Why Weld Symbols Are Important in Manufacturing

[fa icon="calendar"] July 30, 2021 / by Warren McCray

In my years of experience working with manufacturing teams, I've seen both excellent and not-so-great practices around welding when it relates to manufactured products. In the not-so-great cases, the problems are ordinarily a lack of knowledge of how welds are defined. The issues may even consist of a failure to understand how the weld specifications are communicated internally from the engineer designing the product to the shop floor producing the product. In some situations, it's even a lack of understanding of the importance of weld symbols.

The inquiries that I get around establishing internal weld processes and efficient weld symbol communication often consist of whether weld symbols are even required on drawings or how to decide what weld types should be used on a specific product. What size should a weld be? Will the weld hold up under real-world conditions?

Once we recognize that there must be specifications, internal processes, and efficient communication around welding, we gain an entirely new perspective. For instance, you may question who should determine a weld's type and even size on a specific product. The answer to this question is twofold.

The first individual responsible for establishing weld processes is the engineer, who has designed the product for use, understanding how strong the weld needs to be based partially on the terminal environment that the weld will be in (more on how to test weld strength later). If the engineer hasn't thought this through, the result could be a waste of material, over-engineering, or a weld failing in a worst-case scenario. The engineer can communicate this information to the shop floor in many ways: through weld symbols, notes, or by referencing internal weld specifications. The second individual responsible for weld specifications is the team members on the shop floor. The shop floor knows the equipment and machinery available, defining which weld-types are physically possible to create and which are not. In short, there MUST BE communication between the engineer and the shop floor to become efficient.

Even so, more inquiries may come to mind. Does the shop floor understand how to read the weld symbols? Do they have the equipment to meet the required weld specifications? What are the welding assets available? Who is performing the welding; certified welders, novice welders, or precision robotics? All four answers to these questions will affect how specific a drawing will display a weld callout.

When products are involved, it can be even more demanding. Does the weld prevent the leakage of dangerous gases, or does the weld hold two parts together, and leakage is not a concern? Regarding appearance, is it acceptable to have the weld bead shown as is, or does it have to be ground off, making it almost impossible to tell the part was welded together?

These are just some of the concerns that come to mind around welding. There are many other concerns such as material compatibility, customer requirements, X-ray regulations, inspection criteria; the list can go on and on. I will not cover all of these more specialized questions here.

This article will not answer every question you may have; yet, it will touch on some of the most popular questions. Through this, I intend to raise awareness, encourage you to examine your current welding methods, and prompt you to, perhaps, improve your engineering to shop floor welding process. Let's jump right in and cover some of the most common questions:

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Are Weld Symbols Required on My Drawings?

In short, the answer is a resounding "yes." If welding is required for manufacturing, then the appropriate weld symbols are needed.

How Do You Decide Which Weld Type to Use?

You will likely have a few factors to consider when determining type-of-weld:

  • The geometry of the parts being welded together
  • The depth of penetration needed to weld the pieces effectively
  • The function of the weld on the part as a whole

For example: Is the weld needed to prevent leaks or withstand pressure within a pressure vessel, or are the parts just attached with little to no stress and strain on the weld?

Here are some visual geometry examples:

image1

image2 image3

If you look closely at the weld symbol, it reflects the shape of the geometry where the parts are welded together. This visual can help you determine what weld symbol is appropriate for the application.

Does the Shop Understand These Weld Symbols?

Unfortunately, this can vary from one organization to another. Some companies have standards in place that must be adhered to. These standards generally specify the type of approved welds for use on their products, period. Some have certified welders, and a variety of welding processes are supported like:

    • GTAW – Gas Tungsten Arc Welding
    • EBW – Electron Beam Welding
    • RSW – Resistance Spot Welding
 
image4Many high-performance companies use robotic welders to ensure consistent and repeatable welds for their products. I think that this is the best way to achieve a uniform weld. You see, the speed, length, and settings of the welding process can vary from one welder to another. If the welder, for some reason, welds slower than the next, there is a high chance of thermal expansion, which can ruin the product, and you then must scrap the whole part. Welding is more than a skill; I like to think of it as an art. Everyone is not great at it. Experience is a must, even for simple parts. image5Safety is another factor that must not be overlooked. Would you please ensure that you comply with the welding safety standards for your company, state, and OSHA standards before you start welding?

Then there are companies where the welds are not done by certified staff, but they know how to weld based on their years of experience. Typically, they understand how to read welding symbols. However, there is an exception to the rule of knowing how to weld but cannot read a detailed weld symbol. In all cases, every company should have, at the minimum, access to the AWS A2.4:2020 Welding Standard. This guide will create dialogue and reveal the need for training. It will also serve as a reminder that, in good practice, you should only place weld symbols into a drawing after giving it thought.

These practices can also create discussion, and teams can define their internal welding standards based on this specification.

What Size Should a Weld Be?

The answer will vary depending on the application and purpose of the welds and the stress and strain the weld will undergo. There are occasions where the client may have specific requirements, and the welds must be x-rayed and visually inspected.

image6image7

For example, welding together steel plates for a submarine will have a higher welding requirement than plates welded together for a water tower. Both will be watertight, but one must withstand enormous pressures under the ocean. Knowing what stresses or pressures the parts will be subjected to, and the minimum welding specification required by the governing agency is critical. Pressure vessels can explode, causing catastrophic damage to property and loss of life.

image8

For simple welds, designers and engineers can define weld-type based on company history and failure record. You can conduct simulation and physical testing to ensure that a weld does not fail. SOLIDWORKS Simulation Professional, as well as other CAD applications, can assist with this to reduce prototyping, saving you money. Ultimately real-world testing should be conducted in a safe environment, like a certified testing lab. Once the testing has been documented, then the weld symbols for that process will be defined. Proof of the weld durability is confirmed in case of failure and possible litigation.

Companies ignoring these standards and precautions may risk having inconsistent welds with the potential of failure as well as possible lawsuits. Another loss may be material, and labor as excessive welds cost the company increased labor time and material usage. Over-engineered parts due to fear of failure will lead to huge losses over the years. The typical excuse is "we have always done it this way for years." No one dare question the process or validate the process since it functions "well."

These days, with the material expense and labor compensations at an all-time high, companies are forced to revisit designs, reduce costs due to process improvements, and improve the design in a way that will cut down material usage. Often, this is done by sacrificing quality or safety requirements. For example, see the welding examples below. Which weld callout is better than the other? Considering only the weld type and not the size of the weld, which type is best for the two plates being welded together?

image9

image10

The answer depends on the forces that will be applied to the parts. Will the pieces need to endure load weight from the top or bottom? Is there a tensile load? What are the environmental conditions in which the product will be placed? Is the part only subjected to ambient temperature, will it be in a hot environment, or will it be in a location where the temperature ranges go from one extreme to another? Even if you have the proper weld identified, can it be done consistently? Are the parts welded in the morning just as good as the parts welded in the evenings? How can we maintain quality?

As you can see, it is not as simple as one may think. When you consider the hundreds of combinations and various applications, we can understand why there are weld specifications. So the next time you have to call out a weld, maybe the standard 1/4" fillet weld is not the best solution. Are the ends finished? Is there a standard for specific products? If not, with SOLIDWORKS Simulation, you can add the details necessary to define your unique specifications and rest well at night, knowing your team is designing quality parts and calling out the best welds with minimal cost in mind.

Want to learn more about welding symbols and other technical topics? Visit our website at TPM.com or call us at: (888) 313-1688.

For additional free technical training information, visit our blog page at blog.TPM.com.

Topics: Manufacturing

Warren McCray

Written by Warren McCray

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