On 9/13/24 07:14, Stuart Stevenson wrote:
I agree BUT everything has limits. 5 axis is not a general panacea. Machine
geometry matching the desired result is paramount.
A programmer friend always said he could "program" almost anything with a
.020in end mill 40 inches long and it would work on the screen.
On Wed, Sep 11, 2024, 10:01 PM Dave Engvall <dengv...@charter.net> wrote:
There is nothing like machine geometry that fits the job you want to do.
:-)
On Apr 12, 2024, at 9:08 AM, Stuart Stevenson <stus...@gmail.com> wrote:
Good morning,
I am sitting here at 70 wondering how people get along without 5 axis. A
shop here in Wichita sent me 500 parts to run. He was running them on a 4
axis mori seiki. The runtime was a little over an hour. He wanted to
clear
machine time. He furnished programs, material, fixtures, cutters. The
envelope was 8 inches X 4 inches X 1 inch. We called them porkchops. Flat
bottom but with standing ribs at angles and contours. Long, small
diameter
cutters to reach small corners. I programmed the parts for my 5 axis,
made
new fixtures (a plate with locating bushings) and used much shorter
cutters. Machine run time was now 18 minutes. You CAN do 5 axis parts on
3
axis and 4 axis machines BUT (it is a very big but) it takes more time
and
effort.
My maternal grandparents were born in 1894 and 1895, My paternal
grandparents were born in 1903 and 1904. They also had stories.
regards
Stuart
On Fri, Apr 12, 2024 at 10:33 AM Chris Albertson <
albertson.ch...@gmail.com>
wrote:
All very true and well for someone equipt with the income and mental
gear to use that chain of tools profitably. But I'm an old Iowa farm
kid,
we made what we needed. The "store" was 15 miles of horse drawn wagon
over
a mud road the county graded about 2x a year and all of a days ride in a
wagon away. So we grew it, or made it from the woodyard, whatever. 2
miles
to the 1 room school, I rode an old gentle mare the first mile but had
to
walk the 2nd mile because there wasn't a barn for the mare during the
day
any closer to the school when the weather was bad. Grandpa across the
road
had electricity, a 32 volt delco wet glass batteries, charged by a
zenith
windcharger. The prop broke, so mother who was the only girl in the 1929
class on aviation technology at Des Moines Tech Hi School, proceeded to
teach her father how to carve the wing chord in a new prop. Worked well
in
less wind than the one we could get from Chicago. That led to grandpa
having the first electric washing machine in Madison County Ia when the
Maytag hit & miss tried to start backwards, broke the starter gears and
grandma's ankle. A wagon load of shelled corn went to town, and was
replaced by an electric motor and enough heavy wire to convert the
Maytag.
I still wear scars on one hand from getting it caught in the wringer
when I
was 5. We did not want for anything, we "made do" That is a hard habit
to
outgrow.
But today you own a computer, lots of CNC equipment, a 3D printer and
education is free and just a mouse click away. None of the stuff I
wrote
about costs even one dollar. I’m the old ririred guy now. Fusion360
is
free to use. I can print ther prats and then if. Needed sand the same
design to CNC machine or to an injection molder
I think you are right about relativity, Einstein very much admired James
Clerk Maxwell. Someone said Einstein ”stood on the shoulders of
Newton”.
Einstein corrected him and said “I stood on Maxwell’s shoulders”.
Thanks for the story. I always like to hear those “when I was a kid…”
stories. My four grandparents were born in 1902 through 1911 they
could
talk about the days before radio broadcasting and one-room schoolhouses.
One grandfather was a professional boxer in the 1920s and traveled a
lot.
But even more interesting to me, my wife’s parents and uncles were born
in
pre-war Japan. I think they lived through more change than any living
American. Sadly the last of them is in very poor health. My wife is
visting her mom in Tokyo right now.
Maybe when I am older I will talk about the days of manually driven gas
cars.
My electronics education is 100% self taught. My mother gave me an IQ
good enough to pass the CET test w/o cracking a text to study it. I
understand the physics of it including Relativity. Electronics and
Relativity go hand in hand, cannot be separated.
On Apr 10, 2024, at 12:09 AM, gene heskett <ghesk...@shentel.net
wrote:
On 4/10/24 01:57, John Dammeyer wrote:
A friend and I have been discussing exactly how to write the
G-Code to
create a spiral scroll.
His rotary table 90:1 reduction with a 1600 micro-step motor
could be set up
to move N steps for each step of the X axis to create the
spiral. But that
approach seems clumsy.
Say I wanted to cut a scroll with a 6mm pitch using a 3mm
cutter.
Without using G2 or G3 it's really just a triangle isn't it?
Move rotary
table distance A and move X axis distance A'. Do it in small
enough
increments and you get a spiral. But I feel like I'm missing
something
really simple.
Do you need a rotary table to cut a spiral? It is just a series
of locations in (x,y). OK, if you wanted to use only (say) the X and A
axis then you should use polar coordinates, not cartesian. The equation
of
a spiral on polar coordinates is very simple. Then you evaluate itat
many
thousands of points and at each point write gcode to “cut to” that
point.
You would not need the rotary table.
However trade the ultra slow rotary table in for a slow spindle in the
form of that 3NM motor driving a 5/1 worm drive like the rvs30, mounted
to become an A drive, all that on printed table mounts allowing it and
its live center to hang out past the ends of the table, can be a huge
time saver. It can turn up to around 500 rpm. The 3d printer supplies
the vacuum snoot for dust collection. Basically using a 3/4 router bit
at 2750 revs, it cut the time to make a vise screw from hard maple from
2 days (because the bit that carves the threads is a .0625 RN). Just the
rounding of the 2x2 stick took about 1.75 days with that fragile a bit,
now doing the preliminary rounding on the go704, I can now do 3 screws a
day as it only takes around 45 minutes to cut the threads. That's all
the time and getting around that my nearly 90 yo legs are good for.
Like Stuart said, Machine envelope is king. And a 3d printers output
made it possible. Even the stick chuck is 3d printed. And that 500 rpm
lashup including driver, worm and psu, was less than $250. Accuracy is
around .1 degree, the backlash in the rvs30. I could probably hob gears
with it, but haven't actually tried it.
Also why think in micro-steps and worm gear rates, you are using
LCNC to do the kinematics, Use millimeters.
I think this problem shows that in some cases you really can not
write the gcode by hand. FOr continous curves in (x,y) there might be
100,000 or more lines of code in the file, especially if you don’t do
the
cut in one pass. You would nee towrite software to generate the g-code.
Or use existing software, a lot of CAD systems will do this for you
First, a 90/1 is quite high. I have two rotary's, both consisting
of a 3NM 3phase stepper/servo I made by combining the 3NM motor with a
5/1
worm. Using a screw in the worms output hub as a single prox sensor
index
pulse generator. To calibrate a complete rev, I measure the steps by
starting the count on the 3rd turn ans stopping the count on the 103rd
turn, which gives me a scale*100. Shift the decimal point 2 places left
this becomes the scale for the axis in the .ini file. All this math in
linuxcnc is floating point so I can ask it for 33.333 degrees and it
will
run to what it thinks is 33.333 degrees. This stepscale:
STEPSCALE = 22.22222222222 = 1 degree
So one count is about 1/22.22222222222 degrees, probably less
than
the backlash in the rvs39 worm, a pretty cheap worm.
Currently to make one of my maple vise screws, starting at 0
degrees its around 60,000 degrees it turns for around 400 mm of screw
that
y travels. Then I lift the tool, turn it another 180 degrees, re lower
the
tool and bring y back to zero and b=180. Makes a perfect two start
buttress
thread. The B is turning, in perfect sync with the Y motion, at
something
in the 300 to 400 rpm range. That 3NM motor is heating but not
dangerously
so.
There is no reason you couldn't lay it down to make a C drive,
and
simultaneously drive X Z & C to carve an impeller in a quite serviceable
scroll.
The versatility of the closed loop stepper/servo, which does
EXACTLY what the TP tells it to do, without a PID in the path, is
amazing.
I have them rigged to e-stop linuxcnc in about a millisecond if they
make
an error, like losing a step. Tested till the cows come home, has yet to
happen working a job. I haven't hobbed any gears, but it certainly seems
accurate enough to do it.
Suggestions?
Thanks
John
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--
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If we desire respect for the law, we must first make the law
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