Joints composition

Doesn't matter if you want to reduce wear of your links with a point or a linear contact or to deduce hyperstaticity, you are in the right place. Follow the guide !  

Choose the target joint

Set the mobilities and what's fixed

Select a first link

The tool has made a selection for you

Follow the guide

Choose the best combination

What can be the purpose of this tool ? First, it will help you to improve the resistance to wear and the longevity of you links, mainly the ones will a small contact area.

That's not all, we will help you to reduce your assembly issues caused by hyperstatism. Who had an issue assembling two parts that were not isostatic ? Almost everyone. Tired of designing adjustment mechanisms and setting again it too often ?  To reduce this hyperstaticity, we have several solutions :

Solution Skills and tasks  Cost
GD & T ISO GPS, GD &T analysis  High
Deformable components Dimensionning Low
System modifications Spécifications, Lot of modifications, Architecture Middle
Adjustment  Skilled people, maintenance Middle
Modification of a mechanical link Knowing the mechanical links Low

Here you can see that modifying one or more links can solve your mounting or wear issues quickly without redesigning everything, at a low cost.

Tutorial

Lets focus on the first line of the tool. This is the link you want to design, your target. As you can imagine, Blocked is related to a bond, an impossible mobility, while Mobility says that the system is free on those axis. In the following example, we want a link that is capable of transmitting the force only following the x axis (translation only). This link is a ponctual (of axis X). Alright ! But a small headless screw or a small flange will wear faster than fast. How to improve it easily and quickly ?

It's time to split this link in several simple and reliable links. In most cases, you won't need more than two or three links to solve your issue. If you think that's not easy enough, don't worry, the tool is able to make suggestions. Please note that all the links are supposed to be expressed at the same point, indeed, some complexes solutions may not be proposed by this tool.

Time to choose you first link

You will have several possibilities:

  • Sliding pivot of axes X, Y or Z (« PG »)
  • Pivots of axes X, Y or Z (« Piv »)
  • Sliders of axis X, Y, Z (« G »)
  • Ball cylinder contacts (« LA »)
  • Spherical contacts (« rot »)
  • Ponctual cpntacts (« Ponct »)
  • Plannar contacts(« AP »)
  • Finger joint, blocked in rotation on one axis (« Doigt »)
  • Line contacts (« LR »)

Depending on the chosen mobilities, the tool will remove wrong answers.
Wanna try? Sure, let's take 30 secondes to follow the step by step tutorial !



We advise you to open another tab to ease the learning. Just follow the steps and check the boxes. 
Here, the aim is to design a more reliable ponctual contact for when you index something in position or when you want to mount an actuator. We will do that without increasing the hyperstaticity of the system.  

  •  Select Blocked for Z translation

    


  • Chose an planar contact of the Z axis AP Z

   


The internal mobilities correspond to mobilities that are not useful but present. For example, most actuator have a rotating rod, even if we don't use it. Removing this mobility is expensive and not useful, so we can keep it. 

Here, the planar contact AP Z can rotate around the Z axis, as well as the spherical contact Rot. It's redundant but not an issue. 


  • Select a spherical contact Rot



Result


We have a system composed of a planar contact and a spherical contact which results in a more robust and reliable punctual contact (Z direction)



From a weak linkage, we went to a more resistant to wear punctual contact link. Please not that a spherical contact is not usually a sphere in a sphere but can be, for instance, a connecting rod.