What is FDM 3D Printing?

3D Printing has been extensively used to churn out prototypes since the 1980s. It is quickly becoming a standard process for producing consumer items.There are various methods to approach 3D printing, and the most widely used is Fused Deposition Modeling (FDM). FDM printers make use of thermoplastic filaments which are heated to their melting points and extruded layer by layer to reveal a three-dimensional object.

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What is FDM 3D Printing? (source)

The FDM technology is credited to Scott Crump who developed it in the 1980s as the chairman of Stratasys Ltd., one of the leading 3D printing firms. Other companies have adopted the technology under various names like Fused Filament Fabrication (FFF). FDM is the most installed base of 3D printers worldwide and is often the initial technology 3D printing enthusiasts are exposed to.

How it FDM 3D Printing Works?

To understand the FDM process adequately, we need to break it into distinct steps.

Design

The FDM procedure starts with a 3D design and 3D printers commonly understand models stored in the STL format. An STL file has details on the surface geometry of the objects and attributes like the texture to be adjusted by the user.

Thousands of these STL files can be obtained from different websites. The designs can be as simple as bottle openers or as complex as card deck shufflers. The free models are ideal for novices who are just venturing into 3D printing.

The STL files are processed by slicing software designed to segregate the model into horizontal “slices”. The number of these slices can be changed by the user and will affect the resolution of the final print.

Support structures can be integrated at this point for designs that have many overhanging structures. The materials used in this process are often distinct from the materials that make the actual prints since the structures will finally be removed. A 3D printer fitted with dual extrusion features is required to produce designs with support structures.

Extrusion

In the course of printing, the filament is continually unwound from the coil and channeled to the extrusion system comprised of the extruder coupled with the hot end nozzle. The extruder is sometimes called the “cold end” to distinguish it from the hot end. The extruder feeds the hot end with the filament and ensures that the filament material is consistently relayed.
The extruder settings determine the pace of the printing process. You can retract the filament to avoid the formation of blobs.

The stepper motor, the drive gear, and the idler form the essential components of the extruder. The drive gear holds the filament with its teeth using the power it receives from the stepper motor. There are many extruder FDM designs, but the basic system remains the same.

After passing the extruder, the filament moves a short length to the hot end. The hot end features the nozzle and the heating cartridge. The latter provides heat to the nozzle and is typically made of ceramic material. Although most printers are fitted with brass nozzles, you can opt for materials like stainless steel which less abrasive. The system also features thermocouples or thermistors to detect and control temperatures.

Deposition

The hot end deposits the melted filament in thin strands on the print bed. A computer can be used to determine the dimensions of the x, y, and z positions that the object will take. The model is subsequently built layer by layer. The nozzle will move up, or the print bed will move down to trigger the printing of subsequent layers. The cooling of the material hardens and gives structural support for other layers.

FDM is a fairly slow process when compared to other 3D printing processes. Small objects and tall and thin designs take a shorter time to materialize while complex objects take more time. The support materials of prototypes made through FDM can be removed by soaking the product in detergent solution or water. Thermoplastic support can be removed by hand.

The most used FDM material is acrylonitrile butadiene styrene (ABS), which is a popular thermoplastic in the production of many consumer items. Some 3D printers also work with other thermoplastics like polyetherimide (PEI) and polycarbonate (PC). Thermoplastics are able to withstand mechanical and heat stress and they are therefore perfect for making objects that can endure testing. FDM is favored by engineers as they need to test components for fit and form.

SLA vs FDM

sla-vs-fdmStereolithography Apparatus (SLA) is an additive method, like FDM, where models are produced layer by layer. SLA utilizes a curable photopolymer, mostly a liquid resin, which is hardened by channeling UV or focused light. These printers typically build objects from top to bottom. The differences between FDM and SLA are:

Colors and materials- Most FDM printers can handle a range of materials including PLA and PLA blends, TPU, and PVA. Filaments are also acquired in different colors. Some manufacturers even offer a service to produce RAL colors by demand. SLA printers have a limited choice of resin materials. These materials are commonly proprietary and cannot be switched between printers from different brands. The color selection is additionally limited. Most of them come in grey, black, white, or clear. These materials are however more specialized and durable.

Precision and smoothness- The resolution of an FDM printer is a factor of the precision of the extruder movements and the nozzle size. The accuracy of the printed models is also affected by other factors. The bonding force between the FDM layers is lower than that in SLA printing. The weight of the upper layers may squeeze the lower layers and cause several problems like shrinkage of the lower sections, misalignment of layers, and warping. These issues compromise on the smoothness of the surface. SLA printers are more precise than FDM printers. The resolution relies on the optical spot size of the projector or the laser. Less force is applied during SLA printing, and the surface finish is therefore smoother. SLA prints contain details not shown on FDM models.

Removal after printing-Adhesion to the build bed is often a consideration with 3D printing. With FDM printing, models can easily be removed, and a palette knife will easily remove them if they stick to the printing surface. A lot of resin remains on the build bed with SLA printing, and it can be hard to remove the model. You often have to use a palette knife using more effort than in FDM printing.

Printing costs- Most FDM 3D printers use standard filament rolls, and the costs for the filament have been on a downward trend. You can get 1kg of filament for $25. Not only will you need to buy the resin in SLA printing, but the resin tank will need to be replaced after 2 or 3 liters of resin have been used. The tank gets smudged after a while such that the light source is no longer capable of accurately projecting the image in the resin. Resin tanks are priced between $40 to $80. The build base gets marred when removing the model and will need to be replaced as well. The platforms can be priced for as much as $100. A liter of resin will further set you back between $80 to $150.

Postprocessing- After printing is over, you will have to remove the supports if the prototype has overhangs and excess plastic using a cutting tool or just your hands. Models produced through SLA printing are covered in resin which can be removed with a solution of isopropyl alcohol. Most SLA printers come with rubber gloves for this purpose.

FFF vs FDM

The FDM technology was patented in 1989 by Stratasys Ltd. The typical FDM printer features an extrusion-nozzle system, filament, and a build base. The FDM patent expired in 2009, prompting a Rep-rap movement characterized by the manufacturing of various versions of the FDM printers. This technology was christened Fused Filament Fabrication (FFF) since FDM had been trademarked by Stratasys.

The Rep-rap movement sought to encourage the production of complex products without using extensive industrial infrastructure. The industrial systems demanded the heating of the whole print platform and FFF printers removed this requirement to save on costs. The heated chamber is therefore not present with these printers. The material filament moves from the hot extruder via a cold environment into a hot build base. The bed is not heated in some printers. This journey from hot-cold-hot environments generates residual stresses in the model part being printed.
The fundamental architectures between FFF AND FDM printers may be the same, but the quality is quite different. FDM is suited for industrial uses while FFF technology is ideal for hobbyists. FDM works best with engineering-level models which can withstand mechanical loads. FFF comes in handy when producing prototypes that need visual validation.

Advantages of FDM

FDM printers enjoy unrivaled popularity. The rise in the number of 3D printing enthusiasts has triggered large-scale manufacture of desktop 3D printers that are cheap. The software packages that accompany the printers have also become easy to learn. The adoption of FDM technology has been fueled by online guides, instructional videos, and tutorials making it quite accessible to people.

The popularity has had a positive effect on the availability of filament materials. If you want a model that resembles wood, for example, you will easily get the materials for that. You can get standard materials to more sophisticated ones.

FDM has also impacted industrial processes in the way of rapid prototyping. FDM printers can churn out models quickly and in a cost-effective manner. FDM printing is also a fairly waste-free process. Anyone who desires to venture into 3D printing, regardless of their budgets or skills, will certainly get an FDM printer.

Disadvantages of FDM

FDM printing is not recommended for highly intricate designs. Its primary limitation is the diameter of its hot-end nozzle. The uneven surface of FDM prints can also be frustrating. FDM prints have lower strength in the Z-axis which limits their applications. They cannot be used to model objects which need to withstand sustained loads or high impacts. FDM printing is perfect for creating design prints.

Best Cheap FDM 3D Printers

3D printers are increasingly becoming affordable and accessible to the average customers. Top printers to consider include:

1. Flashforge Adventurer 3 FDM 3D Printer

This printer is compact, light-weight, and minimalist. The nozzle is detachable, and it heats quite fast as in 50 seconds the temperature can reach 200 degrees Celsius. It features auto-filament feeding with an inbuilt filament cartridge. The heated print bed is removable and flexible. There is also a built-in HD camera for remote monitoring. The user interface is touch-screen and full-color. The product enjoys a 3.8 rating out of 5 on Amazon.

2. Elegoo Neptune 3D Printer

This package has semi-assembly parts, and you can set up the printer in just three steps. The filament drive is solid and is designed to provide precise extrusion. It is compatible with many filaments in the market including PLA and ABS. The platform is made of silicon carbide to offer excellent adhesion such that your prints will be removed easily. The printer is fitted with a filament detection switch, and it will stop to facilitate the replacement of the filaments if it detects an outage. The Elegoo Neptune features a single nozzle and a 2.8-inch touch screen operation panel.

3. ANY-CUBIC Mega-S 3D Printer

This printer features a patented printing base with excellent adhesion and from which models will easily detach once the bed cools. The extruder is designed to improve printing precision and reduce clogging risk. The printer has a suspended filament rack to save space and make organization easier. It also has a filament sensor while its fast assembly will get you printing in no time.

Conclusion

FDM printing enjoys dominance in the industry. Affordable and compact desktop 3D printers have encouraged many hobbyists to venture into 3D printing. The vast pool of filament materials coupled with a rich database of online resources and guides have only catapulted FDM into increased popularity.

FDM has a couple of limitations, however. The process stretches for a long time and prints are not always smooth or structurally sound, making SLA more ideal for complex designs. Despite these disadvantages, FDM provides the most flexibility and cost-effectiveness of any other 3D printing process.

FDM technology will continue to evolve, and desktop printers will become cheaper and smaller. The filament options will expand further and include more useful selections. FDM is likely to continue enjoying its popularity.

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