Model Railroading > New 3D Printer (Part 3) – Resins

This is Part 3 of a series on my recent experience with a Phrozen “Mini 4K” 3D printer.  (Part 1 & 2 were posted earlier.)
 
After my experience with the Photon S, it became clear that the choice of resin can have a positive or negative effect on the part.  There are a zillion choices out there, some made by companies that I have never heard of.  After looking at lots of reviews, a few bubbled to the top as being worth a try.  Reviews are fine, but nothing beats actually purchasing some resins and giving them a try.  Unless you have a friend that has some resin to let you try-out, purchasing an entire bottle for about $35 to $60 is the only option. 
 
Currently, my resin of choice is Elegoo “Standard” Gray resin.  I trust Elegoo to offer a quality product, and that resin does not disappoint.  Surprisingly, it is one of the least expensive out there.  It can be purchased for about $36 per liter.  (Most resins are around $50 per liter.)  Initially I avoided it just because of the price-point.  If it is that cheap, did they cut a bunch of corners?  Nope.  It works great!  I like the opaque gray color.  (Translucent resin, like Siraya Blue, may cure faster, but I have to give it a coat of primer to see if the details rendered properly.)  I’m nearly half way through a 2nd liter of Elegoo Standard Gray.
https://smile.amazon.com/gp/product/B07Z986566/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1
 
 



Edited 1 time(s). Last edit at 04/11/21 23:25 by tmotor.

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Viscosity
I assumed resins were all thick as pancake syrup, which is true of the Siraya Blue resin.  However, Elegoo Standard Gray resin has the consistency of whole milk.  It flows easily, and mixes quickly when the bottle is shaken.  However, it will also tend to drip (onto the top or face) of the printer when removing a loaded Build Plate.  I am now in the habit of placing a gloved hand under the Build Plate during removal. 
 
The relatively thin viscosity may allow it to print parts successfully at a lower temperature range.  Regardless, I still wrap the entire printer in an electric blanket to maintain a constant temperature.  I have found that a slight temperature fluctuation will cause the metal printer components to expand or contract just enough that lines appear in the part.  No thank you!
 
I Like My Blankie
The Form 3 printer ($3,500) has a built-in heater to keep the interior of the printer toasty.  Initially I thought that feature was overkill, but after seeing the effects of temperature swings I quickly changed my mind.  At $400 there’s no way the Phrozen Mini would ever have an on-board heater, but the electric blanket fix has worked great.  It isn’t going to win any awards, but I no longer have to worry about lines during a print run.  A safety feature of electric blankets is they shut-off after 8 hours.  I routinely have print runs that last longer than 8 hours, so I will turn OFF and ON the switch to reset the timer.  I have my eye on a digital timer (used to control appliances) that will do that for me.  That way I don’t have to worry that I forgot to reset the timer, and have a long print run will be affected by lines.

Water-Washable
A recent trend is for resins to be washable with water.  Some resin manufacturers are offering them.  Though I will probably try one at some point, I’m not sure I want to become an early adopter.  Until I can see a decent track record, I don’t want to commit to a large project with lots of water-washable resin parts, and then have them shrink or crack years from now.  I am fine with Old-School resin using IPA to wash parts that will remain stable.  I may try a water-washable resin for test parts, but not for finished parts. 

When COVID initially hit, supplies of IPA became scarce.  This may have accelerated the drive to have a water-washable resin.  (Not much fun being on Lock-Down, with no IPA to wash resin parts.)

Stretching IPA
After resin has been washed away by the IPA, the resin remains in suspension.  As with most solvents, the more diluted the IPA becomes with resin, the less effective it is.  Fortunately, the resin is still sensitive to UV light.  By exposing it to UV light, the resin in the IPA will harden.  This worked great for the Siraya Blue resin.  It formed clusters of resin, and overnight they fell to the bottom of the glass jar.   Pour-off the clean IPA, good to go.
 
The Elegoo Standard Gray behaves a bit differently in IPA.  It will still solidify, but into very small particles.  They create a cloud.  I tried to strain them through T-shirt material.  It went right thru.  As an experiment, I poured some Siraya Blue resin into IPA cloudy with Elegoo Gray resin.  I hoped the two resins would be attracted to each other, and the well-behaved Siraya Blue would take the Elegoo Gray with it into a solid form.  Didn’t happen.  However, let the cloudy IPA sit for 24 hours, and it will eventually settle to the bottom.   By having one batch settling, and another in use, relatively clean IPA is constantly available.  This “recycling” method has worked well for me.  I have printed over 100 parts, and have only used 2 gallons of IPA so far.
 
Flammable
IPA is alcohol, and is in high enough concentrations to catch fire.  Be sure to have a fire extinguisher handy.  I like to take the paper towels used to clean the printer and tools, and place them under a UV light, or out in the sun.  This hardens the resin, and makes it safe to throw away.  This prevents a box of paper towels soaked in IPA sitting around waiting for a source of ignition to happen by.
 
Gloves
Another consumable is disposable gloves.  I will wash the gloves after each operation, like I’m washing my hands but with gloves on.  The IPA does a good job of removing the resin, and then I use a paper towel to dry the gloves.  This keeps the resin from getting EVERYWHERE, since the gloves are constantly cleaned while I use them.  When I’m done with the gloves, they are placed over the ends of a paper towel tube to dry the body moisture that collects inside the glove.  When I return to process the next run, the gloves are dry and ready to go.  As a result, I can use the same pair of gloves for 10+ parts.  This is partly because I’m cheap, but also to minimize the amount of trash sent to the landfill.  Also, with COVID increasing the demand for disposable gloves, prices have skyrocketed. 
 
Wash & Cure Station
There are a few on the market.  I have had my eye on the Elegoo version.  At first I thought they were just a gimmick, and passed it by.  However, for a production environment, it makes sense.  Suspending the Build Plate in the IPA not only washes the part, but also the Build Plate.  The swirling water will agitate the resin and should do as good a job as an ultrasonic cleaner, and be much quieter about it.  (The high-pitched buzzing of my ultrasonic cleaner took a while to get used to.  Though I accept it as a necessary evil, I would welcome a less noisy option.)  After washing the part, the tank is removed and a turn table is installed to cure the part.  This makes efficient use of limited bench space by having two operations in the same footprint.
https://www.amazon.com/ELEGOO-Mercury-Washing-Machine-Turntable/dp/B08626WF87/ref=sr_1_4?crid=2WCA2IHYTPQHY&dchild=1&keywords=elegoo+wash+and+cure+station&qid=1618208488&s=industrial&sprefix=elegoo+wash+%2Cindustrial%2C207&sr=1-4




 



Edited 7 time(s). Last edit at 04/11/21 23:27 by tmotor.

Would something like this work to keep your printer at a constant temperature? They come in different sizes.



Edited 1 time(s). Last edit at 04/12/21 06:47 by ChrisCampi.

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ChrisCampi Wrote:
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> Would something like this work to keep your
> printer at a constant temperature? They come in
> different sizes.

Hey Chris!
That could work.  If it can be "bent" to surround 4 sides of the printer, and a piece of cardboard on top (to retain the heat), that would be a winner.
Love the built-in digital read-out.  Much more accurate than the 1-10 dial on my electric blanket control.

Dave



Edited 1 time(s). Last edit at 04/12/21 07:51 by tmotor.

4thDistrict Wrote:
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> I bought the Anycubic wash and cure station. The
> investment was well worth it. Makes cleaning the
> parts much easier and less messy. The curing
> process works well and is easy to use. These
> stations are not necessary so they are a luxury,
> but for the price, they can't be beat for how much
> easier the washing and curing steps are. 
>
Hey 4th District!
Those that have used one seem to have the same very positive feedback.  
It is probably time to upgrade my pickle jar.  :-D

Dave



Edited 1 time(s). Last edit at 04/12/21 08:08 by tmotor.

I switched to Elegoo black, and I like it much better then the grey.   Shows detail better.  

Would a finer filter media, such as coffee filter paper, work better than the T-shirt material to filter out the hardened resin? Have you considered centrifuging the used IPA wash to clear it faster? Swing a bottle tied on a string over your head to create enough G-forces to settle out the resin cloud.

Just some ideas to try and help...

Arved Grass
Fleming Island, FL

sixaxlecentury Wrote:
-------------------------------------------------------
> I switched to Elegoo black, and I like it much
> better then the grey.   Shows detail better.  

Hey sixaxlecentury!
Good call.
I can use black for test parts, then gray for finished parts.  (Assuming resins with lighter colors will cover with fewer coats of TTX yellow.)
Dave

Arved Wrote:
-------------------------------------------------------
> Would a finer filter media, such as coffee filter
> paper, work better than the T-shirt material to
> filter out the hardened resin? Have you considered
> centrifuging the used IPA wash to clear it faster?
> Swing a bottle tied on a string over your head to
> create enough G-forces to settle out the resin
> cloud.
>
> Just some ideas to try and help...

Hey Arved!
Now why didn't I think of a coffee filter?  Good idea!
A centrifuge would work well, but I have enough IPA in-play that some can settle while others are used.  But a centrifuge would certainly speed-up the process.
Maybe I can create a jig to put in the washing machine and run it on spin cycle.
Dave

4thDistrict Wrote:
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> An hour ago I filtered my IPA that had been
> siphoned off after letting the solids drop to the
> bottom. The siphoned IPA was not quite crystal
> clear. The coffee filter did not make it clearer,
> so it did not help at all. A waste of time, and
> some waste of IPA due to drips.  In the future
> I'll skip the filtering step. 

Well, it was worth a shot. I figure if it was good enough for my Chem labs...

At least IPA is a lot easier to get today than it was a year ago. :D

BTW, how is the smell of the resins you're using? Do they stink up the area?

Good luck! I look forward to learning more from your experience before I bite the bullet and get one.

Arved Grass
Fleming Island, FL

> BTW, how is the smell of the resins you're using? Do they stink up the area? 

Hey Arved! 
I'm happy to report the vast majority of resins have minimal smell.  If I stick my nose right into it, I can smell something, but just a basic "chemical" smell.  The early resins had reports of "it stunk-up the whole room and I had to leave".  Those days are long gone.  A resin manufacturer would be suicidal to offer a stinky resin these days.  There are too many alternatives with little to no smell.  If a resin is popular, that is the one to try.  If a resin sells poorly, it probably stinks, literally. 

I find the IPA has much more smell than the resins. 

Dave



Edited 3 time(s). Last edit at 04/13/21 06:57 by tmotor.

tmotor Wrote:
-------------------------------------------------------
> sixaxlecentury Wrote:
> --------------------------------------------------
> -----
> > I switched to Elegoo black, and I like it much
> > better then the grey.   Shows detail
> better.  
>
> Hey sixaxlecentury!
> Good call.
> I can use black for test parts, then gray for
> finished parts.  (Assuming resins with lighter
> colors will cover with fewer coats of TTX
> yellow.)
> Dave

Dave,

If you are painting parts TTX yellow, do an undercoat of white.  It will make it exponentially easier to get the yellow to cover.  I should know, I paint 3 foot long TTX flatcars in G Scale.  Adding a yellow undercoat will greatly improve the finish.  

Tehachapi-TJ Over & Out