3D printing observations

Thread Starter

Wendy

Joined Mar 24, 2008
23,479
I'm starting this thread to put various observations I have made over the years about 3D printing.
You cannot lay a horizontal surface unsupported, with the following exceptions :
You can make a vertical Circle just fine . I do this frequently on my prints . As a matter of fact , I find that printing a circle in the X Y axis takes a lot longer than A horizontal circle. I have found the 3D printer works much better in some cases if the circle is in a horizontal mode. This is STL file work much better in the horizontal mode and it cut down on the print time considerably. I make this as a storage method for pill bottles.

I use SketchUp 2016 because it is free and does not require video accelerator. I really need to learn something better but I am pretty decent with SketchUp. Even though it is far from perfect I love my Ender 3 Pro

stl.png
 

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Thread Starter

Wendy

Joined Mar 24, 2008
23,479
Among the things I do on my 3D printer is create inserts for a #6/ 32 screw. It looks something like this (the little tab on the protrusion allowed me to print the protrusion sideways):

Filament bar.png
This image was generated by SketchUp.​

I have started a file called printer notes which I am attaching to this post so people can duplicate it. As I revise this document I will post it on this thread and replace the old document
 

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Thread Starter

Wendy

Joined Mar 24, 2008
23,479
So I have been running some experiments to come up with a template for nuts. the idea is the nut will fit flush in a sheet as shown.

Nut Tests.png
Remember I am doing this in SketchUp 2016. Here is a picture of the finished result:
221128.jpg
I would use super glue to hold the nut in its insert and use it with a 3D printed sheet and fit the screw through the feed through hole. For easy attachment.
 

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Alec_t

Joined Sep 17, 2013
14,411
It looks as though there is enough space around the nuts for them to spin in the recesses. Is that intentional, or does the software automatically add some margin to the nut size?
 

Thread Starter

Wendy

Joined Mar 24, 2008
23,479
I tried screwing the appropriate screw as a part of the test to make sure these can go through the through hole. the nuts are indeed a tight fit. Super glue is forever, you don't use heat around PLA casually.
 

Thread Starter

Wendy

Joined Mar 24, 2008
23,479
Lately I have had a lot of problems printing strong structures in the Z axis the grain of the plastic seems to be in the X&Y and that is where the strength is. I did notice one exception when I had to run a tube( hole) down the length of a structure, it came out very strong so to print boxes I will print walls flat on the tabletop and then figure out how to mesh them later.
 

Ya’akov

Joined Jan 27, 2019
9,265
The greatest strength will always be perpendicular to the layer lines. You can only expect up to about 70% of the filament strength in the best cases fir layer adhesion and usually considerably less.

But there are things you can do to maximize layer adhesion if it is important.
 

Ya’akov

Joined Jan 27, 2019
9,265
PLA is my only option ATM.
PLA is actually stronger and stiffer than ABS. ABS is tougher, lighter, more durable, and more chemical resistant.

When using these terms in the technical sense, they have to be differentiated.

Strength refers to the material’s stress-strain curve. Stress is defined as force over area. So, for example, tensile strength (the ability to resist a stress that would tend to stretch that material. The yield strength is the point at which the material ceases to act like a spring and return to its pre-stressed state. This is the transition between elastic and plastic deformation.

Young’s Modulus is a way of characterizing stiffness by taking the slope of rise over ruin for the elastic deformation portion of the curve (which is the green area in figure below.

1685004294797.png
This figure compares PLA and ABS for 3D printing in terms of tensile stress:

1685004785310.png
You can see that PLA is considerably stronger and stiffer, while both materials are much stronger parallel to the layer lines. On the other hand ABS is the winner when testing toughness, that is, the ability to deal with impact stress. In other words PLA can make better cantilevers but don’t hit it with a hammer.

Two materials to consider that offer better toughness without the difficult printer of ABS are ASA and PETG. ASA (Acrylonitrile Styrene Acrylate) is a “the new ABS”, is a closely related polymer but has several advantages over ABS:

It is less hydroscopic
It is more environmentally stable and can be used outdoors
It is much easier to print because it doesn’t curl as much
It doesn’t produce nasty gasses, and so doesn’t really need an enclosure (though it can help)

It is a very good ABS alternative If you need more toughness than PLA but can’t or don’t want to, print ABS. PETG (Polyethylene Terephthalate Glycol-modified) is a PET copolymer. PET is the stuff water bottles are made of. It is a really very nice material which is tough, stable, and can be found in a “natural” color which is crystal clear. It prints really well, and while it is at a higher temperature your Ender-3 Pro should have no problem printing it. PETG is not related to ABS but it makes beautiful prints and isn’t very expensive.

CNC Kitchen is a really good YouTube channel for this stuff. Stefan does rigorous and extensive empirical testing of materials and printing parameters to determine which is best for strength and print quality. Highly recommended.

 

Ya’akov

Joined Jan 27, 2019
9,265
I tried screwing the appropriate screw as a part of the test to make sure these can go through the through hole. the nuts are indeed a tight fit. Super glue is forever, you don't use heat around PLA casually.
IF you use a temperature controlled iron, thremosetting the nuts would work just fine. You should set it to lightly higher than the nozzle temperature. Glue is fine, though.

I use and recommend threaded inserts. These are designed to be thermally inserted into printed bosses or holes and have a shape that allows the plastic to flow around them and make them very strong. I have a dedicated iron for them, using a special tip that accepts thread-on ends for different sized inserts.

IMG_0352.jpegIMG_0353.jpegIMG_0354.jpeg
l to r: the M3 setting bit in a Hakko FX-88, the M3 sized insert, the various sized tips

It takes only a few attempts to understand the process completely and get great results. Given the limits you have on manual dexterity, you would probably want to print one of the various threaded insert presses that people have designed which makes alignment much more certain.

This one is pure printing except for some screws and a base of wood.
1685007363303.png
 

Thread Starter

Wendy

Joined Mar 24, 2008
23,479
Can you sing that makes me slightly crazy is the variability of the results. I will be printing a project box pretty soon and I will print the sides on the flat of the table then glue them into a box later.
 

BobTPH

Joined Jun 5, 2013
9,292
For boxes I just print the front and back on the bed with overlapping lips where they go together. The sides are printed vertically. Have not had any strength issues. The sides are not strained in any way, so they don’t need much strength.
 

Thread Starter

Wendy

Joined Mar 24, 2008
23,479
I wonder if what I'm seeing is variations between two batches of plastic? I like the PLA low temperature ranges last time I tried to use an ender 3 with ABS the head sensor malfunctioned and i had to replace the entire printer.maybe there are other types of plastic with better strengths it's still low temperature ?
 

Ya’akov

Joined Jan 27, 2019
9,265
I wonder if what I'm seeing is variations between two batches of plastic? I like the PLA low temperature ranges last time I tried to use an ender 3 with ABS the head sensor malfunctioned and i had to replace the entire printer.maybe there are other types of plastic with better strengths it's still low temperature ?
If you want easy to print and very tough, with superlative layer adhesion, high durometer TPU (95-A) will work is amazingly good. TPU is a flexible polymer so you can have feed problems with it, but the TPU 95-A from a good manufacturer will result in prints that flex—but not excessively—and are about the toughest you can print with your FDM printer.

It’s not going to be good for things that specifically require stiffness because it surely isn‘t that. But it is very strong and durable. With some practice you can design for it so that it doesn’t flex much at all, or so it forms things like living hinges and compliant structures.

Get some and try it. You can get a half kilo spool for about 16 bucks from Amazon. I have had very good success with this $25 kilo spool though it’s not the stiffest it prints very nicely.
 

Ya’akov

Joined Jan 27, 2019
9,265
I wonder if what I'm seeing is variations between two batches of plastic? I like the PLA low temperature ranges last time I tried to use an ender 3 with ABS the head sensor malfunctioned and i had to replace the entire printer.maybe there are other types of plastic with better strengths it's still low temperature ?
Oh, I should also mention PLA+, or Tough PLA. This is a PLA formulated for a bit more durability. I have had excellent results from VoxelPLA PLA Pro, which is cheap as dirt (~16/kg) and they offer free shipping on three or more spools. They run a 150 machine print farm and this is filament that have manufactured for that. It really is good stuff.

Easy to print and able to render tiny details, like in this Benchy (0.2mm nozzle on the BBL X1C):

26C576A3-2EFF-4B59-BCFB-0A4D52FDCDB2.jpeg
 
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