Additive Manufacturing Process Steps and Variations

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Questions and Answers

What is one purpose of support structures in additive manufacturing?

To hold up overhanging features during printing (correct)

To improve part aesthetics

To reduce material costs

To enhance machine speed

Which of the following is a common post-processing technique in additive manufacturing?

Material deposition

Mechanical sanding (correct)

Digital modeling

Layer cross-section formation

How can material properties impact the additive manufacturing process?

They affect the layer thickness and build parameters (correct)

They determine the machine's noise level

They influence the design software used

They control the machine's speed

What is a common application of additive manufacturing?

Custom components for aerospace industries Signup and view all the answers

What is one characteristic of AM machines designed for varied materials?

They have numerous setup options that require optimization Signup and view all the answers

Why might some parts require shrinkage or coating allowances during additive manufacturing?

To account for material behavior during cooling Signup and view all the answers

What typically happens if the setup procedure for an AM machine is incorrect?

The part will be built but the quality will be unacceptable Signup and view all the answers

What is one of the first stages in the additive manufacturing process?

Semi-automated stages with manual control Signup and view all the answers

What is the primary purpose of using support structures in photopolymer-based systems?

To support the part since it is printed in a liquid vat Signup and view all the answers

How does the layer thickness in Additive Manufacturing generally affect the build process?

Thicker layers result in quicker builds but lower precision Signup and view all the answers

What is the primary reason support structures are needed in some AM processes?

To stabilize the part during the building process Signup and view all the answers

What is a key consideration when post-processing parts made of different materials?

The heat resistance or melting temperature of the material Signup and view all the answers

Which method is primarily used during post-processing for finishing parts?

Abrasive finishing Signup and view all the answers

Which of the following is an advantage of powder-based systems in Additive Manufacturing?

They do not need supports and are easier to set up Signup and view all the answers

What is a common characteristic of parts produced by AM machines?

They often have small voids or bubbles Signup and view all the answers

How does the performance of AM parts typically compare to those made through conventional manufacturing?

AM parts may behave differently under stress Signup and view all the answers

Which factor does NOT influence the time and skill required for a stage in the AM process?

The color of the printed part Signup and view all the answers

Which of the following statements about support removal in AM is true?

Manual skill is often necessary for support removal Signup and view all the answers

What defines the thinnest wall that can be fabricated in Additive Manufacturing?

The dimensions of the droplet size or laser diameter Signup and view all the answers

What is a key benefit of using power tools in the post-processing stage?

They can improve efficiency in finishing tasks Signup and view all the answers

What is a limitation of using newer photopolymer resins in AM?

They degrade rapidly without UV protective coatings Signup and view all the answers

Why are the properties of parts created by AM often described as anisotropic?

They exhibit different properties in different directions Signup and view all the answers

What distinguishes Zcorp parts created using binder printing in a powder bed from other AM techniques?

They can be colored using colored binder material Signup and view all the answers

Which factor is influencing the ongoing development of AM materials and processes?

Continuous advancements in technology Signup and view all the answers

What are the primary materials used in photopolymerization processes?

Liquid, radiation curable resins Signup and view all the answers

Which radiation type is predominantly used to cure photopolymers?

Ultraviolet (UV) radiation Signup and view all the answers

Which discovery did Charles Hull make in the mid-1980s related to photopolymers?

A technique to create a solid 3D part by layering cured polymers Signup and view all the answers

What application of photo-curable resins is commonly found in dentistry?

Sealing top surfaces of teeth to prevent cavities Signup and view all the answers

What types of radiation are used to cure commercial photopolymers besides UV?

Gamma rays and x-rays Signup and view all the answers

What type of polymerization is primarily associated with acrylates used in photopolymers?

Radical polymerization Signup and view all the answers

Which type of radiation is NOT commonly used for curing commercial photopolymers?

Infrared radiation Signup and view all the answers

What is the role of a photoinitiator in photopolymer systems?

To convert physical energy to chemical energy Signup and view all the answers

What happens during the laser scan VAT polymerization process?

Liquid photopolymer is selectively solidified Signup and view all the answers

Which of the following materials is typically used as a raw material in photopolymer formulation?

(meth) acrylic acids Signup and view all the answers

What is formed during the interpenetrating polymer network formation in photopolymers?

Radically polymerized acrylates and cationically polymerized epoxides Signup and view all the answers

Which subsystem is NOT a part of vector scan VP machines?

Environmental system Signup and view all the answers

After a layer has been cured in a laser scan VP process, what occurs next?

The platform dips down for a new layer thickness Signup and view all the answers

What is the minimum unit size of hardened polymer in the atypical point-wise Microsterolithography process?

5 µm x 5 µm x 3 µm Signup and view all the answers

Which of the following best describes a drawback of using photopolymers in additive manufacturing?

Their chemistries are limited to acrylates and epoxies. Signup and view all the answers

What performance factor in laser scan vat photopolymerization technology is especially noted for accuracy?

0.002 in/in for SLA-250 Signup and view all the answers

Which benefit of mask projection VP technology is highlighted over laser scan SL?

Increased speed of the printing process Signup and view all the answers

What limits the use of stereolithography (SL) processes in many production applications?

The limited chemistries of current SL materials Signup and view all the answers

What is the maximum size of a fabrication structure in the atypical point-wise Microsterolithography process?

10 mm x 10 mm x 10 mm Signup and view all the answers

Which aspect is a contributing factor to the surface finish of SL parts reaching over 100 µm Ra?

Surface orientation during printing Signup and view all the answers

Which of the following is NOT a stated advantage of vat photopolymerization technology?

Excellent flow properties of photopolymers Signup and view all the answers

Study Notes

Additive Manufacturing (AM) Process Steps

AM processes involve a series of steps, from preparation to final application.
The process consists of eight steps.

Variations in AM Machines

Layer thickness varies between machines, with most AM machines building layers around 0.1 mm.
FDM Dimension machines use layer thickness of 0.254 mm.
SL technology uses layer thickness between 0.05-0.1 mm.
Layer thickness impacts build time: thicker layers mean faster build times but less precision.
Fine details in a design can be challenging for some AM technologies: wall thickness, droplet size, laser diameter, and extrusion head all limit the finest details achievable.
Variations between materials within the same process impact the time, resources, and skill required.
Post-processing considerations depend on the material's heat resistance or melting temperature, as well as its properties for abrasive or machining-based processing.

Photopolymer-Based AM Systems

These systems are easy to set up.
Liquid vat systems require supports made of the same material as the part.
Droplet deposition systems allow for modification of support material as it's printed, making them easier to remove.
Photopolymer systems offer good accuracy with thin layers but have relatively poor mechanical properties compared to other AM materials.
Newer resins offer improved temperature resistance, strength, and ductility, but UV protection is crucial to prevent degradation.

Powder-Based AM Systems

No need for supports; powder is deposited layer by layer.
Easy to set up for simple builds.
Zcorp. parts created using binder printing in a powder bed are unique in their ability to be colored using colored binder material.
Several preparatory steps may be required: verifying part correctness, visualizing and manipulating the part, repositioning or reorienting the part for optimal build location, building multiple parts, applying shrinkage or coating allowances, and segmenting STL files.

Machine Setup in AM

Each AM machine has specific setup parameters.
Simple machines may have only a few setup options, while others offer more complex configurations.
Incorrect setup may still produce a part but result in unacceptable quality.

Build Stage in AM

This stage is semi-automated.
Manual control and decision-making are required during early stages.
Once the initial steps are complete, the build process becomes computer-controlled.
Layer-based manufacturing occurs, with a sequence of layer control, material deposition, and layer cross-section formation.
The process repeats until the build is complete or material runs out.

Removal and Cleanup in AM

Ideally, the part should be ready for use after the build.
However, most parts require manual finishing.
Parts must be separated from the build platform and excess material.
Support structures may be needed to prevent warping or collapse during the build.
Removal of supports often requires manual work and skill to avoid damaging the part.
Cleanup is considered the initial part of post-processing.

Post-Processing in AM

Manual stages of finishing parts for specific applications.
May involve abrasive finishing (polishing, sanding), coatings, or other finishing tasks.
Post-processing requirements vary based on the application.
Some applications require minimal post-processing, while others demand careful handling.
Power tools and equipment can assist various post-processing tasks.

Applying AM Parts

Following post-processing, parts are ready for use.
Properties may differ from traditionally manufactured parts.
AM parts may contain voids or bubbles, leading to potential failure under stress.
Material degradation during the build can impact bonding, linking, and crystallization.
Properties are often anisotropic, meaning they vary based on direction.
Despite limitations, AM materials and processes are constantly improving, and many applications do not demand high performance.
AM applications are increasing as technology progresses.

Photopolymerization Processes

Photopolymerization uses liquid resins that cure with radiation, primarily in the ultraviolet (UV) range.
Photopolymers were developed in the 1960s and are widely used in coatings and printing industries.
They are also used in dentistry for sealing teeth and preventing cavities.
In the mid-1980s, Charles Hull experimented with UV curable materials and discovered that solid patterns could be created with a scanning laser, marking the beginning of Stereolithography (SL) technology.
Common radiation used for curing photopolymers includes gamma rays, x-rays, UV, and visible light.

Layer-Based Built Phenomena and Errors

The layer-by-layer construction process can cause visible "stair steps" due to the stacking of layers.

Vector Scan Micro-Vat Photopolymerization

This process uses lasers and X-rays to create microstructures with high accuracy.
The process can create features as small as 5µm x 5µm x 3µm.

Mask Projection VP Technologies and Processes

Mask Projection VP technology uses a mask to project an image onto the photopolymer resin, allowing for faster curing compared to laser scanning.

Commercial MPSL System

This system utilizes Mask Projection Stereolithography (MPSL) technology.

Two-Photon VP

This process uses a focused laser beam to cure the photopolymer resin.
The beam is scanned across the material to create the desired shape.

Process Benefits and Drawbacks

Benefits:
- High accuracy and surface finish.
- Flexibility in machine configurations and size scales.
- Mask projection VP systems offer faster curing times than laser scanning systems.
Drawbacks:
- The range of photopolymer chemistries is limited to acrylates and epoxies, which impacts material strength and durability.
- Photopolymers can degrade over time, affecting their mechanical properties.
- The limitations in material properties restrict the use of SL in many production applications.

UV Curable Photopolymers

They are widely used as photoresists in the microelectronic industry.
Common radiation types used include gamma rays, x-rays, electron beams, UV, and visible light, with UV and electron beam being the most prevalent.

Photopolymer Chemistry

Two main methods are used:
- Free radical polymerization: This method uses acrylates.
- Cationic polymerization: This method uses epoxides and vinylethers.

Resin Formulation and Reaction Mechanisms

Basic materials like polyols, epoxides, (meth) acrylic acids, and their esters are used to create monomers and oligomers for radiation curing.
Most monomers used are multifunctional monomers.
The photoinitiator converts light energy into chemical energy, initiating the polymerization process.
Both di-functional and higher functionality monomers are used in SL resins.
Acrylates and epoxides polymerize through different mechanisms to form individual networks that interpenetrate, creating a strong, complex structure.

Laser Scan Vat Photopolymerization

A laser scans a liquid photopolymer resin, solidifying the resin selectively in the scanned area.
The part is built layer by layer, with each layer hardened before the next is applied.
After the build is complete, the part must be cleaned, post-cured, and finished, which may involve removing support structures and sanding or filing for desired surface finishes.

Vector Scan VP Machines

The machine consists of five subsystems: recoater, platform, vat, laser and optics, and control system.
The process begins with applying a layer of liquid resin to the bottom of the vat.
The platform moves down by the layer thickness, creating a space for the next layer.
A recoater blade spreads a thin layer of resin evenly over the previous cured layer, preparing for the next stage.

SL Scan Patterns

SL scan patterns are divided into types like point-wise, raster scan, and vector scan.
Each type of pattern has unique characteristics and applications.
Raster scan is generally the most common method used in commercial SLA machines.

ACES Scan Pattern

ACES, or "Advanced Curing Engine System," is a scan pattern designed to minimize staircase effects and improve the overall quality of parts.
It uses a more intricate laser path to create smooth curves and transitions.

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Description

This quiz covers the essential steps involved in the additive manufacturing (AM) process as well as variations between different AM machines. It highlights the impact of layer thickness on build time and precision, and explains the considerations for photopolymer-based systems. Test your knowledge on AM technologies and their applications!