Welding in Metal Fabrication Resource

Welding in Metal Fabrication

With metal fabrication each and every operation adds costs to the part being manufactured. Those fabrication processes that involve manual labor generally have a greater cost impact than those performed by machines. Welding is most often a manual process. 

In this Welding Resource we will describe the impact of welding on the costs of metal fabrication and ways to design a part to reduce or eliminate the costs associated with welding. 

Welding Overview

When a metal part includes flanges that cannot be formed or bent into place, the part will require welding to secure the flange. There are other purposes for welding a metal part but we will focus on attaching two metal parts together or attaching a flange to a metal part in this resource. 

Welding is commonly used in metal fabrication. Welding uses heat to bind two metal parts at a junction. The metal material used in welding should match the metal material of the part being welded. The welding will be performed at the seam or joint between the parts so that when finished the parts will be attached together with the weld material, or bead of weld, between them. 

A proper weld will cause the welded material to become one with the completed part, so when placed in service the part will maintain the strength necessary to accomplish its designed task. Due to the equipment and precise nature of welding, the process requires a high degree of skill. Welders should be certified craftsmen with sufficient experience in the necessary procedures of welding. 

Types of Welding

The weld types listed below are commonly used by Short Run Pro in custom metal parts production: 

TIG Weld – This well uses a tungsten inert gas and is often considered the highest quality weld as well as the most expensive weld.
MIG Weld – The MIG weld uses metal inert gas and is generally faster and less expensive than a TIG. 

Resistance Weld – Also called a spot or tack weld, the Resistance weld is a form of electric welding that is used to bind overlapping materials together with small spot welds. 

Stitch Weld - A stitch weld is accomplished by hitting a bead of weld in predetermined intervals on the seam of the metal part to create a stitching of weld material. Because a stitch weld does not involve a solid welding process, the finished seam will be weaker than if a solid weld is used. A stitch weld will also not be water tight.

Plug Weld - This welding process involves cutting a hole in an opposing flange at the spot of intend welding.  A plug weld will then be used to weld the joining parts from the opposite side of the metal part.

While welding is a costly process in metal fabrication, there are ways in which welding can be more economically accomplished. Note that these cost effective measures will have implications on the strength of the weld and therefore the use of the part.

Part Design Consideration in Welding

When determining whether a weld is required on a metal part, the use of the part is paramount in making the final decision. If a part can be designed in a manner to eliminate the need for welding, the design changes made will result in cost savings. However, when fabricating a metal part, the function of the part always trumps cost.  There is obviously no advantage to fabricating a metal part that will not work as intended. 

Below are some design considerations that have an impact on welding requirements: 

  • Is the Part Air or Water Tight?  If a metal part is required to hold liquid or gas contents without leaking it will require full welding at any open seams or joints.
  • What is the Holding Strength of the Part? – When strength is important in a welded part it will be necessary to provide the most durable and strong weld possible.
  • How is the Part to Look When Finished? – When a metal part requires a décor finished look that is absent of gap seams then it will require full welding on the length of the seams.

When designing a metal part in a cost sensitive manner it is important to understand how the weld processing affects the overall price of fabrication. To make a metal part most cost efficient to produce, reduce or eliminate the welding process of the part to the extent possible considering the use of the part. 

For more information on welding visit our Video Resources on Welding.
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