Resin Printing Hack Chat

Do you do the goo?

Wednesday, October 13, 2021 12:00 pm PDT Local time zone:
Hack Chat
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Andrew Sink will host the Hack Chat on Wednesday, October 13 at noon Pacific.

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At its heart, 3D printing is such a simple idea that it's a wonder nobody thought of it sooner. Granted, fused deposition modeling does go back to the 80s, and the relatively recent explosion in cheap, mass-market FDM printers has more to do with cheap components than anything else. But really, at the end of the day, commodity 3D printers are really not much more than glorified hot-glue guns, and while they're still a foundational technology of the maker movement, they've gotten a bit dull.

So it's natural that we in this community would look for other ways to push the 3D printing envelope, and stereolithography has become the new hotness. And with good reason -- messy though it may be, the ability to gradually pull a model from a tank of goo by selective photopolymerization looks magical, and the fine level of detail resin printers are capable of is just as enchanting. So too are the prices of resin printers, which are quickly becoming competitive with commodity FDM printers.

If there's a resin printer in your future, then you'll want to swing by the Hack Chat when Andrew Sink visits us. Andrew has been doing a lot of 3D printing stuff in general, and resin printing in particular, over on his YouTube channel lately. We've featured a couple of his tricks and hacks for getting the most from a resin printer, and he'll be sharing some of what he has learned lately. Join us as we discuss the ins and outs of resin printing, what's involved in taking the dive, and the pros and cons of SLA versus FDM.

  • Hack Chat Transcript, Part 3

    Dan Maloney10/13/2021 at 20:12 0 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...

    Read more »

  • Hack Chat Transcript, Part 2

    Dan Maloney10/13/2021 at 20:11 0 comments

    anfractuosity12:19 PM
    Is the minimum layer height you can achieve dependent on the resin used (i assume different resins may be more sensitive to the UV light?) along with the stepper motor?

    Andrew Sink12:19 PM

    Andrew Sink12:19 PM
    That's a great question, with a LOT of variables

    Andrew Sink12:19 PM
    I use car analogies a lot, so hopefully this makes sense!

    SimonAllen12:19 PM
    What entry level machine would recommend?

    Andrew Sink12:20 PM
    But it's sort of like asking "What's the fastest you can go?"

    Grant - 3D Musketeers12:20 PM
    One of my biggest hurdles and one that is not taken into consideration enough is how toxic resin is for not only humans but the environment @Andrew Sink But with proper precautions and making sure everything is cured, it can work out well and safely

    Andrew Sink12:20 PM
    It depends on the car, how many people are in it, what road you're driving on, etc!

    Dan Maloney12:20 PM
    I think my obstacle to adopting MSLA is the mess, but we've already seen that can be managed. I guess the odor might be next -- I have a small shop, can't really ventilate it well.

    Andrew Sink12:20 PM
    But basically, with layer heights, a widely accepted standard is 50 microns (.05mm)

    Andrew Sink12:21 PM
    An interesting fact is you can print a thicker layer using a translucent resin, as the UV light is able to penetrate deeper through the resin itself!

    Andrew Sink12:21 PM
    Using a thick opaque resin, this would be more of a challenge!

    Thomas Shaddack12:21 PM
    The Lambert-Beer law.

    Andrew Sink12:21 PM
    @SimonAllen, I'm VERY partial to the Elegoo Mars 2 Pro

    Andrew Sink12:21 PM
    It's inexpensive, and it provides reliable results

    Grant - 3D Musketeers12:21 PM

    David Geller12:22 PM
    @Dan Maloney I haven't found the odor to be too bad. In fact, I print in my office, which is a room in my apartment.

    Andrew Sink12:22 PM
    It's also heavy enough to not worry about tipping over, and it's a popular-enough model that there is a large user base online to bounce ideas off of!

    controlmypad12:22 PM
    Since SLA printers have a smaller build volume than Filament printers, is there a way to fuse smaller SLA prints together into a larger piece?

    Andrew Sink12:22 PM
    @controlmypad, GREAT question!

    Nicolas Tremblay12:22 PM
    I have the Mars Pro and it's great with the seperate air purifier.

    Andrew Sink12:22 PM
    There are MANY options for fusing parts, the easiest is by creating models as an assembly (think dovetail joint) to assemble after printing

    alexkollen.edu12:23 PM
    @Dan Maloney a god carbon filter and HEPA filter goes a long ways.

    Thomas Shaddack12:23 PM
    Assemble together with mating surfaces wetted with the printing resin, before the final curing.

    RichardCollins12:23 PM
    The material used for 3D printing is not as important or critical to learning this, as the basic 3D design and compiler (to convert to instructions. Cost and time management, knowing the market or need, having a good application that helps people or groups. On Mars and the moon, they will use molten materials, electrochemical and plasma separation, and the tools will start with "3D". The chemistry, physics of materials will be critical to making things that last. Keep in mind the needs of the rest of the century for reliable tools and methods for other worlds.

    Andrew Sink12:23 PM
    You can also add a bit of UV-curable resin and cure it with a UV light to permanently bond two parts

    Andrew Sink12:23 PM
    Great question, @controlmypad!

    Andrew Sink12:24 PM
    I agree with @Nicolas Tremblay, the built-in air filter on the Mars 2 Pro is another great feature!

    Thomas Shaddack12:24 PM
    When we do the gluing-together-with-resin step before the final curing, we have a lot of unreacted acrylate groups left on the surface and we can achieve higher bonding strength.

    Brian McEvoy12:24 PM
    I made a UV laser holder for tacking parts together.

    Andrew Sink12:24 PM
    I used a tower fan put on its side, and open...

    Read more »

  • Hack Chat Transcript, Part 1

    Dan Maloney10/13/2021 at 20:10 0 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 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...

    Read more »

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