UV resin printers used to be the high end of 3d printing they had very high resolution could make prints with a variety of properties based on the resins used and could be comparable in speed to their filament/FDM counter parts. They were also expensive and messy and complicated to use. Even some of the more consumer focussed machines like the form labs form 1 were several thousand dollars to buy and the resin for the machines was much more expensive than plastic filament used in the FDM machines.
Well they are still messy but their price has come right down in recent years. Partly this is again thanks to phones where older machines used expensive and complex laser based SLA (Stereolithography Apparatus) printing or DLP projector based now they use LCD's with a bank of UV led's blasting through. This means where as a few years ago the cheapest resin printer would set you back thousands now you can get one for 200 bucks.
Enter the Phrozen Sonic Mini 3d printer which I got for just over 200 bucks with shipping it's a neat little unit fully assembled ready to go out the box pretty much. It includes a bunch of tools and things to get started but unfortunately not any resin so that's extra. Luckilly resin for the printers has also gotten cheaper and easier to get so I grabbed some transparent blue abs like resin for 20 bucks and I was back on track.
Now resin for these machines is nasty stuff, in it's uncured liquid state you don't want to get it in contact with your skin or breathe it in it's toxic and pretty unpleasant stuff. You need a well ventilated area to work in to preferably wear a suitable face mask and eye protection and then nitrile gloves.
I took things a step further as I have a full face mask with organic compound filters this is probably overkill but well I have the gear so might as well use it
JOIN ME AND TOGETHER WE WILL RULE THE GALAXY!
Mechanically these machines are incredibly simple unlike FDM 3d printers which need 3 axis and an extruder these things have basically 1 mechanical axis (Z axis) taken care of by a standard lead screw and then X and Y axis are handled by the LCD. The machine I got is a reassuringly chunky metal rail with a strong aluminum linear guide the lead screw runs along lifting the build plate. For such a cheap machine they've made sure the mechanical parts of it are sturdy.
Resin printers basically print upside down they have a build plate in this case a chunk of aluminum mounted on a z screw that at the start is lowered into a vat of photo polymer resin with a transparent film base on top of the lcd screen. The machine then projects the shapes it wants for each layer slice onto the screen waits a bit then moves the build plate up. The UV causes the resin to harden and gradually the model is built one layer at a time.
One of the advantages these machines have is that it takes the same time to expose the whole build plate as it does one small area as it exposes the whole x/y image in one go. So you can stuff the build plate full of things or print one thing and the time taken is the same.
This little machine has a cheaper 1080p LCD with an XY resolution of 62 Microns which is still pretty good so even on this cheap machine you can get some impressive levels of detail it's z resolution goes to 10 microns. The LCD is a monochrome one instead of the colour ones other printers of this type use this allows more UV light to get through and speeds up curing times so makes each layer take less time as little as 2 seconds for 50 micron layers less for thinner.
First thing you have to do is level and height adjust the build plate. If it's not close enough or on the skew-whiff then the resin wont stick to it and the print fails. The method for setting this is pretty easy the build plate attaches to the z axis with a simple locking screw. Then you just losen 4 screws on each side that lets the plate float. Remove the resin tank and put a piece of paper over the LCD it lowers the thing down you press it flat and tighten the screws such that the paper is held in place. Simple once it's set up it returns the build plate to the top and you can reinstall the resin tank.
Before doing this I put in some resin the manual specifies a third of the little plastic tank should be filled. With the resin in the tank I put it back into the machine and locked it in place then put the cheery red plastic cover back on over the top.
I carefully poured some resin into the vat then locked it back into the machine and put the red transparent plastic lid back in place then setup the timelapse and set it printing one of its test prints a set of rings listed as 30um resolution. It prints from a usb stick plugged into the side and is controlled by a nice touch screen on the front. You can see in the timelapse the plate bouncing up and down as it does each layer this is to break the tension on the bottom of the tank where the part may stick to the film and also allow more uncured resin to flow back in to where the part was after curing ready for the next layer.
Battery ran out half way through not a very good angle anyway
So that took about 3 hours to print but once you've printed them you're not done you need to process them. Step one remove them from the build plate and then wash the prints in isopropyl alcohol to disolve and removed the uncured resin. You also need to cleanup the machine empty the resin chamber back into the bottle (but through a filter to catch any cured resin gunk as this would get into future prints and screw them up.
Once they are cleaned up they are still soft the resin is cured but not hard the parts need to be exposed to UV light to fully harden. Now at this stage you can remove the support structures poles and pads that attached them to the build plate and let the shape print correctly. I didn't do this as I didn't realise this was when to do this step as its' easier to snip the supports off while the prints are still soft they tend to shatter when fully cured. Lessons learned :D
So you can just put the parts out in the sun to cure but what if you have no sun or it's night time you need a way to cure your parts snappy. So I build a curing station out of a tub a UV LED strip a small solar powered turn table and some foil.
The nice thing is the UV causes the turn table to turn on it's own so the parts get baked in the UV nicely from every angle. Some 15-20 minutes and the parts are now fully cured.
I tidied up the supports as I said I should have done this earlier but it was still easy enough with some flush cutters and a file to get the bits off and smoothed over. The rings where they had attached to the build plate at least one had gotten a bit of extra gunk in there and that fused with the support making a bit of a mess but the rest of it came out fine. All in all some very nice prints the physical properties are quite hard plastic with a sort of glass like brittleness to it but reasonably tough. The details on the rings seems nice and sharp some very slight banding on some of the areas but the rest is smooth and sharp detail none of the layer lines you get on even the best FDM 3d prints
Pretty good results for a 200 dollar machine I can see making small models or custom minis on this easilly. Though I'd hesitate to recomend going out and getting one they are fiddly and messy to use you have to be careful with the resins in their uncured state (cured they are fine safe to use and touch but uncured its nasty stuff and the alcohol you've used to clean it with is then contaminated you have to dispose of it carefully or pro tip just leave it out in the sun any uncured resin will cure and then you can just filter it out and it's safe to throw away)
there's a lot of messing about that you don't get with the FDM based machines but for specific applications it might be worth it.
Still I had fun with it so far and I can see myself using it for model making stuff or for specific printed parts I might want where I don't want to have to spend a lot of time sanding or smoothing out layer lines. For an enthusiast and making person it's cheap enough that adding it to your tool set is really a no brainer at this point. Like a lot of tools it requires some safety steps but so long as you are prepared and aware it's not too bad.