Most new parts change several times as they evolve from a conceptual drawing to a physical object in the real world. By the time a new part is ready for prototyping, you’ve made drawings, calculations, and prepared extensive documentation (and if you’re working within the automotive industry, you’ve also spent countless hours on the Production Part Approval Process, or PPAP). And now it’s time for functional testing or evaluating fit within an assembly. Even though industry requirements, designs, and manufacturing processes change over time, the goals of prototyping don’t: proving out a concept, mitigating the risk of part failure, getting to market on schedule, and minimizing costs. Here, we offer four tips for working with a precision stamper on prototype parts.
1. Define what you need from the prototype.
What will you do with the prototype parts? Just how many of the part’s dimensions, features, and finishing are included in a prototype depends on what you plan to do with it. It also affects the costs of materials and stamping since more steps, materials, and finishing add to production costs. The key is to determine which features you need (and which you don’t) at this stage so you aren’t paying for manufacturing work and production steps that aren’t necessary.
Usually, prototype parts fall into these three categories:
- First Off Tool (FOT) refers to parts in “as-is” condition right from the die, with no further finishing, and are generally the least expensive
- Correction Loop 1 (C1) parts are manufactured with critical dimensions within tolerances
- Correction Loop 2 (C2) parts have all dimensions within tolerances and most of the finishing the final production run parts will have
A C1-level part is often sufficient for prototyping needs, provided you specify exactly what you want to accomplish with the part and what features are required. For example, if you need to check how the part fits within an assembly, you’ll want to define which dimensions are critical to fit. These commonly include interface dimensions like thickness (for insertion), width, length, and locating features like notches, cutouts, or bends. If you need parts for testing, you’ll probably want to include things like plating and coining that may impact test results or part performance.
2. Factor in materials and availability.
Materials and obtaining them in the timeframe and quantity you need affect costs and production schedules. If the part design calls for a specialty material, such as food-grade stainless steel, corrosion-resistant metal, or a certain conductivity for example, will that affect the validity of this round of testing or does it only matter for the finished part? For example, if you’re checking part fit in an assembly, material probably isn’t critical until you require a functionally representative sample.
The small quantities used in manufacturing prototypes drives up materials costs, if they are available in small quantities at all. If you know you’ll end up using the specialty material, a bulk order may make sense at this point, but it all depends on your budget, projected production schedule, and goals for time to market.
Another important consideration is identifying multiple suppliers for specialty materials, or even a suitable substitute material in case of supply chain problems once production starts. If a material shortage creates production challenges down the road, you can help things stay on track if you’re open to working with more than one source for materials.
3. Provide part prints and key information.
As the part designer, you’re the expert on it and its intended use. But the precision stamper is your partner in creating the best possible part, so it’s in your best interest to provide as much information as possible during prototyping.
Even if dimensions and tolerances aren’t finalized, it’s always better to include a number and then revise it later rather than it is to add new dimensions down the line. Why? Because your stamper will interpret a blank or missing dimension as unimportant to your design, or that it can be any value that works with the manufacturing process. If you don’t provide a ballpark value for a feature, it won’t be considered and could throw off your tests.
Likewise, knowing the design intent of a part helps your stamper understand the goals for it. Armed with these details, they may be able to offer suggestions or modifications to more efficiently and reliably achieve them.
Give your stamper a part print with as much information as possible, even if you have only “rough” or estimated tolerances and specs at this point, for example:
- corrosion resistance requirements, either specific (e.g. 24 hours with no red rust after 72 hours), or simply noting there will be a requirement (e.g. no red rust after 24 hours, exact timing TBD)
- interface points with other parts/assemblies or critical areas of the print
- assembly drawings and models of how the part functions and interfaces, which can guide manufacturing strategies
- notes as to how many dimensions the final product might have, even if the prototype includes only some of them
It’s also helpful to let your stamper know if a part is one of a “family” or group of similar parts. In some cases, it may be possible to save costs with changeover tooling that can accommodate multiple variants of a part.
4. Collaborate with your precision stamper.
Ideally, your intimate knowledge of the part and its design intent will be complemented by your stamper’s experience and expertise in production methods and design for manufacturing (DFM). Some points they can advise on include:
- efficient strategies for batch production (e.g. monthly or quarterly quantities)
- feedback on the manufacturability of parts as designed and options for achieving part goals
- options for specific manufacturing practices to achieve critical dimensions or features (e.g. set bends with a small step to lock it in place, use a 0.010” radius on all sharp corners, coining to ensure there are no burrs)
Be sure to communicate any changes you make as a result of testing your prototype parts, especially if the changes affect the next iteration. For example, if a stamped terminal is being inserted into a molded assembly, and you decide to adjust the mold instead of the terminal, let the stamper know as it may impact tooling or other aspects of production.
As work progresses, be mindful of barriers to collaboration, conscious or not. When you’ve worked closely on a design for the months through the PPAP process, it’s not uncommon to feel protective of the time and effort invested. Do you or your internal team feel hesitant about your stamper’s input? If so, consider whether you are:
- committed to the original design because it was first and seems good enough (especially if schedules are tight)
- experiencing “investment bias” or the “endowment effect,” developing a preference for a certain version because of the time spent on it
- spending an inordinate amount of time on theoretical aspects of the design and not enough on manufacturability (especially if you have limited exposure to precision stamping production methods)
- discouraged by a setback or lackluster testing results
Choosing an experienced precision stamper is only one aspect of successful prototyping. Your role as their customer is to keep lines of communication open and share information to keep your project moving through the development process and into final production. If you’re looking for an expert partner, we can help.