In the previous article, we learned the fundamentals of additive manufacturing, noting its characteristics, benefits and downsides. Now we will compare two of the most common 3D printing technologies, FDM and SLA, and show how our engineers employ them to solve production problems.
Fused Deposition Modeling (FDM) and Stereolithography (SLA) are the most used 3D printing methods among the rest because of the relatively low cost of the equipment required and the wide variety of materials with different properties.
Fused Deposition Modeling (FDM)
The key benefit of FDM technology is its low cost. The cheapest printers are roughly $150. The cost of the materials begins at $15. As a result, the printer is accessible to a wide range of users. Professional 3D printers are more costly, but they are still within reach for most people.
Printing Process. Heating thermoplastic polymers is how 3D printers work. The polymer is spooled into an extruder channel, heated to extrusion temperature, and then deposited layer by layer to the work platform, forming a product.
A product’s color palette. Plastic for 3D printing comes in a wide range of shapes and sizes, while professional (engineering) polymers’ color palette is often limited to gray, black, and white. The most common filaments, such as ABS, PLA, PETG, and SBS, come in a wide range of hues.
Accuracy. The accuracy of the produced model is greatly determined by the printing parameters and material used. The thickness and width of the layer are the most important parameters. The printed item’s surface is ribbed, and the layers are apparent to the human eye. Surface smoothness is accomplished through post-processing. The layer resolution of modern professional 3D printers is 50 microns. As a result, traditional manufacturing methods are more accurate than FDM technology.
Post-processing of a part. After printing, most additive manufacturing technologies necessitate post-processing of a part to ensure proper shape, accuracy, and functionality.
Overhangs are printed with the usage of support structures. Supports may be required in some circumstances to prevent deformation. Supports are constructed from the same material as the product itself, or from materials that are dissolved in a liquid solution, melted at a lower temperature, or physically removed, such as PVA.
The quality of a surface can be improved by priming and painting it. To give a product’s surface unique properties, thin layers of varying types or structures are created, named coatings. Coatings can be decorative, protective, chemical-resistant, and more. Coatings are frequently utilized to offer a product’s surface attractive or protective-decorative properties. The paint coating process includes surface preparation, priming, filling, sanding, painting, varnishing, polishing, and drying.
Finished product properties.
Parts that are made using FDM are strong and elastic, with a consistent set of physical properties. In the majority of cases, they have anisotropic qualities, which means that their strength characteristics vary along different axes. This is the case because of the layered structure.
Conclusion.
Rapid prototyping, proof of concept items, and small-scale production are all made easier using FDM printing.
Many prototypes of a future product can be manufactured for a minimal cost using a printer.
Models with complex geometric shapes can be made with the help of supports.
There are hundreds of 3D printing materials to choose from on the market.
Coatings can be used to improve the appearance and qualities of a printed object.
Stereolithography
Stereolithography is a 3D-printing process in which the resin is polymerized to produce the desired outcome. A part is made by layering a polymer resin and curing it with an ultraviolet (UV) laser beam. SLA printing technologies use light-sensitive thermosetting photopolymers which are available in liquid form.
Printing Process.
The part is grown on a work platform inside a tank of liquid photopolymer. In the very beginning, the photopolymer covers the platform to a thickness equal to the layer thickness. The laser then cures the photopolymer by traveling along a specified shape. The work platform is then raised by the layer thickness, and the procedure is repeated until the product is completed.
Classification of materials used in SLA:
Materials used in SLA are not as accessible as in FDM. Resin costs start at 50$ and can go up to 400$ or more. The following are the most common resins:
1. “Standard” photopolymers that are used for prototyping;
2. Engineering photopolymers
They are distinguished by their mechanical and thermal properties:
- tough;
- durable;
- heat resistant;
- flexible;
- etc.
3. Dental and medical photopolymers are supplied with biocompatibility certificates;
4. Castable photopolymers have no ash content after fire.
Accuracy.
In contrast to FDM printers, the majority of printing parameters in SLA printers are set by the printer manufacturer and cannot be modified. Only the layer height and orientation of the parts on the working platform are controlled by the operator. Layer height in SLA ranges from 25 to 300 microns. Professional printers can attain a resolution of 10 microns, which is comparable to CNC machines.
Post-processing of a part.
In comparison to FDM, SLA post-processing is distinct and has its own unique characteristics. The part remains semi-dry on the work platform after the printing process is completed. The part has its final shape and look, but the photopolymerization reaction is not complete, and the mechanical and thermal properties are not fully fledged yet.
To remove resin remnants, rinse the part in ethanol or isopropyl alcohol. The part can be washed manually or in an automatic chamber.
After that, the supporting material must be removed with auxiliary tools, such as a file, wire cutters, etc. For better treatment, ultrasonic baths are used.
After that, the product is cured in a UV chamber. The polymerization of the material has not yet been completed; the alcohol treatments have softened the component. UV curing completes the polymerization process and stabilizes mechanical characteristics. The part reaches its maximum strength and becomes stable.
Finished product properties.
SLA products, unlike FDM, have an isotropic structure, which means the part’s properties are the same along different axes. This is because one laser pass is insufficient to thoroughly cure the liquid resin. Further passes, as well as complete curing in the UV chamber, aid in the layers’ fusion. Nonetheless, the strength of SLA printed parts is inferior to that of FDM printed ones.
Conclusion. The SLA printing process is widely used in model prototyping. For instance, where transparency is necessary to visualize gas and hydrodynamic processes within simulations, or where the product must replicate rubber qualities. It is widely used in medicine, particularly dentistry, to make biocompatible surgical templates, orthodontic models, retainers, and eliners, as well as in jewelry studios to make high-precision personalized jewelry.
What is better to choose?
Each 3D-printing technology has its own set of benefits. The technology you choose is determined by your requirements. An FDM printer will have an edge on making massive parts, as a SLA printer cannot be large-scale due to the nature of the technology. It is also worth thinking about the type of material you use. This technology employs a variety of materials for various purposes. FDM is the most likely choice if a product with high strength is required, whereas SLA is the best option if high detail and minimal surface roughness are required.
Various industries use FDM and SLA printers in their manufacturing, and they are successful in completing their everyday work.
In our production facilities, we have both FDM and SLA printers. Our engineers have successfully used them in the development of new products. There are a lot of cases in our portfolio where we have employed additive manufacturing technologies for prototyping, proof of concept, and industrial design validation. Some of them were already discussed in our earlier post. We will also share our experience with you in this article.
EnCata’s experience
We were approached by a start-up from Kickstarter to develop the HandEnergy power bank with a perpetual battery. HandEnergy is a small portable power source. Everyone knows what a low battery means: we are cut off from the rest of the world! And there are situations when there is no means to charge the battery when it is needed immediately. The generator enables you to produce clean, “green” energy using only your body’s power.
In this project, our engineers made extensive use of the capabilities of additive technology. Various enclosure prototypes were printed with the usage of FDM and SLA processes.This allowed us to assess each prototype’s ergonomics and test the arrangement of pieces within the enclosure. The project was finished successfully, and we sent the working prototype and CD to the customer, along with the test results.
The self-winding spinner is another intriguing project. The spinner is the world’s best-selling anti-stress toy. It is powered by a central rolling-element bearing that rotates. An inner ring and a ball separator rotate the bearing. The user regulates the inner ring’s rotation, while the ball separator forces all of the balls to spin in the opposite direction. The inner ring is essentially immobile, and the balls drive all of the spinning, but it wouldn’t work without human aid. If you don’t spin the device with your fingers, it will stop. Maintaining continuous spinning in a traditional spinner is nearly impossible, but our engineers have solved this problem. To keep the spinner in perpetual motion, a self-winding mechanism has been incorporated.
Numerous prototypes of the self-winding device were created with the usage of FDM and SLA printing. Prototyping has been used to test the working mechanisms, allowing the best one to be chosen. Additive manufacturing techniques help to build and test a prototype in a matter of hours using. We created ten self-winding mechanisms and gave them over to the customer along with technical documentation, after identifying and approving the best device.
Our engineers employ additive fusion technology in any project that involves plastic. It is a truly quick and easy solution to address difficulties there and then.
