FDM 3D Printing – Fused Deposition Modeling Ultimate Guide

History of Fused Deposition Modeling(FDM) Technology

Fused Deposition Modeling(FDM) also known as Fused FIlament Fabrication (FFF) is an additive manufacturing method invented by Scott Crump in 1980’s. This technology was born when Scott Crump made a frog toy for his daughter using a hot glue gun that contained the mixture of candle wax and polyethylene.

Initially, this process was totally manual and not accurate. In order to automate this process, Scott visualized of building the same shape or object by depositing a series of thin layers one upon another.

img: FDM 3D Printer

Scott Crump later establishes a company Stratasys, which is one of the prominent 3D Printer manufacturers in the world today.

Today, Fused Deposition Modeling (FDM) is popularly used in rapid prototyping, modeling and production applications across many industries. 

What is FDM 3d printing?

FDM Working Schematic

Fused Deposition Modeling (FDM) is a 3d printing process in which a Thermoplastic Material such as PLA, ABS is extruded layer by layer in a pre-determined path on a build platform to form a 3D object. 

FDM Printing Process

FDM 3d Printing process involves an extruder with a heated nozzle which moves horizontally and a build platform which moves in both horizontal and vertical axis. A thermoplastic polymer known as PLA, ABS filaments are fed into the extruder driven by a stepper motor. 

An extruder contains a heated nozzle which melts the filament and forces out to form a 3d object layer by layer.

Once the layer is completed, the build platform of the printer is lowered in micro meters to accumulate the next layer of plastic. Thus a formed 3d object is nothing but a collection of layers formed by melted plastic filament. 

Once 3D design is complete, the materials that hold the model to the printer bed can be removed easily. 

How does FDM printing work?

3D Slicing in FDM
Fig: 3d Slicing FDM

First you need to decide on an object to print. 

Step 1: Design a 3d Model on Computer:

First, we need to create a 3d Model on a computer. There are hundreds of websites, where 3d Models can be downloaded and print them out straight away. You can also create your own design using 3D modeling software. There are loads of software to choose from, but all of them use the same method. Once you’re happy with the design model, you’re ready for Step 2.

Step 2: Slicing:

Once you have your 3D model, it will be sent to 3d Printing software that scans it and slices it into sections to help the printer understand the shape and how to print it. 3D Printers cannot understand 3d models, thus the CAD file is converted into STL (Standard Tessellation Language). This STL file will be the input for the 3D printer and contains different geometrical data for each layer to be printed. 

Step 3: Printing:

Now, you’re ready to print. But first, we need filament. Filament is a material from which the models are to be printed. Filament materials can be plastic, metal and ceramic or even chocolate. The printer has 2 main parts:

FDM Extrusion
Fig: FDM Extrusion
  1. Print plate or Build platform that moves up and down and
  2. The printhead, that can move in any direction. The printhead has a heating element called extruder nozzle and when filament is fed, it gets heated and melts. 

The printhead/extruder then draws the outline of the first slice/layer with the melted filament. Now, the plate moves down so that the next slice/ layer can be printed. This continues until all the slices are printed and the model is complete. 

Fig: FDM Printed Object

Applications of FDM 3D printing

Fused Deposition Modeling  is used in almost every industry starting from the consumer goods, sculptures, jewellery designs, automobiles, Rapid Prototyping, aerospace, Medical, Prosthetics, artistic sectors.etc.

Rapid Prototyping using FDM: 

An ideal way of producing the new prototypes is by using FDM 3D printing technology. It can produce 3D prototypes at relatively low cost and at a faster rate. 

Rapid Prototyping enables large manufacturing companies to quickly produce prototypes and measure its effectiveness. Popular automotive companies like BMW, Hyundai use FDM for prototypes.

DIY Home Models: 

FDM is also favourable for those who print 3d object different models and print at home. For Hobbyists, FDM is a great blessing as they can easily print their passionate objects, models, toys, decorative items.etc

3D FDM Printing Materials

One of the great advantages with FDM 3D printing is the availability of variegated 3D Polymer filaments with optimal properties and cost. 

FDM 3D printing offers a printing flexibility with different kinds of Filament Materials based on the application and usage. Below are the few of those Printing materials:

PLA:

PLA is a material that decomposes naturally. It is a plant based filament that is made of corn starch, sugarcane and does not include any petroleum products. It is the most versatile, popular and economical 3D printing material. It offers the best finishes and the widest variety of colors available with up to 16 available shades.

PLA has good rigidity, but for prototypes or components subject to stress and temperature it is surpassed by other materials with better properties such as PETG.

PETG:

PETG is a 3D printing material indicated for parts that are going to experience moderate stress, when PLA is not enough.

PETG resists impact, stress and temperature better than PLA. It is also sterilizable and resistant to chemicals. 

ABS:

ABS is a printing material with good mechanical and thermal properties. It can be post-processed and pasted with acetone. 

Due to the warping and cracking problems that ABS has, it is not indicated for the manufacture of large parts.

TPU:

TPU is a flexible 3D printing material for making elastic parts that behave like rubber.

Nylon:

For parts with higher mechanical and temperature requirements Nylon PA6 reinforced with fiberglass load can be used. It is the material with the best resistance, rigidity and resistance to temperature.

Characteristics of FDM Printing:

Printing Parameters

The printing process in FDM systems offers several parameters, some of which are widely adjustable while some are rigid. Tunable Parameters include printing bed & Nozzle temperature, Cooling fan speed, printing speed, overall temperature within the chamber.etc. All of these are in operator control and less worrying.

Rigid Parameters include Printing layer Height and Printable object Size. 

Printable object or Build Size:

Build size is one of the constraints while printing the bigger objects in the small Desktop FDM Versions. These have a lesser build size area of 200x200x200mm forcing the bigger objects to be printed into small parts and to be assembled later. This also can save cost.

On the other hand, industrial 3D printers offer build platform size of 1000x1000x1000mm enabling the printing of bigger objects. 

Layer Height:

In FDM, the print quality depends heavily on the layer height being used. Layer Height varies from 50 to 400 microns.  

Smaller printing layer height produces the parts that have smooth finish, clear curve structures but makes the printing expensive and time consuming. Larger layer height on the hand, is less expensive and prints at a faster rate. 

Warping

Warping is a problem caused due to the changing behaviour of plastic under different temperatures. The thermoplastic filament will expand during extrusion due to high temperature and shrinks as it solidifies. The extrusion time differences between the layers will put each layer at a different temperature as they cool down. This drags the underlying layers up creating a curl/bend. 

Warping occurrences can be prevented by

1.    Printing on a hot bed, which sticks the object tightly and maintains good adhesion  with a bed surface.

2.    Cover your printer with a chamber: This maintains the required printing environment temperature (that of a printing bed) during the printing process. 

Layer adhesion:

The strength of the printed FDM part is dependent on the bondage strength or adhesion between the printed layers. Bongage strength is achieved by pressing and melting the surface of the previous layer during extrusion. When the molten material is extruded, it re-melts the portion of the existing layer and sticks tightly. 

Note: Layer to layer bond strength can never be stronger than the inherent base material strength.

This gives us an understanding that strength of FDM printed objects is not the same in all axes. Strength in the XY axis is higher than the bondage strength in the Z plane. Thus, it is crucial to understand the real time usage of the part being printed and the kind of stress it undergoes and then decide printing orientation. 

FDM Structure Support

Printing an object with hanging structure is a major challenge in FDM, as these won’t have any support beneath. It gets complicated, when the thermoplastic fused in a molten form, will not retain its shape for a certain geometries. Thus having a support structure is sometimes essential.

It is recommended to avoid the supports as it will reduce the object quality.

Advantages & Disadvantages of FDM Printing

  1. Cost Effective: FDM technology offers a great flexibility of producing, testing and manufacturing of prototypes as well as the end products at very low prices. Unlike other printing technologies like SLS, SLS metal 3D, FDM costs very less to companies. 
  1. Flexibility to use different printing materials: Any company would love the usage of different printing materials based on their requirements. FDM can become the perfect option offering a broad spectrum of materials that are easily available. 
  1. Less manufacturing time: FDM technology is user friendly and easy to use. This enables them to produce parts at a faster rate as opposed to other technologies.

Disadvantages:

  1. Less Accuracy & Precision: FDM printed parts are not detailed and exact in the curves, edges and hanging structures. Also, the z axis strength will be fragile and weaker.
  2. Visual Appearances: In FDM layer-by-layer deposition will produce the visible lines in the end product and cant be avoided. This also spoils the final finish of the product.

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