Resin for printing - differences, properties?

[JeffreyK]

Hi everyone,

 

I've seen most printer bands as well as resin producers offer several types of resin.

There are usually several different "standard" type resins (apart from the colour the differences aren't really well explained), clear resins and there are water based, "odourless" resins as well.

My questions are:

What would you look for when the objective is to print "our" type of parts, i.e. model parts with the highest possible resolution, similar to cast resin?

Can a water based resin be used for this application? Is there a marked difference in physical properties between water based and standard resin?

Can I switch back and forth between water based and standard resin in the same printer?

Are the resins temperature sensitive? I.e. if I set up a print over night and the room temperatures fall into single figures, will this impede the print result?

 

I need to consider all of this when deciding when to get my own printer, whether I can setup and operate it where we are now or if I have to wait until I have a better work shop.

Cheers,

J

[Stephen W]

good question and something I would like to know too  if any resin printer Guru's can answer.

[bootneck]

Hi Jeffrey,

I can only talk about the Anycubic Photon resin printer, and as a pure amateur; however, I do understand your thinking about printing by modellers.

Also, I have only used Anycubic's resins, both standard (toxic) and plant/water (ECO) based.  I believe the Eligoo machines, and their resins, are very similar.

 

- You can achieve near perfect resin parts with these resins, it just depends on the settings you apply when procesing the file to print.  I normally print my layers at 0.05mm for coloured resins (grey fuselage etc.) and 0.025mm for clear parts (canopies). You can get down to 0.01mm but I haven't tried that yet.

 

- I haven't noticed any quality difference between the standard and Eco resins, the fuselage of this Bell 47 Sioux was produced with plant based (ECO) white resin. The canopy in standard clear.

 

- You can switch between standard and ECO resins on the same printer but you have to completely clean the vat, which holds the resin, thoroughly each time.  You don't want to contaminate the safe ECO with the toxic standard resins.  I use both on a fairly regular basis but I purchased an extra vat so I don't have to mix the two.  Having a second vat is also useful for quick changes if I am printing clear and coloured resins. It saves so much time that it really is worth the expense and I got mine off Amazon.  Again, you don't want to be putting clear resin into a vat that has recently been used for coloured resin without giving it a thorough clean first.

 

- Recommended temperatures for resin printing appears to be around 20C but, here in the UK, I've started prints at 15C without any problem.  You just need to ensure that the resin bottle is shaken well before pouring into the vat.  If the resin is already in the vat, from previous use etc., then just ensure to give it a gentle stir before starting.

 

Overnight prints are not a problem, I tend to do most of my prints overnight and in cool temperatures.  The resin gets quite warm once the printing process starts, therefore there isn't a problem if the temperature drops outside overnight.  I'm sure that this will become a problem in during the winter months and will have to make other plans then.

 

Finally, a spreadsheet has been produced which details the settings for all types of resins for the Anycubic Photon and I've linked it here.  I refer to it regularly when setting up my prints.

 

I'm sure someone will be along later to explain other machines and resins but I hope this helps for now.

 

Mike

[JeffreyK]

Thank you very much for this run down, this is very very helpful!!

 

Jeffrey

[Bangseat]

Just to add, I keep my printer in a loft that gets both very cool and very warm in summer. It can be 40 degrees in there in a heatwave without the air con on, and I have worried about it affecting the printer's performance, but I have had absolutely no problems printing all through the summer, although I do use generous layer times. (Elegoo Mars, printing standard Elegoo grey resin and Monocure Clear). 

[bootneck]

You are welcome Jeffrey.  Just a note on the Bell 47 Sioux model, it is to 1:144 scale and is only 68mm long. I placed the photo just to show how small and detailed a print could be obtained.

 

Mike

[JeffreyK]

Thank you very much everyone!

With Winter approaching I was more worried about low temperatures - there's no central heating and leaving a space heater on overnight isn't a good option.

 

Also, what about noise? I mean the print process is slow and probably quiet, but do the printers make "processing noises", beeps and blips, have noisy fans etc.?

 

Cheers,

J

[bootneck]

No really, there is just a low hum as the each layer prints, which lasts a few seconds.  However, it begs the question about where you are going to use the printer?  If it is in your house then you should only use the plant based ECO resin.  The standard resin gives off fumes, not necessarily smelly, that ar bad for the lungs.  Even just having the resin in the vat can cause breathing problems and coughing fits.  When I first started on this, I had the printer in the spare room and always wore a mask when entering. The problem is that the fumes pervade the house and I developed a severe cough for a couple of weeks before I realised what the cause was.  I even ended going to the doctor's, where I had a Covid test and chest X-ray.  These proved negative so he asked if I worked with any toxics and that is when the dangers became obvious.

 

I now keep the printer in a shed with an extractor fan fitted, plus I fully mask and glove up before going in there.  I spend the minimum time in there until the room as fully ventilated and the resins are back in their bottles.

 

Mike

[JeffreyK]

Thanks, yes - that's why I was asking about the resin differences and if the ECO resins can deliver the same quality results.

As my current work room is right next to our bedroom I may wait though until the situation changes...

Many thanks again,

J

[Caerbannog]

I have an Elegoo Mars and used Elegoo water based resin mostly. I never tried the standard resins as I see no other advantage of the "nasty" resin than that it is about 10% cheaper. But you need to wash with alcohol so the price advantage seems to be eaten up pretty quickly. One issue I found with the water based resin: Be carefull when you wet sand it. On some parts the water kind of disolved the resin and the parts cracked open and warped. Maybe because they were not 100% cured.

[wellsprop]

1 hour ago, JeffreyK said:

Thank you very much everyone!

With Winter approaching I was more worried about low temperatures - there's no central heating and leaving a space heater on overnight isn't a good option.

 

Also, what about noise? I mean the print process is slow and probably quiet, but do the printers make "processing noises", beeps and blips, have noisy fans etc.?

 

Cheers,

J

I've had a string of failed prints since the temperature has dropped, I'm sure it's not a co-incidence!

 

My printer is in the garage, so it's been going down to as low as 10 deg C overnight. When the weather was warmer I had absolutely no issues at all and ran for about 2 weeks of almost non stop printing with no adjustment to the setup.

 

I've bought myself a reptile warmer pad, I'm going to place that beneath the printer and put the box over it to keep it at around 25 deg C and see if that makes a difference, I will report back!

[bootneck]

I wonder if there is such a thing as a small solar heater or heated pad?  We do get some very cold winters here and, being down the shed will mean I have to find some form of heating.  The problem being the cost of keeping an electric heater going would be too expensive.  A solar panel connected to a small heater could be the ideal solution, if it exists would it be affordable?

Mike

[wellsprop]

3 hours ago, bootneck said:

I wonder if there is such a thing as a small solar heater or heated pad?  We do get some very cold winters here and, being down the shed will mean I have to find some form of heating.  The problem being the cost of keeping an electric heater going would be too expensive.  A solar panel connected to a small heater could be the ideal solution, if it exists would it be affordable?

Mike

Hrm not sure! Is there any possibility of getting a extension cable to the shed? The heater I bought is only a small pad heater at 16W and only needs to be on when printing.

[Stephen W]

I was going to mention something like an oil filled radiator with a thermostat would be quite safe fo this sort of thing. You can usually pick them up cheap enough. 
 

Great info on the resin, thank you too!

 

 

[Wm Blecky]

18 hours ago, bootneck said:

That is absolutely the coolest thing I have ever come across related to the hobby.  Thanks for posting the pic.

 

Could you post a closer picture of the kit?  I've seen some "printed" items on eBay and quite honestly, they look pretty rough.  Not something that would encourage me to spend any money on.  But yours is completely the opposite.

[ICMF]

Experienced user here.

 

Simple answer is, there isn't much practical difference between resins from a modelling perspective.  There isn't one brand or type that will give really amazing prints, and another that will be terrible.  Performance is broadly similar between all of them, though specific, properties will be a little different from brand to brand.  So mostly, I just look for what's reasonably cheap.  Any resin that cures at the 405nm UV wavelength will work on any mSLA printer that uses a 405nm LED (ie. any LCD based printer).  Resins for laser-SLA printers typically won't work in LCD printers, as they cure at a different wavelength - you can't use Formlabs resin in an Anycubic printer - but you can use any mSLA-compatible resin in any mSLA printer.  So yes, water-based resins will work, and will work more or less interchangeably with standard resins.

 

And yes, you can use different resins in the same machine.  You can mix them, or when you empty your vat to change resins, you don't have to be meticulous about cleaning - a bit of standard residue won't have any real effect on a vat full of water washable - colour contamination would be a bigger concern.  Or alternatively, you can buy multiple vats, for different types/colours of resin.  However, because there is a certain amount of experimentation needed to dial in the settings for each resin, it would be a good idea to try sticking with a limited selection of resins, rather than changing it up constantly.  

 

As for temperature, that's a bit more difficult - yes, but...  Yes, they are temperature sensitive inasmuch as they become more viscous at lower temperatures.  They'll still cure, but the problem is, when the build platform raises after exposing a layer, the resin needs to flow across the bottom of the vat to expose the next layer.  If the resin is too thick, it'll have problems flowing, which could leave gaps and pockets throughout your print.  Additionally, it will increase the suction forces, which will make it harder to actually peel each layer off the bottom of the vat, which could cause problems - potentially even pulling the print off the build plate.  However.  You also have a honking-big LED letting off a ton of heat, which will gradually heat up the build chamber, raising the temperature of the resin and letting it flow better.  I believe the recommended chamber temperature is typically around 25 - 30`C; the printer will easily run 5 - 10`C hotter than the ambient air temperature, but if you're in the single digits, that could be a problem.  That being said, there are heating units that you can install in your printer that would help - Peopoly make one for their Moai printer, and you can probably find something similar, cheaper on Banggood/Aliexpress.

 

Noise will depend on the printer - the bigger printers being released have larger, more powerful and noisier fans.  The Photon/Mars type printers are pretty quiet; they have a fan that's always on when the machine is printing, but it's comparable to a typical PC cooling fan at average speed.  It's not very noticeable and wouldn't travel through walls.  The stepper motor whirrs a bit as the build plate raises and lowers, but it's a low frequency and shouldn't be a problem in another room.  The newer Chitu Boards are transitioning to better stepper drivers, so you shouldn't hear this with the mono printers.  And depending on the size of your layer, you'll hear a peeling sound as the cured layer peels off the bottom of the vat.  But it's certainly less objectionable than many filament printers, with multiple, grinding fans and a high-frequency stepper motor whine.  There's no problem having a normal conversation directly beside the printer, so unless you're super-sensitive to sound, it shouldn't be a problem.  Oh, and beeping is, IIRC, pretty minimal (mostly when pressing buttons), but literally the first thing I did after plugging mine in was to go through the menu and disable the beeper, so it's absolutely not an issue.

 

For a more detailed answer, it's probably easiest to tackle things chronologically, as a sort of Resin 101.

 

The first 'generation' of resins are what we'd now call 'standard' resins.  Anycubic resin, Elegoo 'Standard' resin, Siraya, FunToDo, Wanhao/Monoprice/eSun, etc.  They're all pretty much the same and all compatible with each other, though different brands may tweak the recipe slightly.  Specifically, some brands may use less (or more) of the activating agent, so they may have different layer times, but they're all the same 'type' of resin.  They have a stronger odour (not terrible, and in line with many modelling products, but it is there).  They're quite hard, but can be on the brittle side after curing. (though no worse than most 'regular' resin parts) And they need to be washed in isopropyl alcohol (or similar), though a few detergents in an ultrasonic cleaner can be used as a passable substitute.  They're really nice to work with, though - they sand, file and polish really nicely.  And, incidentally, they may not all be compatible with RTV resin - you may need to use a specific 'castable' resin with a different chemical makeup if you plan to print and cast masters. 

These resins broadly come in two styles: translucent and opaque.  Both use the same base mix; transparent resins use a dye to add a colour tint, while opaque resins have a a sort of talcum-like additive for opacity, as well as the dye for colour.  The 'opaque additive' tends to precipitate out of solution, so if it's been sitting around for a few days, you definitely need to give the resin a good mix before starting a print. 

Since they use the same base resin, their performance is broadly similar, however, you will see some variance at the extreme edge based on colour and opacity.  The light in an mSLA printer isn't perfectly perpendicular to the LCD - they're radiant lights, not lasers - which means that there is a certain amount of diffraction through the LCD, the FEP and the layer of resin in the bottom of the printer.  This diffraction means that light will bleed around the edges of each layer's mask, curing some quantity of excess resin. (it's a tiny amount, not much more than the equivalent of a coat of paint but still...)  The more light is able to diffract through the resin, the more excess resin you'll tend to cure.  So translucent resins will be a little worse; opaques a little better.  Darker resins will be a little better; lighter resins a little worse.  Now, a big part of operating any 3D printer is tuning the machine to the specific material you're printing, and proper exposure settings will virtually eliminate these differences, but in terms of "what's the difference"...  that's basically it.   

 

The second 'generation' were the 'ABS-like' resins, listed variously as flexible, tough, tenacious, or simply ABS-like.  These changed this basic formula by adding flexible monomers to address the complaints of brittleness, but are otherwise the same as standard resin.  One of the big markets for mSLA printers is with wargamers, printing out miniature figures.  Since their prints get handled more, durability is more of an issue.  Less useful for modelling applications, though they'd be handy for parts that are subject to more stress, like landing gear.  Again, fully compatible with the standard resins.  In fact, it's not uncommon to see people mix a portion of flexible resin into standard resin to get more resilient prints.

 

Next up were the Eco resins.  Basically, they took the formula for standard resin, swapped out the acrylic for a soy-based plastic (probably PLA) and dropped some VOCs so the resin wasn't as smelly.  Most of the typical '3D print enthusiasts' are coming from filament printers, so there was a lot of moaning about how much more onerous resin printers were, with smelly, toxic resins that require a hazmat suit and would eat a hole through your body if you got a speck on your skin, etc (they're not - particularly if you're used to dealing with chemicals from modelling - but it was mostly a case of "it's different so I hate it").  So the Eco resins are an attempt to address that complaint.  The marketing stresses 'plant based' and 'eco' but they're still just as toxic as standard resin.  From the user's point of view, they're basically an ABS-like resin, but with lower odour.  Performance is the same.  They're about as brittle.  They still need to be cleaned in isopropanol.  And they're still an allergy sensitizer that can cause issues with extended contact.  Just... less smell.  You can mix them with standard and flexible resins and they'll work just fine, though obviously they'll smell more.

 

Finally, we got the water-washable resins.  Because the other big complaint was that you need expensive/smelly/dangerous chemicals to clean the prints.  Just like the Eco stuff, it's still toxic and a sensitizer, it's no more 'healthy' than standard resin, it just uses a different chemical for cleaning. And it doesn't use the soy-based plastic, AFAIK, so 'water washable' is an entirely different thing from 'eco'. Again, performance is comparable to standard or ABS-like, maybe a bit less smelly.  The only difference is that you can clean it with H2O instead of IPA.  This is good, because you can use (free) water instead of ($$$, and now hard to find) alcohol, and can clean parts directly in an ultrasonic cleaner.  It is also bad, because a lot of inexperienced and, frankly not-too-bright users will be happily dumping toxic waste down their drains, into the water supply.  You need to expose the contaminated waste liquid in the sun, filter out the solidified resin, then throw it in the trash (incidentally, you can recycle your used isopropanol the same way).  

Water washable resin is the only type that would have any possible compatibility issues.  It will absolutely work with any of the other types of resin, but if you mix it with, say, standard resin, you'll have to wash the print in alcohol.  Basically, it defaults to the 'hottest' solvent in the mix. 

[JeffreyK]

Thank you very much indeed!!! That's a great run down.

As I'm eying up a Phrozen printer, these are the resin choices they offer:

https://phrozen3d.com/collections/3d-printer-resins-phrozen

This is where my confusion started as it's really not clear in what way they all differ and what's best to use.

I'm after the best, sharpest print results (obviously), but with hopefully not extreme brittleness. Yes, the prints will be used as masters for resin casting. They will mostly be primed, but there will be the odd spot not covered with primer and this shouldn't be a problem when embedding the parts in RTV (addition cure). And the masters shouldn't shatter to pieces when de-moulding them.

I really want to dive into it (esp. as the Phrozen Sonic Mini as a pre-order discount), but it does sound a bit like it's too much of a hassle to set it up and make it work in my current situation. Probably have to wait until next year.

 

Cheers,

J

[bootneck]

9 hours ago, Wm Blecky said:

Could you post a closer picture of the kit?  I've seen some "printed" items on eBay and quite honestly, they look pretty rough.  Not something that would encourage me to spend any money on.  But yours is completely the opposite.

Hi Wm,

Here is a view of most of the kit parts.  As can be seen, there are enough parts to allow for at least three versions:

 

1950's, Korea era, version with single tank and squared skids, plus stretchers.

1960's with dual tanks and square skids.  This is also the M.A.S.H. version from the film

Civilian version, with either single or dual tanks and rounded or square skids, or even floats.

 

This is one I am working on and will be a Royal Marines version. I first flew in one of these in 1968.

They should have called it the Dragonfly!

 

I love this kit and, as you can see, I've bought a few already. 

 

A bit of a digression I know, but at least these images show the detail that can be obtained, even at small scales. These printers would be ideal for printing detailed aftermarket parts.

 

Mike

[wellsprop]

Here's my thread regarding my fix for cold weather printing issues!