Resin Printing on the cheap

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

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.


200 quid is a great price for that level of detail and I love the resin printers for being able to more easily make stuff that is a weird shape. The extra faff would put me off as I am time and space poor. I enjoyed reading this through and the videos with the little bouncing Z axis was cool.

brainwipe's picture

I think for almost all people resin printers are not what they should get. These days you can get some amazingly good FDM/filament printers out of china for very low prices from people like Creality or if you spend just a bit more you can get things like the wonderful prusa I3mk3 made in prague which can do down to 50um accuracy should you so desire and with much larger build volumes none of the faff.

There are very few applications where resin printers trump an fdm machine and most of the time you can work round the limitations to get something good enough. If you want really fine detail and you don't want to have to sand and maybe resurface the model with a smoothing product then resin is the best option. I suppose also since its using UV and not a hot end there's no chance of it bursting into flame if left running overnight or something but a lot of modern printers have safety features to mitigate that risk.

I know with machines like this and things like the elagoo mars with their low price point a lot of people are buying resin printers and not realising the associated work required to print and process parts 99% should get an FDM machine instead. Resin is messy nasty stuff and requires some respect and prep to deal with and for most people it's just not worth the extra hassle they're never going to use the machine in a way that justifies all that extra effort and risk. For enthusiasts or makers though it's a great thing to be able to get access to this sort of technology at very inexpensive prices.

Evilmatt's picture

One thing I've come across is there are some newer resins out there which are water washable resins which while still toxic etc will dissolve in water when uncured this means you don't need to use alcohol to clean up you can just run everything under the sink in a suitable tub then leave the tub out in the sun to safely neutralize any resin and filter that out and you can dump the water. Still need to be careful of contact with uncured resin but it simplifies cleanup. I'll probably get some of this stuff to try out it's slightly more expensive but the added convenience plus not needing to buy a load of alcohol makes it worth it I think.

Evilmatt's picture

When I finally have the space, I'm definitely up for a Creality FDM printer. Drone bits, loved toy repairs and mods for Felix's Nerf guns would all be cool to do on it. Not to mention printing out some 3D models for fun with the kids.

brainwipe's picture

Picked up some water washable resin and a cheap ultrasonic cleaner makes getting the uncured resin off a lot easier. Also tried the remove supports before curing trick works to some degree parts are still soft and very fragile so on delicate parts I had some breaks.

The printer uses a slicer called chitubox which is pretty user-friendly just sellect the profile for the phrozen Sonic mini then give it some models I used automatic supports.

Used the new resin and tried slicing some models I got off of thingiverse. One r2d2 a 20*20*20 cube and a cylinder. The cylinder and the cube detached from the build plate before they were finished so I stopped it then.

The leg on the r2d2 broke off while I was removing the supports pre cure and then when I tried to glue it back in the glue got everywhere.

I measured the 20*20*!20 cube x and y pretty close in the 19.7 range.

I also tried sanding the cylinder which took a pretty good shine. Prints were oy 0.5 mm accuracy took an hour or so to run.

I then ran some more modeles the same r2d2 as week as another r driod k2s0 t34. The k2s0 had most of missing the spindly limbs on that model didn't survive support removal and one seemed to have failed when printing. The r2d2 came out best no need to repair it. The t34s legs snapped off and then didn't glue back properly the other r Droid came out fairly good with a leg repair.

I used a slightly higher resolution at 0.3mm and the detail was pretty good I might try one of these again at the highest resolution.

The water washable resin does make things a little easier so I think it's worth the slight price increase.

Evilmatt's picture

The resin is pretty brittle similar to pla I took the r2d2 and the other r6 droid into work to sit on my desk to fiddle with and dropped the r6 and it's leg snapped off. These are small prints and the legs are quite spindly but the properties of this resin lead to a hard fairly stiff but brittle material when cured.

Other resins can have different properties but the default seems to be like this

Evilmatt's picture

Here's a better look at the detail off center rubik's cube for scale :D In case you don't have one of those to hand it's about 1.5 cm tall

Evilmatt's picture


The detail is really spectacular.

brainwipe's picture