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Hack Chat Transcript, Part 1

A event log for Resin Printing Hack Chat

Do you do the goo?

Dan MaloneyDan Maloney 10/13/2021 at 20:100 Comments

Dan Maloney11:59 AM
OK, folks, let's get started. Welcome to the Hack Chat, I'm Dan and I'll be moderating today along with Dusan for Andrew Sink. As you can probably tell from the pre-Chat, we'll be talking about Resin Printing today -- stereolithography or SLA if you want to be proper about it.

Welcome Andrew, thanks for joining us today. Can you fill us in a little on your background?

Andrew Sink12:00 PM
Looks like @Thomas Shaddack picked up a good bit of slack and started doing a deep dive here; thanks Thomas!

Dusan Petrovic12:00 PM
Hello and welcome!

Andrew Sink12:00 PM
Thanks for the introduction, @Dan Maloney!

Andrew Sink12:00 PM
I've been involved in the additive industry for about 9 years, first as a student, then a hobbyist, and currently a full-time additive engineer!

Dusan Petrovic12:00 PM
Hi @Andrew Sink !

Shayan S. joined  the room.12:01 PM

Andrew Sink12:01 PM
I turned my attention to resin 3D printing earlier this year, and I've been absolutely fascinated with it since!

Andrew Sink12:01 PM
To answer the question I posed earlier, that part was printed hollow and upside down using a flexible resin with a 3mm thick wall!

Anthony Velte joined  the room.12:01 PM

Grant - 3D Musketeers12:01 PM
It is pretty awesome!

Andrew Sink12:02 PM
You can see the deformation is lateral in the print, and squishing from top to bottom results in FAR less deformation

alexkollen.edu joined  the room.12:02 PM

Involute joined  the room.12:02 PM

Andrew Sink12:02 PM

Andrew Sink12:02 PM
An interesting side-effect of the layer-by-layer exposure process of an MSLA 3D printer!

Andrew Sink12:02 PM
I'd like this chat to focus on resin printing, with an emphasis on questions from beginners on the "How-To" of MSLA 3D printing!

Dan Maloney12:03 PM
Is there as wide a range of material types in resins as there is in filaments?

Andrew Sink12:03 PM
Let's start with a quick definition of the term

Andrew Sink12:03 PM
There sure are! We'll dive into those in a just moment!

David Geller joined  the room.12:03 PM

Andrew Sink12:03 PM
"MSLA" stands for "Masked SLA (Stereolithography)"

Thomas Shaddack12:03 PM
The breaking depends on the mechanical properties of the resin. Again, degree of crosslinking and the nature of the diluent and the main oligomer. The more the matrix can deform and absorb energy, the tougher it is, the less brittle it will be. ABS, acrylonitrile-butadiene-styrene, uses the butadiene rubber parts of the polymer chains to make softer domains in the material where the stresses dissipate. That's the impact toughening principle in general. I also saw a trick with graphene addition into the matrix, where the graphene particles do crack pinning - cracks going through the material are attracted to the particles, and then they get stuck there as the energy for the crack propagation shoots insanely up. Small fraction of percent, if I rememer correctly, increased impact toughness by almost order of magnitude.

Andrew Sink12:04 PM
It's a VERY interesting process, and the low cost of these machines have made them very popular in the past few years

controlmypad12:04 PM
Newbie Q: What is the average cost of admission for SLA printing?

Andrew Sink12:04 PM
Essentially, instead of a motor and motion system for each axis, the average MSLA 3D printer only has one moving part; the Z axis

Andrew Sink12:04 PM
Great question @controlmypad !

Andrew Sink12:05 PM
I recently saw an MSLA 3D printer from Voxelab that sold new for $111

Andrew Sink12:05 PM
They also sell a model for about $150 or so, and it's a surprisingly decent machine!

Andrew Sink12:05 PM
But it's sort of like buying a bike; you also need a helmet, a pump, and a few other things

Andrew Sink12:05 PM
When a part is made on a resin 3D printer, it needs to be rinsed in a solvent to clear off any excess resin

Andrew Sink12:05 PM
and then it has to be fully polymerized in a curing chamber

Andrew Sink12:06 PM
So you'll want to either buy / build one of those yourself!

Andrew Sink12:06 PM
It can be as simple or as complex as you'd like!

joshua.vader12:06 PM
A coworker of mine got an Elgoo when Covid started and he says he never uses it because its a pain to clean up and maintain - Do you have any shortcuts/advice for maintaining/cleaning SLA printers?

Andrew Sink12:06 PM
Absolutely, great question @joshua.vader !

Andrew Sink12:07 PM
I use a silicone baking mat that stays under my printer during printing

Andrew Sink12:07 PM
So when I remove the part, any resin that drips will stay on the silicone mat, which I can bring outside and allow to cure, followed by breaking off the resin and disposing of it

David Geller12:07 PM
I've been loving resin printing - and the cleanup process has been far less messy than I thought, perhaps because I'm very methodical in how I do things - always have gloves and paper towels at the ready, have my isopropyl alcohol at the ready, etc., etc. Interestingly, I tried the water soluable resins and the results, for me, were terrible. I use Siraya Fast ABS-like resin and it has been a champ.

Andrew Sink12:07 PM
Also, you'll need a lot of paper towels

Andrew Sink12:07 PM
Excellent feedback, @David Geller !

anfractuosity12:08 PM
Do all MSLA printers use an LCD, or does MSLA include ones that may say use a laser + galvos/...? (i'd not heard the 'masked' part of the acroynym before)

Andrew Sink12:08 PM
There is certainly a lot of work involved in the clean-up process, but there are a handful of shortcuts that make life more bearable!

David Geller12:08 PM
Here's the stuff I make (don't worry - I'm not selling here; in fact - if you want want DM me and I'll send it out to you)... https://www.etsy.com/listing/985358329/throttle-switch-for-rad-power-ebikes?ga_order=most_relevant&ga_search_type=all&ga_view_type=gallery&ga_search_query=rad+throttle&ref=sr_gallery-1-8&organic_search_click=1

David Geller12:08 PM
It paid for my resin printer many times over!

Thomas Shaddack12:08 PM
A lot of the resin can be washed off with running hot water, combination of mechanical and thermal effect. The heat greatly lowers viscosity.

Andrew Sink12:08 PM
@anfractuosity, that's a great question!

Andrew Sink12:09 PM
An "MSLA" 3D printer will, by definition, use a masking LCD!

WooDWorkeR12:09 PM
i recommend "animal feeding matts" - they always have a nice lips that prevents resin spills

anfractuosity12:09 PM
aha, makes sense, cheers

Andrew Sink12:09 PM
If it uses galvos or lasers, it's probably an SLA printer, and if it uses a light-based projector, it's a DLP printer!

Andrew Sink12:09 PM
You're dead-on, great critical thinking!

Andrew Sink12:09 PM
These are great questions, everyone!

David Geller12:10 PM
@WooDWorkeR - do you mean cafeteria trays kids use? That's what I use.

Andrew Sink12:10 PM

Andrew Sink12:10 PM
Printing clear parts with resin is another fun strength of this technology!

Andrew Sink12:11 PM
"How do I print a water-clear" part is a really common question in resin printing, and the short answer is, "With a lot of effort!"

Andrew Sink12:11 PM
But using a quality clear resin is a great way to skip to the front of the line!

joshua.vader12:11 PM
How good is the clarity? is it possible to print any sort of lens yet?

Thomas Shaddack12:11 PM
You can even print some rudimentary nonimaging optics. Fresnel lens worked, and focused a LED in usable way.

Andrew Sink12:11 PM

David Geller12:11 PM
Anyone experimenting with dyes and clear resin? I bought both but haven't experimented yet.

Andrew Sink12:11 PM

Andrew Sink12:12 PM
Here's an example of a solid cube, printed and cured, with no post-processing

Andrew Sink12:12 PM

Andrew Sink12:12 PM
Whoops, sorry, those were out of order!

Involute12:12 PM
You could also print a master, make silicone mold from it, then cast with clear resin.

Thomas Shaddack12:12 PM
The clearness depends on both the precursors, which are usually yellowish naturally, and the photoinitiator, which by the virtue of having to be sensitive to 405nm has to be yellowish at least a little bit (but some can photobleach to near-colorless).

Andrew Sink12:12 PM
The first one has been wetted down, and the second one is the original!

Andrew Sink12:12 PM
You can see the difference in the clarity of the part

Andrew Sink12:12 PM
Hey @Thomas Shaddack! Thanks for all the extra information!

Andrew Sink12:13 PM
Clarity depends on many things, but here's a good explanation

Andrew Sink12:13 PM
When a part is printed, the cloudy surface is due to rough imperfections in the upward-facing surface

Andrew Sink12:13 PM
Think of it like a mirror, covered in sand

joshua.vader12:13 PM
would sanding the surface help with the cloudiness or are the flaws deeper?

WooDWorkeR12:13 PM
@David Geller something like this https://www.amazon.com/-/en/dp/B01MEHV8YR/

Andrew Sink12:13 PM
As you reduce the overall roughness, it becomes clearer!

Andrew Sink12:14 PM
So, sanding is a GREAT way to get a clear part

Andrew Sink12:14 PM
But, it's time-consuming

Andrew Sink12:14 PM
So a quick way to cheat is a thin coat of Acrylic Clear Coat!

Andrew Sink12:14 PM
I use Krylon Crystal Clear

Thomas Shaddack12:14 PM
We're encroaching on the field of UV-vis spectrometry. Anything with enough conjugated aromatic bonds will tend to be at least yellowish. If it will tend to make them over time, it will yellow later.

Andrew Sink12:14 PM
This will help fill the valleys between the layers, and give the part a more uniform surface

joshua.vader12:15 PM
@Andrew Sink awesome, thanks!

Thomas Shaddack12:15 PM
I think you can use the resin itself. Thin coat, and cure in place. Or skip on the washing if the part's design allows.

Dan Maloney12:15 PM
Eric Strebel has a video on post-processing CLA prints to make them water clear:

Dan Maloney12:15 PM

https://www.youtube.com/watch?v=nvNXCyDyTTI

YOUTUBE ERIC STREBEL

Andrew Sink12:15 PM

RichardCollins12:15 PM
Like most 3D printers, the resolution and repeatability is a function of price and control software. It would be nice to print lens assembles. I was working on the microscope industry this morning and thinking how expensive it is to machine, cast metals, hand assemble. And the chaos and expense of al those threads, adapters, connectors - more cost to connect than the pieces.

The idea of printing optics as you need them. Want to change, them, make a new one, and throw the other one away or give it to a good cause.

Dan Maloney12:15 PM
Guess it depends on how clear you like your water ;-)

Andrew Sink12:15 PM
This is also visible in the parts themselves, when they are coated with resin, they are highly transparent!

Andrew Sink12:15 PM
@RichardCollins, that's a great point!

Andrew Sink12:16 PM
Printing a lens assembly would be a HUGE win for 3D printing, but currently, there is a lot of post-processing involved in getting those parts to an acceptable level of light transmission and clarity!

alexkollen.edu12:16 PM
As Andrew said clearness depends on many variables. The surface is one major one. If surface finish is an issue some clear paints can help. They generally have a self-leveling effect that will smooth out micro roughness.

Andrew Sink12:17 PM
Clarity is a lot of fun to experiment with, there are LOTS of creative ways to solve the problem of making clear prints!

Andrew Sink12:17 PM
Speaking of which!

Thomas Shaddack12:17 PM
I succeeded in printing a M12x0.5 thread that didn't need chasing with a tap. (Needs a lil' adjustment, making a little bigger or smaller to account for the process variables. Print a couple of threaded holes with different adjustment factors, choose by test.

Andrew Sink12:17 PM

Andrew Sink12:17 PM
Here's a thumbnail from a video I published recently (that was actually featured on Hackaday!)

Andrew Sink12:17 PM

https://youtu.be/ueQ7VoIhCPs

YOUTUBE

Andrew Sink12:18 PM
This was an experiment in printing hollow resin parts, and filling them with paint to provide an opaque backing to the clear nature of the parts

RichardCollins12:18 PM
I worry about global education. Low cost optics for schools leaves most without anything to use, eats up budgets and requires fairly costly human teachers. If the kids can print the experiments themselves, or as needed, it might be possible to teach the two billion first time learners at present, and more later.

Andrew Sink12:18 PM
This allowed the otherwise difficult-to-see details show right through!

Thomas Shaddack12:18 PM
Technically, using two-photon polymerization, it could be possible to get to 100nm resolution. Then even with the ridged surface we could have optical components, as we'd be at quarter-wavelength of blue light anyway.

Andrew Sink12:19 PM
So, let's keep talking about getting started!

Andrew Sink12:19 PM
What are some obstacles you've ran into when resin printing?

Thomas Shaddack12:19 PM
I saw school-grade optics with jello cast into moulds.

RichardCollins12:19 PM
@Thomas Shaddack I was looking for one of those this morning and wondering if they could be 3D printed. It just has to hold for many setups. Thanks!

anfractuosity12:19 PM

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