Flexible fastening element: rivet. How to do it right.

[mihkov]

I often use rivet nuts. Among them there are the most interesting ones, which have a whole bunch of atypical circumstances. I have 2 main questions:

*Attention, we are not talking about adding a Toolbox here, all fasteners are made as parts, they are in a special folder and their IsToolBoxPart property has been reassigned so that they have a cog icon in the design tree and all the resulting properties

nut1.jpg (7.19 KiB) Viewed 1700 times

1. About rivets in general.
We all know that rivets are produced for a certain range of fastened thicknesses. For example, a rivet 4x8 - diameter 4mm for fastening a package from 1 to 4mm (for example). How I made such rivets: I have one detail file for a rivet made of one material: for example, aluminum. In it I have parent configurations for each standard size, for example: 4x6 4x8 4x12 4x20... .
In each parent configuration, I have child configurations for each allowable thickness of the sealed package in increments of 0.1mm, for example. And by inserting such a rivet into the assembly, I select the appropriate configuration. For example, I fasten 2 sheets of 1mm each, take the configuration: 4x8-2mm. Attention question: Who has experience in implementing such fasteners as Flexible? That is, I only have parent configurations 4x6 4x8 4x12 4x20... and when inserted into the assembly, I link one side of the package to the other - the part itself determines the thickness and rearranges the geometry of the rivet to suit the thickness of the package. I immediately see problems: A. if the package is outside the range of a given type of rivet size, for example, the thickness is 50mm, the rivet model will be distorted and errors will appear. B. If the assembly contains many flexible rivets of the same size installed at different thicknesses: for example, a 4x8 rivet is installed on packages of 2mm, 2.5mm and 3mm, will it fail?

2. About non-round fasteners (for example, hex rivet nuts). Hole hardware only supports round holes or slots. Is it possible to use a hole for fasteners and get hexagonal holes on surfaces that do not lie in the same plane and fill them all with an array of riveting nuts, so that they are turned along the axis of the hole?

[AlexLachance]

#1
If you' want to build a flexible sub-assembly, you can make it act as you desire.

Either, you can have the original occurence drive all the other occurences, or you can have all occurences have their flexibility be individual, though I doubt SolidWorks would handle this well.

You could build the flexible sub-assembly to have a limit distance mate which would allow the minimum and maximum and then you could mate it from the level it is inserted to have it be "set" at the appropriate thickness.

Think of it the same way as you would build a hydraulic cylinder assembly to be flexible within it's limits.


#2
Rather then using their shape, use their origins and mate your assembly accordingly.

[TTevolve]

Use a design table and configurations. You can have the original part, plus all the thicknesses in the formed state, they will all count as the same rivet on the BOM regardless of what thickness you select for each one if you use the

[mihkov]

I don't have a problem with the BOM display and don't want to do it as a flexible subassembly. What I want is a flexible part.
For the rivet, this is exactly what she needs.
Now I have an option with multiple configurations for each thickness - but there is no beauty in this solution.

I made such a rivet now by inserting it into the assembly and making it like a flexible one - it asks to indicate the surface of the bottom edge of the package of sheets being fastened. Everything works except one thing. The flexible part does not rearrange the internal equations when changed, and accordingly the tail of the rivet does not change as I wanted. I'll attach the rivet below.

[mihkov]

The result and my conclusion on this problem.
Is it possible to make the fastener flexible and insert it into the assembly - Yes. Is it convenient - No.

What is the problem: Flexible fasteners, such as rivets and all other deformable fasteners, have working ranges. A "flexible" element is implemented in Solidworks in such a way that it only changes the geometry attached to the external reference.
If I want to use equations, this is impossible, they are simply ignored in the Flexible element (they receive the last calculated value when saving the part).

I don’t know how to track the exit from the range using pure geometry without equations.
Accordingly, when inserting rivets and applying “Flexible” to them with reference to the thickness of the package being fastened, which is included in the range, everything is fine (A).
When the thickness of the package is out of range, but the geometry was still able to somehow adjust, everything is bad, but it looks normal (B).
And when the thickness of the package is far out of range, we get an error in the Futures tree and the geometry from the last saved configuration (C).
At the moment, the only way is a table of parameters for 450 configurations for each allowable thickness in increments that are reasonable for you.

[Ryan-3DS]

So here is your enhancement request..probably one in the system for this.
Function: Control flexible component(s) geometry within an assembly using 1) user defined value; 2) user-selected faces (planar); 3) system determined (think next face, through all, etc.)

Or do we need a whole new concept for fastening/joining materials? The current process is to create holes, stack material in an assembly, calculate tenon lengths, and then choose appropriate nuts/bolts/washer stackups. All to join material..would be much easier to have a tool that helps decide joining methods, joining hardware and patterns (if needed)...then create the holes in the material and insert required "parts" into an assembly.

It's crazy how we continue to accept the old methods which are based on a history-based model tree. It's time to move beyond this. Let's let the computer compute and do the real "aided" part of CAD.

Stepping down and away from the pulpit.

[mihkov]

So here is your enhancement request..

While there are no improvements, keep from me a life hack on how to place hex fasteners in hex holes. (To be honest, the fastener has a cylindrical concentric surface with a hexagon, but if it didn’t exist we would have created an auxiliary axis).
1. In the assembly, you create holes for fasteners with a 3D sketch; the points must be on the plane (sketch mate) and in the middle of the hexagons (auxiliary line at the corners of the hexagon + mate at the center).

2. A hole with a drilling diameter, if the hexagon is 7.1 mm, then the hole is 7.2 mm - so that we bite off the body of the assembly. If you are chamfering so that the hexagonal fastener is flush, then the hole can be 7mm, and the cutout will be chamfered and the binding will be concentric to the chamfer (the binding is important for aligning the fastener to the face)

3. We match the hexagonal fastener to the first hole. There must be a concentric attachment (to align the fastener along holes that do not lie on the same plane)

4. We make an array of fasteners tied to an array of holes, and select the option to align elements by holes (not by the original one).

Done.