The Real-World Cost of a 3D-Printed Prototype
Kyle Maxey posted on May 15, 2017 | 4859 views

Short run, small scale manufacturing is becoming more popular and more accessible these days. Because the price of CAD software, prototyping and short-run additive manufacturing has continued to fall, just about anyone with a bit of training can begin designing. But just because you have the skills to design doesn’t mean that a design is going to come out perfect on your first go. Inevitably, something will go wrong in the model or prototyping or manufacturing stage. The trick to transforming a design into a manufacturable product is to try to foresee these issue before they appear, and design around them.

In this article I’ll be taking you through a design assignment that I got from Roopinder Tara, Director of Content at ENGINEERING.com. Just in case you need to know, I’ve been designing products for performance artist and small design firms for the past four years, and I’m also an instructor at my local community college where I occasionally teach students about mechanical design, prototyping and manufacturing.

The Task

Roopinder's sketch. It was my job to make it real.

Roopinder's sketch. It was my job to make it real.

I was stationed at my desk, pecking away at a story due the next day. The phone rang, and I recognized Roopinder’s number immediately. After exchanging requisite pleasantries, Roopinder got to the point: he was interested in creating an award for our authors who write articles for ENGINEERING.com that garner over 10,000 views.

Roopinder had a good idea of what he wanted the award to look like, and he sent over a few preliminary sketches. After some quick discussion about how the award would be manufactured, we decided that 3D printing would be the way to go.

There was just one catch: the award had to be designed and prototyped in 10 days. Not a lot of time to work with, but enough to get the job done.

Getting Started, and Dealing with Design Issues

With Roopinder’s sketches in hand, it was off to modeling. As you can see from the sketch, most of the modeling was straightforward. In less than half an hour I had most of the project sketched and extruded. The base, numerals and letters were easy to render, but there was one component of the model that confounded me.

As you’ve already noticed from the sketch, one of the critical parts of this design is the geodesic sphere that hangs in the middle of the award. Not only does this piece of geometry replace the “0” in “10K”, it also references ENGINEERING.com’s logo, sending home the message that this award is for achievements earned by writing well-received work.

Turns out modeling a geodesic sphere like the one that makes up ENGINEERING.com’s logo isn’t as easy as it might appear. I knew that it was going to be the sticking point of this design from the very beginning, but I hadn’t grasped exactly how tough that geometry would be to create.

If you think about it for a bit, you’ll realize that there’s no good way to make a complex geodesic sphere in a plane-based 3D modeling program. At least, that is, if you want to create a single model. Sure, you could make a component that could be assembled together, but that’s just trading off one problem, modeling, for another, assembly.

I was at an impasse, and I started to worry that I might not be able to deliver this project on time.

After speaking with a few designers that I know and a couple college professors, I realized that my conclusion was right. This geodesic was going to be too hard to create for a project that had to be turned around in short order.

My impasse turned into a quandary. And then, finally, I figured out what I needed to do to get the job done. The best solution for this problem wasn’t to model the geodesic myself, but to search for a pre-made model online.

After scouring a few sights, including GrabCAD and others, I found three geodesic sphere models that looked similar to the design that Roopinder had envisioned. I sent him links to these models and several hours later I had his response.

I was off and running again. And then I wasn’t.

The first model that I imported into my CAD package appeared as if it was going to work, but when it came time to export the model to an STL, the geodesics geometry wouldn’t knit and couldn’t be exported. I fiddled with the model for a bit trying to transform faces into solid, but to no avail.

On to the second model. It failed, too.

I was down to my last option, and if that didn’t work, I didn’t know if the project could move forward.

Fortunately, model number three worked perfectly. The entire design could be exported as an STL, which meant that it could be uploaded to a third party prototyping service like Protolabs or Xometry for a quote.

Problem Solved, Off for a Quote

Getting a quote for a model these days is incredibly simple. You hear industry evangelists preach that manufacturing and prototyping technologies have never been more integrated than they are right now. Now, most of the time these proclamations are just smoke, but, to be honest, that one rings true.

In the CAD software that I use, I have integrated options that allow me to grab quotes from several prototyping service bureaus. With a simple click I can send off my model for a quote and have a price and lead time in hand within a few hours. However, for this project I decided to visit each company’s website so that I could grab more compelling graphics for this article and also get an unadulterated quote experience.

First up was Xometry.

Once on the site it’s hard not to be taken away by how Xometry’s user interface cast a spell that whispers “I’m easy to use”.

Hovering in the top right corner of the site is an orange button begging each and every visitor “Get Instant Quote” (there’s an even more enticing button to the left advertising a SOLIDWORKS add-in).

As instructed I clicked the orange button and was whisked away to a portal where all needed to do was drag and drop my prepared .STL file. After a minute or so of processing by Xometry’s algorithm, my model has been checked for holes, missing faces and other manufacturability maladies that might upset any rapid prototyping protocol.

None evident. Please proceed.

First, materials need to be selected. To pare down my choices, I selected an option in the Xometry interface to filter out material options that weren’t plastic (metal options like aluminum, brass/bronze, copper, steel and titanium are also available). ABS plasticmade via Fused Deposition Modeling (FDM) was easily the cheapest option, so I chose both options and there appeared my price. Yikes. $391.82 for a lightly filled (aka hardly solid) model that’s 6.7“ x 4.63” x 4.33”.

For some, that’s an acceptable prototype price. For this project, it wasn’t.

On to Proto Labs, another familiar and easy to use service bureau.

I’d used Proto Labs to print a few small parts for an engine model in the past, so I was a bit more familiar with their quote process. Once on the site, a familiar interface greeted me. Orange, or whatever hue of alert these bureaus have unanimously chosen as their initial interface option, shouted from the corner. “Get Quote”, its refrain.

With a click, I was again shipped off to an option screen to select what manufacturing method I was interested in using (3D printing, CNC machining, injection molding or overmolding and insert molding). Of course, 3D printing was my game, but from this screen you can already tell the biggest different in Proto Labs and other easy-to-use bureaus is the breadth of their manufacturing capabilities.

3D Printing clicked. On to another screen.

Login. New screen.

After a few more steps than I’d really like to have to take upfront, I was asked to begin my quote by choosing either a plastic or metal material. Plastic selected, I was given several options for material. I chose PA-850 Black Nylon and an SLS process.

Proto Labs quote. A different process and material, but representative of what once can expect when prototyping a part of this model's size in plastic.
Proto Labs quote. A different process and material, but representative of what once can expect when prototyping a part of this model's size in plastic.

For those of you who are fans of design that adorned dot matrix printer paper, the following Proto Labs UI will kill it for you. Laid out in a sensible striation of white and gray rows, users can add models by clicking the actually-too-small button that reads “Upload Parts” in the bottom left hand corner. A few seconds later, the model is processed and it’s time to select my units. Once defined my price is ready. $751.86.

I blanch. Sorta. Looks like this prototype is going to be built somewhere else.

Now, I know it’s possible other service bureaus, like those run by Stratasys or 3DSystems, or maybe even other third party vendors, may have been able to offer me a better price, but in a pinch I went with the guys I’ve worked with before. That said, it’s wise to shop your business around when you’re running a short run production operation. Some of the big guys will even take the time to sit down and talk you through options in person if you live near a bureau. I actually had that happen once while working on a project for a recognizable music act (maybe it was her cache more than mine?).

Prototyping prices fluctuate. Search for good value.

Printed, and Ready to Go

Given the overwhelming costs that were delivered by both Xometry and Proto Labs, I decided to use my own 3D printer to build a scaled prototype that Roopinder could hold in hand to get an idea of the size and look of the final model.

My machine is a Formlabs 2.

The process for printing this model is easy: upload the .STL, choose my material and then set it to print.

After doing some quick math, my half-scale model of Roopinder’s award came out to $18.33.

Six hours and forty-nine minutes later, my print was done and it was time for some post processes before shipping it off to Roopinder. But before that, let’s looks at the results.

A half-scale 10K model in the palm of my hand. A few days labor, now off to Roopinder for the final say.

A half-scale 10K model in the palm of my hand. A few days labor, now off to Roopinder for the final say.

Not bad. High Resolution, Accurate Geometry, Easy to process. Oh and cheap too! Off to Roopinder to see if this thing gets made.

Lessons Learned

One of the most important lessons that I learned during the quick project is that regardless of how simple a project might seem, ample time should always be set aside for unforeseen issues, like my geodesic geometry conundrum.

Another take away, and this was a revelation to me, is that the internet is rife with model resources that can be leveraged to make modeling easier. Sure, I was aware that McMaster-Carr has a great cache of models that can save designers time, and I did know that sites like GrabCAD exist, but I’d never actually employed an outside model in a real world project. In all honesty, the last time I called down a McMaster-Carr model was during school while working on mechanical design. Point being, these online resources can save designers valuable time and make more complex jobs much easier. Use them.

Finally, don’t ever underestimate how much it will cost to have a project prototyped. With plastic, full scale models of my 10K award design running upwards of $600, additive manufacturing isn’t as cheap as it is convenient. Although I only priced out plastic models for this piece, I did take a look at what it would have cost to have the award sintered in various different metals. Not surprisingly, these creations would have cost anywhere between $6,000 and $21,000 making them prohibitively expensive for all but the most well-heeled.


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