Understanding 3D Printing Technologies and Inspection Methods

Introduction

3D Printing, also known as additive manufacturing (AM), revolutionizes how objects are created. This technology builds objects layer-by-layer using various methods and materials. This article explores seven main categories of 3D printing and the inspection methods used to guarantee the quality and reliability of printed parts.

Main Categories of 3D Printing Technology

Metal Extrusion (FDM/FFF): 

This method dispenses material through a nozzle, building objects layer by layer. It works with various materials like thermoplastics, metals, and even food. Leading providers include Stratasys, MakerBot, and Ultimaker.

Material Jetting: 

Here, inkjet heads deposit droplets of building material onto a powder bed. This allows complex, multi-material objects. It's suitable for photopolymers, waxes, and even metals. Major providers are 3D Systems and Stratasys.

Binder Jetting: 

Similar to material jetting, a binding agent glues powder particles together instead of building material. This method works with materials like metals, sand, and ceramics. Leading providers include 3D Systems and ExOne.

Sheet Lamination: 

This technology bonds sheets of material (paper, metal) to create 3D objects. Providers include Helisys and Fabrisonic.

Vat Photopolymerization (SLA/DLP): This method uses light to cure liquid resin into a solid object. It's limited to photopolymers but offers high accuracy. Leading providers include 3D Systems and Envisiontec.

Powder Bed Fusion: 

This method uses lasers or electron beams to melt powder particles together, creating a solid object. It works with polymers, metals, and sand. Major providers are EOS and SLM Solutions.

Directed Energy Deposition (DED): 

This method uses a laser to melt and fuse materials as they are deposited. It's ideal for repairing or modifying existing metal parts. Leading providers include Optomec and Trumpf.

Inspection Methods for 3D printed parts

To ensure quality, manufacturers use various non-destructive testing (NDT) methods to inspect parts without damaging them. Common NDT techniques include:

- Visual inspection

- CT scans

- X-ray

- Leak testing

- Eddy current testing

- Mechanical property testing

- Metallography

- Hardness testing

These NDT methods are crucial for:

Identifying defects

Monitoring material properties

Checking dimensions

Guaranteeing part quality

New 3D Printing Inspection Method

Dr. Ben Dutton is developing Laser Ultrasound technology for NDT inspections in the additive manufacturing sector at the Manufacturing Technology Center in Coventry, UK. This technology can evaluate powder beds during direct deposition processes and inspect components with complex structures. Laser Ultrasound can detect imperfections just below the surface, unlike traditional camera methods limited to surface photos. This ability to penetrate deeper layers makes Laser Ultrasound a superior inspection method for identifying potentially fatal flaws.

Conclusion

Understanding 3D Printing Technologies and implementing effective inspection methods are essential for producing high-quality parts and advancing the field of additive manufacturing.