TEAM Lab Equipment: SLA 3D Printing
Basic Overview of SLA Printing
SLA 3D Printing is a technique whereby an object is etched into UV-curing liquid resin via laser, in a series of layers. This printing technology is good where strength and good accuracy are both important characteristics, or where geometry may be too complex to achieve via FDM printing. In general, this printing technology may not be appropriate where wall thicknesses exceed ~10mm, or with large-scale parts.
Our Machine: Formlabs Form 2 with automated Form Wash and Form Cure stations.
Materials: Type: Methacylate Photopolymer Resin Properties: (Similar to ABS) Higher yield point than Polyjet Prints.*Contact for Mechanical Properties
Accuracy: Good accuracy: 0.025mm to .1mm Layer Thickness. 0.1-0.3mm Overall Accuracy depending on geometry. Minimum Feature 0.3mm.Support Structures: Posts which must be cut from body of printed part
Maximum Build Dimensions: 4.9×4.9×6.5 inches (125x125x165 mm)
Build Time: Total: 4 hours to 24+ Hours (dependent on geometry & size)
*Turnaround time is workload dependent. Expedited parts may come with an additional fee.
Cost: UC: Photo-Curing Resin: $4/10 Grams + $3/hr of build time + Setup and CleaningOutside UC: 32% Premium (above cost)
Pros: Very rigid plastic with good impact resistance, great accuracy.
Cons: Support Posts may leave blemishes, small build chamber
Formlabs SLA materials from 3Dhubs.com
In Depth Overview of SLA Printing:
SLA 3D Printing is a technique whereby an object is etched into UV-curing liquid resin via laser, in a
series of layers. This printing technology is good where strength and good accuracy are both important
characteristics, or where geometry may be too complex to achieve via FDM printing. In general, this
printing technology may not be appropriate where wall thicknesses exceed ~10mm, or with large-scale
parts.
Vs. FDM
In comparison to FDM printing, SLA prints will typically yield at lower forces, but can be significantly
more complex in shape.
Vs. Reinforced FDM
In comparison to reinforced FDM printing, SLA prints will typically yield at much lower forces, but can be
generally more complex in shape.
Vs. Polyjet
In comparison to Polyjet printing, SLA prints are much stronger, but slightly less accurate. SLA prints can
also be significantly less expensive, in cases larger objects.
The system the TEAM lab uses is known as an Inverted SLA – As the name suggests, the build process is inverted such that the part is drawn from a vat of liquid resin.
Figure 1: Inverted SLA (via Formlabs)
Materials:
One advantage SLA printing has over our other systems, is the wide array of readily available printing
materials; the following are materials that we generally have on-hand, ready for printing:
“Standard” Resin: In terms of strength and accuracy, this material represents a good midpoint between
FDM PLA, and Polyjet Vero-Class Materials. Available in clear, white, and black.
Figure 2: Standard SLA Print Resin in Various Colors (via Formlabs)
“Tough” Resin: Generally, our preferred SLA printing material. Good for snap-fit features, assemblies,
and general “medium duty” use. One potential drawback to this material would be that when thin, it
may become less rigid than the standard resin. In terms of strength, it is closer to that of FDM prints
(stronger) than polyjet prints (comparatively fragile)
Figure 3: A 3D Printed Clip in SLA "Tough" Resin (via Formlabs)
“High Temperature” Resin: Resin with a Heat-deflection temperature of 289 degrees C, @0.45MPa. This
material is good for static applications that will undergo elevated temperatures, and can be utilized in
production processes like casing, injection molding, and thermoforming.
Figure 4: High Temperature Resin Print, Embedded in Machined Aluminum Cavity. Used for Injection Molding (via Formlabs)
“Durable” Resin: An SLA polymer designed to simulate Polypropylene plastic; Elevated impact strength,
wear resistant, and ductile material. Best used in cases where parts may require deformation with low
wear (snap-fits, ball joints)
Figure 5: An Assortment of "Durable" Resin Prints (via Formlabs)
“Dental SG” Resin: Autoclavable, Class 2 biocompatible resin. Designed for printing surgical guides and
similar devices.
Figure 6: A Dental Surgical Guide
“Dental LT” Resin: Clear class IIa biocompatible resin. High fracture and wear resistance that ideal for
direct-printed orthodontic devices.
Figure 7: Dental Splint printed in "Dental LT" resin (via Formlabs)
Techniques:
Designing for SLA Printing:
Part Thickness
In practice, SLA prints are best kept small-scale, with a maximum wall thickness of 5-10mm; due to the
mechanics of our system, thick parts (greater than 10mm thickness) tend to result in a poor exterior
surface finish (rashing/ragging), and dimensional inconsistencies.
Support Structure
Parts out of this printer will come with [automatically generated] support pillars attached (in most
cases), as seen in the example below. The connection points between the support structures and your
part will be small enough to sever by hand, or with a small pick/blade/set of plyers. If a perfectly
smooth finish is required, plan to perform some light sanding at these locations. Note that up-faces will
be absent these defects, as no support structures will touch these areas. If your part is hollow, there is a
chance that support structures may become trapped inside, but this can occasionally be overcome with
clever design or orientation. Occasionally, a part may need to be split, and print in two or more pieces.
Figure 8: An Example Part, and it's Required Support Structure (via Formlabs)
Preparing Files for SLA Printing:
The team lab requires two sets of files for each 3D printed part – the original parametric model file
(Solidworks/Inventor/Fusion360/etc), and a millimeter scale STL file (point-mesh file)
Safety:
In cases where biocompatibility is an important characteristic, always ensure prints have undergone
proper cleaning/decontamination protocol before use. Consult the supplier’s documentation on the
topic to ensure compliance.
Technical Specifications:
Maximum Volume – 145x145x175mm
Layer Resolution – 25, 50, or 100 microns (some materials may be more limited)
Tolerance (closeness to intended value) - ~100 microns
Laser Spot Size: 0.140mm
Materials: Photopolymers, Proprietary.
Sources and Resources:
Ultimate Guide to Stereolithography: https://formlabs.com/blog/ultimate-guide-to-stereolithography-sla-3d-printing/