Week 5: 3D printing test (group assignment)

This week we followed the 3D scanning and printing class (see video here)

This week we had group and individual assignments. This page is about the group assignment that we did for testing the 3D printing process.

Preparing the print job (Cura)

We used fo our test the 3D tolerance test available on thingverse

In our FabLab we have various machine available: three RepRap with nozzles of 0.4mm or 0.6mm, an MakerBot and a Formlab stereolithography (SLA) machine.

We used for our test a RepRap (3) with a nozzle of 0.4mm. The material we are going to use is PLA 1.75mm filament (3mm filament is available for the bigger nozzle).
This machine has a modification move the filament motor away from the extruder moving part.

After opening the Cura we open our .STL file and lay the part flat on the machine bed.

Screenshot-2-Cura-final-part

The software comes with presets setting for each machine. No major modifications are needed, but these are some of the important parameters.

IMG_0_Print_settings

  • Layer height: is the main setting influencing quality. Lower mean better resolution, but also longer printing time. Max layer height usually is around half the nozzle diameter.
  • Line width: is usually similar ot the nozzle size.
  • Wall thickness/line count: determines the thickness of the vertical walls. Bottom and top layers usually have higher thickness to avoid bending and appropriate support.
  • Infill density: is the main setting that we can change based on the structural requirements of our part. Low infill (10-15%) is faster to print but will make our part less resistant. High infill (30-40%) is slow to print and makes our part more resistant. Low infill also requires more top layers to be added to the default values.

  • Temperature: optimal temperature for PLA is between 205-215 C and can be varied adjusted based on the speed and need of cooling of the material.

  • Support: is important to enable for structures that have hanging part that would otherwise fail to print or fall down.

  • Build plate adhesion: to help the adhesion to the plate differnt support structures can be printed like ‘skirt’ (mainly to clean the nozzle before printing), a ‘brim’ or ‘raft’ (that give an increased level of support and help adhesion to the bottom layer)

  • Retraction: is useful to adjust to avoid material to be extruded when the nozzle moves between separate parts of the piece
  • Travel speed: default is fine. Too fast will resul in a failed print. For fiberflex material requires circa half speed of PLA.
  • Cooling: should always be enable for better quality

Switching to the ‘layer wiev’ in Cura we can check the artifact and layer paths generated by the software with each setting variation.

Screenshot-3-Cura-internal-layers

Once all the parameters are set, we are ready to save the file as GCode.

The printing process (RepRap)

Once we have saved the GCode file in Cura we can send it to the printer via Octoprint

  1. Open octoprint (bookmarks for each machine are saved in the browser).
  2. Upload the file to Octoprint: save the file locally to the machine.
  3. Prepare the printer: IMG_3_Printer_setup.jpg.jpg
    • Remove the bottom plate, clean it from existing residual material and apply a little hairspray (helps the bottom layers stick to the plate)
    • Setup the filament in the extruder: cut it 45 deg to make it easy to go in the extruder hole.
    • Extrude for a bit of material on a side of the plate to clean the nozzle.
    • Press “Auto home”. If the plate is not aligned disable the stepper and move it to home manually to adjust and level it.
    • Extrude a bit more of material before running the print job.
  4. Run ‘Print’ from the Octoprint interface!
    IMG_4_Printing_progress

This is the final result before removing it from the plate:

IMG_5_Finished_part_on_the_plate

Lessons learned

This is the final result detail of our print :)

IMG_6_Finished_part_detail

  • On a side little extruded artifacts are present: in this case these are easy to cut with a knife. For optimal future results these can be fixed changing the retraction parameter.

IMG_7_Finished_part_extra_extruded_filament_detai

  • We have issues with missing details: thines holes, overhanging semicircle. These can be fixed by adjusting the line thickness if the nozzle resolution allows it.

IMG_8_Finished_part_missing_details

  • The machine running Cura in our lab is very slow and low on resources. I tried to export the Cura configuration from that machine to my Linux environment but without success. The configuration file structure varies across versions and crashes the program on my machine. More time could be spent in this to create a common configuration to be shared.

Happy 3D printing! :wave: