Hi, I’ve recently purchased a Nobel 1.0 SLA printer which is my first SLA printer that I’ve owned. After looking through pictures for slicing SLA prints, I’ve noticed that a lot of parts are printed on top of a load of support material whereas the same parts could easily be printed without any support on FDM. Is this something that I just need to get used to doing and if so, does this mean my customers should be expecting to pay a lot more for support material through 3D hubs compared to FDM?
You will have to forget a lot of what you know when moving to SLA from FDM. With FDM, a flat surface parallel to the build plate is ideal for obvious reasons but that isn’t the case for most SLA machines. When you cure each layer, it gets stuck to the bottom of the vat. Most machines, including the nobel, use a method of lifting with a tilt to peel the print off the VAT after each layer cures. If you have a large flat surface anywhere in the print, the bond to the vat can easily overcome the strength of the part and break or detach from the plate, leaving part or all of the print still stuck to the vat. That’s why you see SLA parts printed with a slanted orientation on “pin cushion” type of support. Also, the material sticks to the build plate in a way that usually makes it very difficult to remove in one piece without breaking. It’s easier if the part is suspended on supports. Then you just cut the supports to remove the part and can scrape off what’s still stuck to the plate.
Meshmixer has a feature that will orient your part with the smallest layer surface area as well as fantastic support generation which is easily customized. Many machines come with software that do this as well but I built my own machine so I don’t have any experience with them. I believe meshmixer is probably best for this step anyway, even if you are using proprietary slicer.
I would incorporate the work involved in this step into the “startup cost” for an SLA print as well as incorporating the support structure into the “build volume”
-Jesse
Just following up what @MindFuLL already said - another important reason SLA parts are printed at an angle is to allow resin to drain from a hollow part. If a part is printed hollow (common because it saves resin and solid parts are not necessary for models) and liquid resin is allowed to pool into it, you can end up with cupping, or even parts exploding, when the liquid resin is trapped inside the part. Printing at an angle with clever orientation allows you to drain out excess resin without multiple drain holes ( I can usually get away with one small drain hole per part).
I do occasionally print flat to the build plate (I have a Form 2, which is very forgiving of this) if the part cross sections are very small. For example, the planetary gear on my Hub page was printed flat to the build-plate with no issue and so was a Voronoi style Squirtle 22 but these are not the norm. Printing flat to the build-plate is also more abusive to resin vats; printing at an angle reduces the amount of time the laser shines through a particular section of the vat so the vats last longer. Once you get to know your machine, you may be able to print some models flat to the plate.
Are you using the SLA/DLP preset? If not this is a good place to start. Slightly increasing the tip diameter can definitely help but would obviously result in larger support marks. Slightly tweaking the orientation or angle of the supports can make a difference as well. You want to be mindful of the side being “peeled” first. This is where there is the most danger of separation.
