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In a project budget, hardware regulary takes an important part of the budget. Making your hardware by yourself achieve the dual goal to get a suitable piece of hardware and to reduces the overall cost. Hinges made out of metal or wood are not easy to make and a good hinge will probably take you a lot of time. Through, not anyone is skill enough or tooled properly to succeed.

As the local store is not that close to my home, I was regulary tempted to 3D print pieces of hardware for my projects. If you need a knob, a cleat or a handle, plastic might be strong enough. But hinges should bend without flex, and hold a good amount of weight. I tryed a lot of printed hinge designs, but I was regulary desapointed.

Most of printable hinges are not heavy duty, even if it uses screws as axis. I mean especialy those which uses screws as axis. Because steel is stronger than plastics and always contributes to make the hinge fail. Ins some cases, the screw thread grinds the plastic on the barrel side. The hinge get some play quickly and gets fragile.

The full plastic hinges are not better. Plastic is a reasonalbly weak material, and you need oversize dimensions to get some stiffness and some strenght. As nobody wants to add a big Fisher Price alike piece of hardware to his project, most designs are small hinges with consequently a small shaft and a small bushing. So the 3d printed hinges fails to hold more than small pannels, like plexiglass or so. Unfortunately, even with light weight materials to move, 3D printed plastic hinges breakes easily. The main reason is the way they are printed.

The weakest hinges are those printed in three parts : two leaves and a printed axis. In most cases, that hinges needs to be mounted verticaly or the shaft can get out. Then there's the two parts hinges, mostly ball jointed, and obviously it cant hold a lot. Then comes the single print intricated ones. And there's a dilema. If your hinge lay on the printbed, you will get a good shaft and barrel strenght, but it won't be round enough for a good motion. If your hinge is printed standing up, you will get a good motion, but the shaft or the barrel will not have enough material to get a good cohesion between the layers and will be weak. ..

Step 1: A Design That Solves the Problems.

The idea was to get a strong shaft and a strong barrel in a reduced area. The only way to get this, is to draw a variable diameter shaft and barrel.

The shaft needs strenght especialy at its attachement points, but as you get far from theses points, you don't need much strenght. On the contrary, the barrel will be stronger at the centre. So the overall hinge will be stronger than a constant diameter axis and barrel in the same build volume. As the gap between the axis and the barrel is small and constant, the variable diameter don't brings extra play.

After a lot of trys, the best ratio was fifty support fifty hinge, spared as 2+4+2 = support/hinge/support. The profile of the hinge gets larger smoothly until the barrel area. The countersunk screw holes makes the screws as discreet as possible while pushing strongly the hinge to its support. I added teardrops holes to avoid overang trickle on the holes while printing.

I rounded all horizontal sharp corners to get the smoothest possible motion on the printer. So the print runs faster and is consistantly more quiet !

Step 2: Printing !

At its original size, the perfect hinge is 40x40mm (1-37⁄64in or 1,57") It is reasonably scalable. I printed it at 150% with no noticeable extra play. Joshua downloaded the hinge from thingiverse and printed it out at 75% with no issue.

Of course, the hinge is meant to be printed verticaly to get a very smooth motion. If your printer is a bit out of calibration you may have to breake the hinge for its first opening. You can do it by hand, holding one leaf of the hinge firmly on a table hedge from one hand and pushing down with the other hand. My 10 years old child manage to do it.

I recommend PLA or PETG as printing material, because ABS and Nylon bends too easily.

You can get the last version of the hinge and read printing specifications on the perfect hinge thingiverse page. (and see my face too, if that matters uh...)

Note, the Perfect Hinge is actualy my most downloaded part ever.

<p>Would it be possible to leave a hole for the (metal) axis, so you can fit it at the highest point and then continue printing? </p>
<p>Hi Thomas. I'm glad to have you here too. That hinge was designed to get the best possible strenght, so you don't need any metal part. On a 3d printed part, whatever it is, if you want to use a metal insert you need a lot of plastic around it to hold it in place. If not you will create a weak point. So, in most cases, using a metal insert is not a good idea. Here, the variable diameter plastic shaft gives extra strenght on the hinge. There's no weak point, that's the idea. You may find a lot of hinges on thingiverse which uses m3 screws as axis. All are incredibly weak except the extra thick ones. But the extra thick ones are not stronger than the variable shaft hinge, because the limit is plastic lamination itself. Quite the contrary, metal brings a lot of stress on plastic parts. That's why I called it the &quot;perfect&quot; hinge, because it gives the best possible strenght while using a small amount of plastic and it prints on a single step. As you don't need any hardware in it, it's also cheap and quick, because you can use it just out of the printbed. I don't claim this is the best hinge ever, it's still plastic and some other designs may be better in different situations. But if you need a flat hinge of 40mm for medium duty purpose, you probably should consider this one, just at it is. </p>
<p>Thanks for the excellent explanation. I guess I should try to find more time to finish my printer so I can experiment with this :-)</p>
<p>You're welcome mate. I should have mentioned that metal insert can be still interesting, but only if you want to avoid wear problems. For example, screwing directly in plastic is possible, of course with screws with a thread made for plastic, which is a long thread, because you need enough material between threads. So if you use the right screw it will be ok UNTIL you don't have to remove the screw frequently. In this case, the plastic will get loose quickly. So you will want a metal insert to avoid wear problems. But, like it is always with metal vs plastic, you need enough plastic to stand metal stress. This will be compression stress in this configuration.<br><br>Anyways, you'll see when you'll get your first printer : there's a lot to learn about that technology. May I suggest you document yourself about the &quot;3d printing paradox ?&quot; But this is one of the coolest tool I never had !</p>
<p>lol - that looks puzzling :-) Now, winter ante portas means more time for indoor hobbies.</p><p>I have seen metal threads you can insert during printing. So they inspired me to think about using a metal axis. The time will come xD</p>
Nice design! I printed out and it worked great! I tried to design my own in fusion 360 but when I printed it printed the barrel as one piece. How did you design this to make it where the pin prints still? Thanks!
<p>I guess you forget to introduce a gap between the male and female parts of the barrel. Depending of your printer's precision, you want a gap at last 0,2mm wide. For most commons printer, the perfect gap should be around 0,3 to 0,5mm wide. Try it out ;) </p>
I bet that is what I forgot to do. I had originally done that but had a problem and had to redo one side. Thanks!
<p>Nice fully-3D-printable hinge. What other materials do you suggest printing this in, besides PLA and PETG?</p>
<p>Thanks Dylan. Well, I gave a try with ABS. My opinion is the hinge can twist a little bit with ABS because the material is softer. Trough, the hinge stays very strong and if it don't have to deal with a heavy pannel you may not see the difference. I did not try nylon because I thought it will be soft even more. I haven't try more materials. Probably Carbon fibre reinfoced PLA, POM and Tribo should do it great, but I did not try yet. Cya</p>
<p>DO you have the parametric or STL ?</p>
<p>Hi Bastien, I gave the link to the part on thingiverse (open source) at the end of the instructable. I guess the link works. Feel free to ask again if the link is broken, I'll repair it. </p>
<p>Oh, and I forget to say the perfect hinge is not parametric. As I said on the Instructable, a user printed it @ 75% with no issue at all. But I recommend to design another version and do some prototypes prior to use it if you need drastic dimensions changes for your project.</p>
<p>Super Thanks I will start printing this Original and I will check it ,</p><p>Well done , thank you for your support</p>
<p>Hi Sebastian there is a link to thingiverse in the description</p>
<p>Thanks Daggs !! </p>
<p>Really nice. Thank you for posting.</p>
<p>You're welcome guy ;)</p>
Most Impressive.
<p>Thanks Flint ! </p>
<p>Impressive! </p>
<p>Thanks Jason. I was surprised myself how strong it was !</p>

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