Prototyping Versus Production—Still Think They’re Different?

The line is blurring as digital players like Xometry add more capacity to their networks.

Xometry has sponsored this post.

In the traditional mass production world, there were some basic rules: products went from the drawing board, to prototypes, to pilot production and finally to mass production. In today’s economy, however, 1,000 or 10,000 unit minimum orders are frequently impossible. Customers want high levels of customization, and they want it at mass production prices. It’s a challenge across every manufacturing sector, and the pressure is on for designers to deliver prototypes which may be more than just prototypes.

Prototypes—often made by hand—frequently go through several iterations, from fit or functional checks to proof-of-concept units for stakeholders from engineering, purchasing, marketing and even end-users. Automotive OEMs are a typical case. For devices that are expected to be mass-produced, the next step would be pilot production, or a short run used to build a small fleet of cars for test and validation purposes before approval for production. These pilot runs could be in volumes from dozens to hundreds, and are still an essential part of “running off” new assembly processes before mass production. Pilot units designed to validate assembly processes were frequently manufactured with short run or nonproduction tooling, merely to compress development time for complex and time-sensitive products such as motor vehicles.

But what if tens of units represent the actual production run? This grey area between prototype, pilot and production has traditionally been the territory of the custom shop, supported by a local or regional network of equally small supplier companies. This system worked for decades, but ironically its inflexibility shows up not when order volumes fall, but when they increase to true mass production volumes. An order increase from 150 to 15,000 can be just as deadly to profitability for a traditional niche manufacturer as having no order at all.

So, what are production volumes? For marketing, the optimal lot size is whatever the customer orders, but scale economies and the many step functions between no-tooling, prototype tooling and production tooling can make or break the profitability of a job. The ability to make money at the 100-unit level is not a guarantee of profitability at the 1,000-job task. Flexibility matters.

Xometry Enables Mass Customization at High Volumes

Xometry allows for the custom sourcing of parts through an integrated network of over 5,000 suppliers across 46 U.S. states and 22 countries. The on-demand manufacturer offers capabilities ranging from a 3D printing service and a CNC machining service to injection molding, sheet metal fabrication, urethane casting and more. Xometry’s applications extend from prototyping to production, and the platform is self-healing during a pandemic that has been rampant with supply chain disruptions.

(Image courtesy of Xometry.)

(Image courtesy of Xometry.)

“We’re mostly building discrete parts, which are then being put into assemblies,” said Greg Paulsen, director of applications engineering at Xometry. “We also have assembly services, which we’re launching more and more—so we’re moving further along the value chain.”

Xometry has no minimum orders, significantly lowering barriers to entry when it comes to production-viable methods and materials. The distributed manufacturing platform is also capable of producing large volumes at high levels of customization, with the ability to pull off the production of as many as a million parts.

“Millions of dollars worth of equipment infrastructure is now a web widget, which is something really unique,” said Paulsen. “For me, the bigger change is just that accessibility.”

The ability to address fluctuating or fast-turn customer demand without causing chaos in established production systems is the secret of success for companies who use smart contract manufacturing. It is not only a benefit for quality and delivery; CapEx is the ultimate in opportunity cost. Dollars not spent retooling for a production run are dollars that can be spent to develop new products or expand operations. There are advantageous network effects, too.

Distributed manufacturing platforms such as Xometry can provide flexibility by enabling companies to try out a new concept with less upfront risk. This frequently allows designers to iterate their way to success with actual hardware, rather than devoting time and resources to expensive design tools such as computer simulation.

Regulated industries are especially vulnerable to costs incurred through mandated changes. The so-called ‘letter agencies’ are generally oblivious to development cost—and if the FDA, DOT, EPA or UL change a regulation, customers may not be willing to absorb additional costs or delays. The ability to rapidly iterate designs through Xometry’s integrated network offers significant advantages when dealing with regulatory agencies who may take weeks or months to certify new products or designs.

Nonregulated markets such as consumer goods can still use the distributed model to their advantage. Test marketing with functional prototypes that work, look and feel like production units speeds the market research function, and enables design engineers to incorporate user feedback quickly and at low cost.

Design Considerations in Prototyping and Production

Design changes create multiple costs in traditional manufacturing operations. The first is an information management problem, requiring potentially dozens of renderings in the hands of everyone from subcontractors to production personnel to be revised, and policed to ensure everyone is “on the same page.” Production equipment must be reconfigured and frequently retooled—and if further changes are expected, even simple tasks such as die or mold changes can wreak havoc with production scheduling. The ability of new products to cause chaos with production timelines for existing products is a well-known phenomenon in manufacturing. The distributed model can be an excellent solution to this problem.

For Paulsen, it is essential to evaluate where customers are within their product development cycle, in order to distill their immediate needs against a long-term vision of their requirements.

“I use the phrase ‘six weeks, six months, six years,’” explained Paulsen. “Where do you see this product six weeks from now? Sometimes customers think they are in production, even though they just have an idea that isn’t quite there yet. They may not have evaluated the market. It could be a concept model, or iterations for rapid prototyping. At six months, you can have a lot of different processes, up to pilot runs with thousands of real end-use products. It may not even be the same process for creating 100,000 parts. For example, CNC machining may evolve to die-casting and injection molding, which may further evolve to multi-cavity steel production tooling for really big volumes.”

With the increased availability and ease-of-use of computer aided design (CAD) packages, more engineers not traditionally involved in design are now rendering parts. One consequence of this is the risk of renderings that do not correctly address geometric dimensioning and tolerancing (GDT) issues. Some engineers have a tendency towards over-tolerancing, due to their lack of background in design for manufacturing (DFM). Excessively tight tolerances on a nonessential dimension can double—or even triple—the cost of a part. Xometry serves to educate customers on how close a tolerance they would need for each process, whether it is CNC machining, 3D printing, stamping or milling. The aim is to strike the right balance between manufacturing cost and part function, at the lowest reasonable cost.

(Image courtesy of Xometry.)

(Image courtesy of Xometry.)

“Xometry has plenty of resources for those who are in the design phase,” said Paulsen. “We offer over a dozen different manufacturing technologies, with each process having its own unique guidelines and nuances. Along with our free design guides, it is interesting to have conversations about prototype designs and production-viable methods. We discuss things like design for injection molding, eliminating undercuts and drafts, reducing tool pricing, adding variable wall thicknesses. We even talk about how to consolidate some of these features to reduce part count overall—which becomes important when upfront tooling costs are a driver, especially if you’re just entering a market.”

Plastic injection molding is a typical example. Production tooling is very expensive, and low-cost prototype molds historically lacked durability and produced parts below production spec and surface finish, requiring postprocessing. A 100-shot tool life, however, was acceptable during the development process. Today, newer prototype molds have life that may be measured in thousands of shots, blurring the line between prototype and production runs. The ability to use a single cavity test mold to run a significant volume of parts can have the effect of driving designers to optimize their parts early, in order to take advantage of the head start that more durable, low-cost tooling can provide.

“The design may just get to a ‘good enough’ stage where they’re looking for market validation of 1,000–2,000 parts,” described Paulsen. “Some things like ribs and wall thicknesses may not be fully simulated, but they may mold. We give customers around ten good shots off the mold as T1 samples, which are not counted against the production run.”

“Before going through a secondary process like mold texturing, we make sure the parts fit and function is correct,” continued Paulsen. “If there is some light grooming to do on the T1s, we do it to get acceptance. Once accepted, that is the production part. We add tolerances to those parts and carry out coordinate-measuring machine (CMM) inspection to hit critical tolerances. Sometimes there’s a little bit of discovery post-mold as well, especially if you’re not doing full-on production.”

Once prototype designs have been refined, texturing processes are applied to the mold. Xometry has a number of best practices for dealing with issues such as sink marks and gating.

“Texturing is an amazing tool for mitigating sink,” said Paulsen. “Adding matte texture to an additive component can also help hide some of its layer lines without investing in prohibitively expensive add-ons.”

Paulsen recommends strategizing production methods based on the end use of the part.

“Say I’m doing a part that will eventually be die-cast in high-level production metal, or even investment cast,” explained Paulsen. “CNC machinery is an extremely viable option for low volumes. You may need to modify your CAD. As you move further down the line, DFM rules for CNC machining are typically the same as for fused deposition modeling (FDM) 3D printing. So, if you want to validate a shape in a day for putting it together with the rest of the assembly, you can use a 3D printing process to do that.”

While working towards a molded process, 3D printing methods can be utilized while thinking through the design, particularly powder bed fusion processes such as multi jet fusion (MJF) or selective laser sintering (SLS). Higher-fidelity 3D printing processes such as PolyJet or stereolithography (SLA) can subsequently be used for fit checks. It may be advantageous to use both processes during product development. Finally, molds can be committed for volume production.

“The tooling conversation can take place in parallel as iterations occur, because you can start getting budgetary costs and talking with our tooling team as your revisions are updating,” said Paulsen. “Once the components fit together as part of the finalization process, we could go and kick off a tool with you.”

In some cases, it doesn’t make sense to move to tooling at all.

“Because of their fairly low z-height, smaller pieces are very production-viable with additive manufacturing,” asserted Paulsen. “Carbon digital light synthesis (DLS) is one of those additive components that can scale up to the thousands for small pieces and can actually be your end-use production tool. The only caveat is the surface finish and material properties of the parts. If the parts function mechanically, they are generally accepted by the marketplace.”

The Xometry Difference

Platforms such as Xometry are great for just-in-time manufacturing or the reduction of inventory stock.

“If you need twelve a year, you can make twelve a year,” said Paulsen. “If you need one today, we can get one on order. The pricing is low enough to be justified, versus buying hundreds extra units of a part in order to hit a minimum order threshold.”

“It’s a fuzzy line now between prototyping and production, especially when it comes to what the expectation is,” added Paulsen. “What is the ultimate goal? I like to take all these processes instead of categorizing them in certain echelons—just put them on the same playing field and compare pricing and lead times by toying around with our site. They are all tools in a product development cycle, and you have a little bit of everything on your desk by the end of it. We build a relationship that is more than just ‘I make your parts.’ That’s something we really value, and it helps our customers save in the long run.”

To learn more about Xometry, visit their website.