The assumption is that engineers already use 3D printing machines for prototyping and will soon use additive manufacturing machines for production. But is that an accurate assumption? Results from a recent survey give intriguing data.

Leslie Langnau • Managing Editor

3D printers were initially developed to build prototypes of an engineer’s designs. Over the past few years, it became obvious that these systems can also be used for final part production. Thus, some observers see a territorial battle between additive manufacturing (AM) and traditional machining technologies. The reality, though, is that such a battle won’t occur, at least not for many years, if ever.

First, CNC machining technology is not standing still. Siemens, for example, introduced four-axis turning on lathes. Two turning tools, opposite one another, machine the work piece simultaneously—reducing machining time. Such developments will make it all the more challenging for AM to reach machining speeds.

Second, a recent survey* we conducted with our engineering audience showed engineers still have a strong preference for traditional machining, even for the task of creating prototypes.

Here’s a closer look at the questions we asked and the answers we received.

How many prototype iterations?

We asked our audience how many prototypes they make before reaching the final design. On average, 30% of the respondents make three prototypes for a new product; 21% make two prototypes.

A criticism of some 3D printing machines is that they don’t deliver a high enough quality prototype. But, just how high a quality is really needed? We asked respondents to rate quality on a scale from 1 to 5, with 1 equaling a rough prototype and 5 equaling quality and accuracy that replicates the final design.

For the initial prototype, nearly one-third (32.05%) of the engineers responding wanted decent looking quality. More than one-quarter (28.21%) of the engineers wanted an initial prototype that was better than a rough realization. For about 17%, a rough prototype was good enough.

Not unexpectedly, after the first iteration, more engineers (38.36%) wanted a higher quality prototype. Nearly one-quarter (23.29%) wanted a prototype that is closer to the final look needed.

At the third iteration, more respondents (31.94%) are looking for a version more finished than the second prototype iteration; 29.17% are looking for a near finished version; and 22.22% do not use prototyping for this stage.

Which customers need high quality prototypes?

The needed quality of a prototype varies for the different departments designers interface with. We asked, “On a scale of 1 to 5, rank the quality needed for manufacturing, the end customer, marketing, upper management and other.” One equaled a rough prototype and 5 equaled a prototype that replicates the finished product.

Of course, high-quality prototypes are needed for the end customer, said 50% of the respondents replying to this question. Then, 30% said the marketing department needs high-quality prototypes.

Only about a quarter of the respondents needed a high-quality prototype for manufacturing. For the other departments, the need was low.

Prototyping equipment

When asked what process was used for the initial prototype, the surprising answer was CNC machines, with more than two-thirds (67.61%) of the respondents turning here first. The next most popular process for initial prototyping was stereo-lithography and extrusion, at 42.25 and 43.66% respectively. About one-quarter (25.35%) used polymer powder bed technology. 18% use polyjet, and 18% use laser sintering. Finally, 17% use injection molding.

For the mid-level prototype, again CNC was the favored choice at 55.71%. Stereolithography and fused deposition modeling came in at 43% and 30% respectively. Injection molding came in at 22.86%.

For the final prototype, CNC machining received 71% of the replies. At this stage, though, injection molding comes in at a distant second of 37.66%. Stereolithography and extrusion came in at 28.99% and 21.74% respectively.

What type of 3D printer?

In general, there are three classes of 3D printing machines: professional units that typically cost more than $25,000; professional desktop units priced between $25,000 and $5,000; and entry-level desktop units that are priced at $5,000 or less. The majority of the survey respondents use a professional 3D printing machine when they use a 3D printer. But the next most used printer, said 61.76%, is the entry-level type, especially for initial design and prototyping tasks. About one-fifth (20.59%) continue to use entry-level 3D printers for second and third stage prototyping.

Whether an entry-level 3D printer satisfies prototyping needs, though, the answers were 52.94% saying yes, 47.06% saying no. The respondents were given a chance to write in the features they would most like to see from entry-level 3D printers. Better quality, more material options, larger build size and higher resolution were the most often requested, with materials and size leading those choices.

Based on their experience with entry-level 3D printers, 43.28% would consider buying a higher priced professional 3D printer. 32.84% would not. The reasons range from no budget or no need to a need for a variety of 3D printing processes and cost.

Outsourcing versus in-house

3D printers were initially created out of frustration—it took weeks to get a prototype from a service bureau. Today, though, outsourcing is still a popular way to get prototypes—64.18% of respondents outsource the prototype soon after the CAD design. 38.81% outsource when they are closer to a final product design, and 37.31% outsource after they have done a few rough prototypes in house.

Service bureaus have improved on prototype deliver time, which seems to satisfy engineers. Most respondents need their prototype in about 3 to 7 days (55.22%). Less than a quarter (22.39%) need a prototype in two days.

3D printing is also viewed as helping to lower the cost of prototypes, especially when compared to outsourcing. However, according to our respondents, cost is not a huge issue. 40.30% said cost somewhat affects their choice. 31.34% said it affects a lot, and 28.36% said not much at all.

Materials

When it comes to the material respondents want for their prototypes, 59.70% want a material that can handle testing and fit. Almost 20% want the exact material needed for the final design. Materials desired include carbon fiber, stainless steels of the 303/304 and 174 variety, low carbon steel, and higher resolution and high temperature materials.

Based on these results, one might be tempted to question the future viability of the 3D printing/additive manufacturing industry. First, these results cover only a small segment of the 3D printing population, and the questions did not address the unique capabilties of this industry, such as cost-effectively making geometrically complex parts. While these results are interesting, they are only part of the bigger picture. n MPF

*Survey was conducted by email over the Design World subscription list.