SLA (Stereolithography ) is often compared to the FFF (Fused Filament Fabrication) / FDM (Fused Deposition Modelling) process of 3D printing and always shows very impressive results. The detail level is far superior for SLA but there are a lot of complications to the process. Due to the huge numbers of dentists, dental labs and orthodontists contacting us recently I thought I would share some of what I have learned.
The most common comparison is the strength of the parts created from resin vs those created with fused filament which always comes out on top. Next are the many resin handling issues which make filament printers much easier and safer to use.
It is easy to discount FFF/FDM completely by just looking at pictures of the excellent smoothness of an SLA print vs an FDM print. The SLA process can create a smoother and more detailed surface finish and and can create a fully solid, partially transparent part which is difficult to achieve on FFF /FDM machines without post processing. This makes it harder for those of us demonstrating fused filament fabrication printers to keep a viewers attention.
To someone viewing the printed results of 2 models side by side it would be hard to choose the FFF / FDM print if visual quality or surface detail was the goal. In a comparison of useability which requires strength, the FFF /FDM print is far more likely to come out on top particularly due to the huge selection of material types available. The SLA materials tend to be closely linked to specific printers, it is unlikely a 3rd party resin will be allowed or compatible. This limits the SLA user to the resins developed by that manufacturer. In a comparison of workflow the SLA process is quite scary, warning labels and notes on resin handling and cleanup dominate but the consumption of core components of the SLA printer along with litres at a time of IPA (Isopropyl alcohol) and the expensive resin is certainly worth exploring before any decision is made to exclude filament printing. The accuracy of the two methods should theoretically be the same but I have yet to see an SLA print which has been perfectly dimensionally accurate while my Robox is within 0.01mm in all axes without my input all day every day. Cost comparisons are far further apart than the price of the printers would suggest. SLA resin cost is high, plastic filament cost is low. This expensive resin is wasted with every print, plastic filament is only extruded as required. This cost in particular is not shown in “part cost comparisons”, nor is the very wasteful rinsing in IPA to remove excess resin following a print or the cost of the consumable resin carrying and curing parts, or the disposal and storage as well as low shelf life for expensive SLA resins. Oh and the space required for SLA printing is rarely mentioned, you really need a spare room and some strict policies to control the spread of sticky resin the smell and the harm to the environment.
In the chart below I’ve listed some positives and negatives of each method along with typical usage and costs. Blue indicates the best in my opinion for each row. I obviously support filament printers in this, perhaps your comments can sway my opinion?
My conclusion is this:
SLA is not a threat to FFF / FDM printing, if anything the 2 methods can work side by side as their benefits do not overlap. Personally I would not let the resin (or the smell of it) near my home or my family but if I had a dedicated space within a business and the training and staff to run this then I would consider SLA as an addition to several far lower priced FFF /FDM printers. I could print many iterations of a design on the filament printers and perhaps a surface model on the SLA machine once the design was final, actually it might be best to just outsource that part…