, with dovetail column would work a lot better. (I
say fabled because I know of only a few people who have them and Rong Fu
doesn't seem to promote them.) An RF-45 would make a real nice CNC
conversion. Anyone have one out there?

My question to the group is: Who is now using EDM in their home shop and
what are you using it for?
I know about the tap busters, but what about die work? How about wire EDM?

Thanks,
Dan Falck
Nashville, TN.

In a message dated 5/10/99 8:32:25 PM Pacific Daylight Time,
dmino@... writes:

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

I am not sure but the larger magazine racks often times have it. If you
don't find you can order it from Nuts and Volts. e-mail editor@...
or Http://www.nutsvolts.com
bill

On Mon, 10 May 1999 13:55:16 -0500, Jon Elson <jmelson@...>
wrote:

Well, I really don't think it would be that big of a project. But, knowing that,
I went with precision ballscrews and relatively cheap shaft encoders. You
can get a much greater resolution that way. A leadscrew with .200" lead
(5 TPI) and a 1000 line encoder (counting all transitions for 4000 counts/rev)
gives resolution of .00005" per count. If you can get a .100" lead screw
(I have one for the Z (quill) axis) you get .000025" per count - that's 25
micro inches. Great for EDM feed.

Good point. Lack of lash in the screws sure DOES help out in other ways,
don't it! And if you used steppers on those screws, at those
resolutions, you would even get to watch the motors twitch! B)

Gar

On Mon, 10 May 1999 10:21:57 +0100, Andrew Werby <drewid@...>
wrote:

[I've got an Immersion Microscribe digitizing arm
...
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.]

Not to mention that the arms themselves could be made using available
carbon-fiber tubing, which is VERY stiff. My guess is the trick is in
the encoders. For example, just using the highest res rotary encoders
from USD, a 360deg pie chopped up via quad into 8192, sensing the
position of the end of a mere 10" arm, yields about a 0.008" resolution,
just in the first arm's position, so with 4-5 joints, it adds up pretty
fast. Unless of course I've inadvertantly used some "new math" and
comfoosed meself.

[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". ]

Excellent, yeah I saved lots of stuff too; probly not very organized,
tho. Good to know your notes are there.

[While these are handy devices, the thing I drool in my dreams about is a
home-made laser-scanner.

I think this feeling is shared widely. I know that the esteemed "Dr.
Foot" aka Chris Ellacott in his recent postsNaspirations here on
applying 3D-digitizing to his "orthotics", fancies laser digitization.

Maybe someone onlist who's familiar with the technology could comment on
the relative difficulty of making a laser-based scanner.

Gar

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

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:
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)
5) CNC mill ( to mill the finished/corrected model)

There are laser scanners out on the market, but they are expensive - this thing could be on the small side because you (I) would just be scanning a surface the size of the bottom of your foot.

Would love to hear comments
Chris Ellacott
footman@...

Peter:

Very good point you raise here. I am very aware of the reflected beam
that can arise with lasers and will do my best to encase the table while
the laser is on and/or working. Anyone who comes near the machine while
the laser is on will be required to wear special glasses as well. Also
the machine will have it's own room for working that has only one window
and a lockable door.

Thanks very much for mentioning it to me.

Don Hughes

PTENGIN@... wrote: