Resin 3D printer

🛸 Location: Chemistry lab

Another 3D printer. It uses liquid resin which gets solidified using UV light rather than solid plastic which gets melted into a new shape. It's slower (each print takes a day or 2), dirtier, and requires more effort, but it promises more detailed objects and even translucent objects, compared to the filament printer.

The printer itself: Anycubic Photon Mono SE
A curing cookie box with UV light inside
A nail curing device with a power supply
A roll of toilet paper
A small jar with isopropyl alcohol to wash prints
A box with:
- bottles of resin (grey, transparent)
- film replacements
- resin filters
- vials with extra resin
- rubber gloves
- face masks
A tray with:
- a knife to pry prints off the build plate
- a silicon spatula to stir resin in the vat
- a syringe to measure resin
- a brush to spread resin to make prints shiny
- a metal sponge
The experiment log and a pen

This is experimental

This printer is currently in the experimental state. Please don't use it without first talking to someone who has some experience.

How to not mess up

Read this before starting.

Our health and environment

Using the printer involves dangerous chemicals and processes:

the resin is a skin irritant - wear gloves and glasses. Always wash your hands after handling objects in the printer station.
the resin stinks and can't be healthy - make sure there's enough ventillation (there's a pipe in the wash room)
isopropyl alcohol for cleaning is an irritant and stinky
the printer emits near-UV light, which leaks outside and damages living organisms - rather be outside the room when it's working
drop used toilet paper in the chemical waste bucket on the floor

The materials and equipment

Resin is sensitive to sunlight (405nm wavelength) and hardens after a day or so even in the relative dark.

Wipe resin from surfaces using toilet paper when you leave the station.
Use brown containers to store extra resin
After using a brush or syringe or some other tool with resin, wash it well with isopropyl alcohol.
Cover containers with resin with thick bags after placing in the box

If you want to put resin back in the bottle from the vat, filter it with a proper filter to avoid hard pieces getting in.

Hard flakes from failed prints damage the foil which will need replacing earlier.

Mechanics of usage

Read this before designing any object for printing. Maybe you realize you don't actually want to bother.

You'll need:

toilet paper
toothbrush
isopropyl alcohol

First-time preparation

Unscrew the vat, carefully slide it out (don't scratch the display underneath)
Clean out the remaining resin with a silicon spatula, and by rubbing a piece of cloth soaked in isopropyl alchol (unless you want to re-use the resin).
Use the screen interface to lift the arm up a lot.
Unscrew the hex bolt on the side of the lifting arm. It should be possible to wobble it without a lot of force.
Use the interface to level the arm: press the "home" icon.
Once the arm is flat on the display, adjust the rotation and repeat leveling if needed
Hold the arm to the display and tighten the screw.
Save the setting in the software.
Fill in the vat with resin. Make sure the entire bottom is covered, and that there is enough extra resin for the object.

Every-time preparation

Start a new entry in the log
Take out the vat.
Wipe any spilled resin off the UV screen.
Scratch off hardened resin from UV screen with a fingernail.
Slush the resin in the vat, look against a light for unevenness floating on the surface. Hard pieces have the same color as the fluid so they are invisible.
Fish them all out with a toothbrush.
Slide in the vat, screw it in.
Close the lid.
Power off the printer.
Insert USB stick with the prepared file
Power on the device
Select the file in the interface
Start printing

Printing

Leave the room, leave ventillation on, and come back in a couple hours.

Finishing

The object will be stuck to the top plate and everything will be sticky with resin.

Unscrew the big screw on top of the lifting arm
Slide out the build plate from the arm
Use the knife to gently pry your object off the build plate, and put the object on toilet paper
Wipe the remaining resin from the build plate.
Replace the build plate and screw it back on.

Finishing the object

Excess resin

If your object has fine details, you want to get rid of excess resin, because it will harden with exposure to natural UV light and take details away.

Toilet paper

soak with isopropyl alcohol, wipe. It might be enough.

Toothbrush

soak with isopropyl alcohol, brush. It might be enough.

Isoprop bath

Put object in the jar with isopropyl alcohol, shake for a minute.

Curing

Curing in the sun works well. The print will start curing after seconds in full sun.
There's an experimental curing box with UV light inside. It seems to need several hours to cure unwashed resin. Please write your experiences using it in the paper log.
There's an experimental nail curing machine. It has no box and switches off after 60s.

Sources say exposure to oxygen prevents curing.

Shiny and translucent objects

Objects come out matte after cleaning. Shiny/translucent surfaces take a lot more care.

Remove flakes from the surface. Use cotton swabs if needed to reach difficult spots. Form them into a spike with your fingers if you need to access corners.
Dip brush in resin, cover the surface with a layer as thin as you can.
Cure fast! The resin will not stay in place for long.

More ideas for translucent

Internet suggests solutions like varnish, spray, or dipping in resin.

Nail polish varnish scratches off easily, smells, and feels slightly rubbery

Software

Designing models: various software, e.g. OpenSCAD.

Slicer: PrusaSlicer takes in STL files. Make sure to set all the parameters correctly (wiki doesn't accept config files, you have to ask the person).

Delivery: USB stick. Place the resulting .pwms file in the root directory of the USB stick.

The USB stick must be MBR (ms-dos), Fat32 formatted (primary partition).

The experiment and material log

The printer requires a surprising amount of experience to operate well. It also needs maintenance in case of problems. The log helps us kep track of things when they go wrong.

Suggested format:

Type (print, clean, etc)
Name of the object
Material used
Exposure time, or any other parameter that changed
Print outcome
Curing procedure
Curing outcome
Anomalies

For example:

PRINT: 3 big pyramids
Resin: translucent raspberry (1/128 Rose Red pigment)
Exposure time: 2s

One pyramid missing a support.

Resin leaked on the screen through foil

Flakes of resin over the models

Cleaning: isoprop bath, flakes still on. Removed with a swab. Applied resin wth brush.
Pyramid without support (A) curing under the nail polish lamp.
Pyramids with supports (B, C) curing outside in the sun.
Pyramid A 3x60s. Still did not cure fully.
Pyramids B, C have pollen got all over them.

Random tips

Large objects can be hollowed out by the slicer.

You can print directly on the base if you select "Pad: around object". The first layers will have excess resin form into a hardened rim.

You can save resin on big objects by creating a hollowed-out profile. Wall thickness of 1mm should be enough for more uses.

This is a monochromatic model, meaning it's fast. 1.5s is enough exposure time for 0.05mm layer height. When it's cold, use 2s.

Nail polish varnish scratches off easily, smells, and feels slightly rubbery

Problems

The object is stuck to the plate so hard it breaks while scraping

Reduce exposure time for the first layer from 40s to 20s.

No object, only supports on the plate

Slow down retraction, also add more supports and position the object better. More info.

Rationale: the plate pulls the object up and away from the membrane. That's a strong pull (makes noise) and weak or off-center supports may not survive it (pay attention to rotating forces?).

Increase the exposure time.

Rationale: the supports are just too weak.

Gaps in object

Increase wait time after dropping and before light on (tested and works).

Rationale: the build plate needs to settle at the minimal penetration height. This takes time because resin is very viscous.

A few supports broken

The side attached to the plate is too flat

Use supports and cut them off later. The first layers will be overexposed in order to stick to the plate, and have relatively bad quality.

Increase wait time after dropping and before light on.

Rationale: the rim forms from resin slowly being pressed out under extreme forces acting on the first layer.