Couplings, joints and cams

Couplings, joints and cams

3D printers are incredible machines. The FFF 3d printers are, for the most makers, affordable manufacturing automatons able to produce objects with an extraordinary precision. They almost literally can produce everything, what you can draw.  In a recent past, I needed to create a tent like construction which I can build and dismantle easily. There was nothing on the market, but lucky me,  I own a 3d printer.  I decided to use overall available 10 mm aluminum tubes for the construction rods and started to develop couplings, which I use to connect the tubes with.

evolution of the coupling

It took a lot of attempts until I was satisfied with a design.  The design, which works by using a cam mechanism to fix and release the tubes, is easy to print without any support structures. It includes hinges that are strong enough to bear the force and can be printed from almost any material. In the picture above you can see three evolutionary stages in the design process. During this process, I have designed and tested a large variety of couplings which can be used for constructions for almost any kinds. I have already published the first package  in our shop. The STL files of the parts are also available for download as single parts for free. The next package will follow soon. And the evolution is continuing.

 

The attributes

The couplings are to connect aluminum, iron and wooden tubes and rods of a 10mm diameter.  It doesn’t work with plastic tubes because they are usually too flexible and deform easily.

The names of the coupling are a little bit cryptic but it was the easiest way simply to number all the designs and versions.  If you want to have an overview of what’s available, select 3D Model – > Couplings category in the shop to list all the parts. I will publish some examples of the usage later.

The couplings profile size is 20 mm x 20 mm.  The couplings with square profile names start with SQ.  Soon, I will publish couplings with an octagon profile. I believe you don’t need to be Sherlock Holmes to figure out why their names start with HX. 

I believe you understand how cam lock mechanism works. “It works the same way as a beach umbrella!”, said a guy visiting us on  Maker Faire while moving the handle up and down, looking inside the couplings hole. A nice article about cams you can read on Wikipedia.

Part of the development was to find the best displacement shape. I ended with 4 cam designs.

The Cams

The cam designs are marked from A to D. In the picture, the numbers above each cam describe the diameter at each quarter. It starts with 10 – cam unlocked and ends with a higher number.  The higher last number simply means higher force which the tubes are locked with.

To stay simple:

The A, B cams are to be used with hard tubes, like aluminum or iron.

The C, D are for materials which deforms a little by the cam. Suitable for wooden rods.

The second one is always stronger but needs more power to lock and release.

This is a recommendation only. Just experiment and share your experience. Let me know if any cam doesn’t work as expected.

To attach a cam to the coupling you will need a 20 mm long M3 hidden head bolt with a standard (hexagon) nut.

The part SQ02V03 uses 35 mm long M3 bolt. either 30 mm long M3 bolt and square nut in the middle. To use it with a standard nut you will need 33mm long bolt (which is not the standard).

The Printing

The printing of the couplings is easy. If your intent is to use couplings inside at room temperature the PLA is the best choice.  Coupling will be  strong enough with standard slicer settings:

  • 2 vertical perimeter shells
  • 20% grid infill

If you want to make it stronger use, go for

  • 3 vertical perimeter shells
  • 30% infill, grid or cubic pattern

If you want to use couplings outside or have them more temperature resistant use other material like ABS, PET or ASA – especially if you want to use the couplings outdoors.

The couplings are designed to be printed without supports. Anyhow for successful print, the parts must be printed in a defined orientation.  The published STL files should have the models in printing positions. Some parts have a small pin which must point upwards for printing.

A recommended material for cams is ABS. It should work also with PLA, but ABS is a little bit more pliable and flexible which work well with ALU tubes. I recommend printing the cams with

  • 100% infill

Don’t hesitate to share your experience

Please inform us if you find some flows on models, zip files or any other content. Contact us if you miss some information.

I am also always curious what kind of usage you will find for the couplings. Share your experience with us. We will be lucky if you find the couplings handy for your projects.

Support us by buying any of the paid packages. A purchase is also possible if you have already downloaded all parts for free 😉

Share this post

Leave a Reply

Your email address will not be published. Required fields are marked *