Here is an article written by our engineering team that will guide you through one of the most common fabrication processes in the engineering industry: Welding.
Welding is an expedient and convenient way of joining variously shaped materials together permanently and with high strength. Welded components are light as they eliminate the need for bolts or fasteners. It is a great way to make low-cost prototypes as machining is eliminated. There are three main ways of welding parts together.
1. Fusion welding allows the parts to be joined to flow into each other via melting.
2. Pressure welding is achieved by compressing the parts together to be joined via plastic deformation.
3. Fusion welding uses a filler material to help join parts together.
When designing a component to be welded, there are various factors that must be accounted for. Due to the thermal stresses of welding, the parts will tend to warp or distort. This must be accounted for when planning for the final dimensional accuracy. Warpage can be prevented by the usage of jigs and fixtures. Assembly of components to be welded and welding techniques must be planned well in order to prevent incorrect weld size or profile. This is also important to ensure proper penetration of the weld to tight spaces. Workmanship, quality and consistency of the welder is paramount in order to minimize surface defects and incomplete fusion that may lead to weld cracking while the component is in use.
When choosing the material for a welded part, it is important to understand the material properties and composition as much as its suitability for the end application. As a rule, almost all metals are weldable. Low carbon steels are considered excellent for welding. Steel types with their equivalent carbon content exceeding 0.5% are considered not weldable especially as an industry rule in this region. Certain plastics can be welded using appropriate techniques as well. Do take some time to read our whitepaper on prototyping metals to determine what material suits your prototyping needs here: Prototyping Materials
If components fabricated via welding require good dimensional accuracy, jigs and fixtures are employed to minimize warpage and distortion during welding. As they can be reused for the fabrication of multiple parts, initial cost, long term maintenance costs and adjustment costs must be considered when choosing the material for fixtures and jigs.
When designing jigs and fixtures; orientation, assembly, disassembly, accessibility and simplicity are key factors that must be accounted for. A well-designed jig can be retrofitted to fabricate many different parts, repeated parts, ensures a uniform weld with optimum accessibility, can be simply adjusted for new part fabrication and easy disassembly after job completion.
Gas welding is ideal for portable situations such as new construction sites. This is because it does not require electricity. Thus, gas welding equipment are naturally portable, cheap and versatile. Welding temperature is lower than other welding methods allowing for thin sheets to be welded.
Arc welding uses an electric arc created between it’s electrode and the workpiece. The metal electrode generally chosen is one that is also the filler material. Arc welding is used to join parts of thickness more than 2 mm. It is faster, ensures localized heating and higher depth of penetration than gas welding.
Similar to arc welding but includes an inert gas buffer to prevent oxidization of the weld due to atmospheric gases. This is usually an automated process as the welding machine needs to feed the consumable metal electrode (filler).
In TIG, a separate filler metal rod is required as the electrode used is tungsten. The inert gas used depends on the application and the density requirement of the gas. TIG welding is excellent for welding thin to moderate parts of about 1–5 mm thickness.
Some lesser-known types of welding include friction welding, resistance welding, laser beam welding and electron beam welding.
If you’d like to know more about the manufacturing methods and materials discussed in this paper, do take some time to read our whitepapers published on the following topics available here:
Surface Finishing for Metal and 3D Printed Parts
Tolerance Guidelines for Sheet Metal Design
Drafting technical drawings for CNC Fabrication
Factorem’s ISO 2768 Machining Guidelines
When we get customer enquiries, they sometimes request for parts fabricated using welding. As to which method of welding is applicable to each component needs careful consideration on, material, application and design of the part. The table below is a summary of the common welding processes so that you can make an informed decision.
Thanks for reading!
