The REALLY FLAT print bed

In the pursuit of a better print bed situation, I decided to embark on this project.

Materials needed:

Superglue <- available just about everywhere

[From Robo 3D shop] - Update: you can find these on partsbuilt.com
Buildtak sheet
(optional) print bed

[From Amazon.com]

Double-sided thermal tape -> https://www.amazon.com/gp/product/B06ZY1JNJV

Borosilicate Glass plate -> https://www.amazon.com/gp/product/B01IB2CC7W

From a pharmacy:

Nitrile Disposable Exam gloves

Caveats:

While the project will give a really nice flat print bed, the downside of this project is that the print volume of the C2 printer is reduced a tad. [ X,Y,Z - from 125x125x145 mm to 125x125x140 mm]

Second item: In the Octoprint start script, you will need to disable the auto-level command (gcode G36) and substitute the home command (gcode G28). What I discovered is that with a flat surface (like the glass plate), the auto-level routine miscalculates the correction to be applied in the Z axis. While printing a large area model, this miscalculation causes the bottom of the model to be distorted.

Instructions:

1) Before removing the print bed, use a black magic marker to mark the front of the print bed. Writing Ft or front will suffice.

2) Remove the standard print bed. Turn the bed over to expose the 4 magnets. With the superglue, put a very small drop at the bottom of the magnet wells. If you look carefully at the print bed, you will notice a slight gap between the print bed and the bottom of the magnets. It is at that position that you apply the superglue. Be very careful to not use too much glue as it will be difficult to remove the excess.

3) After giving the superglue a few minutes to set, turn over the print bed and remove the Buildtak sheet.

4) Cut 9 squares of thermal tape. Remove one side of the tape and apply the thermal in the following pattern (apologies that the middle pieces are not perfectly centered in the graphic):



Press down to get good adhesion to the print bed.

5) Carefully remove the covering sheet from each piece of tape. Before handling the glass plate, put on a pair of nitrile exam gloves. You don't need fingerprints on the glass. If by chance you handled the glass plate and left fingerprints on the glass, use 91% isopropyl alcohol and a paper towel to get the glass squeaky clean.
Center the glass over the print bed. Then press the glass to the print bed.

6) Apply a fresh sheet of Buildtak to the glass plate. Try to center the Buildtak in the center of the glass plate. Also, be very careful to not get air bubbles under the Buildtak. You are striving to get the Buildtak as flat as the glass plate which you are applying the Buildtak to.

If you notice air bubbles, carefully lift a corner of the Buildtak to the point where the air bubbles are, and then using the free hand, rub the Buildtak so as to work out the air bubbles. When finished, the buildtak should be free of air bubbles.

7) Place the new print bed into the printer and run the Z offset wizard.

Finished project:




Next post - software changes.

 

Octoprint:

Log into Octoprint. Click on the Settings menu and select GCODE script from the left panel. Make the following changes and then click on Save button.

 

Cura (or other slicing software):

In Cura 4.0, Select Preferences, -> Configure Cura, -> Printers -> Machine Settings button. Change Z (Height) from 145 mm to 140 mm. Then Close & Close.



For other slicing software, like Simplify 3D as an example, you will need to find the machine settings and make the change as needed.

 

Question: Is it worth doing this project?

Answer: Depends on you. For myself, after shimming the modified print bed, I just feed the printer with filament. Other than adjusting the filament material and or profile in Cura, I print and get the finished model off of the print bed.