Hack Chat Transcript, Part 3

A event log for Resin Printing Hack Chat

Do you do the goo?

Dan MaloneyDan Maloney 10/13/2021 at 20:120 Comments

Andrew Sink12:39 PM
I've made mechanical assemblies printed fully dense on the Mars 2 Pro, and shrinkage was not something I had an issue with

Thomas Shaddack12:39 PM
The radical polymerization leads to sometimes fairly significant shrinkage. (Low single percents in linear dimensions, worst case.) This can be mitigated by using bigger molecules with lower total mass contribution of the acrylic groups, or adding fillers (either discrete particles or dissolved polymer - but both can wreck your viscosity).

Thomas Shaddack12:41 PM
There are other chemistries that don't suffer from that, eg. cationically polymerized epoxies. But I didn't see any such printing resin yet.

Andrew Sink12:41 PM

Nicolas Tremblay12:41 PM
Talking about fillers. Any recommendations? how about mixing resins?

Andrew Sink12:41 PM
Another fun fact about resin printing (possibly my favorite fact), is the super fast print speed for printing in parallel!

Andrew Sink12:41 PM
Because the resin is exposed one layer at a time, your build time is always a function of the tallest part

Brian McEvoy12:41 PM
Are there any resins as strong as nylon?

Andrew Sink12:41 PM
So, build time roughly equals number of layers!

Andrew Sink12:42 PM

Andrew Sink12:42 PM
This means, when printing multiple parts, your cycle time drops DRAMATICALLY!

controlmypad12:42 PM

Andrew Sink12:42 PM
So, filling a print surface with parts comes with no time penalty

Thomas Shaddack12:42 PM
Fillers, any way how to prevent the particulates from settling? Any way to have a high particulate loading without crippling increase in viscosity (eg. the aluminium hydroxide for fire-retardant resins)?

Andrew Sink12:43 PM
FDM 3D printing is a volumetric equation, so printing 2x parts will take roughly 2x time

David Geller12:43 PM
Though cleaning all those little figurines....

Andrew Sink12:43 PM
Want to hear something fun?

Andrew Sink12:43 PM
Cleaning all of them took the same amount of time as cleaning one of them, @David Geller!

Andrew Sink12:43 PM
I processed them as a batch, so they were all washed together, and cured together!

Andrew Sink12:44 PM

Andrew Sink12:44 PM

Andrew Sink12:45 PM
So, resin printing can be ideal for printing lots of small things quickly!

Nicolas Tremblay12:45 PM
@Thomas Shaddack , not exactly, just in general, taking a stock resin and modifying it with X to give you better Y and Z.

David Geller12:45 PM

Andrew Sink12:45 PM

Andrew Sink12:45 PM
Interestingly enough, I had originally intended to make 24 parts, but 2 of them failed

Andrew Sink12:45 PM
So the cycle time (time per part) could have actually been lower!

Andrew Sink12:46 PM
And with some optimization of the placement of the parts, it could be driven down further than that!

Involute12:46 PM
On the right side, are you counting time to remove supports?

Andrew Sink12:46 PM
@Brian McEvoy Great question "Are there any resins as strong as nylon?"

Andrew Sink12:46 PM
Nylon is a thermoplastic, unlike most resins which are thermosets

Andrew Sink12:46 PM
Thermoplastics tend to be more mechanically tough, and can be deformed readily before breaking

Andrew Sink12:47 PM
Most thermoset resins tend to be on the brittle / stiff side, so it's hard to compare to Nylon, a material that is desirable for its ability to be deformed

Thomas Shaddack12:47 PM
The toughness may be influenced by using a less brittle less-crosslinked resin formulation.

Andrew Sink12:48 PM
@Involute, No, I didn't count the time to remove supports, but it probably added something like 20 - 30 seconds per model

Andrew Sink12:48 PM
The supports for that model were VERY well designed, and quick twist was all that was needed to remove them!

Nicolas Tremblay12:49 PM
A carefully supported model helps there

Andrew Sink12:49 PM
It sure does, @Nicolas Tremblay!

Thomas Shaddack12:49 PM
Here we should touch the concept of Tg, glass transition temperature. Below that, polymers are generally brittle, above that they are more tough. A piece of rubber in liquid nitrogen is an example of freezing a polymer below its Tg.

SimonAllen12:49 PM
I want to print some coins for Dungeons and Dragons. They have some fine detail. Will I get a better print with a resin printer than an ABS filament printer?

Thomas Shaddack12:49 PM

Andrew Sink12:49 PM
Hi @SimonAllen!

Involute12:50 PM
Any general statements about support-removal damaging/marring the surface of the model with resin vs/ FDM?

Andrew Sink12:50 PM
Absolutely, most resin printers will be capable of providing you more detail than an FDM printer, but you'll want to scroll up to read about the process involved before making a decision!

Andrew Sink12:50 PM
@Involute, another great question!

Andrew Sink12:50 PM
Support material on FDM (Stratasys / Industrial) tends to be a secondary soluble material, but most home printers will create a support structure from the same material

Thomas Shaddack12:51 PM
Resin support break-off can tear a little piece from the material, making a dimple in the surface. Fortunately this can be touched up with a little drop of the resin and a bit of UV light.

Andrew Sink12:51 PM
Resin supports are actually integrated directly into the model, so removing them can leave a small divot in the model. Typically, a quick prime is all that's needed to remove those, or they can be sanded flush

Andrew Sink12:51 PM
I've found I spent less time concerned about resin support removal; it's much harder to "fix" FDM support removal!

Andrew Sink12:51 PM
OK! This has been a ton of fun, but we're down to the last 9 minutes!

Andrew Sink12:52 PM
Are there any questions that I missed? Anything that you're interested in learning about? Speak now!

Thomas Shaddack12:52 PM
Removing supports with a scalpel is much easier when the print is still not fully cured, when it is still a bit elastic and rubbery instead of hard and britlte.

Andrew Sink12:52 PM
Resin printing is a VERY satisfying experience, but typically, it can be a bit messier than FDM, and the post-processing requires some discipline to keep a tidy space!

Shayan S.12:53 PM
What would you say is the most valuable advice you can give to someone who is already somewhat versed in resin printing (i.e. what do you know now that you wished you knew before)?

Andrew Sink12:53 PM
Great question, @Shayan S.!

David Geller12:53 PM
@Andrew Sink - just watched some of your videos. Excellent content. Very pleasing narrating style.

Andrew Sink12:53 PM
The MOST IMPORTANT thing is always safety, so even though it's a chore, ALWAYS wear gloves, and ALWAYS be careful

Andrew Sink12:53 PM
Barring that, don't cheap out on materials or tools

Andrew Sink12:54 PM
I've seen people go absolutely wild trying to "fix" a printer, and the problem was material that was well past its expiration date!

Thomas Shaddack12:54 PM
And don't panic. Occasional contact with the raw resin won't harm you. Repeated frequent job-like contact may lead to sensitization and allergies.

David Geller12:54 PM
I always wear eye protection and gloves for all my resin-related tasks. Always.

Andrew Sink12:54 PM
OK, @Thomas Shaddack, that's actually pretty bad advice, sorry!

Andrew Sink12:54 PM
The proper amount of skin / resin contact is 0!

Andrew Sink12:55 PM
Smart move, @David Geller!

Thomas Shaddack12:55 PM
ALARA. As Low As Reasonaby Achievable.

Andrew Sink12:55 PM
I got my start on YouTube making videos for college courses; my mom held the camera and told me to "SLOW DOWN", my natural speaking voice is WAY fast

Andrew Sink12:55 PM
So when I make my videos, I have her in mind, so I speak slow and clear!

David Geller12:55 PM
@Andrew Sink - agree about fixing vs. materials. I had bad print after bad print until I switched to a Siraya Tech resin and, since then, every single print has been spectacular. I'm on an Anycubic.

Andrew Sink12:56 PM
That's great!

Thomas Shaddack12:56 PM
Speak slow and clear, so people can watch you at 150% speed. :P :D

Shayan S.12:56 PM

Andrew Sink12:57 PM
The Siraya Simple Clear Resin is a favorite of mine; it's about as clear as you can get, even post-curing

Andrew Sink12:57 PM
and it

Andrew Sink12:57 PM
it just works.

Andrew Sink12:57 PM
Most slicers have very conservative settings, so if you're having consistent part failures, check A) the model, then B) the resin

Andrew Sink12:57 PM
Tweaking settings is a fast way to get to a frustrating afternoon!

Nicolas Tremblay12:58 PM
I can't recommend Elegoo water washable resin. It stinks.

Andrew Sink12:58 PM
I originally liked the Water Washable resins, but I had issues with parts cracking after printing, so I've moved away from them

Andrew Sink12:58 PM
They don't seem to be as reliable long-term, and the smell does tend to be much worse

Thomas Shaddack12:59 PM
Also, adjust the exposure per layer vs layer thickness. There is a tradeoff between the time and the strength achieved in-printer, and the bottom adhesion force. If the latter is higher than the strength of the part, it will tear off.

James Nugen joined  the room.12:59 PM

Andrew Sink12:59 PM
I use Elegoo Standard Photopolymer as my "daily driver", it's cheap, comes in interesting and easy-to-see colors, and works well on most machines!

Andrew Sink12:59 PM
Alright, with that last comment, my time is up!

Nicolas Tremblay12:59 PM
My printer got banned to the garage because of it. Glad I got the air purifier.

Andrew Sink12:59 PM
I want to take a minute to thank @Dan Maloney and the rest of the @Hackaday team for having me this afternoon!

Dan Maloney12:59 PM
We're up against our allotted hour now, so I'm going to call an "official" time on the chat. Of course the channel is always open, so feel free to keep the conversation going. But we'll just say a big thanks to Andrew for his time today, and a great Hack Chat. Great questions too from everyone -- thanks!

controlmypad1:00 PM
Thank you Andrew and HAD, very informative!

Dan Maloney1:00 PM
Oops, crossed in the mail...

Andrew Sink1:00 PM
I appreciate the chance to talk about resin printing, feel free to reach out on Twitter if you want to ping me with anything else!

Nicolas Tremblay1:00 PM
Thanks @Andrew Sink and @Thomas Shaddack <

Andrew Sink1:00 PM
Haha! Thanks @Dan Maloney! Have a great afternoon, everyone!

SimonAllen1:00 PM
Thank you Andrew

James Nugen1:00 PM
Are there any resins that would make functional gears?

Thomas Shaddack1:00 PM
All of them. For different mechanical requirements.

controlmypad1:01 PM
Yes thank you @Thomas Shaddack!

Thomas Shaddack1:01 PM
Thought. A resin with built-in reducing agent that would cover itself with copper when immersed in copper sulfate. (Then continue with electroplating. Voila, small metal parts!)

Thomas Shaddack1:02 PM
Another thought I am nurturing. Borrow the thermolabile crosslinkers from reworkable epoxies, where they have issues with their too low thermal stability. Print a hard stiff thing. UV-cure. Bake thermally to a rubbery thing.

Nicolas Tremblay1:03 PM
Just a dip in the reducing agant before post-cure?

Thomas Shaddack1:03 PM
That maaaaaaaay work...

Nicolas Tremblay1:05 PM
or a 50/50 solution, agent/resin to dip. And may need some oxygen protection?

Thomas Shaddack1:07 PM
A related thought is some reducing agent that is activated by another wavelength (molecule splitting similar to the photoinitiator, without the radical). Then we could print "two-color", with locally activating the reducing moieties, and then selectively deposit metal just by immersion. Voila, potential way of printing metamaterials for microwaves and millimeter waves.

Nicolas Tremblay1:07 PM
I had the same idea a few years ago. Relatively easy on paper.