Better Car Hinges By 3D Printing

We often use 3D printing to replicate items we might otherwise make with traditional machining methods. Fraunhofer’s new door hinge for a sports car takes a different tack: it tries to be better than the equivalent machined part. The company claims that the new part is half the cost and weighs 35% less than the normal hinge.

Using tools in their 3D Spark software, the team analyzed different factors that led to manufacturing cost. Some of these were specific to the part while others were specific to the process. For example, orienting the part to minimize support and maximize the quantity that fit on the build surface.

By simulating the force on the hinge, the tools could remove material where it didn’t make much difference. This allowed a 35% reduction in weight. Less material also means less print time, further saving costs.

Honestly, nothing they did should be news to anyone involved in 3D printing. Orienting a part in a sensible way makes sense. We’ve seen the removal of unnecessary material both in 3D printing and traditional manufacturing. The interesting part is the use of tools to help automate these optimizations. We can’t tell what the pricing of the software is, and we are guessing it isn’t aimed at the hobby 3D printing market. But it is interesting what can be done and we suspect a little elbow grease and simulation in available software could net similar results.

In theory, any tool that can do finite element analysis ought to be able to determine the material to remove. We’ve noticed carmakers are embracing 3D printing.

30 thoughts on “Better Car Hinges By 3D Printing

  1. ” By simulating the force on the hinge, the tools could remove material where it didn’t make much difference. I am not an engineer but I read this and thought “finite element analysis”. Then I saw you mentioned it in your penultimate sentence. Surely car manufacturers already do this. Are we comparing like for like? Does this model allow for forces in a crash situation as well as in normal use?

    1. Of course the original manufacturer would try to remove unneeded material – to some extent.

      But there is always a trade off, especially with a complex, machined part.

      Every edge, cavity and fillet requires machine runtime and produces tool wear. Maybe there’s a few extra tool changes required, and if the work is on a different surface the part may need to be handled and re-fixtured to get it into an orientation where some of the pockets can be made – if they can be reached at all with a reasonable tool.

      You could, I suppose, use a machine with more degrees of freedom that could turn the part for a better angle …. but at what cost?

      3D printering typically has no such shape limitations, it’s just as easy to make a complicated part as it is to make a simple one.

      On the other hand, one advantage that conventional subtractive machining has is that the material tends to be pretty isotropic, it’s equally strong in any direction and doesn’t have internal planes where you have to worry about bad cohesion from a sub-par sintering. Also, it’s probably been through a rolling mill (a cheap step) that gave it a good grain structure.

      So many trade-offs. Great time to be an engineer.

      1. All 3D Printing methods have limitations on shapes. Even SLM parts.
        And Isotropic properties of SLM aren’t much of a problem, as you might think it is.
        A dailed in machine and process yields pretty consistent results.

        Pricing however is another beast in it self.
        In Aerospace 3D printing has a hard time being really competetive.

        1. I’d say that Aerospace is one of the few places where metal 3D printing’s cost does find justification. Raw manufacturing costs are such a small part of an aerospace product’s cost, and weight is of such importance, that it can easily find use. Compared to the astronomical QA costs for composite parts, a qualified printing process and inspection of critical dimensions can be a real cost-saver and breath of fresh air.

          The most obvious example is all of the printing going on in rocket engines nowadays. You can cut out many quality failure points in complicated plumbing while clawing back pipe losses and saving weight. I think that some engine nozzles are being 3D printed (superdraco maybe?). I vaguely recall news of some metal printed bracket in a Boeing airliner of some sort.

          There are likely plenty of 3D-printed brackets in products such as the Navy’s new jamming pods and other newer designs. The beauty of topologically optimized parts is that strength analysis is baked into the design process, and fatigue analysis is directly adjacent.

          It’ll take a while longer for DMLS and the like to really catch on in automotive and manufacturing, though. Weight is simply far less important.

        2. we have some applications for it. But you have to remember aerospace is conservative to the core.

          one of the applications where it does work well is hydraulic/pneumatic manifolds. the ability to make curved channels and shrink-wrap the cavities is supremely useful. plus for certification purposed you’re obliged to pressure test 100% anyway, so you don’t need much in the way of safety factors (proof pressures are incredibly high anyway).

          the problem lies in that quite a lot of companies boast about having an SLM printer, but few know what to do with it. The printers are only used for rapid prototyping and sit idle a lot of the time. Since it’s stil seen as a new field is is assumed the printers will depreciate like milk and should be written off in 5 years. This means while actual cost can be quite low, getting a decent quote for production work is really, really hard.

          Also print quality is dependent on thermal conductivity of the material, which means aluminium tends to result in nasty surfaces, which results in nasty fatigue properties (not that they are needed for manifolds, if you design for it). Also also, while TiAlV6 prints gloriously and has better strength properties than the base grade 5, aluminium is available mostly as AlSi10Mg, which is not the strongest alloy around. T6, while good for a cast part in the same material is useless in SLM parts. Scalmaloy is, again, glorious, but so expensive to license few offer it and you might as well use Ti with thinner walls.

          Most companies want an arm and a leg, 20 samples and your first born child to machine printed parts too. While this is functionally largely the same as machining castings, which has been done for donkeys years and for pennies, they see a printed part as magic and the customer as having deep pockets. Again, companies that have an AS9100 certification are usually not short on work, and like doing things that they have done for ages and know they can make money on, and can do without getting blamed for crashing planes.

          so yes: Aerospace can benefit for SLM parts, and some do, but the peculiarities of the industry, and the companies that offer the service both being stuck in the 70’s makes it a little hard. The only real development is in engines, and printed fuel nozzles have become regulars. For us personally, competing with ASML for supplies is an uphill battle.

      2. Other factors relating to costs in machining is managing coolant loss via the swarf and evaporation. Also, swarf needs to be disposed of. Any reduction in swarf in mass production can achieve large savings.

    2. It’s typically called topological design and is, as you intuited, another layer of analysis on top of FEA. It’s only really come into vogue over the past few years as tools have become more accessible.

        1. Even if they design it so deliberately weakened it will fail to fatigue shortly after their warranty runs out, its just a a hinge, but a new one one on it, its hardly forcing you to ditch the entire car… There are heaps of components on a car that will be replaced in its lifetime because the whole is still good but this cheap/easy enough to replace part has worn out – its nothing new there…

          And in practice to be sure it meets safety standards etc its probably along with most of a cars frame/body/seating actually still very over engineered for the loads it will see in normal use – after all the crash protection ratings are a selling point even if they are not legally required in your area.

          1. “its just a a hinge” but it’s also an example of designing a part for a specific lifetime. Apply to the rest of your car and you have a car that becomes a clunker in a specific time frame.

  2. Fraunhofer is not a “company”: it’s my tax Euros at work.

    The scandal is that their results are nevertheless often (MP3, I’m looking at you!) patent-encumbered.

    Stealing from the unwashed masses to give to the rich. Nice trick.

        1. Frauenhofer does a lot of science. Not only application but also basic research. That all costs money. If you want it done without patents and licenses you need to give them more public money. With the licenses and patents people in other countries also pick up some of the cost because they also benefit from the technology. Also all that research is incredibly important for the industry to stay competitive.

    1. Based on their website, the part from your tax money is about 30% (Grundfinanzierung) and the rest are from sources available for other companies, too. The patent income is presumably a part of that 70%, so if that would be left out either less development could happen or more of your tax money would be needed.

  3. Is this part made from stainless steel?

    Stainless steel for some unknown reason prohibited and unwelcomed for use in car body, engine, transmission and suspesion parts. You could find something from stainless steel only in some expensive exhausts and it will be some crap like martensitic AISI 410, and if you want a good, everlasting exhaust you have to make it by yourself from something like AISI 304/316.

    So, all that holes in such part will be eventually filled with wet dirt and part will began to rust very quickly. Since the part was designed for lowest possible weight, any rust will immidiately make it too weak to do the job. It would be a luck, if such part will be just door hinge or some not very important internal mount or arm. If you will have such thing as some suspension or transmission part, you are in a great trouble.

    PS: Does anybody know a car where complete body and most parts that subjects to moisture, anti-ice reagents and dirt made from stainless steel? All that suspension arms, radiator fan housings, etc. Will buy for any price. I knpw about DeLorean, but unfortunately it have only outer panels made from stainless steel, not the whole body structure and other important stuff.

    1. I’d pay more for a car with stainless steel body/frame/suspension/exhaust parts, but it does mean a price disadvantage. Not only is the material more expensive, but forming and welding are more difficult. I doubt that a stainless steel engine block and heads makes any sense at all.

      1. It’s incredibly heavy as well. With modern fuel economy standards, there is no benefit of stainless steel. It would take decades to offset the carbon cost of manufacturing a car predominantly out of stainless steel to recoup the benefits of materials longevity.

        1. > It’s incredibly heavy as well.

          Why do you think so? Stainless steel have the same density with slighlty larger strengths. (AISI 304 – 8000kg/m^3 with 500Mpa, 945 – 7900-8100kg/m^3 with 450Mpa).
          Body parts made from stainless steel have the same weight as ones made from regular steel if the sheet thickness is the same. And you don’t need to paint them, so no additional weight of primer/paint/varnish.

          > With modern fuel economy standards, there is no benefit of stainless steel.

          There is no any difference at all in comparison with regular steel in fuel economy.

          Yes, some cars have aluminium body, or even titanium ones, so lighter weight, but they are mostly from top segment, where customer have no any problem in just buying new car every year. Also, aluminium rusts too, and in some conditions even faster than steel.

      2. > forming and welding are more difficult.

        In no way stainless steel is harder to form and weld. It is one of the easiest and pleasant material to weld and due to higher plasticity over regular steel, it could be formed into much more complex shapes. Check out the stainless pans, sinks and other widely accessible press-formed things. Big stainless stell sink made from AISI 304 will cost much less and will have more complex shape than any front wing stamped from that shitty steel foil. You could easily form body parts from good stainless steel on regular dies and that dies will even last longer. In USSR some people who work at car factories sometimes made a stainless steel body parts on factory equipment to replace them on their cars. Ypu still could find old Volgas (GAZ-24) with stainless bottom, trunk or fenders. But it become impossible to do after the fall of USSR. IDK why and how, but now nobody will agree to do it for you for any money. Also I didn’t hear anything about making stainless body parts on West or third-world factories. Everything I could find was one stainless steel Jeep, but AFAIR, stainless steel panels was copied by hand, not at the factory. There also was a story when fans of WV Golf Mk2 tried to order a batch of stainless steel fenders from some aftermarket spare parts manufacturer like Klokkerholm and similar who routinely made them from regular steel. All that manufacturers just immidiately roughly cut any conversations on that matter, not even talking about the price. So, you can’t even order anything for any money in that sphere. Even in batch quantities.

        > I doubt that a stainless steel engine block and heads makes any sense at all.

        Agree, that is why I didn’t mention engine in list. Rust is definitely not the main problem for engine.

        Stainless steel is more expensive, yes, but you don’t need to paint stainless steel car body at all. And painting a car body part cost much more than that part itself. So, stainless steel car body could be even cheaper than rusting one. And will last nearly forever. Just replace weared rubber bushings and joints on your car, and you don’t need to buy a new car ever. You could even replace engine to something more effective or even electric, when it become reasonable. No trash, no unnecessary environment abuse with making new cars or utilising old. But somehow that way of environmental care is not in the list of ecologists and manufacturers at all.

        1. In the late 1970’s in the Philippine islands craftsmen were hand forming new Jeep body parts from stainless steel for Jeepneys. Those were originally built from Jeeps left there from WW2 and the Korean war years but circa 1978 all those had been cut up for stretching the back end to seat many riders. So they had to build new from scratch, and use stainless so the bodies wouldn’t rust. That was a good thing on islands surrounded by salt water.

    2. There is no equivalent to HiTen steel for sheet in stainless. This is critical for safety, remember first euroNCAP test on chinese cars that weren’t using these kind of specials steels.
      For intricate parts, nothing beat GS cast iron: cheap, highly castable and good rust resistance.
      And the final nail in the coffin is price. Stainless is really expensive.
      There is a good reason that they use a sport car example, where cost doesn’t really matter, but for the masses, no way.

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