Perspective on 3D printers from a mechanical designer

3D printed part that would be (extremely) difficult to make another way. Photo credit: Axel Hindemith Lizenz: Creative Commons CC-by-sa-3.0 de

This is in part motivated by Jon Evan’s recent article on TechCrunch ( but more to add to the discussion of new manufacturing technologies from my experiences that have been brewing for a while.  I agree with Evan’s thesis that 3D printing is alike 2D printing only in name, but my experience is that 3D printing are a great tool, but will not be a total revolution in manufacturing as some suggest.

I am starting a PhD in Mechanical Engineering soon and have been using 3D printers, waterjet machines, and laser micromachines for three or four years now on a prototyping basis.  I am writing this mainly directed for the software tech crowd that has recently become more interested in hardware.  Some of my conclusions:

1. We will not see 3D printers in everyone’s home

I don’t see 3D printing as being a new fixture in everyone’s home.  This is because 3D printing:

  1. requires design input, which requires developed skill and time
  2. is a slow process, and
  3. materials are (currently) poor quality from an engineering perspective

I do see growth in residential use, but only by the same kinds of people who have a wood working shop and welder in their garage, or who do I/O software or robotics projects. They are a nice cross-over between software and hardware.

3D printing needs design input, and for more than the most trivial parts, this requires computer aided design software and the skill to use it.  It’s far more work than most people are willing to invest.  If you are just going to make parts of other people’s designs, why not just outsource the production to them as well?

3D printing is slow, with even small parts taking hours to make.  Unless it’s a custom part (that you’ve designed yourself), its much quicker (and cheaper) to find something off the shelf.

3D printing materials are apparently better than they used to be, but I still find they crack often and easier than would be acceptable in most uses.  Yes, there are examples of parts that are made by 3D printing that work fine for their use, but a molded, casted, or machined part will be stronger.

2. 3D printing will not revolutionize manufacturing

For the same reasons listed above, 3D printing is not a great production technology.  But, more importantly, the economies of 3D printing are only efficient below about 10-20 parts.  After that, casting or injection molding is typically cheaper, except in a few cases I will discuss later.  At large volumes, the per-unit cost of a plastic part in injection molding could be well under a dollar, and the same part in 3D printing could be over $100.  The exception is where 3D printing is making a part that is “impossible” by other methods or that would require multiple parts and assembly.

 3. 3D printing is good for prototyping and one-offs (but not the only way)

For doing something once, whether for prototyping or if you only need one, 3D printers can be a great tool.  One cool application is surgical planning or even custom implants by 3D printing (such as  And it makes sense because everyone is different enough to justify and one-off part for them (and medical device costs are high enough to allow it).  But replace overseas injection-molded parts with a 3D printer in your garage?  It doesn’t make sense in nearly all instances.

There are other rapid prototyping methods such as CNC waterjet cutting and laser machining that get less attention although they are, in my opinion, more useful prototyping tools.  Typically, sheet metal is cut, then folded into a 3D prototype.  These are nice because they are typically stronger than 3D printed part, are quicker, and time scales with complexity rather than size. There are also many types of 3D printers including those that “print” rubber-like materials, hard plastics, and metals.

New rapid prototyping methods are game-changing for developing new products on a shoe-string budget, and I would wager that most of the recent success stories on Kickstarter ( were developed with the help of 3D printing prototypes.  In this, the technology really does allow for cheap innovation where design is the major innovation.  I would go as far as to say these technologies are lowering the barrier-to-entry of hardware projects to a similar level as software, at least until the product goes to production.  Great news for hardware entrepreneurs!

As an aside on Kickstarter since I brought it up, it is interesting they recently banned virtual renderings of design projects.  Rapid prototyping allows for moving from virtual models to prototyped models easily, quickly, and cheaply.  The problem is that the prototypes in no way prove the company is ready to handle the demands of transitioning into production, or that the prototype has had any reliability testing.

4. 3D printers allow for making things that are impossible any other way

This is probably the second biggest advantage of 3D printers, after their usefulness in rapid prototyping.  3D printing allows for making shapes that are impossible using other methods, or require multiple parts and assembly in other methods.  3D printing in particular allows for printing parts that have irregular voids or holes that curve are very difficult to make with other methods.  Mechanical Engineering Magazine ( has had a few good articles on this over the past year, or the image I posted above is a good example.

5. 3D printing (and other rapid prototyping) machines are less reliable

3D printing and other automated machines, especially lower end ones, continue to have reliability issues.  Most of my experience is with industrial machines (costing in the $50-100k range), and even these have a crippling amount of downtime.  There are also issues that occur while parts are being built.  At best, you catch these early and can restart the part.  At worst, you come back later to find you part is a mess and the machine is damaged.  These machines typically don’t have feedback, so the machine can’t tell if its made a mistake.  Good ol’ lathes and mills, even of the CNC variety, are much more reliable.  But rapid prototype machines may improve in the future.

 6. 3D printing users need to decide between ownership and out-sourced services

3D printing machines are becoming less expensive, but still lock up a lot of capital.  For most users, their machine is probably going to spend most of its time waiting for a job, and only a fraction actually printing.  I have used a few services, my favorite is Protogenic by Spectrum Plastics (  I have found they have the best prices and have the best customer service of any vendor I’ve ever worked with.  Typically a part is delivered within 5 business days of ordering, and prices aren’t that much more than the material used in your own machine.  Therefore, the only reasons I can see for ownership of a 3D printer are:

  1. High usage
  2. Need for extremely quick turnaround times
  3. Desire for confidentiality (although most venders will agree to NDAs)
  4. Teaching CNC control theory (ie in engineering schools)
  5. To geek out

For most reading this article, this last point may be the main selling point for getting a 3D printer.  They are certainly fun and interesting toys.  And they do have niche roles in manufacturing, design, and maker culture.  But it’s time for a reality check: 3D printing is not the beginning of the end for injection molding, milling, casting, and other traditional manufacturing technologies.

Edit: there has been a vibrant discussion of this on HackerNews.  Thank you all for your thoughts and comments:

17 thoughts on “Perspective on 3D printers from a mechanical designer

  1. mech1

    your hopes might not become reality.. for example… it might become painless to print a design you find on amazon.. you don’t necessarily need to design it, material prices will come down as it become popular …

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  3. Jack

    I agree, I think 3D printers are analogous to paper printers, only more so.
    While paper printers have found a use case for printing small documents, they haven’t replaced printing of books, newspapers, posters, etc, and small print/photocopy shops do good business.
    3D printing is much less consumer friendly than paper, so I see the kinko model being how most people will experience it, rather than having one at home.

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  6. Matthew

    Hi, this blog is excellent regarding Printers, i really like reading your posts. Keep up the good work! You realize, lots of individuals are looking around for this info, you can aid them greatly.

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  8. Jigar Patel

    I do not like 3D printing. I only believe in physical prototype. I have made cam follower prototype for clean energy. I did not have proper 2d drawing. Without proper drawing it takes little more time and physical exercise but I like to work that way.

  9. jessedepinto

    Very intelligent thoughts. I agree that it will never replace/disrupt manufacturing; there is always a need for multiple processes to make a single product, one process is never enough.

    But of course it’s no fun to always agree, so let me play devil’s advocate. I believe 3D printers will find their way into everyone’s home. I disagree with the tech constraints that you base your opinion on, specifically:

    1. requires design input, which requires developed skill and time
    2. is a slow process, and
    3. materials are (currently) poor quality from an engineering perspective

    These are all describing 3D printing in it’s current state and the past few decades for the most part as well. The different is democratization. This tech will be experimented in thousands of garages and R&D labs. Of course we’re not dealing with Moore’s law since it’s hardware, but I believe the open source community can be just as potent. The open nature that evangelized 3D printing to where it’s at today has incredible power/ influence in the future. I have faith that the collaborative nature of 3D printing will allow it to advance at or near the rate of moore’s law.

    1. graehamd Post author

      Democratization could perhaps account for the “design input” issue. Already there are places where designs can be bought and traded online, and I do think they will grow. But if I’m buying a design online, and I have to be restocked on materials, why not just buy the thing online to start with? It could be quicker to get the thing, but I can think of very few instances where it makes a big difference to get a product in hours rather than in a day or two from Amazon.

      Democratization does not account for issues with the process being slow (especially relative to injection molding), or that materials deposited layer-by-layer are weaker than those made as a solid piece (particularly for FDM). These are fundamental issues with how the process works. I haven’t seen a convincing counter-argument to this, only hand waving and an appeal that quick growth of additive manufacturing now must surely continue at the same or a faster rate.

      I’ve seen an call for a “Moore’s Law” for 3D printers a few times. What evidence is there of this? A quick Google search found this as the most promissing link, which isn’t a very promising dataset to suggest a Moores Law relationship

  10. Andy

    I know this is old entry, but I came upon it and read it.

    1) It is always unwise to predict the future of a technology that is just now blossoming. It is very easy to find yourself in a bad position later on.

    2) I think the metal 3D printing holds some promise. After all, laser welding is heating of metal powder and layering it onto a base metal at very small deposition rates. We use this oil and gas to fix (enlarge) shaft diameters, among other things. Even if the bond of 3D printing was not as strong as welding, it will certainly still have uses. In fact, another method of fixing shaft diameters is to currently spray hot metal onto the shaft (HVOF). Obviously, this bond isn’t as strong as a welding bond, but we don’t need it to be (and it is still very strong). Sometimes, welding is the method we use because it is the easiest to use, not because our experience / calculations show it to be necessary.

    3) As you wrote this article a year ago, maybe 3D printing was only for the strong willed (?), but today I know for a fact that Shapeways can take a pen / paper sketch and turn it into a finished a product. Another company, 3-Sweep, can take a single photograph and turn it into a 3D object. There are multiple software companies that make it very easy (and free) to draw a 3D model and send it to a printer with many different material options.

    4) How much longer do you think it will be before so little expertise is needed that anyone can replicate or modify an existing object sitting in their home? How much longer until the design process is simplified to the point where anyone can create a brand new object and then manufacture it?

    The future is impossible to predict and as someone who works in one of the slowest evolving engineering fields, even I am starting to wonder when we will be able to manufacture a complex centrifugal compressor impeller with an additive technology instead of ordering an over-sized forging and hogging out material at the expense of time and tooling. Who knows?

    Let the economy and the ever evolving technological progress within it tell us what is possible and what is not possible. Let’s not fool ourselves into thinking that we know what lay ahead.



    1. graehamd Post author

      Thanks for your comments Andy.

      The post was a reaction to future predicting of others. Of course we can’t tell the future, but I think there is great value and learning in the process of trying to do so. I worry when hearing politicians talking about 3D printing as a savior of domestic manufacturing independent of other forces.

      I never said nor thought that there isn’t a role for additive manufacturing in the future. Instead, I don’t see them displacing injection molding and casting for high-volume parts, nor CNC/removal techniques where material properties are critical. I do think we will find an inherant limit to additive manufactured parts that is below those of the bulk material. This said, there are certainly opertunities for additive manufacturing where customization is required, and in prototyping and low-volume production.

      Yes, the article is a year old, but this actually isn’t that long in 3D printing technology. While its only been in the public eye for a few years, the core technology has existed for several decades. The examples you give as innnovations around 3D printing actually echo my opinion that additive manufacturing is good for niche, low volume applications.

      In terms of how long until product design becomes democratized, I think this discussion is independent of additive manufacturing. I work with a lot of young engineering students, and the learning curve with current technologies for them to become competent designers of even simple things is quite long. Design remains a quite manual process. To be honest, I’m not sure if “making” will ever be mainstream. Pre-industrial revolution it was. But society decided that it was better to specialise, and buy different things. If it does become mainstream, it will I think be through software that allows easy sharing, collaboration, and modification of design. But I don’t see much value in custom made doorstops and coffee mugs, other than a novelty factor that will quickly wear off.


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  12. sean

    I also realize this is old but I can’t help but comment.

    I agree in the near future 3d printing is not for everyone. I do disagree that it won’t be for everyone in the future. Your entire argument is based on the fact that 3d printing will never advance–ever.

    A company already exist now that no longer 3d prints with 2d layers it actually 3d prints. This in turn binds the polymers very similar to injection molded parts. The company is called Carbon3d (Google it). The printer will pretty much be able to work with most polymers as well. Since the parts it makes are no longer bonded in a layer fashion but more like it would be during an injection molded part it really does create the possibility to actually replace injection molding in certain cases. In addition the printer can print up to 100 times the speed of current 3d printers. You put that kind of advance in 3d printing in combination with a metal 3d printer that can actually be purchased for a few grand and you really have changed the way things can be manufactured. Is there some post processing of sanding or whatever, sure. But will it be any harder then assembling a piece of IKEA furniture, doubtful.

    Like someone has mentioned above. It’s pretty clear that you will be able to download digital STL files of models from a company like Amazon just like you would an mp3. Who’s to say that we also can assume that STL files will soon be replaced by a new file type that not only improves STL pitfalls but also can include a universal materials ledger inside the file. If this happened you literally could just be any one at home and upload the file to your printer and the printer will tell you what medium to insert in to the tray, ie: Nylon XXX, ABS XXX, Rubber XXXX, Stainless XXX.

    I would even bet that real 3d printers like I mentioned above in the future will have multiple material trays so that the user only has to load the materials before it starts printing.

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