One of the main uses of 3D printing within Teaching Labs is in the production of 3D prints of molecules from an X-ray diffraction structure.

This guide explains how to prepare a ball and stick model prints in full colour from a CIF file and print using the Bambu Labs H2D in Teaching Labs with multicoloured printing. These instructions can be adapted to obtain prints using alternative printers.

Requirements

A Crystallographic Information File (CIF file) for the desired structure. CIF files are provided by the scXRD service in the department or can be obtained from the Cambridge Structural Database of the Cambridge Crystallographic Data Centre.

Software

Mercury is software designed for viewing X-ray structures which can output CIF files into STL or VRML formats

MeshLab to convert VRML files into OBJ files for multicolour printing

Bambu Studio for slicing the model for printing (or appropriate 3D print vendor software for other printer manufacturers)

Scale

We recommend preparing and printing using molecule settings in Mercury of 15 mm Å⁻¹ (1.5 × 10⁸ : 1) or 10 mm Å⁻¹ (1 × 10⁸ : 1) and have produced models using both settings. Smaller than this results in very fragile models.

Single colour or multicolour printing

The above instructions for full colour printing can be modified to print scXRD structures in a single colour. These are much quicker to print, and are also suitable from printing using the 3D printers in YorCreate.

Element colours

The colours of available filaments is listed on the Bambu Labs H2D printer page, with models usually printed using PLA filament. In Mercury you can see the full atom colour list by opening the periodic table example (For Windows this is usually located at C:\Program Files (x86)\CCDC\ccdc-software\mercury\examples\PeriodicTable.mol2) and a screenshot is also reproduced below. It is possible to change Mercury display colours, but in general it is sensible to try and minimise deviating too much from the typical assignments.

There is only a limited range of filament colours available and/or are used enough to be worthwhile stocking, so some compromises have to be made with the assignment of colours to filaments.

MeshLab

1. File | Import Mesh and select the WRL file that was exported from Mercury

2. File | Export mesh as and select Alias Wavefront Object (OBJ) and in the saving options select normal, face select colour and select all.

Bambu Studio

1. Ensure the printer information has been synchronised

2. File | Import (long option) and choose OBJ file

3. Press reset, then color match and select the colours to be appropriate for the molecule and click ok

4. Click auto orientate and check a suitable orientation has been applied

5. (bit of notes about a setting file, but for now this is cloud synchronised)

6. Under Process change the dropdown to Molecule

7. Toggle advanced above molecule

8. Check supports are Tree hybrid, etc (KG to sort)

9. Slice (Filament saving)

10. Can reposition prime tower

11. Check filament changes

12. When click print turn on timelapse, nozzle, bed levelling, +1