Articulator calibration for printed models: why the bite is off
Articulator calibration for printed models: why the bite opens or shifts after mounting, how to check the articulator and the plates, and what to fix first.
A case looks perfect in exocad, the models are printed, mounted in the articulator, and the bite is open by a fraction of a millimeter or the midline has moved. The design is rarely the problem. Usually the articulator, the plates or the print do not match what the software assumed. This post is for labs that mount 3D printed models in physical articulators, and it explains where the error comes from and how to find it.
Why the error appears
The software calculates everything on a defined geometry: the distance from the models to the hinge axis, the position of the mounting plates, the articulator type. A physical articulator is a mechanical object with tolerances, and two articulators of the same model are never identical. If the real one differs from the geometry the software uses, the printed models land in a slightly different position.
Mechanical articulators have always had this issue. With plaster, the mounting absorbed the differences, since the model was fixed where it actually sat. With printed models and plates, the position is defined in the software, so the articulator must match it.
The three usual causes
The articulator
Wear on the joints, a loose screw, a pin set to the wrong value or a different articulator than the one selected in the software all move the model. Systems that connect printed models to the articulator often provide a calibration part or procedure, and it should be done when the articulator is new to the workflow and after any repair.
The plates and the print
Plates and model bases are printed, so their dimensions depend on the printer. A resin that prints slightly large makes the base sit high on the plate, one that prints small leaves play. Long models can also bend during post-curing. Before blaming the articulator, print a test part and check the printer exposure calibration.
The seating
A base that does not seat fully on the plate, because of a support remnant, resin residue in the retention or a magnet not flush, lifts the model. It looks like a calibration error and is a cleaning problem.
A simple check routine
- Mount a known test model on the articulator and compare the closed position with the software.
- If the difference is the same on every case, the articulator or its setting is the likely cause: calibrate it.
- If the difference changes from case to case, look at the printing and the seating first.
- Keep a record of which articulator was used for which case. In labs with several articulators, a model mounted on the wrong one gives exactly this error.
Articulator type in the software
In exocad, the articulator type chosen in the Virtual Articulator defines the geometry. It should match the physical articulator the lab uses, and the digital facebow data, when present, should come from a system calibrated for the same articulator. The virtual articulator guide explains the parameters.
For systems like RotoClick, calibration is part of the setup and adapts the system to articulators other than the one it was designed around.
When to ask for help
When the error persists after checking the print and the seating, a remote session on the lab’s own case usually finds it faster than trial and error. Remote support covers the exocad settings, the Model Creator plates and the checks on the printed models.
Frequently asked questions
Why does the bite open after mounting printed models?
The usual causes are an articulator that does not match the geometry the software assumes, plates or models printed with a dimensional error, or a model base that does not seat fully on the plate. Calibration and a test print find which one it is.
How often should an articulator be calibrated?
When it is new to the workflow, after any repair or impact, and whenever printed models start to differ from the screen. Labs with several articulators should calibrate each one and keep them apart.
Can the printer cause the problem?
Yes. A resin that prints slightly too large or too small changes the fit between model and plate, and long models can warp during post-curing. The printer should be calibrated before blaming the articulator.
Does exocad need to know which articulator is used?
Yes. The articulator type selected in the Virtual Articulator defines the geometry the movements are calculated on. A different physical articulator needs its own setting or a calibration.