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3D SLA Process Accuracy Aspects

A comprehensive insight into Stereolithography (SLA) 3D printing services

Part of a Vat Photopolymerization family Stereolithography (SLA) is a 3D printing process that involves layer by layer curing of resin using UV beam. 3D SLA printing service is one of the most prominent service that is used to produce 3D plastic parts. The final products are intricately designed, highly accurate, and have a smooth surface finish and are used as prototyping parts or as small functional metal parts. Regarded as one of the first 3D printing technologies, the process was patented in 1986 by its founder Chuck Hill.

SLA is the most cost-effective 3D printing service in use today and is quite popular for its high resolution and highly accurate design & finishes. The materials used in the printing technology are photosensitive thermoset polymers in liquid form. Compared with the DLP (Direct Light Processing) technology, the SLA is considered an effective and affordable printing technology amongst Vat Photopolymerization technologies. Here is a brief insight into the technology, process, materials used, and the benefits of an SLA process explained by the best plastic moulding manufacturer in India.

What is Stereolithography (SLA)?

  1. Stereolithography (SLA) makes use of UV laser to cure photopolymer resins layer by layer. The process of solidifying the liquid resins is known as Photopolymerization. The process involves four primary parts as follows.
  2. The bottom-most part of a SLA machine contains a tank filled up with liquid resin or liquid photopolymer (clear plastic liquid).
  3. A perforated platform that can be moved up and down and immersed in to the tank, which is guided by the printer
  4. High-powered UV laser beam does the curing of liquid resins
  5. Computer interface that controls the movement of platforms and the flashing of UV laser beams.
    Here is a brief overview of the printing process or the workflow of Stereolithography 3D printing.


Also Read: 3D Printing - Complete Guide

Stereolithography (SLA) process to cure photopolymer resin at the 3D printing company in India

SLA workflow

Stage 1
The build platform is positioned at the height of one layer inside the tank of liquid polymer.

Stage 2
The computer-controlled UV laser beams create layers over the platform by curing and solidifying the liquid resins. Beams are focused on pre-set paths with the help of galvos, a set of mirrors arranged. The laser beams scan the whole cross-sectional area to ensure that the required areas are solidified.

Stage 3
As soon as a layer is cured and solidified, the platform moves back to its original position, and the sweeper blade coats the surface again. The process is repeated until the final product is formed.

Stage 4
Sometimes the product may need high thermal and mechanical exposure to get it cured properly. This is done by post-processing the printed product under UV light.

Photopolymerization explained:

The process that involves the solidification of liquid resin is known as Photopolymerization. In this process, the UV rays solidify the monomer carbon chain that composes the liquid resin. The monomer carbon chains under UV rays' impact become unbreakable bonds, making it impossible to reverse the whole process. Since the products are made from thermoset polymers, SLA 3D printing service is irreversible and does not melt when burnt.

Other features of SLA 3D printing services

Few aspects like support structure, layer adhesion, and curling play a vital role in successfully printing the final product. Here is a brief go through of each aspect.

Support structure: SLA 3D printing service require support structures. These are normally printed along with the final product and have to be removed manually after the printing. Both top-down and bottom-up printers use support structures differently.

Curling: Curling is the shrinkage happening between the layers formed and can hamper the final printed product's accuracy. This happens during the curing process when liquid resins shrink considerably under UV rays and cause large internal stresses, which results in the curling of the structure.

Layer adhesion: The curing process during the printing is not enough to solidify the SLA parts. Hence, to improve the product's mechanical properties, the printed materials are kept in a cure box under intense UV light. Exposing them to sunlight also facilitates curing.

SLA materials

Following are the most commonly used SLA material for 3D printing services in India.

Standard resin: Used for making visual prototypes or art models. These tend to be highly brittle, despite having high tensile strength.

Clear resin: Used to make products like fluidic devices or LED housing. Clear resins are transparent materials that attain clear transparency at the post-processing stage.

Castable resin: Used to make intricate designs in jewel making and small components. Castable resin tends to burn out easily.

Durable or tough resins: These materials have high impact strength and elasticity and are used to make prototyping parts that have moving parts.

Heat resistant resin: A high thermal stable material, these materials are used for making heat resistant parts, fluid-flow, and hot air equipment, etc.
Dental resins: The biocompatible liquid resins are used to produce orthodontic fixtures that can stay in a human body for as long as one year.