Hi,
I figured out that my UV-resin printers can also expose fotosensitive PCBs.
I always like to try new things with my equipment, but I’d be limited to two 35um layers and there are no vias unless I drill them with my CNC mill.
Is it worth the effort?
There are cheap online alternatives, but I’d have to wait for every new batch.
Probably not worth it. The problem is filling the vias with conductive material.
With the current cost of 4 layer PCBs done professionally this is an educational exercise and worth trying but won’t save you money.
My opinion might be wrong depending on your end objective of course.
Cheers,
Valentine
The PCB services are astoundingly good value for the money. As a teenager I experimented with making my own pcbs and if you keep it simple and need something fast it is useful. I used toner transfer and you can actually get pretty good single sided boards like that pretty quick and easy. But I don’t think I would want to mess with your approach.
Only if you want to develop a simple single sided board last minute or really on super tight budget then its worth it. Else the PCB services are so extremely affordable nowadays (even ones not located in Asia). Its just not worth the hassle unless for your own entertianment and proof of concept. 
Thanks to all,
I think it’s outdated technology. And it’s quite messy with all the chemicals it needs.
It also wouldn’t make sense to put the required stuff on the shelf and wait for the once_in_lifetime_ situation, where it would be the only solution.
Because until then, the PCBs are aged and the UV-laquer wont work anymore.