Printing Tests with Silicone and Different Sized Nozzles

By: Anh Do

 

The final stage of the 3D printer assembly is nearly completed. We also started testing the printer with different deposition materials and nozzles last week.

Goal:

The goal is to create test prints of our 3D printer. The test model was a 20x20x05 mm block. From the tests, we decided the suitable deposition material and nozzle for our Bio Printer.

Tools:

  1. Hardware: Bio printer, 12cc syringe with nozzles/needles in various sizes. The dispensing needles can be purchased here.
  2. Software: Slic3r bundled with Pronterface host software
Slic3r is a tool which translates digital 3D models into instructions that are understood by a 3D printer. It slices the model into horizontal layers and generates suitable paths to fill them.

Slic3r is a tool which translates digital 3D models into instructions that are understood by a 3D printer. It slices the model into horizontal layers, generates toolpaths to fill them and calculates the amount of material to be extruded

Pronterfacesq

Pronterface is a free 3D printer controller software for 3D printers developed by kliment

For more information about Slic3r and Pronterface and how to set up  the printer, please visit this link.

 

Materials:

  •  CVS Aftersun Tropical Aloe Vera Moisturizing Lotion: Aloe Vera gel is the clear, jelly-like substance that looks similar to the expected bio-gel printing material . We choose Aloe Vera gel to do the test print since with the small amount, the gel can hold its form. Also, it can be cleaned up easily, and does not clog the nozzles after a period of printing time.

Aloe Vera gel is the clear, jelly-like substance.

  • Silicone: As mentioned in the previous post, silicone gel acts as an elastic solid after a short flow time. Thus, it can permanently hold the printing structure. However, it is hard to clean up the leftover silicone inside the syringes tube and nozzles.

Testing procedure:  The test was done after the printer was calibrated. Visit this links for x,y- axis calibration blog and  z-axis calibration blog

  • Load the deposition gel to the syringe
The silicone was inserted from the tip of the syringe in order to eliminated air bubbles

The silicone was inserted from the tip of the syringe in order to eliminated air bubbles

With air mixed in with the building material, the flow from the nozzle tip will not be uniform, and results in poor dispensing

Loading material

Insert nozzle after loading the material

  • Place the syringe  in the support house. The syringe was hold firmly with the foam tape.

Syringe was in place

 

The foam tape was attached in order to firmly hold the syringe

The foam tape was attached in order to firmly hold the syringe

 

  • Add the test bock.stl file in Slic3r. The file can be found  here.

Slic3r

  • Run Pronterface and execute the file.

Printing test block

Printing result:

Aloe Vera Gel – No nozzle:

The gel could not hold its form

The gel could not hold its form

Even though the Aloe gel was thick, it could not hold the block form after the third printing layer. Therefore, this gel was not suitable for this Printer.

 

Using silicone: With Silicone, we tested how smooth the flow was when changing the nozzle sizes. By that, we could find the settings to improve the printing quality.

When changing the nozzles’ sizes, we also need to change the nozzle diameter under Printer Setting tab in Slic3r. The nozzles’ sizes were given in gauge, so we need this table to convert the inner diameter of the nozzle into mm.

Use the table to look up the accurate inner diameter of the nozzle in mm

Use the table to look up the accurate inner diameter of the nozzle in mm

Printing with 18 gauge green nozzle:

The silicone was dried and did not come out smoothly

As shown in the picture, the model had the same dimension as expected. However, the cube was hollow since the gel didn’t come out as fast as the movement of the syringe. The nozzle went  under printing layers.

Possible cause: high printing speed, big nozzle size and small layer height setting

 

Printing with 22 gauge black needle:

22 gauge Black needle

The gel did not come out as fast as the nozzle’s movement

Again, the silicone did not come out smoothly. However, the under layer printing occurred

Possible causes: the needle was too small, or the linear actuator’s rotating speed was slow.

 

Printing with 20 gauge pink nozzle

20 gauge pink nozzle

Under layer printing

 

Too much flow rate when the Filament Setting was changed smaller as default (15mm)

This test had the same problem with under layer printing, especially when we changed the setting of filament diameter lower than the default value (15mm)

Possible causes: incorrect filament setting, small layer height setting.

 

Conclusion:

Even though the printer works, we still need to adjust the printing setting in the host software for a better printing quality. Some perimeters should be modified in Slic3r and Pronteface in order to eliminate the first testings’ problems.

  1. Nozzle diameter
  2. Filament diameter
  3. Layer height setting
  4. Speed of the linear actuator.
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