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Posted · How To Increase First Layer Print Success with Poor Bed Adhesion

For example: I have a Tina2, which does not have a heated bed and has permanent cooling*.  Bed adhesion is therefore a significant problem trying to get a good first layer of print.

 

[* There is a single hot-end fan which cools both the heat break and the work-piece, so it would be inadvisable to turn off the fan.]

 

I use a brim to stabilise the first layer.  The outer lines of the brim give the nozzle a chance to get going, and often they detach from the bed and I pull them out of the way.  Once a circuit has printed properly, the next line inside has something to anchor to in addition to the bed itself, and then the brim completes successfully.

 

Next drawn is the wall of the print.  This needs to be set to "Wall Ordering: Outside To Inside", so that the first line of the wall is in contact with the brim, otherwise "Inside To Outside" would draw the first line of the wall away from the brim with risk of it failing.  Straight lines are generally OK, but the moment the nozzle turns a corner the sideways tension can overcome the adhesion and pull the line off the bed.

 

Once the wall has been drawn (outside to inside), the fill starts as diagonal lines connecting the inner walls.  If "Inside To Outside" causes the inner wall to fail, the infill has nothing to attach to and will likely fail as well.

 

Skirt is of no use in this situation, because it only primes the nozzle and does not provide any stabilisation (it is offset away from the model).  Raft overcomes this problem, but can be difficult to remove from the model afterwards.

 

Therefore, brim plus outside to inside wall ordering seems to be the best compromise... except for one problem:

 

If the model contains any overhangs, they will require support - even for quite steep angles where otherwise no support would be necessary.  By printing inside to outside, if there is a slight overhang the inside wall provides support for the outside wall... so long as the inside wall is printed before the outside wall.  Clearly, this is incompatible with the outside to inside requirement for the first layer.

 

This resulted in my wish-list item for a first-layer override setting for wall ordering, and a feature request on GitHub:

 

https://community.ultimaker.com/topic/7804-wish-list/?do=findComment&comment=338031

 

https://github.com/Ultimaker/Cura/issues/20167

 

As stated on GitHub, I was using a work-around by slicing with both outside-to-inside and inside-to-outside settings, then splicing the first layer from the former onto the rest of the layers from the latter into a hybrid .gcode file.  @GregValiant then chipped in with an idea to modify a support blocker as a cutting mesh to modify the slicer settings for just the first layer, which (after further discussion and help) I adapted to the solution presented here (see also https://community.ultimaker.com/topic/46624-per-model-settings-on-side-toolbar/#comment-340339).

 

The attached file is a Cura project file containing a pre-loaded 100x120x0.2 block assigned as "Mesh Type: Modify settings for overlaps", "Cutting mesh", "Wall Ordering Outside to Inside".

 

When saved, the project file includes all the Cura settings which would then override the existing settings when the file is loaded. By opening the project file as a zip archive, I found the "Cura" folder within can be deleted - the result is that, when opened, the block is loaded complete with its cutting mesh properties, but no other settings are loaded so the existing user settings are preserved.

 

100x120mm is the appropriate size for my printer's build plate (Tina2). That can be scaled within Cura to suit any other printer (and then re-saved, but note the paragraph above).

 

0.2mm thickness (Z dimension) is chosen for the following reasons: I found that the override takes effect if it represents at least half of the current layer height. That means the override will work with any first layer thickness up to 0.4mm, and will not affect a 0.15mm second layer as long as the first layer is no less than 0.125mm.

 

I hope this is of use to someone, it is definitely an improvement for me.

 

First Layer Override: Wall Ordering.3mf

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    Posted · How To Increase First Layer Print Success with Poor Bed Adhesion

    This subject of increasing the initial layer bed adhesion came up in another Github posting a couple of years ago.  I had written a post-processor for the person and I suppose it might have some value for non-heated bed printers.

    Unzip it and place the "InitLayerZWallsV2.py" file it into the "scripts" sub-folder in your Configuration folder.  It will be available with the other post processors as "Initial Layer Walls Z-Adjust v2"

    InitLayerZWallsV2.zip

     

    It goes through the first layer and drops the Z for the inner and outer walls (by a user input amount).

    Then it goes through the second layer and increases the flow for the inner and outer walls by an appropriate % to make up for the fact that the wall layers are taller and need the extra plastic to maintain line width.

    So the gcode would look like this.

    ;TYPE:SKIRT
    G1 F600 Z0.2 ; Initial layer Z
    ;TYPE:WALL-INNER
    G1 F600 Z0.15 ; Walls Z
    ;TYPE:SKIN
    G1 F600 Z0.2 ; Initial layer Z
    ;>>>>>and the second layer
    ;TYPE:WALL-INNER
    M221 S125.0 ; Adjust Walls flow
    ;TYPE:SKIN
    M221 S100 ; Reset flow

     

    The overall effect is to simply over-extrude the walls on the initial layer but the poster insisted that increasing the flow wasn't the same as adjusting the height.  They were wrong but I did it that way since it didn't really make a difference other than about another minute to add the second layer flow adjustment.

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    • 2 weeks later...
    Posted · How To Increase First Layer Print Success with Poor Bed Adhesion

    I am now looking at whether the first layer inherently suffers from under-extrusion, and whether is is possible to add compensation into the cutting mesh for the first layer (see above).

     

    https://community.ultimaker.com/topic/46657-first-layer-thickness-–-compensate-for-z-offset-fdm/

     

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    Posted · How To Increase First Layer Print Success with Poor Bed Adhesion

    It's worth noting that a brim isn't just there to make sure the first lines of your actual model adhere fine, it's to help them stay adhered instead of warping while you're printing. Printing on an unheated bed is doable (if you're using PLA). In my experience (and that experience does include a printer with an unheated bed) the key is surface area. Not the size of your model, I'm talking a smaller scale. A rough surface has a ton of little nooks and crannies or just slight changes in height that there's a lot more contact area than it looks like (or than a flat surface).

     

    So with my unheated-bed printer (and no part cooling fan, either) I just did the classic thing. Blue painter's tape. Brush with very stiff bristles. Cover the bed in the tape, give it a good scratching up with the brush, print. Scuff it up a bit more between prints. When the tape starts to wear away, just replace it with some fresh stuff (and don't forget to give that new tape a half-decent brush before you try to print). Got to about a 90% success rate for initial layer adhesion. If you're going to start doing this from not having done it, remember that you'll need to adjust your Z offset because the tape adds a bit of height to the bed.

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    Posted · How To Increase First Layer Print Success with Poor Bed Adhesion
    On 2/5/2025 at 12:48 PM, Slashee_the_Cow said:

    It's worth noting that a brim isn't just there to make sure the first lines of your actual model adhere fine, it's to help them stay adhered instead of warping while you're printing.

     

    Sure.  I don't think I said any different.  What I'm saying is that by rearranging the order features get printed, there is something to anchor lines to instead of leaving them to their own devices and the whim of drag. I have found it beneficial.

     

    On 2/5/2025 at 12:48 PM, Slashee_the_Cow said:

    Blue painter's tape... 

     

    But of course!  Nonetheless, I have experienced warp pulling the tape off the bed... (off topic for this thread)

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