Understanding Sheet Metal Fabrication Stages: Prototype, Batch Production, and Mass Production (Updated for 2025)

Last updated on March 24th, 2025 at 09:32 am

Do you know the differences between the prototype, batch production, and mass production stages of custom sheet metal fabrication?

While most metal fabrication shops use similar equipment to create parts, shops have different mindsets and approaches regarding these three manufacturing stages.

Understanding the specifics of each stage will help you know what to look for when seeking a sheet metal fabrication partner.

Prototype Sheet Metal

A prototype is a mock-up of your part that enables you to test the function, quality, and finish before manufacturing the part at a higher volume. Prototypes are typically made in quantities of 1-25. (At our metal fabrication shop, the exceptions to this rule are assemblies with more than five fabricated components and tubular frames.)

During the prototype stage, also referred to as part development, you may find that you’ve overengineered certain features. You’ll then have the opportunity to optimize your design for manufacturing at scale-which is crucial to maintaining reasonable costs and lead times.

Prototyping also allows you to validate product interest. For instance, you might take a prototype to a trade show and gather feedback to determine if there is a market for a product before you invest in scaling it.

Prototyping at Approved Sheet Metal

At ASM, we often say that we love “Quantity 1”-the prototype.

Some metal fabrication shops take on prototypes merely as a stepping stone for securing production work and may show limited interest in helping customers perfect their designs. But at ASM, we specialize in prototypes. We find it highly rewarding to set customers up for success from the very beginning of their manufacturing journey.

We excel at part development because we have not only the engineering expertise and technology to make exceptional prototypes but also a genuine interest in helping customers optimize their part designs. Our team even provides design reviews to identify potential red flags in customers’ designs.

Although our prototyping costs may run slightly higher than other shops, the work we put into improving a part’s manufacturability often results in cost savings in production一not to mention a higher-quality end product.

Batch Production

Once your prototype has been validated for fit, form, function, cosmetic appearance, and market demand, you’re ready to move on to low-volume production (i.e., batch production). This stage can be considered an introductory or growth period for your part.

During batch production, parts are manufactured in batches ranging from 25 to the hundreds or even the thousands. Here, the attention paid to optimizing manufacturability in the prototype stage begins to pay off.

For example, custom tooling can become quite costly during batch production, particularly if the tooling wears out quickly. A strategically designed prototype can help you avoid this outcome. In a case like this one, we would have likely recommended design changes during prototyping that would allow us to use standard tooling in production.

Batch production at Approved Sheet Metal

We frequently handle prototyping and batch production for customers, as well as standalone batch production.

Partnering with our metal fabrication shop for both manufacturing stages ensures that your part will be designed for manufacturability from the beginning. We know what red flags to look out for in the initial stage of your project and can ensure a frictionless transition from one stage to the next.

Mass Production

As the name implies, mass production is the highest-volume phase of production. However, how shops define mass production can vary. At ASM, we define mass production as sheet metal manufacturing in volumes of thousands or higher.

Mass production is entirely different from batch production. In this stage, high-quality tooling and automation capabilities become extremely important. A metal fabrication shop specializing in mass production services might have an entire line and set of tooling dedicated to a single project to accommodate the volume of parts required.

Mass production at Approved Sheet Metal

At ASM, we don’t typically offer mass production, as our capabilities are better suited to prototyping and batch production. However, we do consider mass production requests on a case-by-case basis. Depending on the part, we might be able to manufacture mass production volumes-so be sure to ask.

Surface Finishing and Secondary Processes

Surface finishing plays a crucial role in the performance, durability, and appearance of sheet metal parts. From prototypes to mass production, the choice of finishing method affects manufacturability, cost, and assembly fit. Understanding how these secondary processes impact different production stages can help engineers make informed design decisions.

1. Common Surface Finishing Processes

Each finishing process serves a specific purpose, whether it’s corrosion resistance, wear protection, or aesthetic appeal.

Process	Purpose	Typical Thickness	Considerations
Powder Coating	Corrosion resistance, aesthetics	0.003″ – 0.010″	Thick coating may affect part fit; masking needed for critical areas
Anodizing (Type II)	Corrosion resistance, color options	0.0002″ – 0.001″	Can reduce hole diameters; good for aluminum parts
Anodizing (Type III)	Hardcoat for wear resistance	0.001″ – 0.003″	Adds significant hardness but may impact reassembly
Zinc Plating	Corrosion protection	0.0002″ – 0.0005″	Minimal effect on fit but still requires tolerance adjustments
Wet Paint	Aesthetic appeal, light corrosion resistance	0.001″ – 0.004″	Thinner than powder coating but requires proper adhesion
Electropolishing	Smooth, corrosion-resistant finish (stainless steel)	Negligible material removal	Improves surface quality but doesn’t add coating thickness

2. Impact of Surface Finishing on Production Stages

• Prototype Stage:

  • Finishing is often secondary to design validation, but quick-turn finishes like anodizing or wet paint may be applied for functional testing.
  • Engineers should anticipate how coatings will affect tolerances in later production runs.

• Batch Production:

  • Finishing considerations become more critical, especially for repeatability and fit.
  • Masking strategies for critical surfaces (e.g., grounding points, threaded holes) should be established.
  • Testing with small batches can help validate coating thickness and its impact on assembly.

• Mass Production:

  • Process consistency is key-automated finishing lines are used to maintain uniform coating thickness.
  • Bulk processing efficiencies (e.g., racking parts for powder coating) must be considered.
  • Tolerances must be adjusted in CAD files to account for finishing buildup.

3. Best Practices for Engineers

✅ Adjust Hole Sizes & Clearances – Account for coating thickness to prevent interference fits.
✅ Specify Masking Requirements – Avoid coating buildup on mating surfaces, threads, and contact points.
✅ Choose Pre-Finished Materials When Possible – Pre-anodized or pre-plated sheets can reduce post-processing time and cost.
✅ Test with Coated Prototypes – Ensure fit and finish before scaling up to batch or mass production.
✅ Work with Your Fabricator – Define finishing requirements early to avoid costly modifications later.

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Sheet Metal Fabrication Stages: Prototype, Batch Production, and Mass Production FAQ

What distinguishes the prototype stage from batch and mass production in sheet metal fabrication?

The prototype stage involves creating a mock-up of the part for testing functionality, quality, and finish before scaling up production. It’s typically for 1-25 parts. Batch production follows, producing parts in low volumes (25 to hundreds or thousands), while mass production is high-volume (thousands or more).

Why is prototyping crucial in sheet metal fabrication?

Prototyping allows for testing and validation of designs before committing to larger production runs. It helps optimize part designs for manufacturing at scale, ensures market interest, and identifies potential cost-saving opportunities by refining the manufacturability of parts.

What sets apart Approved Sheet Metal’s approach to prototyping?

At ASM, we specialize in prototypes and prioritize helping clients perfect their designs. Our team offers engineering expertise, conducts design reviews, and invests in improving a part’s manufacturability. While our prototyping costs might be slightly higher, the resulting cost savings in production and higher-quality products make it worthwhile.

How does batch production differ from prototyping?

Batch production follows successful prototyping, manufacturing parts in increased quantities ranging from 25 to thousands. Optimizing designs during the prototype stage helps in batch production by avoiding costly custom tooling and ensuring smoother transitions between manufacturing stages.

Does Approved Sheet Metal offer mass production services?

ASM primarily focuses on prototyping and batch production but considers mass production requests on a case-by-case basis. While our specialization lies in earlier stages, we’re open to discussions regarding mass production depending on project specifics. Clients are encouraged to inquire about mass production possibilities for their parts.