Things I should know about resin 3D printing

Introduction

"Start with Why?"

This Christmas - after my child announced she would like a 3D pen I caved, and purchased a resin printer. It was - as is often the way with me - half the information, and then precision guesswork.

Since then I have learnt a tonne of stuff about what to do and what to avoid.

I have wasted time, resources, and money - broken things - and made things.

I have been meaning to pull together a list of thoughts for some time. Alas in a typically me way - rather than get started on somethign that might end up pants, incomplete, or something I hate a year down the line - I did nothing. here is something now over something better another day.

What is 3D printing

Like 2D printing - 3D printing is sending instructions to a machine that makes something - usually from something you have on a screen.

As we all know, despite years of technological advancements, printing 2D things rarely goes to plan all the time. 3D printing is pretty much the same ;D

2D printing - there are lots of different ways to approach the same end product (suddently I am getting flashbacks to Computer science class at school) - line printers, dot matrix, ink jet, laser, colour sublimation and so on into obscurity. These days however we tend to think of two methods - Laser and Ink Jet (or electrostatic and bubble jet as I guess they should be called).

3D printing can be simplified down to types also. Solid and Liqued. Melting into place, and setting solid. The type with the reel of plastic that is melted into place on a bed that can move in X, Y and Z axis - and the resin type - where a stationary fluid bed has a build plate move in the Z axis (up and down).

Back when I was working for a media company in the .com era I went to an expo and saw my first 3D printer. It must have been 2000 or 2001 at the latest. As with all new advances the mechanism was needlessly complex (as with computer networks, jet engines, the list goes on). A powder sat in a fluidized bed (air moving through it so it moved around. A build plate sat under teh surface, and moved into the bed, and a laser fused teh powder into a solid from above.

I saw an adjustable wrench being made, and a length of chain. Which were akin to Love Spoons appearing infront of my eyes.

Having gotten over the awe - I asked "what the point" was... beyond rapid design and build... and the answer stayed with me.

"Imagine you needed to fax a tool to a space station"

... and I did.

Some 15 or more years later - this prediction came to pass.... although I am very pleased to say that Fax was not involved anywhere.

What is resin printing

Resin printing works through a mechanism called Stereolithography:

"Stereolithography (SLA, SL, or resin printing) is a form of 3D printing technology used for creating models, prototypes, patterns, and production parts in a layer by layer fashion using photochemical processes by which light causes chemical monomers and oligomers to cross-link together to form polymers Those polymers then make up the body of a three-dimensional solid. Research in the area had been conducted during the 1970s, but the term was coined by Chuck Hull in 1984 when he applied for a patent on the process, which was granted in 1987." -- wikipedia

In simple-ish terms, a very bright diffused UV source sits behind an LCD screen. On top of the screen is a vat with a transparent bottom to it. The transparent layer is a slippery or non-stick material that has a drum like tension.

A build plate sits against the bottom of the tank, submerged in photoreacting fluid.

A 3D model in an STL format is organized for printing, and then "sliced". Sliced is a term that is what it sounds like - it is horizonatally chopped into thousands of slices. These slices will for layers, or key layers when printed. A slicer may generate for example 2000 layers for an item that is 5" tall.

The first few slices are "burnt in" as they require less detail, but greater adhering to the build plate. These longer exposures take up the first few layers.

Every time the plate slowly lifts out of the fluid, there is an audible plop noise as the tension against the tank / vat bottom film is broken and it snaps back into place. The build plate then lowers down to a height fractionally above where it was before. For me this is around 0.05mm above where it was before. Enough space and time is allowed for the fluid to return to the space the last layer occupied before it was moved,... and now the next layer is layed down. Sticking to the previous layer. The bond is hopefully stronger than the bond to the film on the bottom of the tank.

Exposure happens once the plate is in place with the small gap (now reoccupied with resin) between the last layer on the build plate, and the bottom of the tank (often referred to as a vat). There is a short delay to ensure there is fluid in the void, and then the UV source turns on. The LCD screen - rather than showing a picture - merely masks. What would have been the cold cathode rear is the UV source. The areas of the screen that are now not black allow the UV light into the tank. The photoreacting agent in the fluid breaks down, creating free radicals. These attach to the cross polymers and polymers in the fluid to cause them to bond to each other. The lamp then turns off. There is a short pause. The build plate now slowly lifts - the pop of seperation from the film occurs and repeat. As the thousands of layers are layed down, the print takes shape.

Summary

  • Two main types, melting polymers, and hardening polymers.
  • Resin printing occurs through photoreactivity with a print plate pulling the print away from a tank and light source.
  • An LCD screen masks off the UV light that solidifies the resin
  • A print is made of slices or around 0.05mm each.

Things you should know

The fluid resin is toxic.

There is no getting away from the fact it is nasty.

There are degrees of nasty - but generally speaking it should be handled with caution. This is not plastecine, this will make you very poorly from a number of vectors.

To borrow from someone else's sunshine and joy:

"The resin used in 3D printing is highly toxic. It not only affects the people using it but also creates an impact on the surrounding environment. Anyone exposed to the resin can develop serious health issues. In addition, improper usage of 3D printing resin can cause harm to animals as well as the environment."

My highlights:

  • Fumes are poisonous and have immune implications
  • The resin should not come into contact with skin.
  • Reaction to contact to the skin is likely to change over time and exposure to the fluid.
  • Given issues with skin - eyes and mouth / consumption are a solid no.
  • Resin that is on you, then exposed to UV or sunlight - well thats just making matters a lot worse.
  • Be mindful of the implications of skin contact for any that has found its way on to clothing.

It is worth noting that some resins give off substancially lower levels of VOC (Volotile Organic Compounds) fumes - such as the Eco, or Plant Based Resins. These have been on a very long journey since they were last soya beans - but the idea appeals to me, and the lack of a pressing needing to wear a rated resperator is always welcome.

Pictures of printers on workstops in the house, or resin composting down are verging on a knock from advertising standards - however open spaces, a room with good ventialtion, a stable temperature (or other solution more on this later) would be ideal. For me - a brick garage.

Set resin is safe. Safe in a non active, plastic kind of way. You probably dont want to be eating it or using it with food or drink - but the photoreactive and polymers part have done their thing, and are no longer directly contact or fumes harmful.

After the print has been cured on a window ledge (slowly), or in a curing station (quickly) - you are probably going to want to protect it from further exposure. This can be done with either a UV blocking varnish, or an undercoat layer of polyeurathane. Continued exposure to UV will cause disolouration, and the print to become increasingly more brital.

Summary

  • Contact toxicity.
  • Toxic Fumes.
  • UV brittleness.

Starter Kit

Works Space

Printing is neither quiet, or odour free (even with Eco resins - they are just less toxic). In an ideal world a room that is ventilated and not occupied, or an outbuilding. Whatever the case, ideally with a stable temperature.

For me this is a brick built stand alone garage, and cheating on the heating with a heater modules inside the case (more on this later). It is a reasonably steady 10C out there in the winter due to my work lab, fridge, and freezer.

Nitrile Gloves

Box of - enough so I dont have to worry too much about running out.
While using resin is not like using Coppaslip (open can and now somehow everything is golden and shimmering) - its close. You smear it on things, and then you notice once its dried to a removeable crust. Workflow you fall into helps here - so you have things ready when you need them, as opposed to faffing with resin covered gloves.

Respirator

More of a concern for non eco resins which are VOC heavy.
I had a 3M half face respirator already - and simply added some rated filters for the job.

Here are the amazon descriptions for the items I am using:

  • 3M 7502 Soft Silicone Half Face Mask, Medium
  • 3M 6075 Formaldehyde A1 Organic Vapour Filter, Pair

Paper Towel

I started off using a tub of alcohol wipes. These work. But they are small, they are not adsobant, and they cost quite a bit for what they are, and a faff for getting out and then opening up.

I switched to kitchen towel. Its cheap, easily available, and if I run out I can steal the kitchen one ;D

It is more adsorbant, grippy (soaking up resin), and works a treat alongside a spray bottle of IPA (see below)

IPA

No, not India Pale Ale (brewed to survive the long journey to hot climates) - this is Isopropyl Alcohol. Also known as Isopropanol, Propan-2-ol, or Rubbing Alcohol.

This is a solvent that will dilute and remote resin.

You will find 99% pure available on Amazon et al in 5L and 1L containers.

If you have a wash tank you will need at least 4L and ideally one for a spray bottle.

After a print you will want to liberate your print from the build plate, and wash off the excess resin. You will then want to wipe down any surfaces that now have resin on them. This is the tool for the job.

The best part is it evaporates to leave things clean and dry.

Be mindful that this is again another fume heavy fluid.

Be also minded that the resin doesnt disapear in any wash tank - its in there, and will set once exposed to UV.

Spray Bottle

Something chemically resilient to IPA (no one likes sweating containers!). Replacing alcohol wipes, with the kitchen towel - you can now spray a larger area and wipe. Good times. Far less faff (for me). Here is an example:

  • Jantex CD816 Spray Bottles, 750 mL, Yellow

Peddle Bin and Storage Box

I have a child, dog, and a mind like a seive.Make things easier for everyone:

Keep the new clean and opened things in a storage box clearly marked with a lid that closes. Mop up any spillages properly and dispose of the materials used.

Keep the rubbish you generat in a bin with a lid that closes, that is clearly labelled. Ideally one that is touch free so we dont get resin transfer and contamination.


Completely Avoidable Problems

This should probably be at the top of the page in a READ THIS FIRST. But here we are.

Time after time after time I read "I have broken my printer".

It is quite easy to do - and its even easier on the Anycuboc Photon Mono X as there is no toughened glass layer ontop of the LCD screen.

In my case it was unclear as to whether this was a tiny hole in the FEP, or a smear from failure to clean away a drip that had hid itself underneath. Either way - it was an expensive learning experience.

Damaged FEP

The film starts out clear, and rapidly starts to collect scars from its day job or repeatingly letting go of your print, while submerged in a reactive fluid and exposed to high levels of UV. Yoda voice: "Old you would look too."

If you see signes of wear - specifically any pronounced dents or scratches - keep a very very close eye on them, and the screen that sits underneath them.

Sometimes you will notice them due to prints failing in a certain place, or just not being right.

Changing the FEP is a pain, as there are ALL of the bolts - and ideally you want to leave it in the sunshine to completely cure before you start on the dismantling.

The mechanism is like a drum - which is why it is so tight to the point of resonating with your voice. The film is bound between two layers of steel in a ring that sits in the vat. As you bolt it into the vat, the ring is drawn over a ridge and the tension is increased in all directions.

Its a faff - but if you have any doubts - get it done. Its a lot cheaper in the long run.

My boss advised me that two vat's was also the way to go - and yes - I can second this. It means that you can do this having allowed one to cure in sunlight, and then transfer the fluid from one to the other once you are done. Wise words.... although I didnt appreciate that at the time.

Damaged Screen

This basically falls into three catagories from my experience and observation:

Cured resin on the screen

Either through a hole, obvious or tiny in the FEP, or through a smear from a drip when replacing the vat - the reallity is that there is now resin on the screen. If the UV exposes this - it will cure, and this will then be very hard to get off. You may only notice it through the FEP with transparent resins, or when removing the tank. It will likely result in in a lack of detail, if not failing prints.

It MAY be possible to remove the resin using a 'plastic razor'. However the likely outcome of this is that it will remove the polorizing layer on the screen. Without the polorizing layer, the LCD will appear to always be clear, and UV for that area will always pass through it.

Attempt to remove resin from screen has gone wrong

So now you have a fixed one problem, and been presented with another. No loss really. So probably worth the attempt.

The screen on the Anycubic Photon Mono X - for a reason best known to the manufacturer does not have a glass layer on the top. There is the active LCD, and then a stuck on layer polorizing filter.

It is possible to peel this off WITH CARE, and replace it with a new one. It is important to ascertain the correct orientation, so the highest contrast between dark and light is obtained. YouTube is your friend.

Another handy hint - use a phone to view from above - staring into a high power UV source is not on my to-do list.

Screen has cracked or broken

Once upon a time someone I know was peeling off their polorizing filter having done the above - and they had got to the last few mm. They gave it a final tug, and the screen shattered. So close. There are times you will need a new screen and there is no other way around it.

Anycubic Photon Mono X makes use of parts from Chitu Systems. You can either order direct (I have no experience) or for the same price from Amazon. I went with the latter. Their lead times are huge - so expect 2 to 3 weeks and a shipment from abroad.

There appear to be two types of screen. Thankfully (for me) they are easily identified by the shape of the ribbon cables coming out from them. Look at yours, look at the one in the picture - choose wisely.

They are held in place by the black tape around the edge, and rest on a shelf. They are not bolted into place. The shiny metal plate at the front protects the ribbon cable, and is glued down with some double sided tape. So removing things is not too hard at all.

Chitu systems also provide a tempered glass screen specifically for this screen - you know - the one that you would have expected to be on there. You may as well get that while you are there ;)

There is a second scenario that I can envisage - and that is that you have failed to notice that something has fallen into the vat or is stuck to the FEP.

Given that there is NO subtelty in the mechanism for lowering the build plate (it lowers to a point dictated by a light beam being broken, fine adjustments are made through bolts adjusting the level, it is completely unaware of where the screen is - if it its passing through it) - I should imagine it is perfectly possible to plough down the build plate into the vat, attempting to level it all. A point of pressure punctures the FEP, shatters the screen, and you are the proud owner of resin inside the printer. Not that I overthink or anything - but this is clearly a possible outcome.

Screen Parts:

  • 8.9 Inches Monochrome LCD Screen for Anycubic Photon Mono X Replacement 4K Light Curing Print Screen with 3840x2400 Resolution (TM089CFSP01)
  • Tempered Glass Film for Anycubic Photon Mono X/Elegoo Saturn 8.9 inch LCD Screen, for PJ089Y2V5/TM089CFSP01 Protector

Prints Stuck to FET

I make use of transparent and clear resins. As a result its quite easy to see when something has failed and is enjoying its new life on the bottom of the vat.

First up - STEP AWAY FROM THE SPATULA

Trying to pick this off the bottom with a tool is likely to result in a damaged FEP and pain in your world.

Head over to soemthing like tinkercad, and create a rectangle 1mm tick the size of the build plate.

Remove the build plate (<-- super important).

Slice and print the tiny slab.

On completion, remove the vat from the printer, push up lightly underneath, and you will hear it pop away if not see it change colour. Now gently - starting with a corner - catch this with a blunt plasic spatula - not using an edge, but rather trying to catch its edge. Work along and remove this from the bottom of the tank. Place in a plastic bag and allow to cure before disposing of this.

Added bonus the botton of the FEP is now super clean. Its a drag but it could be much worse. These things happen.

Protect Your Screen

I have tried two things thus far after trashing my screen early on.

Tempered glass screen protector. Providing a hard surface that is easier to clean, and sits flush ontop of the polorizing film layer. This is working well, and has caused no issues up to this point.

It is fractionally smaller than screen, so can be applied after the screen has been stuck into place.

Parts List

  • Tempered Glass Film for Anycubic Photon Mono X/Elegoo Saturn 8.9 inch LCD Screen, for PJ089Y2V5/TM089CFSP01 Protector

I also, having been burnt, I improvised with a larger cut sheet of FEP that I secured in place with some Kapton tape. The intent was to ensure that should there be a catestrophic failure of the FEP, that there were no clear paths around the screen into the printer.

The reallity however was that maintaining a consistent tension across the screen was impossible. The Kapton tape didnt hold tension well enough.

Making use of the spare edge / retension strips that came with the screen had better results - but I still found it unreliable. This being said - it clearly works for some.

Parts List

  • ANYCUBIC 3D Printer 2pcs FEP Film for Photon Mono X Teflon Film Replacement sheet 8.9" 260 X 175 X 0.15mm for Photon Mono X UV LCD SLA Resin 3D Printer
  • Kapton Tape Temperature Heat Resistant Kapton Tape Polyimide Film Adhesive Tape 33M Length for 3D Printer High Masking, Soldering, Powder Coating

Another option I have seen is to use a non glass screen protector. I can see this having serious milieage - however have yet to look into the required size, or indeed viabillity.

No doubt I will at some point learn to regret this lack of curiosity!


Things I have learnt since

Workflow

Calibration

R_E_R_F - what on earth does that mean? I have no idea. But I do know what it does or helps with: CALIBRATION.

This particular file name as R_E_R_F.pwmxis treated by the printer in a very special way. It allows you to print a single build plate with several exposure times being used.

The outcome is you get to see - in one print - how time impacts your print.

There are two things to keep in mind with the example below - one is that for me the first one always ends up stuck to the FEP, and then its the whole print a slab dance again unfortunately. The other is that this has no control over how high you have the UV intensity set. For some reason there is a setting on the photon mono x that allows this to be increased and decreased {shrugs}. I set mine to 80 and work from there.

The pwmx file, on its own, on the USB stick - and off you go.

Documentation

  • https://ameralabs.com/blog/town-calibration-part/

Print List

  • https://www.thingiverse.com/thing:4929779

Eco and Plant Based Resin

Dealing with IPA

Heating under the hood

Parts List

  • SHNITPWR 12V 10A 120W DC Power Supply Adapter 100V~240V AC to DC Converter 12 Volt 10 Amp Transformer 5.5x2.5mm for 5050 3528 LED Strip Light 3D Printer
  • 100W 12V Energy Saving PTC Car Fan Air Heater Constant Temperature Heating Element Heaters
  • DC 12V All-Purpose Digital Temperature Controller Thermostat with Sensor

Magnetic Build Plate

Magnetic Build Plate Issues

NFEP

Part Name

  • Chitu Systems NFEP Film 260x185mm Thickness 0.15mm for Anycubic Photon Mono X/Elegoo Saturn and othter 8.9 inch UV Resin 3D Printers,Better Durability

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