Designing high performance parts that are low cost, light weight and durable isn’t the end goal of mechanical engineering – it’s the start. It’s in the manufacturing of the part where we find the true test of design excellence.

Converting renderings into reality is a major issue for many design engineers. As designs become more and more complex, it’s also common for engineers to specify manufacturing processes that are beyond their available in-house capabilities. Many designers may also have no local resources available for prototype and pilot-run production.

Maryland-based Xometry has created a novel solution to the capability and resource problem that’s deceptively simple: connect part designers with part makers across the U.S. who offer a broad range of capabilities.

“It’s about efficiency,” said Greg Paulsen, director of the project engineering group at Xometry. “We take a process that has traditionally not been very streamlined and not been very fast, or the most friendly, in terms of engineering time, and we’ve been able to cut that time dramatically. It’s not about the design time; it’s the time that an engineer has to take to sit down and go through the process of tweaking and making compromise changes based on each manufacturer’s ability to make the part.”

“When you have extra hours in your day,” Paulsen added, “You can design more products, or do other things that you actually enjoy doing, instead of going through the monotonous process of ordering parts.”

Xometry and their nationwide network of manufacturing partners offer a wide range of manufacturing processes:

This wide range of capability addresses a key element of product development; namely the problem of moving a part or device from prototype to mass production.

Urethane casting parts. (Image courtesy of Xometry.)

Prototypes are often simplified functional models and can be made quickly and cost effectively with 3D printing or urethane casting processes. Pilot or test run quantities, typically in the tens of units, may require machining or fabricating techniques. Lastly, mass production will very often use a full CNC or automated fabrication process to achieve the lowest unit costs.

The product designer must also frequently order parts through a RFP system that must talk to different shops at each step in the development process, adding time and complexity to the work flow.

Greg Paulsen explains it this way:

“As an engineer, you typically prepare a data package up front, which would require 3D CAD files and usually a 2D drawing and a 3D isometric. Often accompanying that is a spreadsheet asking for the quantities and price breaks. Then you are going to zip it up and send it out via email to several potential vendors, who in turn may send it to subcontractors for other technologies such as CNC machining.”

For multiple vendors with multiple processes, the problem begins to create the management equivalent of “tolerance stack”— when pricing or performance issues with one vendor ripple through the chain, forcing a re-quote or, in the worst-case scenario, a completely new RFP. If a new quote shuffles the manufacturing batting order, what happens to quality and delivery?

“You can see a high variability in the cost of the same part amongst multiple vendors,” related Paulsen. “And then you have to decide, ‘what is quality’? If a shop is much cheaper, is it because they just do it better? Or can they produce with the quality that I need? There are a lot of questions in that variability.”

And variability comes in two forms: process-derived and designed in. The former can be addressed by choosing a manufacturing technique that’s capable of delivering the accuracy and repeatability demanded by the design.

This is not a trivial issue, especially in additive manufacturing, where the difference between the 3D printer’s optimal performance and what it can do with your part can be miles apart.

Paulsen noted that the success or failure of a part is often determined long before metal is cut or powder sintered. “When you talk about accuracy and repeatability, it often comes down to design. When I speak to an engineering client, the conversation usually comes down to a discussion of build time vs. cost. They say, ‘I have a design like this. I need it at this time’. I then describe the processes and the tradeoffs available. This is also where our team of expert design engineers can step in to offer suggestions to streamline the process.”

Xometry routinely works with customers to suggest design improvements in order to enhance manufacturability. Design for manufacturing is dependent not only on the part attributes, but also on the process used. Right angle internal corners, for example, are difficult to machine, but are relatively easy for a laser sintering metal 3D printing process. But can 3D printing deliver the cost and surface finish needed?

It’s all about tradeoffs, which a part designer can ideally handle by thinking ahead to the manufacturing processes available. Often a simple, non-essential attribute change can cut costs dramatically. A chamfer in place of a knife edge is one example, or having a radius in place of a 90 degree angle. Thinking about changes for manufacturability also opens the door to alternate or multiple processes such as urethane casting or sheet forming.

Thinking About Multiple Processes

3D printed parts. (Image courtesy of Xometry.)

Why use more than one process? In the traditional product development life cycle, prototypes and pilot production runs are often not built to full production specifications, especially in terms of materials. Prototypes may be needed strictly for form and fit checks or for cosmetic reasons, and can be made faster and more economically using non-production technologies.

Using technologies such as 3D printing or urethane casting makes it possible to produce quantities in the dozens to further validate the design before cutting metal for production tooling. Manufacturing flexibility also gives designers an extra advantage: the ability to check one component of the design, rather than the entire part.

As Paulsen explains, “If you are, for example, building a part that is eventually going to be made in one process, but all you want to do is test a feature or set of features or a fitment, you can. That’s the beauty of additive manufacturing, is it is very forgiving on what you ask it to make. You could actually create a cut or a slice with just that feature.”

“I highly recommend that users who are working on larger-scale assemblies actually look at their parts by their functional features and test each one individually. This is especially true if there’s a gasket seal on one end, for example, and the rest of it is very generic and very tried-and-true. You can save a lot of money by just testing that gasket seal area without actually building the whole part for every single iteration.”

CNC machined parts. (Image courtesy of Xometry.)

Material substitution is another area where significant cost savings could be realized. For CNC machined parts, low-cost utility grade aluminum or mild steel can substitute for expensive alloys for simple functional fit checks.

In some cases, metal part prototypes can be built additively, often from commodity resins. Low-cost materials represent one method of savings, but they can often be processed more quickly and cheaply as well, said Paulsen. “I may start in a very common commodity material which will be significantly more efficient, with both material savings and reduced cutting time in terms of CNC feed rate. For customers coming from a machining background, that’s what I see most often.”

Paulsen continued, “On the other side, if you’re doing a fitment or a setup, we most commonly use selective laser sintering (SLS) with white nylon powder. It’s watertight, very forgiving, durable and has some ductility to it. It’s possible to add features like tapped holes and inserts to make the part work for a functional test. And sometimes it turns into an end use part, especially if it’s a non-cosmetic piece. We see a lot of prototypes that eventually become a CNC piece, which started off in SLS.”

Faster Parts Through Faster File Handling

The ability to tweak, redesign and test multiple prototypes before making a production commitment is a time and money saver, but not all part designers are knowledgeable in all manufacturing technologies. This means that designers working with Xometry who are accustomed to a conventional RFQ process may not be taking full advantage of the benefits of the service.

Once 3D models are uploaded, Xometry uses computer algorithms to interpret the 3D model, determine the manufacturability and provide instant feedback based on the process that the user chooses, and then prices the job instantly. This allows the designer to use the Xometry interface as a costing tool, changing variables such as part quantity, material and desired manufacturing process to find the optimal cost/performance/delivery targets. Telephone and email support from Xometry is also available.

(Image courtesy of Xometry.)

“Nobody knows nine technologies perfectly,” states Paulsen “There may be someone who is the best CNC designer in the world, but they’ll go to FDM and say, ‘I’ve never built a part in FDM in my life’. We completely understand that, so we’re here to help our customers after they upload their parts.”

“They’re trying to make that trade off, and we can usually go look at their quote and help them make very quick decisions on going from here to there, and what the trade-offs are. That’s including our live feedback that we already have on our site with visual feedback.”

“For example, if I go from CNC, the part may look perfect. If I go with the same part and move to FDM, there may be thin wall features that are called out because I may not be able to build this, or if I do, the wall won’t be as structurally sound in this process.”

Paulsen recommends using the design guides available through the Xometry website, and suggests using the online quotation tool experimentally to get a feel for the available processes and capability.

Xometry works with all popular CAD file formats, but users in the SolidWorks community can use Xometry’s add-in and see the cost implications of design changes in real time during the design process.

The time and cost savings are obvious: used extensively, it should be possible to optimize parts before the actual quotation process begins, allowing the part designer to make internal decisions about the cost-benefit of specific part attributes. Need another hole in that bracket? Add it to the model, and instantly see how much cost it adds.

This also allows the designer to make speculative models; projects that may not be destined for production, but which demonstrate a principle or general theme that warrants further exploration. The effect is to remove considerable risk from the part R&D process, allowing more sensible budgeting in product development.

This is a new way to order prototypes and production parts, but just as importantly, it’s a new way to cost those parts.

“We offer transparency in the system,” said Paulsen. “We give you immediate feedback on the quote You can stop, make changes, click around and see the impact between different processes. Xometry’s system is itself a sort of manufacturing technology. Getting from part-to-part depends on the production technology, but can be held up in multiple ways during a conventional quotation process. Taking the paperwork out of the process, and letting part designers do what they do best, may be the most important part of the process.”

To learn more, visit the Xometry website.

Xometry has sponsored this post. All opinions are mine. --James Anderton