Joining parts
On 2019-07-19 09:01, Frank van der Hulst wrote:
I know you're looking for purely 3d printed solutions, but sometimes
it's just easier to glue things together. In those circumstances I
design matching 2mm holes into the parts. Then glue short pieces of
1.75mm filament into one set of holes to function as alignment pins
for assembling the parts.
I think that is a very practical and sensible approach, nice idea. What
kind of glue do you use for PLA joined this way?
Carsten Arnholm
Yes, of course. I'm developing software for Furniture Manufacturing. His
base is a powerful smart product configurator based on "Mass
Customization" principles.
But our brain needs images to see the power of this tool. My program
generates the images as OpenSCAD scripts and launches it to show the
currently product configuration.
You can draw many types of parts. The more complex are in .scad files or
in STL files, to make it as many standard as possible.
At this moment I'm drawing profiles, maybe wood profiles or aluminium
profiles. If I use an OpenSCAD script, with only 2D instructions, it
works well of course. But after I need to extrude a plain image and I
want to do it based on an STL file, to maintain the unity of the software.
Next is the code used to generate the aluminium profile I've used as
example:
module InternalCross(){
translate([0, 0, 0]){
rotate(-45)
translate([-0.75, 1, 0])
square([1.5, 26]);
}
translate([20, 0, 0]){
rotate(45)
translate([-0.75, 1, 0])
square([1.5, 26]);
}
}
module Corner(){
$fn = 100;
offset(.5) offset(-.5) square([1.5, 7 ]);
offset(.5) offset(-.5) square([7 , 1.5]);
}
module CornerSquare(){
$fn = 100;
offset(.5) offset(-.5) square([4.5, 4.5]);
offset(.5) offset(-.5) square([4.5, 4.5]);
}
module CentralSquare(){
square(7.52);
}
module CentralRound(){
circle(d=4.2, $fn=100);
}
module nutProfile20x20(){
difference(){
union(){
InternalCross();
Corner();
translate([20, 0, 0]) rotate( 90) Corner();
translate([20, 20, 0]) rotate(180) Corner();
translate([ 0, 20, 0]) rotate(270) Corner();
CornerSquare();
translate([20-4.5, 0, 0]) CornerSquare();
translate([20-4.5, 20-4.5, 0]) CornerSquare();
translate([ 0, 20-4.5, 0]) CornerSquare();
translate([6.25, 6.25, 0]) CentralSquare();
}
translate([10, 10, 0]) CentralRound();
}
}
module BasicProfile20Female(Length){
union(){
difference(){
linear_extrude(Length)
nutProfile20x20();
}
}
}
linear_extrude(height = 40, center = false, convexity = 10, twist = 0){
nutProfile20x20();
}
(I can't send you the images of the result, because I've tried it but
the forum has currently a problem with inserted images into the messages.)
Use this code to after render it to generate the STL file. And after,
use the code of the previous message to extrude it.
Really works, with the projection() instruction.
Thanks again!
On 19/07/2019 09:47, nop head wrote:
Glad to help!
I can see why you needed it now. Where did you get the profile STL from?
On Fri, 19 Jul 2019 at 08:43, Juan C.Cilleruelo
<juanc.cilleruelo@gmail.com mailto:juanc.cilleruelo@gmail.com> wrote:
Thank you very much!!!!
It's just what I looking for!!!
/*---------- PROFILE 20X20 => ALUMINIUM PROFILE 20x20 ----------*/
linear_extrude(height = 40, center = false, convexity = 10,
twist = 0){
projection(){
import("PROFILE20X20_001.stl");
}
}
On 19/07/2019 09:11, nop head wrote:
All those statements are true. To export and import 2D shapes you
need to use a 2D format like DXF or SVG.
You can convert a 3D shape to 2D with projection(), so if you
have a flat object in an STL file you can make it 2D and then
linear_extrude it.
On Fri, 19 Jul 2019 at 08:04, Juan C.Cilleruelo
<juanc.cilleruelo@gmail.com <mailto:juanc.cilleruelo@gmail.com>>
wrote:
I've discovered the next thing in OpenSCAD and I want to know
if it's a
logical situation or is a limitation or if it's a bug behaviour.
1st : I can't use linear_extrude() with modules that use 3D
instructions, only with those that use exclusively 2D
instructions.
2nd: I can't export to STL a drawing that uses exclusively 2D
instructions.
if I want to generate an STL file with only 2D instructions,
I need to
apply at least a 0.1 of linear_extrusion to the drawing.
3rd: As a consequence of the first, I can't use
linear_extrude() to
extrude an imported STL, because its content is always in 3D.
Did anyone know a tip or trick to save 2D drawings into an
STL and to
extrude an STL file imported?
Thank you all in advance!
_______________________________________________
OpenSCAD mailing list
Discuss@lists.openscad.org <mailto:Discuss@lists.openscad.org>
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
_______________________________________________
OpenSCAD mailing list
Discuss@lists.openscad.org <mailto:Discuss@lists.openscad.org>
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
Depends on the strength needed... hot glue where strength isn't needed,
otherwise epoxy. If your parts mate perfectly, then cyanoacrylate would be
good.
On Fri, 19 Jul 2019, 19:52 , arnholm@arnholm.org wrote:
On 2019-07-19 09:01, Frank van der Hulst wrote:
I know you're looking for purely 3d printed solutions, but sometimes
it's just easier to glue things together. In those circumstances I
design matching 2mm holes into the parts. Then glue short pieces of
1.75mm filament into one set of holes to function as alignment pins
for assembling the parts.
I think that is a very practical and sensible approach, nice idea. What
kind of glue do you use for PLA joined this way?
Carsten Arnholm
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
I actually designed a part to answer exactly this question.
https://www.thingiverse.com/thing:3579313
If you print male and female parts that are exactly the same size,
they are unlikely to fit together. If you taper one, you can press
them together up to a point at which they get stuck. Where they get
stuck depends on the accuracy of your machine and to some extent the
type of plastic you are using. How much they gets stuck depends on
the smoothness of the part and the slipperiness of the plastic.
The idea is that you print this part which has a taper, then you slide
the sides together, and measure where they get stuck and calculate a
tolerance from that. In retrospect, this part only measures your XY
tolerance; the Z tolerance will be different. I suppose you could
try to rotate the part and print it, but if I had designed it for
that, I might not have made it so long and skinny.
Measuring the tolerance from this part only gives you a starting
point. There are other factors that might change the tolerance over
the life of a printed part. ABS stretches. PLA stretches a bit less
but also rubs and changes shape. Some of the size of the tolerance
comes from wobble in the printer, so if there are bumps in your PLA
part, some of those bumps are smoothed out a bit each time you slide
them together. TPU does both but not permanently; I thought I could
get away with zero tolerance for TPU but found that isn't true, it
also needs some tolerance to make parts fit.
For sliding parts, my original Makerbot Cupcake with ABS needed
0.25mm. My Ender 3 with PLA needs a bit more than 0.1mm.
For a friction fit, using the bumps in the Z axis isn't a bad idea,
assuming the part doesn't delaminate under pressure and fall apart
afterwards.
ABS friction fits nicely. PLA seems to bind to itself less, so I'd
not try a XY friction fit there, as others have mentioned, I'd want to
make a peg that snaps in, although that works well in ABS too.
I'm not sure how legos do it; I would imagine they have an extremely
small dovetail taper or something. Weather or not they use a taper,
they do use extremely tight tolerances.
The best way to find out how the snap pins work is to print Emmet's gear
cube https://www.thingiverse.com/thing:213946
There are two versions of the hole inset, one which allows rotation and one
which is fixed. They hold very solidly, but can be pulled apart with enough
effort. The smallest I have been able to make useful pins is 4mm long with
a 2.5mm diameter, anything smaller than that is too fragile to use.
The fully customisable pins are at https://www.thingiverse.com/thing:3218332,
and the output options include a test socket you can print to try it... The
code generates an STL for the pin, which is printed flat, and an STL for
the socket, which is difference'd from the surface you want to embed the
pin in.
On Fri, 19 Jul 2019, 07:26 Steven Dick, kg4ydw@gmail.com wrote:
I actually designed a part to answer exactly this question.
https://www.thingiverse.com/thing:3579313
If you print male and female parts that are exactly the same size,
they are unlikely to fit together. If you taper one, you can press
them together up to a point at which they get stuck. Where they get
stuck depends on the accuracy of your machine and to some extent the
type of plastic you are using. How much they gets stuck depends on
the smoothness of the part and the slipperiness of the plastic.
The idea is that you print this part which has a taper, then you slide
the sides together, and measure where they get stuck and calculate a
tolerance from that. In retrospect, this part only measures your XY
tolerance; the Z tolerance will be different. I suppose you could
try to rotate the part and print it, but if I had designed it for
that, I might not have made it so long and skinny.
Measuring the tolerance from this part only gives you a starting
point. There are other factors that might change the tolerance over
the life of a printed part. ABS stretches. PLA stretches a bit less
but also rubs and changes shape. Some of the size of the tolerance
comes from wobble in the printer, so if there are bumps in your PLA
part, some of those bumps are smoothed out a bit each time you slide
them together. TPU does both but not permanently; I thought I could
get away with zero tolerance for TPU but found that isn't true, it
also needs some tolerance to make parts fit.
For sliding parts, my original Makerbot Cupcake with ABS needed
0.25mm. My Ender 3 with PLA needs a bit more than 0.1mm.
For a friction fit, using the bumps in the Z axis isn't a bad idea,
assuming the part doesn't delaminate under pressure and fall apart
afterwards.
ABS friction fits nicely. PLA seems to bind to itself less, so I'd
not try a XY friction fit there, as others have mentioned, I'd want to
make a peg that snaps in, although that works well in ABS too.
I'm not sure how legos do it; I would imagine they have an extremely
small dovetail taper or something. Weather or not they use a taper,
they do use extremely tight tolerances.
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
Thus arnholm@arnholm.org hast written on Fri, Jul 19, 2019 at 09:51:43AM +0200, and, according to prophecy, it shall come to pass that:
I think that is a very practical and sensible approach, nice idea. What kind
of glue do you use for PLA joined this way?
I was just reading last night that:
"PLA is soluble in solvents, hot benzene, tetrahydrofuran, and dioxane."
and "PLLA can be solvent welded using dichloromethane."
[ https://en.wikipedia.org/wiki/Polylactic_acid#Materials_properties ]
Read the Material Safety Data Sheets on those first, as they may be
carcinogenic and pose other hazards.
Dichloromethane "is also used extensively by model building hobbyists for
joining plastic components together. It is commonly referred to as
"Di-clo." " So it's use for gluing plastic seems fairly common.
[ https://en.wikipedia.org/wiki/Dichloromethane ]
Other than that, I've used Cyanoacrylate/superglue to glue PLA.
PLA is also soluble in ethyl acetate, which is a lot safer.
On Fri, 19 Jul 2019, 15:40 Bryan Lee, leebc11@acm.org wrote:
Thus arnholm@arnholm.org hast written on Fri, Jul 19, 2019 at 09:51:43AM
+0200, and, according to prophecy, it shall come to pass that:
I think that is a very practical and sensible approach, nice idea. What
kind
of glue do you use for PLA joined this way?
I was just reading last night that:
"PLA is soluble in solvents, hot benzene, tetrahydrofuran, and
dioxane."
and "PLLA can be solvent welded using dichloromethane."
[ https://en.wikipedia.org/wiki/Polylactic_acid#Materials_properties ]
Read the Material Safety Data Sheets on those first, as they may be
carcinogenic and pose other hazards.
Dichloromethane "is also used extensively by model building hobbyists for
joining plastic components together. It is commonly referred to as
"Di-clo." " So it's use for gluing plastic seems fairly common.
[ https://en.wikipedia.org/wiki/Dichloromethane ]
Other than that, I've used Cyanoacrylate/superglue to glue PLA.
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
Dichloromethane definitely is carcinogenic. If you want to make a
permanent join on PLA (which I don't hence I was asking for friction fit
snaps) I'd recommend (aside from adhesives) maybe trying to heat or
ultrasonic weld it.
On Fri, Jul 19, 2019 at 10:40 AM Bryan Lee leebc11@acm.org wrote:
Thus arnholm@arnholm.org hast written on Fri, Jul 19, 2019 at 09:51:43AM
+0200, and, according to prophecy, it shall come to pass that:
I think that is a very practical and sensible approach, nice idea. What
kind
of glue do you use for PLA joined this way?
I was just reading last night that:
"PLA is soluble in solvents, hot benzene, tetrahydrofuran, and
dioxane."
and "PLLA can be solvent welded using dichloromethane."
[ https://en.wikipedia.org/wiki/Polylactic_acid#Materials_properties ]
Read the Material Safety Data Sheets on those first, as they may be
carcinogenic and pose other hazards.
Dichloromethane "is also used extensively by model building hobbyists for
joining plastic components together. It is commonly referred to as
"Di-clo." " So it's use for gluing plastic seems fairly common.
[ https://en.wikipedia.org/wiki/Dichloromethane ]
Other than that, I've used Cyanoacrylate/superglue to glue PLA.
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
On 2019-07-19 16:40, Bryan Lee wrote:
Other than that, I've used Cyanoacrylate/superglue to glue PLA.
Thanks for the replies. I was mostly interested in something easily
available and superglue fits the bill.
Carsten Arnholm
I was just recommended this:
https://smile.amazon.com/dp/B0778LB4RX
Thus arnholm@arnholm.org hast written on Fri, Jul 19, 2019 at 05:15:13PM +0200, and, according to prophecy, it shall come to pass that:
On 2019-07-19 16:40, Bryan Lee wrote:
Other than that, I've used Cyanoacrylate/superglue to glue PLA.
Thanks for the replies. I was mostly interested in something easily
available and superglue fits the bill.
Carsten Arnholm