Supports
Hold the part the way the real one is mounted, because the supports decide the answer as much as the load does.
--fix "bolt holes d=4.5" --fix "wall x=min"A support is an optional kind followed by the faces it holds. With no kind it is fixed, so
--fix "x=min" holds every point of the faces at the minimum x still. Pass --fix as many
times as you need.
| Kind | Example | What it means |
|---|---|---|
| fixed | x=min, holes d=4.5 |
every point on the faces held still |
| fixed in some directions | fixed-z faces 7, fixed-xy faces 3,4 |
only those directions held, the others free |
| bolt | bolt holes d=6.6 |
the hole and the washer ring around it held still, with an outer radius twice the hole’s |
| roller | roller y=0 |
slides in its plane but cannot move off it, for symmetry planes and sliding fits |
| wall | wall x=min |
rests on a rigid wall that it can push on and lift off, solved as contact |
The words fix, clamp, clamped, bolted, slider, symmetry, rest and support also
work, as fixed, fixed, fixed, bolt, roller, roller, wall and wall respectively,
so --fix "clamp x=min" is the same as --fix "x=min". Only fixed supports can hold some
directions and not others, as in clamp-z x=max.
Picking the right kind
A fixed face is perfectly rigid, which is stiffer than any real mount, so the stress right at its edge climbs as the mesh gets finer. Wobbl knows this and reports the stress a short distance away, listing the edge peak separately as an artifact of the support. A bolted hole is the better choice for screws and bolts, because only the hole and the washer ring are held. At bolted and fixed holes Wobbl also runs a bearing check, which divides the force through each hole by its projected area and compares that with the bearing limit.
A wall is for faces that rest against something without being attached, like the back of a shelf bracket against the wall it hangs on. The part can push into the wall and lift away from it, which Wobbl solves as contact. A coarse first solve finds the patch in contact, every mesh starts from the patch the last one found, and the loop stops when fewer than 2% of the contact nodes change state.
A part that is not held
Wobbl refuses to solve a part that can still slide or spin, and names the motion that is free.
the fixtures leave the part free to spin about z. Add a fixture that stops it, for example fix a hole or a face that is not parallel to the existing onesTwo rollers on parallel faces, for example, still let the part slide along them. Add a support that stops the motion it names.