Stereolithography (SLA)

Stereolithography, also known as vat photopolymerization or resin 3D printing, is an additive manufacturing (AM) process where a light source cures liquid resin into hardened plastic.

Materials Used

Formlabs printers can run a large range of materials. Currently, SHU Digital Workshops run:

• For standard, hard plastic parts: Clear & Grey

• For flexible parts: Flexible 80A

• For wax parts used for casting: Castable Wax

• For injection moulds: Rigid 10k

Sample parts are on show in HPO workshop if you’d like to see how your parts will come out, or discuss suitable material options. 

Note: Due to the printing method, SLA parts can be quite brittle, so please handle with care and bear this in mind for your project requirements.

What can I print on it?

This technology is well suited to complex parts or parts with delicate features. Large, bulky parts with flat surfaces don't typically print well, but if you want parts to be watertight, SLA is for you. 

One of the main design considerations is that we have to be able to remove any uncured resin after printing, so if you have a hollow structure inside your part without any access holes, it will be full of resin, which will cure solid in the post curing step.

This is a great design guide made by the machine manufacturers, which gives advice on wall thicknesses and tolerances.

If you’re unsure if the part you’re designing will print, or if you want some general guidance before finishing your design, come and have a chat with one of the Digital Workshop Technicians and we can give you some advice.

Printing Workflow - How to print on the Formlabs Form 3, 3L and 4

1. Design your part: Use any CAD software to design your model, and export it in a 3D printable file format (STL, OBJ or 3MF).

2. Set up the file for printing: Bring your file to one of the Digital Workshops technicians, and we will set up your file on the machine software ready for printing, including deciding where to add support material for easy removal after printing.

3. Prepare the printer: The technicians will then get the printer ready by loading resin and performing machine checks.

4. Print: Sit back and relax as the machine does it's magic. 

5. Wash: The parts will have excess resin on the surface once printed, from dipping in and out of the resin tray. Washing in isopropanol alcohol (IPA) removes the excess resin from the surfaces.

6. Dry: Using compressed air, the technicians will dry your parts as much as possible. Any excess IPA left on the surface will contain trace amounts of resin, so moving on to the cure step before parts are fully dry will result in a tacky surface finish. 

7. Cure: Once washed and dried, the parts can then be placed in the Form Cure, which uses heat and UV to give the materials their desired properties. Note: the Castable Wax resin does not need to be cured.

8. Support Removal and Finishing: When you collect your parts they will have support material still attached. Use snips, a small blade or even sometimes just your hands to remove the supports and then sand back any support marks to give a good finish. 

9. Optional - Spray painting: Students can then take their parts to spray paint in Sheaf workshop.

How much will it cost? 

The cost of printing your part(s) will depend entirely on the size of the part and how much support it requires, as well as which resin you decide to use. 

All resins are charged at a price per millilitre, and you'll be given a quote before your parts start printing, so you can decide how to proceed.