Sheet metal manufacturing and quality control

The manufacturing of sheet metal plays a crucial role in creating a wide range of everyday items, including car bodies and appliance parts.  In the context of a highly competitive market, precision, uniformity, and quality are paramount.

The ultimate goal is to deliver products of the utmost quality.

Considering this, it’s evident that quality control (QC) is a fundamental element in reaching ever-higher standards and satisfying customer requirements. Keep reading to learn more.

What is sheet metal?

When we talk about sheet metal, we refer to a sheet derived from a roll of metal.  The advantages certainly include a great adaptability to numerous surface finishes at all levels with very low processing costs. In fact, it does not require additional machining operations, which is why it is used in various sectors.

Sheet metal manufacturing: production

Sheet metal manufacturing usually involves a series of processes that include laser cutting, stamping, bending, among others.

A process like stamping is usually divided into subprocesses that are necessary to achieve the final product.

• Bending
• Hemming
• Blanking
• Ironing
• Curling
• Piercing
• Cutting
• Stretching
• Drawing
• Reducing/necking
• Embossing

Of course, with the most recent developments in manufacturing technology, sheet metal manufacturers have taken their skills to the next level.

By using CNC machines, they can now achieve the very complex geometries required by many applications while complying with the tightest tolerance specifications.

Sheet metal manufacturing: Every metal has a different use

The uses of sheet metal vary based on the type of metal being used.

It is certainly interesting to list some types and match them to the most suitable form of application.

What kind of metal is used to produce shop signs? What about the components of aerospace engines?

Let’s find out!

• Carbon steel sheet is often used when corrosion is not a concern.  It can be used for anything from car bodies to store signs. The reason for its versatility is because it is relatively affordable and has superior tensile strength when compared with copper and aluminum.
• Galvanized steel sheet is a form of carbon steel sheet metal that is frequently used in automotive parts and greenhouse equipment, buckets, irrigation pipe and marine vessels.
• Stainless steel sheet is typically more expensive because it can withstand corrosion and is widely used in aerospace engine components, marine structures and vessels, pharmaceutical processing equipment and food handling equipment. Stainless steel sheet also has good aesthetic appeal that makes it popular for signage and appliances.
• Aluminum sheet is lightweight and quite resistant to corrosion. Aluminum sheet is used for boat components, marine structures, cookware, automotive parts, and aerospace parts.
• Finally, copper sheet is known for its electrical conductivity and is used in resistance welding equipment or certain types of battery systems. Because of its malleability and superior aesthetic qualities, it is also commonly used in home decor and other forms of artwork.

If you are interested in sheet metal production techniques, you can check out the free Masterclasses offered by the Italian company Dallan Spa.  They specialize in the production of profiling lines, punching machines and laser cutting of thin materials.

Sheet metal manufacturing: Quality Control

However, to be competitive, sheet metal manufacturers can’t stop at basic processing. Especially when many of the parts they make will end up in important structural applications, including beams, cross sections, rail tracks, the body of different vehicles, and even the fuselage and airplane wings.

Among the things just mentioned, sheet metal manufacturers need to guarantee their products are strong and durable enough to cope with the operational demands of such applications.  They also have to make sure surfaces can resist exposure to extreme temperatures and harsh environments. Think of the components in the body of an airplane and you will get the idea.

How to make this possible?

Many people think quality control refers to identifying defective products and discarding them before sending a batch into the market.

However, according to ISO 9000:2015 section 3.6.2, quality is “the degree to which a set of inherent characteristics of an object fulfils requirements.” And this means that manufacturers must ensure that the parts are made to design specifications and will function properly.

Dimensional verification

Quality Control in the sheet metal industry usually involves the verification of dimensional properties such as straightness, flatness, circularity, concentricity, cylindricity, perpendicularity, parallelism, profile, and runout.

These dimensional properties are usually verified with measuring instruments such as calipers, micrometers, and the resulting measurements must fall within the expected tolerances.

But quality control in the sheet metal industry is not just about dimensional verification.

Destructive and non-destructive testing (NDT)

Manufacturers also need to guarantee hardness, strength, and durability. To do so, they need to verify those properties on the final product. This is generally done with destructive and non-destructive testing (NDT) control instruments, which include:

• Instruments for checking the applied force
• Tensile strength tests
• Compression strength tests
  
• Flexion strength tests
• Cutting strength tests
• Hardness testers

As mentioned above, surfaces must resist exposure to extreme temperatures and harsh environments, but metals are usually prone to change or lose their mechanical properties in these situations. We all have seen how corrosion attacks metal parts near the ocean.

Sheet metal manufacturing: corrosion resistance

Apart from using metals that may have a higher corrosion resistance, manufacturers can use some surface finish techniques like coating to improve these properties. Naturally, this also requires quality control to guarantee that it actually works.

Let’s look at the case of our customer Dukometal SA as an example.

Quality control for sheet metal coating: Dukometal SA

While Dukometal SA specializes in sheet metal manufacturing with stainless steels, they offer a powder coating service they call “Thermopowdering” which they use to provide an even higher level of quality.

Dukometal SA’s powder coating is a type of thermosetting powder coating typically applied by electrostatic spray deposition (ESD) and then cured under heat.

They offer specific advantages, such as:

• Emitting little or no volatile organic compounds (VOC), unlike liquid coatings.
• Creating a more durable finish than conventional paint.
• Producing much thicker coatings than conventional liquid coatings without running or sagging.
• They can be recycled, so it is possible to achieve nearly 100% use of the coating.
• Capital equipment and operating costs for a powder line are generally less than for conventional liquid lines.
• Horizontally and vertically powder-coated surfaces have a more uniform appearance than liquid coated items.
• A wide range of specialty effects can be achieved that would otherwise be impossible with other coating processes.

Dukometal SA quality control

When it comes to the quality control of these types of coatings, several aspects must be considered.

The coating obtained needs to be tested for crack resistance and the stripping performance. This can be done with a Cylindrical Mandrel Tester which should be in compliance with standards ISO1519 / ASTM D522 / DIN53152.

Adhesion of the coating is also critical. This will ensure the metal is not exposed caused by coating peeling. Therefore, a cross hatch adhesion tester is recommended.

Coating thickness is verified with a coating thickness tester to guarantee the uniformity of the coating.

The properties of powder coatings need to be determined before, during and after the temperature induced curing step to understand how a certain formulation will work with a specific processing step, as well as the actual application of the finished part. Therefore, Dukometal SA relies on our portable pH and conductivity meter to verify anywhere and anytime they need it.

Instrument calibration

It is also important to keep all these instruments calibrated, otherwise false results could mislead the quality control inspections.  This is why we not only provide our calibration services to Dukometal SA but also to all our customers.

We’ve come to the end of this article on sheet metal manufacturing and quality control.  If you’ve found it interesting, you can share it with your colleagues and on social media. Content is even more useful when it is shared with others.

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