Manufacturing guy-at-large.

Filtering by Tag: manufacturing

Share

Measuring process signatures is hard

Added on by Spencer Wright.

From a NIST report titled Measurement Science Needs for Real-time Control of Additive Manufacturing Powder Bed Fusion Processes:

Finally, metallic debris from the [heat affected zone] can coat a window or viewport used in an AM imaging system, and disturb temperature measurements by changing the radiation transmission through the window. This is particularly troublesome in electron-beam melting (EBM) systems, and prompted Dinwiddie et al. to create a system to continuously roll new kapton film over the viewport in order to provide new, unsullied transmission.

This is a very important and totally nontrivial challenge. Measuring process signatures (which this report defines as "the dynamic characteristics of the powder heating, melting, and solidification processes as they occur during the build") is key to the industrialization of additive manufacturing. If the systems we have for measuring those factors are unreliable, machine manufacturers need to develop improvements for them ASAP.

Share

The six questions I think about when I think about industrial additive manufacturing

Added on by Spencer Wright.

Prompted by an impromptu back and forth with Jordan, I was compelled to write down the things I spend so much of my time thinking about. Some of these I have a better grasp on than others, but they're all problems that I'm excited to see developments on - and work on myself.

1. What are the process parameters that affect finished part shape?

I'm in the middle of a NIST report that goes through many of these. The sad thing is that knowing what the parameters are is only half of the battle; then, you need to control those parameters on-the-fly (which is not something that all machine manufacturers currently allow).

2. What are the most reliable and effective methods of measuring, recording, and processing those parameters?

Industrial additive manufacturing machines tend to be harsh environments for sensors and sensor hardware. Once we know what parameters to measure, we'll need to build measurement systems that are robust, accurate, and reliable.

3. Given two identical finished parts with two different production process chains (additive, subtractive, etc.), how can one determine which process chain will be more expensive to complete?

This is hard. I believe that it'll be easier to automate process chain comparison than it will be to automate process chain creation; in other words, coming up with a list of steps to manufacture a part will remain hands-on, but assessing the cost difference (time/money/energy) between two process chains will be increasingly automated. Regardless, these are big problems.

4. Given two different designs, each of which has the same end functionality, how can one determine which design will be more expensive to build?

This feeds into question 3. In many cases today, design decisions are made based on a hunch. If it were easier to estimate the production cost for parts with complex production process chains, designers would be able to make more informed decisions.

5. Given the same input design and two different additive build orientations, how can one determine which build orientation will produce the most high fidelity net near shape, at the lowest cost?

Also feeds into question 3. Manufacturing engineers need to pick a build orientation quickly and be guaranteed high fidelity end parts; today, those decisions are made mostly by gut. Bonus points if this data is also made available to designers, so that they can make even more informed design decisions.

6. Given the same input design and build orientation, how can one determine which support structure design will produce the most high fidelity net near shape?

Given the early effort that startups (namely 3DSIM) are putting into this question, it stands to reason that it's an easier one to solve than question 5. It's also possible that they think it'll be easier to commercialize support structure optimization software in the near future. Either way, I see this as just part of a bigger need that 5 and 6 are pointing at together: additive manufacturing engineers need better tools to set up and process builds.


These issues outline the biggest roadblocks that I've experienced on my path to commercially viable additively manufactured parts. If you have different experiences, or know of developments on what I've described here, I'd love to hear from you.

Share

3D printing titanium and the bin of broken dreams

Added on by Spencer Wright.

Note: What follows here describes my early experiences designing and building metal 3D printed parts. Since this post was published, I've had a number of parts printed successfully; you can read more about the current state of this work in a recent update, here.


Last December, in an industrial park in Cincinnati, I watched as Dave Bartosik set up a build platform on an EOS M280. The part he was printing is one that I began designing a full fourteen months earlier, before I had any idea of the intricacies of metals 3D printing, nor the complexity in bringing an additively manufactured part from design to prototype.

My part, being sintered from titanium 6/4 powder.

My part, being sintered from titanium 6/4 powder.

While consumer 3D printing community has coalesced around openness, the industrial market tends to be opaque. Sure, anyone can design parts with free software. But the process of bringing those designs to life requires hundreds of engineering hours, tens of thousands of dollars worth of software, and millions of dollars worth of tooling — and even then, developing a single working prototype is a long and expensive process.

To many people, 3D printing offers a new manufacturing paradigm. It stands for rapid iteration, customization, and distributed fabrication. But today it’s arduous and costly, and the knowledge base needed to enter the market is concentrated in a select few people.

Here, I’ll share what I’ve learned about 3D printing titanium parts so far — and what other designers should expect out of the process as well.

A primer on 3D printing metal

Within the maker and startup communities, a 3D printer is essentially an extremely accurate, robotic, hot glue gun, capable of making complex plastic parts within a few hours. For some people that means making functional models more quickly, and with less interaction with outside suppliers, than if they were machined or injection molded. For others it means a couple of desk trinkets, and for the really ambitious it provides a peek into a new way of bringing products to market, replete with on-demand, custom-to-order parts, produced just walking distance from where they’re used.

My background is in short-run manufacturing. I spent a few years building custom bicycle frames, and later ran a small prototyping shop, where I designed and tested robotic door assemblies on fast development cycles. When people talk about the need to iterate rapidly, I get it.

For five years, I worked in a shop that could make machined and welded parts on demand. There were always hiccups — prototype development is often more art than science — but in general we could, with a day’s notice and a bit of help from McMaster-Carr, take a 3D model and create a useable part from it. So when I think of 3D printing metal, I keep those kinds of capabilities (which are shared by easily thousands of shops around the US) in mind.

Metals parts are 3D printed in one of three ways:

  1. Binder jetting, in which powdered metal is sprayed with glue to get it to stick together — and later infused with a second metal to make the bond permanent. The most common binder jet printers are made by ExOne. In general, binder jetting is used to create prototypes or parts that require low strength.
  2. Directed energy deposition, in which metal is sprayed or fed at a part — and melted to that part by electric arcs or lasers upon contact. DED machines vary significantly; see DMG Mori and Sciaky for context. Directed energy deposition is even more niche than binder jetting; its application is mostly limited to repairs and very large aerospace parts.
  3. Powder bed fusion, in which a bed of powdered metal is selectively fused (through sintering or melting) by a laser or electric arc. The most common powder bed fusion machine is probably the EOS M280, but Concept Laser, Arcam, and Renishaw (among others) all have their own offerings. Powder bed fusion has a variety of uses in both production and prototyping. It supports a wide range of materials (the most common being titanium, stainless steel, and cobalt-chrome) and with care can be used to create lightweight, strong, and highly customizable parts — just like mine. But the process is far from easy and is definitely expensive.

Though it’s used extensively within the aerospace, medical, and tool & die industries, there are no metal powder bed fusion products on the consumer market today. Which made me think: why not?


The powder bed fusion process

When it comes to machine design, humans aren’t nearly as creative as you might think. The basic model for milling machines has been around for more than a century, and despite the fact that the process has changed significantly during that time, the overall layout of industrial tooling today is much the same as has been since the Civil War. Today’s powder bed fusion machines are no exception: If you squint just right, they look a lot like CNC vertical mills.

Powder bed fusion machines consist of three core parts: The build platform, a material source & recoater, and a source of thermal energy.

During operation, a thin layer of powder is spread by the recoater blade across the build platform. Then the heat source — either a laser or an electron beam — scans across the build platform, melting powder selectively as it goes. Where the metal is melted, it fuses to the metal around it, creating a solid part. After one layer is scanned, the recoater blade spreads another layer of powder and the process repeats.

Printing things this way is slow; a part the size of a juice glass might take ten hours. The recoater takes a few seconds to spread each layer, and although the laser is moving incredibly fast, it takes some time to scan the cross section of a part line by line. Add to that the fact that each layer is about eight ten-thousands of an inch thick, and you see how anything larger than a thimble would take a long time to complete.

Although powder bed fusion can be done by both lasers and electron beams, lasers are far more common. Electron beam melting (EBM) is notoriously difficult to control, and although it has some advantages, EBM parts tend to have very coarse surfaces and require more post processing as a result. EBM also suffers from relatively low market penetration; by my count, there are fewer than five service providers for EBM in the US.

By comparison, laser sintering (which I’ll refer to as DMLS, for direct metal laser sintering, though that is technically an EOS trade name) is almost ubiquitous. I’m aware of about seventy US shops offering metal laser sintering in-house, and even consumer-facing providers like iMaterialse offer DMLS. And although EOS sells far more metal laser sintering machines than any of their competitors, the market is still competitive — and that competition is beneficial to the industry as a whole.

Within the aerospace industry, DMLS has a high adoption rate — at least in an R&D context. In fact, my collaborators and primary tour guides to the industry (Dave Bartosik and Dustin Lindley) both began their careers in additive at Morris Technologies, the aerospace DMLS giant that was acquired by GE Aviation in 2012. Between the two of them there’s about as much experience printing titanium parts as anyone else in the world.

But for all the work that has gone into understanding the properties of additively manufactured parts, the process is still very much in its infancy. It is not in any sense a mature technology, and the result is that each new part you design for DMLS — and, indeed, each new copy of the part that you print — is very much an experiment. Small variations in geometry and orientation can have huge effects on the way that a part prints. The laser’s scanning path is a closely studied subject, but much is not yet understood about it. Even keeping those variables constant, it’s often the case that building the same part on a different machine will produce very different results.

All of which is to say that DMLS is anything but plug-and-play. Even when a design has been optimized specifically for the process, it often takes dozens of tries before a functional part comes out of the printer. And the process of troubleshooting a failed build — even at the most advanced DMLS shops in the world — still involves a lot of trial and error.


Part constraints

In general, parts that benefit from 3D printing tend to have the following traits:

  • Benefit from weight reduction
  • Benefit from customization
  • Complex geometries
  • High inventory costs and/or long lead times

My seatmast topper, in full and half-section views. Note internal cavities in the center neck area.

The part I’m building is a seatmast topper for high end road bicycles. Cyclists want lightweight, custom parts. Custom bicycles are increasingly popular with consumers, and they carry high price tags and long lead times. Broadly, it’s my suspicion that more and more bicycle components will be produced on-demand through 3D printing — if only for the simple fact that within high end cycling, sexy sells.

At about 60 grams, my part is fairly lightweight. It’s also relatively small, and fits easily within nearly every DMLS machine’s build platform. And because of its function (seatmast toppers are used to hold a bicycle saddle onto the frame) its structural requirements are fairly predictable. These factors, plus the fact that seatmast toppers are easy for almost any cyclist to install on their own bike, make it a good candidate for 3D printing.

But that doesn’t mean it’s easy to print. My part consists of two cylinders, oriented 90° apart and joined together by a funneled neck. The part’s wall thicknesses fall between 1mm and 1.75mm — roughly .039"-.068". And it’s critical that these walls not vary much in thickness; if they end up just .010" thinner (for comparison, a sheet of paper is about .004" thick), the part could be unusable.

Harder yet, the inner diameters of both of the cylinders must be accurate and consistent. Again, variations of just .005" can have a big effect here — and if the cylinders end up with oval cross-sections, the part won’t work at all. And the titanium 6/4 that my part will be made of (which is named for its 6% aluminum, 4% vanadium content) is notoriously prone to built-in stresses, meaning that we’ll have to be very careful setting up the build parameters and support structures to prevent the part from turning into a pretzel during the process.

As with almost all 3D printed metal parts, mine will require some degree of post processing; at an absolute minimum, the clamp bolt threading will need to be tapped. But because of the physical tolerances listed above — and the mechanical and aesthetic properties of DMLS parts, which tend to be rough and unpredictable — it’s likely that extensive finishing will be required on both the inner and outer surfaces of the part.

In short, my part’s manufacturing process chain was always going to include some subtractive steps. There are many feature types that 3D printing simply isn’t intended for, and I knew going in that this part would require more than one process as a result. But until we picked a build orientation — and built parts that passed fit & finish tests — we wouldn’t know for sure what our total process chain would look like.


Build orientation

My prototyping partner, DRT Medical— Morris, prints titanium parts on an EOS M280 — the workhorse metal 3D printing machine for American job shops. Based on my research, EOS’s market penetration outmatches each of their competitors by five to one. As of November 2014, EOS only lists eighteen service-ready M280s in the US, but their data is clearly incomplete; I wouldn’t be surprised if the real number was triple that. Moreover, the vast majority of DMLS machines are purchased by OEMs, who use them for internal capacity only, and my suspicion is that the proportion of EOS machines behind closed doors is similarly large.

The M280's build platform measures 250mm (x) by 250mm (y), and is has a maximum build height of 325mm (z), including the build plate. My part is about 70mm long (x), 37mm deep (y), and 90mm tall (z).

bk1033 drawing.jpeg

A common misconception about 3D printing is that the unit cost doesn’t vary much with quantity — that printing one part is just as efficient as printing a thousand. Granted, 3D printing doesn’t require tooling per se, but non-recurring engineering costs are absolutely to be expected. In addition to the time spent determining an optimal build configuration, there are significant changeover costs when a DMLS machine operator goes from printing in, say, titanium to stainless steel — which some low-volume service providers might do on a weekly basis. Moreover, metal 3D printing providers don’t normally print multiple orders in one build. In other words, if I buy a titanium part at the same time as another customers does, they’ll usually run those orders in two separate builds — even if both parts might fit on the build platform at the same time.

The exact math is hard to reverse-engineer, but there are generally four variables that determine the cost of a DMLS part:

  • Finished part mass. There are two subcomponents here: Raw material cost, plus the time it takes the laser to sinter the part. Raw powder costs between $300 and $600 per kilogram. My part weighs about 60 grams, which puts the material cost in the neighborhood of $30. But that 60 grams will take about eight hours to sinter, and the cost of sintering time adds up quickly. As a rough guide, expect to spend on the order of $100–200 per hour for part build time.
  • Support structure mass. DMLS parts require solid support structures to tie them to the build platform, and those structures are made of the same metal powder that the part is. If your part has a lot of overhanging geometry or requires additional support structures for other reasons, you’ll pay for those (and the time it takes to sinter them) as well.
  • Part height. Across all types of manufacturing, capital expenses (tooling, etc.) are paid off over a period of years. In DMLS, part height correlates directly with time spent recoating the platform with new powder, and that in turn equates to a higher tooling cost that the supplier needs to pay off during your build. As a result, designers are incentivized to orient their parts as close to the build platform as possible, to reduce build height and hence reduce recoating time.
  • Number of parts per build. Because the setup and powder recoat time can be shared across multiple parts, buying in batches (when possible) will generally be less expensive than buying one-offs.

Build configuration 1: Part on it side. Ten parts, ~40 hours. Image courtesy DRT Medical — Morris

In my case, those last two factors act directly against each other. If I orient the part on its side, I can fit about 10 parts per platform, with a ~40 hour build time — about 4 hours apiece. But if I orient them vertically (upside-down ends up being more favorable), I can print 24 parts in a ~85 hour build — about 3.5 hours per part.

Build configuration 2: Part upside-down. 24 parts, ~85 hours. Image courtesy DRT Medical — Morris.

At this point, Dustin and I spent some time thinking through the manufacturing process chains for each of these configurations. It’s very likely that we’ll end up needing to machine the inner diameters of both of the part’s cylinders, and we wanted that process to be straightforward and involve as little custom tooling as possible (post processing DMLS parts often requires extensive custom tooling). As far as we could tell, build configuration 2 was going to be slightly easier — mostly because the long ID could be machined while the part was still on the build platform. But the difference was very difficult to quantify, and in the end our build orientation was determined for a much simpler reason: powder availability.

The DMLS powder market is, like most things in this industry, changing rapidly. Powdered metal is expensive to produce, and the particle size, shape, and consistency are critical to finished part characteristics. And while prices are going down rapidly (double digit percentages year-over-year, I’m told), service providers are still stuck with having a large chunk of money tied up in raw powder powder at any given moment. Add in lead times, and the fact that titanium powder isn’t particularly fun to handle, and you can see why job shops would only want to keep as much powder on hand as they absolutely need.

In the end, we ended up building my part on its side simply because DRT was getting towards the end of a batch of powder, and the taller orientation was going to require more than they had on hand. Which is possibly, given the small quantities these parts will probably be produced in, the right orientation anyway — and was a less expensive build to boot.

At this point, our goals were explicit: Determine the minimum amount of post processing necessary to produce a working part.


Stress & build failure

It’s critical to remember that 3D printed parts move as you print them. The same is the case with other manufacturing methods as well (injection molded parts shrink as they cool, machined parts warp as they’re cut, etc.), but DMLS creates extreme thermal gradients, and the net effect is that stresses are built into the part layer by layer.

Build orientation affects stresses in *huge* and unpredictable ways. See this paper, by Amanda Wu, a researcher at LLNL, for more.

Build orientation affects stresses in *huge* and unpredictable ways. See this paper, by Amanda Wu, a researcher at LLNL, for more.

Predicting built-in stresses is an incredibly difficult task, and is the topic of a lot of basic research. At the moment, the best we can hope is to analyze and understand the stresses that are built into parts once they’re complete; predicting them before they happen is still a long way off.

Despite the fact that stress prediction is very much a dark art, the correlation between laser sintering and welding is not a trivial one; many of the same principles apply to both. But when approaching a new part, it’s almost always the case that the best way to deal with potential problems is through trial and error — and then adding and removing support structures as necessary.

This is a key point: powder bed fusion involves welding your part to the machine while you build it. The build will definitely fail if the part lifts off the build platform (when this happens, the recoater blade strikes the part. In general it doesn’t damage the machine, but I’m told it can be… exciting), so a lot of effort goes into designing clever — and hopefully not too massive — solid and lattice support structures to keep the part where it’s supposed to be.

Even if the build itself doesn’t fail, internal stresses can still render it unusable. This is why most parts are stress relieved (a heat treatment process) after they’re built and before they’re removed from the build plate: doing so allows the crystalline structure to relax, preventing failure later.

Going into the build process, I was warned many times that cylinders oriented parallel to the build plate are notoriously difficult to build. The stress profile around the circumference of the cylinder will tend to vary widely, and the result is that you generally wind up with a big oval. But other than orient the part at a 45° angle to the platform (and risk ovalizing both cylinders), our options on this part were limited. So, we started as simply as possible, and iterated as needed.


Support structures & Iteration

Once the build is complete and the part is wire EDM cut off the plate, support structures are removed manually.

Once the build is complete and the part is wire EDM cut off the plate, support structures are removed manually.

While I was in Cincinnati, I visited MicroTek Finishing — a major player in the metal 3D printing world. While there I spoke with Tim Bell, who related an anecdote about his time at Morris Technologies, the aerospace 3D printing giant that was acquired by GE in 2012. Tim was a product development leader at Morris, and he talked of a large bin that they had in their shop. It was called the Bin of Broken Dreams, and into it went an endless stream of failed parts.

My part has now been printed in six different build configurations. We (and by we I mean Dave Bartosik, whose creativity and enthusiasm for getting the build to work was inspiring) added solid supports in a number of places, chasing built-in stresses around the part with each iteration. The latest prototype, although nonfunctional, is nevertheless a big improvement on the earlier builds — and the process has taught us a lot about the idiosyncrasies of my design.

To begin, Dave let Materialise Magics (the industry standard for support structure generation software) do its thing with no manual intervention. Magics generates mesh support structures, which are scanned every other layer of powder (solid regions of the part are scanned every single layer). As a result, they’re very easy to chip off the part — but don’t have the same strength that solid supports do. As internal stresses proved to be an issue, Dave added solid supports to keep the part undistorted and tied to the build platform.

Build 1

In this build, the part is laid on its side and supported only by mesh supports. The build failed at only 15.6mm in the z-direction, when the recoater jammed on the saddle clamp end of the part, which had lifted from the build platform.

Build 2

Here, the seatpost clamp cylinder is firmly fastened to the build plate. But the stresses just concentrated on the other end of the part, pulling the bolt boss and some of the front edge off of the platform at a height of 22.7mm.

Build 3

Both ends of the part — the saddle clamp and the bolt boss — are firmly anchored to the build platform. But this created a complex bending moment, pulling the center of the part upwards; the build failed at 22mm.

Build 4

Here we’ve got solid supports on both the saddle clamp cylinder and the bolt boss, and added an additional solid rib to the middle of the part, tying it down there. This is the first build that completed; all of the others had failed midway through. We’re clearly getting closer, but the bottom of the part has distorted, pulling in and looking like a big “D”.

Build 5

To prevent the bottom of the part from distorting like in Build 4, we added a second solid rib. It helped, but only below the centerline of the cylinder; above that, the wall still pulled in.

Build 6

Build 6 finally produced a part that’s generally round and complete. This was achieved by extending the lower rib up the side of the part, giving external support to the entire bottom edge of the seatmast clamp cylinder. But although the top and bottom of the seatmast clamp are both basically round, the internal stresses still needed to go somewhere — and ended up bulging out the middle of the tube instead.

Throughout each of these builds, three things have remained consistent. First, the surface finish on the exterior of the part leaves much to be desired; it will definitely need to be finished in a separate step. Second, the surfaces that needed to be EDM cut from their solid supports (the saddle clamp and the bolt boss) are irregular, and will need to be smoothed into the rest of the part. Third, the internal diameters will almost definitely need to be post-processed by machining or EDM — even the saddle clamp, which overall had passable surface finish, was undersized by .020" — about four times the desired variance.

The net effect is that after six build iterations — each of which took almost two full days to set up, build, stress-relieve, and cut off of the build plate — we still don’t have a functional prototype to test.


Takeaways

What to take away from this? Well, prototyping is hard — but everyone knows that. My primary observations have more to do with the state of the industrial marketplace, and the maturity of metal 3D printing processes, than with the fact that we’ve now put six parts into our own bin of broken dreams.

File processing

As with consumer 3D printing, industrial 3D printers work exclusively from STL files. This produces a total break in the design-to-manufacture process. When I export an STL to send to a manufacturer, all of the underlying feature data is lost; all that’s left is a shape. This is drastically different from the conventional manufacturing world, where parts are regularly built directly from underlying design files.

Tolerances

For the vast majority of machined parts, any single dimension is expected to be accurate to within .005", regardless of size; in other words, a quarter-inch hole should be between .245" and .255", and a one-inch hole should be between .995" and 1.005". For a relatively small cost, designers can specify even tighter tolerances, and the means of achieving them are predictable and not overly complicated. But with additive, tolerances accumulate across the part at a rate .005" for every inch of distance. That’s fine if you’re building a one-inch part (whose dimensions will be between .995" and 1.005"), but larger parts can be problematic; a ten-inch part will be between 9.950" and 10.050" — a decidedly generous tolerance. Moreover, these tolerances don’t always stick; many of our early prototypes didn’t come close to meeting them. And when a part prints out of tolerance, the way to fix the problem is essentially to fiddle with the underlying design and then build it again.

Intellectual Property

Across the metal 3D printing industry, a stream of contract manufacturers told me the same thing. DMLS build processing is hard, they say. And the only way to maintain a competitive edge is to invest countless time and money into R&D — and then guard institutional knowledge vigilantly. On many occasions this is referred to as intellectual property, but the truth is that it’s closer to expertise; what’s being developed is craftsmanship, not patentable tools or methods. But whatever the name, the effect to designers is stifling. Regardless of manufacturing method, the design-to-manufacture process benefits from transparency; if a build fails, then I as a designer want to know the reason — and adjust my underlying design accordingly. Until the additive supply chain opens up to sharing its experience in the design-to-manufacture process, new DMLS products will be few and far between.

Undistributed Manufacturing

Today, 3D printing metal parts via a distributed supply chain is a myth, full stop. And while I’m as excited about that vision as the next guy, distributed manufacturing will continue to be a pipe dream for the foreseeable future. A distributed manufacturing ecosystem can only exist once there’s a robust network of suppliers capable of making parts repeatably. And while it’s my sincere feeling that the most hardworking, intelligent, and visionary people in manufacturing today are working in 3D printing, there simply isn’t currently a rich network of DMLS suppliers. For instance, the closest DMLS-equipped shop to New York City is a 200+ mile drive away. Meanwhile, MFG.com lists 68 machine shops within a 150-mile radius. If distributed 3D printing is to become a reality, the install base must increase by orders of magnitude — and the reliability and repeatability of the processes must improve dramatically as well.

In-Process Monitoring

In conventional manufacturing, parts are checked between operations to ensure that critical dimensions will be met. But the current generation of industrial 3D printers have little in the way of in-process monitoring, with the result that distortion isn’t detected until the build fails altogether. Although there are hints that this may be changing (B6 Sigma has announced some ambitious plans recently, and a lot of primary research is being done on the subject), the fact remains that until we’re measuring and analyzing the factors (thermal gradient, sound, vibration, etc.) that indicate build failure before it happens, trial-and-error will be the only way prototypes are developed.

The Process Chain

3D printing is very, very good for certain things. But it is not a one-stop process. For now and the foreseeable future, additive manufacturing will be a poor method of creating a number of important mechanical features, including many aspects of fastening and articulation. In addition, the surface quality of 3D printed parts will be unacceptable for anything requiring tailored aerodynamic features, and will be similarly poor for products whose fit and finish are of high value for aesthetic reasons. This is not to say that those aspects won’t improve; they will. But while I expect additive manufacturing to be an important part of the way parts are produced in the future, it’ll be a long time before it’s used to produce a wide range of products. And for those products which are well suited for 3D printing, their total manufacturing process chain will include subtractive tools (machining, honing, polishing, etc.) for the foreseeable future.


Next steps

My part has come a long way. Just having a physical prototype in hand makes a huge difference in understanding its benefits and drawbacks, and I continue to believe that with continued research and prototype development, I will find a way to make it commercially viable and attractive to high end cyclists.

But there’s much work to do. Moving forward, I see three primary directions to explore:

Keep the current build orientation, and continue to iterate on support structures as necessary.

At this point, it’s clear that we need to rethink the way we’ve been mitigating internal stresses. The external ribs are working somewhat, but even if we can add enough of them to make the build work, they leave ugly marks on the outside surface which require additional post-processing. Instead, I plan to experiment with reinforcing the inner diameter of the seatmast clamp cylinder. One thought is to create an internal lattice (like those that Frustum’s software creates), which would provide rigidity during the build and then be removed via machining afterwards.

Change the build orientation

Turning the part so that it’s upside-down on the build platform — with the seatmast clamp on the top — will offer significant advantages. The saddle clamp already has a thicker wall than the seatmast clamp, and is likely to resist distortion more easily. And with the seatmast clamp oriented in the z-axis, it’ll be in much less danger of distortion.

Try EBM

The electron beam melting process preheats the entire build platform to just under the melting point of titanium, and so generates much lower thermal gradients — and as a result less internal stress — than DMLS. EBM also generally requires fewer support structures, which is helpful for part cleanup. However, the surface quality and minimum feature size of EBM is significantly worse than DMLS, so EBM would probably require a longer overall process chain, with more material removal than DMLS would.

Regardless, I’ll be continuing this work over the coming months. These technologies are changing rapidly, and any ambitious product designer would be wise to pay close attention to their development. And only by experimenting with actual parts can anyone hope to keep up.

I believe that functional, engineered consumer products made by additive manufacturing are an inevitability. But as a product manager today the viability of metal 3D printing is totally opaque, and that will only change by careful study of the efficiencies (and inefficiencies) of the additive manufacturing toolchain.

Join me in working to make that a reality.


Thanks

First, thanks to Dustin Lindley (of UCRI) and Dave Bartosik (of DRT—Morris), without whom all the cool stuff described above would have never happened. Thanks also to Greg Morris (who originally connected me with Dustin, Dave, and Chuck Hansford at DRT), to Clay Jones and Jordan Husney for their creative inspiration and infectious enthusiasm throughout the process, and to Clay Jones and Mike DiGiulio for reading early drafts.

Lastly, thanks to Undercurrent, which is providing critical funding for this project — and which I am proud to call home.

This article originally appeared in three parts on 3D Printing Industry.

Share

encounters in sinophobia

Added on by Spencer Wright.

"hey, well - china sleepy."

as a recently freelance guy who's looking for some extra cash and every-possible-way to network, i've been moonlighting (daylighting) as a bike mechanic. this is not exactly a career move for me, but it turns out that working on bikes is something i'm halfway decent at - and, moreover, that diagnosing customers' reported issues is something that i'm well suited to. and anyway i do need the cash.

despite myself, i enjoy working there. the clientele are high end and polite, and my coworkers are totally pleasant people. they're kind, thoughtful, and respectful of each other and myself; i would even go so far as to say that i like them. i bring value to the shop, and the shop brings me value too, and there's a mutual respect that's important to have in one's life.

in a lot of ways, though, i'm not exactly one of the dudes. the kinds of things that i'm most interested in - structured systems; means of production; frameworks from which to assess the world - don't always fit into the shop discourse. i'm a stickler for argumentative reasoning, and in my experience, bike mechanics tend towards a top-down distribution of knowledge. it's not an uncommon or surprising tendency, and is one that i think is pervasive - to much benefit - in many industries. manufacturers distribute specific guidelines for how parts should be installed, used and serviced, and individual users are instructed to follow those guidelines closely. it is not a system that rewards innovation. then again, neither is commercial airline navigation, and as Atul Gawande has documented so well, the track record of professions which implement and follow preplanned procedures usually have lower levels of failure.

i hesitate to say that i pick fights about, for instance, whether a torque wrench should be stored at its lowest setting regardless of the consequences. more likely, i suspect, is the exact opposite relationship. i consider the null hypothesis because of the consequences. not only does a rigorous examination of an argument or statement of fact ostensibly increase the likelihood of my making an accurate judgment, but it has a significant social effect as well - and not one that is exclusively positive. and while i can't accurately say that i enjoy being alone in insisting that a particular widely held opinion might be wrong, i also can't deny that i have tended to put myself in that position time and time again. what this says about me and my ultimate desire to be liked - or disliked, as the case may be - i can only surmise.

- - -

i can't say why i chose to take a class in contemporary Chinese film my first quarter at college, but i did, and my decision to do so is something i have returned to often since. it's not that i took the class itself particularly seriously, but i found the content to be highly compelling. i would go on to largely ignore China for he rest of my college career, but i always took an interest when anyone i met had been there or spoke Mandarin. my enthusiasm for the history of the group of civilizations comprising what we know of as China is largely unconstrained, a fact that i have made real (and somewhat pitiful) efforts to encourage in myself and those around me. when my sister spent a year in Beijing, i downloaded some Mandarin instruction tapes and made lame attempts to get through the first couple of lessons. when i worked with a Tibetan carpenter (and friend) for the better part of year, i pestered him to tell me about his life and travels, and encouraged him to bring in some Tibetan music. and to his credit, he did - and to the discredit of the shingling contractor i had hired, an awkward period ensued.

it's tough being a bike mechanic. wages are generally low. the work is dirty and requires both technical knowledge and (unlike many auto mechanic jobs) a significant amount of customer service. moreover (unlike most construction jobs), information turns over rapidly, and mechanics are expected to keep up with new technologies as they develop.

as a part time employee whose specific intent is to be just passing through while i figure out my career, these factors don't particularly bother me. besides, i've made my peace (after years of frustration and hurt) with the bicycle industry. at this point in my life, it's just a skill i have, and a way to support (part of) my lifestyle. it also serves as a place where i can test my ability to maintain a positive outlook and interact pleasantly with a wide variety of customers - not skills i have spent much time developing in the past few years.

and so, when a job i'm working on offers resistance to my efforts, i react mostly with bemusement. not surprisingly, i have opinions about the quality of the bikes i encounter, and much of the stock product that even the nicest shops (of which my employer is certainly one) carry falls below my personal standards. i find working on these bikes to be a particular pleasure, specifically because i would, generally, consider them unacceptable for my own use. for despite my (arbitrary and capricious) standards, most bikes are simply a pleasure to ride. this fact has been a revelation to me: i will, regularly, find myself genuinely enjoying the test-ride of a bike which, just minutes earlier, i had proclaimed to be "complete crap." to be totally fair, it is the case that i have a history of taking pride in accepting my own wrongness - a phenomenon that an astute critic might point out is equivalent to acting more right about my own mistakes, and hence more right generally, than even my most astute critics. regardless, i revel in my own ability to truly enjoy the bikes that i, from a technical standpoint, like the least.

and all of this, of course, is from the standpoint of the mechanic. from a consumer's perspective, the case is even more stark. crappy product is, often times, far and away the best option. if you disagree, i would be happy to up-sell your $800 Felt for a $10K American-made bike, but i can tell you with all honesty that the incremental return on investment will be infinitesimal.

it is my impression that these facts are highly troubling to most mechanics. anyone scraping by in NYC working for $15 an hour knows that there are a few billion people in the world that would kill for a fraction of that wage, and i think it's not lost on such Americans that their hold on such relatively high wages is precarious. sure, many of these people have delusions of grandeur as likely - or unlikely - as my own (it's not only i that am making a stop as a grease monkey on my way to a career). but i have put in my time defining myself as someone of the bike world, and after i was done, i put in my time defining myself as someone apart from it - and now i'm just a guy who can, if called upon to do so, build, diagnose and fix bikes. it's possible that some of my coworkers feel similarly of themselves, but i have seen no indication of that.

viz. their highly confused attitudes towards Chinese production. keep in mind, these are, from all appearances, totally kind and fair-hearted people. a few of them speak Spanish fluently and are fond of conversing with the delivery guys (who ride, almost without exception, bikes that are dirty, poorly maintained, and generally unpleasant to work on) in their native language. certainly, nobody would think of making derogatory comments about blacks, Native Americans, or homosexuals in the shop. and yet, when the issue of the poor quality of inexpensive stock bicycles come up, they find it acceptable to deride not the Western companies that sell and distribute the product, but its country of origin.

"china sleepy" is the most succinct manifestation of their sentiments. the phrase apparently is meant to reference the laziness, or perhaps exhaustion, of the individual Chinese worker who produced the item in question.

i had not heard the epithet until recently, and it reminded me of one i encountered on jobsites many years ago: afro-engineering. i can't say i'm a fan of either phrase.

it would be one thing if these kinds of slurs were simple racism, but they're not; they are pointed criticisms of the purported inability of a culture (or, more often, group of only marginally related cultures) to produce product of a particular quality. never mind that manufacturers like Foxconn build some of the most technologically advanced devices in the world. disregard similarly that the pyramids at Giza (located wholly in Africa) remain some of the most fantastic engineering feats in history, involving a peak workforce of perhaps 40,000 workers. these sentiments ignore all reason to the contrary: the other is incompetent. end of story.

drill down a little, and you'll find the speaker will shift from the individual worker to the planners of China's economic policy. and sure, the Chinese government pegged the yuan to the dollar for about a decade. but that relationship has, since 2005, changed, and the result (as documented by Edward Lazear in the Wall Street Journal) is interesting:

The dollar-yuan exchange rate did not change from 1995 to 2005, and during this period China's exports to the U.S. increased sixfold, or at a rate of about 19.6% per year. Then, from 2005 to 2008, the value of the yuan relative to the U.S. dollar appreciated by about 21%. China's currency was "stronger" and its exports in dollars were more expensive—so Chinese exports to the U.S. should have fallen. Instead, China's exports to the U.S. continued to grow at about the same pace, averaging 18.2% per year.

The only period during which exports from China to the U.S. fell to any significant extent was during the recent recession, dropping by about one-third from late 2008 to early 2010. The dollar-yuan exchange rate was unchanged throughout this entire period. The obvious explanation for the decline in Chinese exports to the U.S. was the decline in demand for consumption goods in general.

clearly, these are complicated issues; far be it for me to attempt to reach any meaningful conclusion, here or elsewhere. my policy is simple. if you don't understand it, be interested in it - not scared of it.

a few nights ago, i was riding through the East Village and decided to stop into Dumpling Man for a quick dinner. i normally prefer the grittier spots in Chinatown, but Dumpling Man was on my way and i wanted to double-check my initial impressions of it, which was that it was okay (they serve fucking dumplings, after all, and i love dumplings) but not great.

i ordered some seared pork dumplings (texturally interesting but not particularly flavorful) and some xiaolongbao (which were abysmal) and sat on the street. the chef appeared to be Han Chinese, but the manager (or anyway the man at the counter) was white, though he seemed to speak Mandarin fluently. about halfway through my meal, a couple of girls walked up and, after some hesitation, entered the small restaurant. i could hear them discussing options with the manager, who advised them on filling options and order quantity before breaking off the conversation to holler out the window to the chef, who was leaving. they yelled back and forth, laughing at each other - completely in Mandarin - for a minute or two, and the girls stood at the counter in amazement.

i don't know what they really thought, and it would be dishonest for me to speculate. moreover, it's not as if my position - the enlightened westerner, just here to experience all the cute foreign ways of other cultures - isn't problematic.

i went to Shanghai in 2011, for an expenses-paid work trip. i had wanted to travel to China for years, and the opportunity to do so - and to visit factories there, no less - was a gift. the trip was organized by mfg.com, a website whose service is essentially linking buyers of manufactured goods with job shops capable of providing those goods. the buyer base is, as i understand it, largely Western, but it seemed to me that mfg.com's real customer base is worldwide suppliers, and that the product that they sell those customers is access to the eyeballs of a Western clientele.

the trip was fairly busy, but i found plenty of downtime - not least because i never acclimated to the time difference during my five-day trip. and so i explored on foot, visiting a variety of what seemed to be normal Shanghainese neighborhoods. i walked down sleepy streets lined with old sycamore trees. i found little food courts and gestured at crisp sesame pancakes and greasy dumplings, and found myself in low-slung slums where public services were totally ad hoc and sheet metal was the primary construction material.

i was a bit astounded that my tripmates didn't act similarly, but try to this day to understand and appreciate their methods of approaching the culture. they were mostly confined to the hotel restaurant - a place i eschewed - and squirmed as we were served eel and turtle at dinner on the town. to be fair, many of these people had worldwide procurement experience that my small-time resume couldn't touch, and many of them were able to capitalize on the opportunities the trip provided in ways that i certainly didn't. nonetheless, i got the feeling that they viewed the country as an other place, where i tried to see it as just another one.

it wasn't until my last day there that the most significant reason for this difference occurred to me. the trip organizers had scheduled a van to take a few of us across the sprawling city to its airport, and i met up with my vanmates in the hotel's parking lot ten or fifteen minutes before our departure time. the hotel was new, modern, and nice. my room cost about $200 per night, but the equivalent in New York would likely have been double that. the neighborhood was clean and had plenty of amenities acceptable to both Western and Chinese visitors. and parked in the small driveway in front of the hotel was a shiny red Ferrari. the car likely had a sticker price in the $200K range, though who knows how much the import to China cost. it was a nice vehicle, but not one that struck me as particularly unique.

i spent my formative years in Southampton, New York - one of the most vibrant resort communities in the US. in the summer, Ferraris were almost ubiquitous, and one learned to recognize cars that were interesting, as opposed to just expensive. but my vanmates - who were by all appearances intelligent, informed, and even worldly people - didn't have such a sense. and so it was i who snapped the photos of a woman from Atlanta, leaning gingerly over the hood of an Italian supercar in a nice neighborhood in Shanghai. who else was going to do it?

the previous night, i had taken a subway, and then a bus, to a decidedly normal neighborhood in Pudong, Shanghai's rapidly developing expansion zone. my companion, a Shanghainese college student who had been hired as a translator for our trip, had somewhat awkwardly agreed/suggested (we were both being a bit coy) that it would be fun to take me to Pudong for my last afternoon in town. we were both exhausted, but i was enjoying my last few hours in the country, and as she went up to her parents' apartment (i wasn't allowed), i must have looked like some weird caricature of a tourist, far from his hotel but seemingly unbothered.

she took me to a greenmarket and helped me buy mangosteens. we walked past open air restaurants, ate noodles from a cart, and went to a supermarket, where i browsed wide-eyed and insisted on buying green tea oreos. and then we returned to her street, where she asked for my business card and i awkwardly (and perhaps inappropriately) hugged her. i was emotional. i liked her, and i deeply appreciated her willingness to befriend me despite the fact that i was, for all intents and purposes, just some Western businessman in China for a few days.

- - -

ultimately, my gripe with "china sleepy" is that i don't understand who it's meant to be a criticism of. the factory workers i encountered in Shanghai, Suzhou and the surrounding area certainly didn't seem sleepy. their bosses - enthusiastic business owners, desperate for Westerners to come in and justify the doubtlessly large investments they had made in their factories - weren't sleepy either. and the companies - Western, Chinese or otherwise - that contracted the factories we saw to make parts? they're getting ahead any way they can, just like the rest of us.

the last thing i want is to condone, wittingly or not, the mistreatment of workers. and i'm no more likely (my enthusiasm for cheapish bikes notwithstanding) to buy inferior product than the next guy; i surround myself with the same collection of silly knick-knacks that one would find on Kaufmann Mercantile and Canoe. but to denigrate the work ethic of more than a billion people, and to categorically label their collective output as "crap," seems to me an injustice of equal magnitude.

and ultimately, it's more productive - and more fun - to like, and to be genuinely interested in, China. a culture doesn't survive four millennia, and multiple fractures and reunifications, without developing at the least a compelling storyline or two. it behooves us to appreciate China for that, and it behooves me to appreciate its people for the kindness and generosity i experienced there - if not for the opportunity to ride an affordable bike around the block (after a little fiddling, of course) on a beautiful afternoon in june.


  1. i quit my job and relocated in early february.

  2. cf. The Checklist Manifesto, or, for a quicker read, his 2007 New Yorker excerpt from the same.

  3. you should totally know about the null hypothesis. from wikipedia: In statistical inference of observed data of a scientific experiment, the null hypothesis refers to a general default position: that there is no relationship between two measured phenomena, or that a potential medical treatment has no effect.

  4. n.b., "Chinese" isn't a language; you probably meant Mandarin. or Cantonese, or Shanghainese, or the five or so other linguistically distinct languages spoken in China.

  5. if indeed.com is to be trusted, bike mechanics (a.k.a. "bike shop;" "bicycle shop") make $20-32K annually, and are subject to significant market volatility. my current wage, were i working full-time, would annualize at just over $30K; well below what MIT claims to be sufficient for one adult and one child in NYC. it's not exactly a position you build a family on.

  6. i was self employed, building custom bicycle frames, from 2008-2011. my business had some limited success, but my concept, as it were, never really blew up, and in the end i mothballed it. it was a painful, but in the end appropriate and informative, decision.

  7. as estimated by Craig B. Smith, mark Lehner et al and reported in a 1999 report of Civil Engineering.

  8. the Wall Street Journal, 2013.01.07: Chinese 'Currency Manipulation' Is Not The Problem. google cached copy downloaded 2013.06.06.

  9. mfg.com's representatives on the trip were rather cagey about their business model and the quid pro quo relationship that they seemed to have with the suppliers we visited in and around Shanghai. nevertheless, it was clear that someone was paying for the trip, and the two buses full of buyers - whose employers had only bought them plane tickets to Shanghai (the rest of the trip, from transportation and lodging to hotel buffets and dinners at classy Shanghainese restaurants, was paid by the organizers) - certainly weren't footing the bill, at least directly. moreover, at times i had the distinct feeling that i was being courted, and that the suppliers who were courting me had been promised something in return for whatever cost of entry that mfg.com had stuck them with.

  10. the development of modern Pudong is legendary. in 1990, the area was low-lying and largely undeveloped; in 2010 it was home to some 5 million residents. i saw a small fraction of the city; its size is astounding. cf. this magicalurbanism.com post, with pictures.

  11. read: she was a girl, maybe twenty years old, who came on the trip with us for no explicitly specified reason. i have no reason to think that anything even vaguely sexual transpired between her - or any of the other handful of similar girls who came along - and my Western counterparts, but the fact remains that the relationship between the two groups was somewhat troubling. i would like to think that i related to her on a genuine and friendly level - we became friends on facebook, and i received a postcard from her a few months after my trip - but in all honesty i can't say what her (or my own) intentions were. for what it's worth, it was genuinely interesting to gleam her reactions to the factories we visited; she provided a perspective i could not have seen otherwise. she also humored my pronunciation questions quite charmingly, and, as described further here, invited me into her neighborhood and showed me a totally compelling view of her city.