Page 22 - ITAtube Journal 2/2019

Technical Papers
Huntingdon Fusion Techniques
WP-309 – 3-D Printing for the Marine Industry
Figure 1. Illustration of the WAAM Process
Figure 2. Propeller 200 x 240 x 240 mm. Material: 1.5125 G3Si1.
Figure 3. Bell housing 230 x 380 x 380 mm. Material: Aluminium alloy.
The marine industry in general has been slow to embrace the 3D printing concept. The use of continuous liquid metal deposition under computer numerical control has created opportunities to produce complex shapes such as forgings and castings whilst avoiding the need for expensive tooling and the time delays in fabricating moulds.
Notwithstanding this slow start, development work at Delft Technical University in 2017 has led to the production of the world’s rst metal deposited marine propeller.
The majority of published documents on 3-D printing have been restricted to high precision applications, particularly in the medical sector. Whilst these examples illustrate the potential for producing small complex shapes the process is slow and expensive. Less well promoted are applications in which large engineering products using metals have been produced faster and less costly than using traditional methods such as casting and forging.
THE CONCEPT OF 3-D PRINTING
Several methods for 3-D printing using metals are now in regular use by specialist organisations. Essentially they involve using a targeted heat source to melt or sinter metal alloys and progressively build up a complex three-dimensional shape. A computer numerical control system, usually a multi-axis robot, guides the heat source. Solid metal in the form of wire or powder is fed into and is fused by the heat source.
One version uses a laser or an electron beam as the heat source in conjunction with metal powder, Direct Metal Laser (DMLS) or Electron Beam (DMEBS) sintering. This powder technique is most effectively applied where smaller, delicate objects are required. An example is the production of body implants [1 – 3].
The welding version of 3D printing, Wire and Arc Additive Manufac- ture (WAAM), is performed by laying down progressive beads of metal, [Figure 1]. This technique is more suited to the production of larger and heavier engineering components as evidenced by the manufacture of marine components and airframe structures [4 – 6].
In terms of applications for WAAM and DMLS/DMEBS the welding version is most suitable for heavier and larger products whilst the powder alter- native is best applied where smaller, delicate objects are required. In other words, welding is essentially a bulk deposition technique and powder is a precise and highly controlled process.
EXAMPLES OF WAAM MANUFACTURE
Several applications of 3-D production have been made and are appro- priate to illustrate the potential in the marine industry. These are illus- trated in Figs 2
DRIVING FORCES BEHIND WAAM DEVELOPMENT
The primary driving force behind the development is the potential to make huge savings in materials and therefore costs .
ITAtube Journal No2/May 2019
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