Fused Deposition Modeling (FDM): A Comprehensive Guide to Additive Manufacturing, Study Guides, Projects, Research of Manufacturing Processes

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Additive manufacturing

Abstract

Certificate

Introduction

Introduction to AM

Additive manufacturing it is process in which digital 3D design of object is use to build component layer by layer by deposition of material. Additive manufacturing is also known as 3D printing or Rapid Prototyping(RP). Additive manufacturing is totally distinguished from conventional manufacturing. In conventional manufacturing we remove material from a block to get final object it is top down approach and also called as subtractive manufacturing. While in additive manufacturing we add material layer by layer and it is bottom up approach. The history of rapid prototyping can be traced to the sixties, when an engineering professor, Herbert Voelcker, question himself about the possibilities of doing interesting things worth the computer controlled and automatic machine tools. (1 p. 2). Voelcker’s theories changed the designing method in the seventies, but the old the old method for designing by a computer. In 80’s Carl Deckward a researcher from university of Texas came up with a good revelatory idea. He pioneered the layer based manufacturing, wherein he thought of building up the model layer by layer. (1 p. 3)

Definition of Additive manufacturing

Additive Manufacturing : It is defined as the process of joining material to make object from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies. (2)

Basic process of Additive Manufacturing

i. Create a CAD model of the design.

ii. Convert the CAD model to STL(standard

tessellation language) format.

iii. Slice the STL file into thin cross section

layer.

iii. Direct Energy Deposition :-It use highly focused

thermal energy delivered via plasma acr, electron

beam or laser to fuse and melt material jetted into

heat chamber from powder metal. Most of additive

process used metal, although some direct energy

deposition system use ceramic powder or polymers.

iv. Material jetting :-It is uses drop-on-demand

(DOD) technology. Material jetting process can

compare with 2 inkjet printers and 3D printed

objects.

v. Binder jetting :-It is similar to material jetting,

although it employs powder material and a binding

agent. Nozzles of 3D printer deposit tiny droplets of

a binder on layer of powder metal.

vi. Material Extrusion:- Fused filament fabrication

(FFF), or Fused deposition modeling(FDM) are well

known additive manufacturing process. These

process is often used to produce prototypes because

the process is fast and inexpensive.

vii. Sheet lamination: -It use ultra-thin layer of

solid material are bounded by adhesive. It is possible

to use various material in this process called

laminated object manufacturing(LOM).

The build: The nozzle is heated to melt the plastics filament and is

mounted to a mechanical stage which moved in both horizontal and

vertical direction. As the nozzle moved over build platform in the

required geometry, it deposit a thin layer of extruded plastic to form each

layer. After being squirted from nozzle it form bond with the layer

below. The entire system is carried out in chamber which is held at

temperature just below the melting point of the plastic.

The completion: Once all the layer are drawn and model is complete,

then model is removed from thr build platform, and support structure is

removed from part.

• Fig 2.

Materials Advantage Disadvantage

ABS

Good strength

Good temperature

resistance

Tendency to

warping

PLA Good surface finishes Low impact strength Nylon (PA) High strength

Wear resistance

Low humidity resistance

PETG Good strength

Easy to print

Non-reactive to food

TPU Very flexible Difficult to print PEI High Strength to weight

Excellent fire and chemical resistance

High cost

Defect’s in FDM

The melted plastic which is being deposited onto built-in platform it is necessary to give it enough time to cool before printing another layer on top of it. So if thickness of layer is very thin then 3D printer need to pause for seconds between layer else the part get deformed due to heat. Like metals thermoplastics also expand and contract as they heated and cooled, so there is slightly change in shape then original 3D part. Warping is most common defects in FDM. When extruded material cool during solidification, there is slightly decrease in dimension. As different section cool at different rate, their dimension also changes at different rate. This cause internal stresses that pull layer upward, cause it wrap as shown in fig 2.

Fig 2.

However, warping is depending on particular thermoplastics being used. In ABS (acrylonitrile

butadiene styrene) warping effect is maximum. The method to reducing

warping such as build in heat chamber this is patent by standpoint

technology. And warping can also be avoided by increasing adhesion

between part and build platform.

Post processing

FDM part can be finished to very high surface finish by various post processing technique like polishing, sanding(fig-2.6.1), panting chemical, priming(fig-2.6.2), cold welding(fig-2.6.3), expoxy coating, vapor smoothing(fig-2.6.4) and metal plating(fig-2.6.5).

Fig-2.6. 1 Fig2.6.

iii. Material

used are very cost

effective, typical

part cost under

US$20.

iv. A good variety of material is available including

color ABS and medical ABS, investment casting wax

and elastomer.

Limitation

i. Accuracy is relatively low and is difficult to

build parts with complicated details.

ii. Poor strength in vertical direction (tensile

strength)

iii. Required more time for building mas part.

Fit, Form and Function Testing. Determine function and performance of specific part and help to evaluate your model.

iv. The surface

finish of the parts is

inferior to that

produced with

stereolithography.

Applications

Due to wide range of FDM material available, any application can approach.

Precise, Detailed parts

FDM produce durable models, even they can still produce small intricate parts as show in figure.

High Heat Application

FDM part can withstand high heat tolerances. So FDM part can be used in application which subjected to high heat

4. Ramesh. A textbook of rapid prototying. p. 52.