First support layer not sticking.

[wirlybird]

Hi all,
Frustrating problem here. I am doing a print with a big support section. The first layer of the support part is having a bad time sticking. The actual first layer of the print sticks fine.
One thing I think I can see is that I am not getting a squish on the first support layer and then the nozzle catches on the next pass. I think if I got the same squish as the rest of the first layer it might be better.

I have included the factory file.

Thanks for any ideas.

[CompoundCarl]

It has the same "squish" as everything else on that layer. If you look at the gcode, it's pretty easy to check that. So it seems like it's being printed the exact same way as everything else as far as I can tell from the gcode

[wirlybird]

Thanks for checking it out. I am lowing the "lower" separation value from 1 to 0 since the supports are on the bed to see if that helps.

When I watched the first layer I could see good squish on the main part but the support first layer looked like a more round bead being put down.. That was why I thought about the squish being different.

Thanks again.

[Derrick]

5 suggestions:

Use as fat of a first layer as you can. So for 0.2 mm layer height, set the first layer to ~150%, not 90%. This will help buffer any height variation across your substrate.

Include a skirt and/or brim to cover 75% of the support area with a fully solid first layer.
Edit: You could also add a manual block of 0.2 mm (or whatever your first layer is) height selectively in the area you want it to print. Try Tinkercad.com if you don't already know CAD. The supports will generate on top of this block, but there will be a 1 layer gap.

Print the first layer at 220 or 230C, then set layer 2 to your normal 210C.

Increase your pillar support resolution to 2.5 or 3 mm.

If all else fails, try this:
https://www.amazon.com/Platform-Sticker ... 01H35YR7Q/
I print PLA at 35C on this. It sticks amazingly.

[wirlybird]

Interesting ideas. I like widening the skirt to cover the support area or making a .2mm shape and placing where the supports will go.
I am still fuzzy on the increased first layer thickness and what really happens there - 90% vs. 150%.

Those blue plates look like what came on the bed originally. they do stick pretty good.

[dkightley]

I am still fuzzy on the increased first layer thickness and what really happens there - 90% vs. 150%.

Sort of simple, really, if you read the guide thread re the Layer tab.

With a layer thickness of 0.1mm and a first layer thickness of 90%, the slicer will lay down a layer of 0.09mm thickness...but still squirt out the same amount of plastic as if it was laying down a layer of 0.1mm. At 50%, the layer will be 0.05mm, and again the amount of plastic being squirted out would be the same as if a layer of 0.1mm is being laid down. With a first layer thickness of 150%, the slicer will lay down a first layer of 0.15mm....however the amount of plastic being squirted out will be for a layer of 0.15mm thickness; ie approx.two times the amount.

All of the above is totally unconnected to any other setting...such as Layer Width or Extrusion Multiplier. These settings have an additional effect on the amount of plastic the slicer will command be squeezed out! Note also that the layer thicknesses are based on the nozzle starting out at exactly the right height in relation to the bed for a layer of 0.1mm to be formed should the layer thickness be 100%.

[wirlybird]

Thanks for the reply and explanation. So, let me see if a restate thing right!

Given a .2 layer height - if I go less than 100% then the layer will be "squished" by that percent as you said - such as 90% would yield a .18 layer, a 10% reduction in layer height.

Conversely with a .2 layer height if I go 150% I would get a resulting layer height of .3.

So, when the layer thickness percent is less than 100 it will squish the layer but still extrude the same amount of material for the default layer height, where, if the layer thickness is greater than 100% the layer height will be a multiple and extra material is extruded.

[dkightley]

My only correction:

So, when the layer thickness percent is less than 100 it will squish the layer because it is extruding the same amount of material for the default layer height, Whereas, if the layer thickness is greater than 100% the layer height will be a multiple and extra material is extruded because of the increased height.

[wirlybird]

Great! I think I am catching on!! Really appreciate the time in explaining this.

How do you think I would go about this. I would like to have a .2 first layer (.2 general layer height) to maintain dimensional accuracy. I would also though like to get some squish to help with adhesion on the first layer.

I am thinking to get the squish I need to go below 100% but I lose layer height.

This may be more a hypothetical but I am curious how to go about it.

[dkightley]

Easy....

Set the first layer height to say 150%....and in the GCode tab, lower the Z axis by whatever the extra 50% is.

Eg for a layer height of 0.2mm, 50% is 0.1mm, so lower the global Z axis by 0.1mm....to -0.1



And btw, the accuracy of the model height will not be affected by varying the first layer height. It will still be + zero, - 1 layer height.