On 4/11/24 11:41, Chris Albertson wrote:
On Apr 10, 2024, at 12:47 PM, gene heskett <ghesk...@shentel.net> wrote:
On 4/10/24 13:03, John Dammeyer wrote:
Hi Gene,
Just like I can't get my head around Fusion360 or similar CAD.
I find that many people’s problem is that they are still thinking that CAD is
used to “draw” a part and that somehow the final product is a “‘drawing”.
This is completely contrary to how it works.
What you do is make the part, just like you would in the shop. There is no
“drawing”. In the shop you might start with an extrusion then cut it and mill
a pocket and then make some holes and then what ever until it was the right
shape. With CAD now, the first step is usually drawing the profile for a
custom extrusion.
If you try and hand code gcode or use OpenSCAD you are limited to very simple
shapes and can never exploit the full capability of the milling machine. Just
TRY and hand code a typical hand-held power tool or even a triangular pocket on
the side of the sphere in hand-written gcode.
So, if you want to model a part in CAD, just think how you would make it in a
very well equipped shop.
All extremely true. But as I approach my 90th, its a bit late to try
and learn a 10 grand a year CAD/CAM program that can do all that. What
I need in rebuilding a burned up 3d printer, I can knock up in OpenSCAD
in an hour or 2, and have in my hands ready to bolt it in, in the time
it takes a QIDI XMax-3 to print it. May not impress the girls, but it
will work.
AlibreCAD has gone downhill since they trashed their relationship with
MecSoft which correspondingly trashed AlibreCAM.
I'll take a closer look at your approach later today.
My approaches subroutine will take a loop as the primary slicer because each
piece of the scroll will need to start at the root of that slice but the curved
pie slice is wider at the outside.
A spiral is a continuous curve, already we jhave assen the curve’s equation.
You just marchthrough the point the equation producse and it is literally
“perfect”, no approximation. The only problems left are
1) The method is “too perfect” and will generate to make points and be slow
2) doing it all in one pass is a poor machining technique.
The target is to carve each slice from its apex point but widen the rim so that
your 3mm wide fin is all that's left, then advance to the apex of the next pie
slice. So the subroutine will start at 6 common points around the central axis,
and you wind up with 6 3mm wide fins in the scroll shape.
That won't be the most efficient shape but will get you started. To improve the
efficiency, that central subroutine will need to be converted to use G4 nurbs
to describe the spiral path. But that's for next week. And I expect Andy might
have some better ideas on the nurbs points. I have a good idea what they can
do but zip about the math involved. Flow thru a venturi etc type math.
Thanks
John
-----Original Message-----
From: gene heskett [mailto:ghesk...@shentel.net]
Sent: April 10, 2024 3:42 AM
To: emc-users@lists.sourceforge.net
Subject: Re: [Emc-users] Carving a spiral
On 4/10/24 03:37, John Dammeyer wrote:
Hi Marcus,
Here's the problem.
My Alibre CAD/Cam can produce a spiral slot in a disk using X and Y
motion.
I looked at alibre, could not get my Iowa farm kid head around it. Far
easier for me to write my own gcode.
In linuxcnc, you can trade the axis names around to fit your hdwe.
How far can you tilt your Z? Mine can do a full 90, aka lay the spindle
horizontal. Either way IIRC. I can then use X as X, A as A, and a
single straight line move to carve the spiral using Z while A is turning
N degrees to carve the spiral. So the gcode then becomes a subroutine to
do that, and a 2nd loop routine to handle the start of the spiral and
possibly a master outer loop to do any incremental cuts to get to the
depth needed. Maybe 80 LOC total.
If your head cannot tilt that far, then you''l have to cobble up a C,
facing up which I CAN do but its a 90/1 drive and will restrict the
speed as It can't turn fast enough. Also has a std stepper motor, push
its speed and it stalls. Someday I'll put a good motor on it.
A Warning though, most of the combo gizmos they sell for $300 or so on
ebay are belt drive and no-where near strong enough for this. I did use
my 90/1 as A when making my tap hats. Used it to drill & tap the 4 grub
screw holes. I setup workstations on the length of the go704's table,
put a piece of brass rod in the spindle, drilled the hole for the tap,
move the brass to a clamp, drilled and tapped for a locking to an r8
collet screw hole, moved the brass to the A chuck and drilled and tapped
all 4 grub screws. All in the same gcode file with pauses and automatic
tlo offset corrections as the drills were different lengths. Made a
regular production line out of it, took longer moving the brass around
than the total run time for the machine.
If I tell it to use my 4th axis it's like the video you posted.
Designed
for creating a spiral on something horizontal to say the X axis.
I think I'd have to buy the 5th axis capability in order to be able to
have
the rotary table turn while the cutter moves in the X direction as the
spiral is created.
So if I wanted to move the rotary table N degrees while moving X a
spiral
would also be created. I guess I'm having trouble figuring out the math
for
the G-Code.
It just one command with prelimiinary. in your case position incut at N
degrees
John
-----Original Message-----
From: marcus.bow...@visible.eclipse.co.uk
[mailto:marcus.bow...@visible.eclipse.co.uk]
Sent: April 10, 2024 12:00 AM
To: Enhanced Machine Controller (EMC)
Subject: Re: [Emc-users] Carving a spiral
As I recall, someone on this list posted a note or a link about how to
create a fusee for a clock (essentially a tapered spiral, running from
large diameter to smaller diameter while spiralling - rather like a
tapered woodscrew thread). Is a constant-diameter version of that what
you had in mind?
https://www.youtube.com/watch?v=KAAajypWQyw
Sadly, I can't remember who contributed that note on this list. I do
think there may be a routine somewhere in the LinuxCNC electronic
resources.
Marcus
On 2024-04-10 06:55, 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.
Suggestions?
Thanks
John
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Cheers, Gene Heskett, CET.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
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.
Cheers, Gene Heskett, CET.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
Cheers, Gene Heskett, CET.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
