# Assembly joints for solids and shells **URL:** \ **Category:** Feature Requests\ **Created:** [September 14, 2026, 5:43pm UTC](https://prepomax.discourse.group/t/assembly-joints-for-solids-and-shells/3671 "2026-09-14T17:43:39Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [September 14, 2026, 5:43pm UTC](https://prepomax.discourse.group/t/assembly-joints-for-solids-and-shells/3671/1 "2026-09-14T17:43:39Z")
> [@Export individual (selected) meshed parts](https://prepomax.discourse.group/t/export-individual-selected-meshed-parts/3665/5): > > and a little teaser for the next version Predefined joints handled by coupling and equation constraints? Awesome! ---
**Author:** ![arnie](https://avatars.discourse-cdn.com/v4/letter/a/ba9def/32.png) [@arnie](https://prepomax.discourse.group/u/arnie)\ **Post date:** [September 14, 2026, 6:18pm UTC](https://prepomax.discourse.group/t/assembly-joints-for-solids-and-shells/3671/2 "2026-09-14T18:18:11Z")
Wow ! Can’t wait to try it. ---
**Author:** ![Matej](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@Matej](https://prepomax.discourse.group/u/Matej)\ **Post date:** [September 14, 2026, 7:01pm UTC](https://prepomax.discourse.group/t/assembly-joints-for-solids-and-shells/3671/3 "2026-09-14T19:01:00Z")
I need some more testing, but it looks promising. It uses rigid-body equations and should work for small deformations. ---
**Author:** ![MisiaKu](https://avatars.discourse-cdn.com/v4/letter/m/e5b9ba/32.png) [@MisiaKu](https://prepomax.discourse.group/u/MisiaKu)\ **Post date:** [September 14, 2026, 7:05pm UTC](https://prepomax.discourse.group/t/assembly-joints-for-solids-and-shells/3671/4 "2026-09-14T19:05:18Z")
Very interesting image. Are the yellow symbols a new type of joint? ---
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [September 14, 2026, 7:15pm UTC](https://prepomax.discourse.group/t/assembly-joints-for-solids-and-shells/3671/5 "2026-09-14T19:15:03Z")
> [@MisiaKu](#): > > Are the yellow symbols a new type of joint? As mentioned above, they are joints modeled with rigid bodies and equations. ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/3/3ffbeec32f61e9f9df563889653b326e1277f432.png) ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/d/d941da8a6d934dc0572fb73bfc09709357ddf7c2.png) ---
**Author:** ![Matej](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@Matej](https://prepomax.discourse.group/u/Matej)\ **Post date:** [September 14, 2026, 8:22pm UTC](https://prepomax.discourse.group/t/assembly-joints-for-solids-and-shells/3671/6 "2026-09-14T20:22:02Z")
I think their use for shell elements is limited (problems with \*Rigid body), and to work at all (CalculiX bugs), some workarounds were necessary, but the tests are promising. ---
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [September 14, 2026, 8:32pm UTC](https://prepomax.discourse.group/t/assembly-joints-for-solids-and-shells/3671/7 "2026-09-14T20:32:18Z")
Did you consider using coupling constraints with orientations instead of rigid body constraints in some cases (e.g. for hinge) ? ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/d/d8505b060b7ebc1048cea4f977fd3f5f3c53209d.png) They could help avoid the known limitations of rigid bodies. ---
**Author:** ![Matej](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@Matej](https://prepomax.discourse.group/u/Matej)\ **Post date:** [September 15, 2026, 8:53am UTC](https://prepomax.discourse.group/t/assembly-joints-for-solids-and-shells/3671/8 "2026-09-15T08:53:52Z")
> [@FEAnalyst](#): > > Did you consider using coupling constraints with orientations instead of rigid body constraints in some cases (e.g. for hinge) ? For solid elements, the rigid joints work. But for shell elements, I tried the kinematic coupling on the shell edges, which crashes CalculiX with the access violation. So I did not investigate it further. But I did investigate the possibility of using springs instead of couplings-rigid\_connections. This is a penalty-based approach that yields approximate results but has no problems with shells/solids. So will probably add it this way. ---
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [September 15, 2026, 8:56am UTC](https://prepomax.discourse.group/t/assembly-joints-for-solids-and-shells/3671/9 "2026-09-15T08:56:00Z")
> [@Matej](#): > > But for shell elements, I tried the kinematic coupling on the shell edges, which crashes CalculiX with the access violation. I’ll check it and report to the CalculiX team if needed. Couplings still need a lot of improvements, especially when it comes to their use with 2D elements. But I thought that node-based surface would suffice for kinematic coupling to work with shells. ---
**Author:** ![Matej](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@Matej](https://prepomax.discourse.group/u/Matej)\ **Post date:** [September 15, 2026, 9:15am UTC](https://prepomax.discourse.group/t/assembly-joints-for-solids-and-shells/3671/10 "2026-09-15T09:15:22Z")
I will have to find the example I created to see if I used a node-based surface. ---
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [September 15, 2026, 9:19am UTC](https://prepomax.discourse.group/t/assembly-joints-for-solids-and-shells/3671/11 "2026-09-15T09:19:49Z")
It seems to be working with a node-based surface: [Shell edge kinematic coupling.pmx](https://prepomax.discourse.group/uploads/short-url/buQJxlgZ0w8xKLQxIJ5cDiIsMwC.pmx) (83.1 KB) ---
**Author:** ![Matej](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@Matej](https://prepomax.discourse.group/u/Matej)\ **Post date:** [September 15, 2026, 1:44pm UTC](https://prepomax.discourse.group/t/assembly-joints-for-solids-and-shells/3671/12 "2026-09-15T13:44:31Z")
I tried your model in CCX 2.22, and it solves, but not in Nlgeom. But it does not solve at all in CCX 2.23. So, for now, I will only support rigid and spring joints. Spring joints work for Nlgeom. ---
**Author:** ![Matej](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@Matej](https://prepomax.discourse.group/u/Matej)\ **Post date:** [September 15, 2026, 1:47pm UTC](https://prepomax.discourse.group/t/assembly-joints-for-solids-and-shells/3671/13 "2026-09-15T13:47:11Z")
I moved the conversation about joints to a new topic. ---
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [September 15, 2026, 1:52pm UTC](https://prepomax.discourse.group/t/assembly-joints-for-solids-and-shells/3671/14 "2026-09-15T13:52:24Z")
> [@Matej](#): > > but not in Nlgeom Yeah, it’s probably the same issue as rigid body + shells + Nlgeom. > [@Matej](#): > > But it does not solve at all in CCX 2.23 That’s strange. A regression in ccx 2.23 ? I have to discuss it with their team then. ---
**Author:** ![ANYS](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/anys/32/7737_2.png) [@ANYS](https://prepomax.discourse.group/u/ANYS)\ **Post date:** [September 15, 2026, 2:31pm UTC](https://prepomax.discourse.group/t/assembly-joints-for-solids-and-shells/3671/15 "2026-09-15T14:31:58Z")
Did you try a frequency analisys to see if the model is properly constained?. Kinematic needs special care. ---
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [September 15, 2026, 3:33pm UTC](https://prepomax.discourse.group/t/assembly-joints-for-solids-and-shells/3671/16 "2026-09-15T15:33:52Z")
I have to investigate it further anyway before submitting a bug report. This was just a quick test to see if it works at all or crashes.