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Resin Printing process
Resin printing builds up components one layer at the time just like FDM, but the printing process is very different.
Resin printing is known as SLA (Stereolithography) or MSLA (Masked Stereolithography). These two names refer to two slightly different processes, but can be viewed as the same for the purposes of this brief guide.
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Resin printers use special liquid resin that solidifies when exposed to UV light. By controlling where and when the resin gets exposed to UV light it is possible to print plastic parts. Same as any other 3D printing technology, the parts are printed layer by layer.
Practical difference between SLA and FDM is that SLA almost always requires the use of printed support structures. These serve the function of holding the parts in place during printing.
In addition to printing process itself, all parts require post processing to remove excess material and supports, and to cure the parts.
Although resin printing is more involved process than FDM, it can produce incredibly detailed parts. It is perfect for things like verifying designs for injection moulding, printing miniatures or prototypes that need to mimic injection moulded parts.
Material choice for resin printing is somewhat limited as it needs to be in a form of UV sensitive resin.
Pros
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Produces very high detail
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No layer lines
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Great for prototyping for injection moulded designs
Cons
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All parts require post processing
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Not well suited for production
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Supports are generally required which results in some surface damage
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Resins and solvents used require special handling
Available materials:
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Siraya Tech - Blu
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Siraya Tech - Build
Resin Print Size
Maximum build size is 192X120X245mm​
How to design parts for Resin printing?
Like any other manufacturing technique, resin printing has it's own best practices and things to be aware of.
Below we have highlighted some key design considerations for resin printing.
This is not a exhaustive guide and only serves to familiarise you with the process.
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Print orientation
With resin printing, models are generally not directly printed on the build plate like they would be when using FDM process. Supports are used to offset the model from the build plate. These supports for resin printing are easy to remove, but always leave a contact mark on the part.
This provides overall more flexibility for design of the parts. For best results the print orientation should be considered during part design as it can significantly impact the final result.
Example of how part would be orientated for FDM printing.
Example of how part would be orientated for resin printing (including supports).
Overhangs
As layers get produced by the printer, the top layer has to be connected to the layer below it. It is not possible to print in the air without having support from the previous layers.
If the part has an overhang that is greater than about 45 degrees in relation to the build surface, then supports are needed. Ideally the the design should not have steep overhangs, but that is often not possible. If the overhang is too steep, then a supports will be used to allow printing. This however has the downside of surface damage where the supports are connecting to the part.
Tolerancing
General tolerance for resin printed parts is around +-0.3mm and is a good rule of thumb to follow.​
Resin prints can be significantly more accurate than this, but print orientation and part geometry significantly affect this.
Although resin printers can produce incredibly small details this does not directly translate to the part being dimensionally as accurate as the detail might suggest.
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For connected parts/features that need to sit inside each other we recommend minimum of 0.5mm clearance.
If you are looking to produce a batch of parts we always recommend getting a sample printed for fit trial.
Thin walls and Feature sizes
Resin prints can be incredibly detailed with feature sizes smaller than 1mm still being visible.
However, small features like thin walls or thin extrusions that stick out can be subject to distortions and damage during printing and post processing.
If dimensional accuracy is a priority then its best to avoid thin walls (less than 1mm thick) and generally small features.
However, if dimensional accuracy is not a priority then features smaller than 1mm can be printed. For small features limiting factor is quiet often their strength.
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