is there a way to solid-fill an object?
On 7/11/25 05:59, John David via Discuss wrote:
I am playing with merging a couple of STL/OBJ/3MF files, into a castable
3D printable object. A couple of the object models were made from 3D
scans, and are hollow. What I would like to do is to fill everything
under the top surface of that object. I could write something in
C/C++/Python to do this, but I was hoping that the functionality is already
in OpenSCAD.
I wasn't aware that PLA could be used as the lost wax in that process,
so this thread is very educational.
And because its hollow, it also might be used to make gantry parts for a
3d printer. I bought, several years ago a 400 mm cube capable tronxy
printer, came with a broken firmware, but it had a major problem in that
something composed square, wasn't square on the build plate due to the
incorrect corexy geometry. And that turned out to be quite bitchy to
correct requiring sub mm adjustments to the belt anchoring geometry at
every place a belt turned a corner, 8 pulley locations total. At the
same time I replaced the X bar, an alu and steel thing heavy enough to
kill an elephant, with linear bearings on carbon fiber tubing. That was
about a year of printing new carriage anchoring plates, originally steel
& heavy enough in flying weight to seriously limit its top speed. Many
of those parts are now made with PETG+CF and lower infill's to save
weight. I've also replaced the puny std steppers with better closed loop
stepper/servo's running on 72 volts, raised the bed voltage for 125C
heat and designed a 290C hot end that in several hundred hours on
another printer I also rebuilt, has not clogged its nozzle while
printing anything up to polycarbonate. I have it about 75% wired now.
I'm past the geometry problems now but might have been able to cast some
of that.
All this because I wanted to print some parts of a huge woodworkers
bench vise at a usable speed. Using a normal printer, it takes 2 weeks
to make one vise, with 2 higher speed printers, 2 days. But I'm 90,
diabetic, chest full of hardware to keep me going, so I'm well aware I'm
running out of time. Thank you ALL for teaching me about OpenSCAD.
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
You say "very thin shell", but I suspect that you really mean that the
scans are not watertight, that they do not form a complete surface.
Suppose that you had a cube, but it was missing one of the sides. (In
OpenSCAD, you can construct such a thing with polyhedron(), but you
can't do much with it.) What you have then is not a solid object. It
has five zero-thickness sides; it has no volume whatsoever.
Now suppose that you had a cube, and you subtract a slightly smaller
cube from the middle of it. That's a whole different sort of object.
It is hollow - it has emptiness in its middle - but surrounding that is
a non-zero-thickness shell.
Which of those two scenarios do you have?
I suspect the first, because to set up the second the scan software
would have had to generate a second surface slightly inside the first...
and why would it do that?
Assuming that I'm right, your options in OpenSCAD are very limited. If
the object is convex, hull() might repair it. Other than that, any
rendering operations will fail. You need a mesh editor. Or, if you can
re-do the scans, the scan software may have a "make watertight" operation.
If I'm wrong, if what you've got is a 3D object with volume, but with
emptiness in the middle, your options are unfortunately also limited,
though not quite as limited. What you want there is fill(), but for
3D. We don't have that. But you could manually place shapes inside the
gap so as to fill it up. How easy that would be would depend on how
complex the object is and how thin its shell is.
Gene:
If you only need to do these prints a few times, maybe time to consider
using a commercial printer farm. I know there are seriously fast
printers out there, too expensive for most of us to purchase, but worth
buying a few hours on.
Jon
On 7/11/2025 8:52 AM, gene heskett via Discuss wrote:
On 7/11/25 05:59, John David via Discuss wrote:
I am playing with merging a couple of STL/OBJ/3MF files, into a castable
3D printable object. A couple of the object models were made from 3D
scans, and are hollow. What I would like to do is to fill everything
under the top surface of that object. I could write something in
C/C++/Python to do this, but I was hoping that the functionality is
already
in OpenSCAD.
I wasn't aware that PLA could be used as the lost wax in that process,
so this thread is very educational.
And because its hollow, it also might be used to make gantry parts for
a 3d printer. I bought, several years ago a 400 mm cube capable
tronxy printer, came with a broken firmware, but it had a major
problem in that something composed square, wasn't square on the build
plate due to the incorrect corexy geometry. And that turned out to be
quite bitchy to correct requiring sub mm adjustments to the belt
anchoring geometry at every place a belt turned a corner, 8 pulley
locations total. At the same time I replaced the X bar, an alu and
steel thing heavy enough to kill an elephant, with linear bearings on
carbon fiber tubing. That was about a year of printing new carriage
anchoring plates, originally steel & heavy enough in flying weight to
seriously limit its top speed. Many of those parts are now made with
PETG+CF and lower infill's to save weight. I've also replaced the puny
std steppers with better closed loop stepper/servo's running on 72
volts, raised the bed voltage for 125C heat and designed a 290C hot
end that in several hundred hours on another printer I also rebuilt,
has not clogged its nozzle while printing anything up to
polycarbonate. I have it about 75% wired now. I'm past the geometry
problems now but might have been able to cast some of that.
All this because I wanted to print some parts of a huge woodworkers
bench vise at a usable speed. Using a normal printer, it takes 2
weeks to make one vise, with 2 higher speed printers, 2 days. But I'm
90, diabetic, chest full of hardware to keep me going, so I'm well
aware I'm running out of time. Thank you ALL for teaching me about
OpenSCAD.
Cheers, Gene Heskett, CET.
--
This email has been checked for viruses by AVG antivirus software.
www.avg.com
On 7/11/25 12:35, Jon Bondy wrote:
Gene:
If you only need to do these prints a few times, maybe time to
consider using a commercial printer farm. I know there are seriously
fast printers out there, too expensive for most of us to purchase, but
worth buying a few hours on.
I've already invested the time & money. I probably have $3.5G's in an
Ender 5 Plus, with the only thing left of the $600 OEM being some of the
frame. And about that much in a tronxy400 I'm still working on. My
record of thinking inside the box is very poor. I'm the same guy they
IQ tested in Iowa in the 7nth grade at 147, made a 98 on the AFQT when I
tried to get in the military in '52 so I'd be eligible for the GI Bill
but that got me 4F'd, got a 1st phone in '62 w/o cracking a book and
became the 1st to pass the CET exam at that College in '72 w/o ever
attending the place. Switched from TV fixing which I'd been doing since
'48 when I quit school, then switched to broadcast engineering in '64.
Culminating as the Chief Engineer of the local CBS affiliate for the
last 18.75 years of my working life.
Been collared 3 times, took on 5 kids that came with the women, made 6
more with them, and attended enough funerals that I only have 4 boys
left. No windows experience to speak of. Bill G. and I agreed to
disagree in '86. I've also converted 4 old lathes and mills to cnc,
wore out 5 rifle barrels on 2 boxes of factory loaded ammo. I loaded the
rest. Education from reading the letters off the pages of McGraw Hills
Electronics. I don't just talk about it, I DO it. I write my own bash
scripts and my own g-codes. Now I'm 90, diabetic with a chest full of
hardware to keep me going. WYSIWYG.
Thanks for the suggestion Jon B., but I hope to close out my remaining
time outside that famous box selling a better bench vise to famous
woodworkers.
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