Print NEVER sticking!

[alberto2000]

Printrbot Simple Metal with Heated Bed, Gear-Extruder Upgrade

I have had this issue since ever: the prints will NEVER stick to the bed! I've used hairspray, gluestick and now water/woodglue-mix ... nothing helps! The Z-Axis is correctly calibrated. As you can see in the image, the first few brim lines do stick perfectly well, but then after a while the printed material seems to "lift" upwards - not sticking!

I'm printing (printrbot green) PLA at 190deg on a bed at 60deg



Can anyone help me? This is killing me.

[alberto2000]

So I raised temp hotend to 210 and bed to 90 and then it "kinda" sticks just still very sketchy...

Any idea what is going on?

[RetireeJay]

Do you have a caliper? You could print just the first layer of a print, then kill the print, remove it, and measure the thickness of the layer. If you're using a 0.4mm nozzle, then the thickness should be significantly less, like 0.25 or less. The thinner the layer, the more force you've exerted to squish it onto the bed. Adjust your first-layer Z offset appropriately.

How thin can you go? You've gone too far if:
(a) There's no layer there at all, and your extruder clicks. In other words, zero clearance and the nozzle is blocked; nothing is coming out.
(b) You have a first layer, but every time the printhead lays down a new trace beside an existing trace, it plows up some of the existing trace so after the first layer is done it looks like a freshly-plowed field with little ridges for every pass of the printhead. If your Z correction is not right, you might see this plowed-up effect towards one side or one corner of the print.

I generally specify my first layer as double-width and a bit thicker than the other layers in the slicer in order to get more "squish".

Of course, all the potions and enhancers you add won't do any good if the surface is not clean to start with. Isopropyl alcohol is good for most cleaning purposes.

And, in the end, there can be bad batches of filament that just don't behave right. Try a different spool, one that you know worked before if possible.

[alberto2000]

Hi Jay

Thanks a lot for your thorough response.

I'm glad to say I finally got the print to stick after setting the first layer to 150% thickness in Slic3r, exporting the gcode and printing with OctoPi.

Currently printing my first Benchy, looking good so far! Will post an image of the result when ready.

Thanks a lot!

[Mooselake]

Did you readjust the head to bed distance, probably the probe offset, otherwise the Z home switch screw, after installing the new extruder? Even if you used the same hotend it will have moved when you removed and reinstalled it.

You can do a quick check by homing with a piece of copier paper between the bed and nozzle, there should be a slight drag when you try to pull it out. To be more precise bring the bed and extruder to operating temp as they'll both expand slightly I suspect you'll find that the gap is too far.

Once it settles down let us know what you think of the geared extruder. I have the DIY printed beta version (for a short time they sold a gear and bearing kit and you printed the rest) and would never go back to the hobbed gear version for 1.75mm filament, it's that good. I also have the Ubis 13HF which can melt a lot of plastic, and the geared gadget does a great job of keeping up.

Kirk

[alberto2000]

Thanks guys. I finally solved this. It was all about the first layer extrusion width / amount. I've set it to 200% now and it sticks super well on water/wood-glue mix and bed ad 60deg

[Mooselake]

If you're setting the first layer extrusion width in slic3r that percentage may not be what you think. IIRC it's based on layer thickness and not the calculated extrusion width, the hover help in the settings should tell you what it really is. Cura, KISSlicer, etc you'll need to review the docs.

Your first layer picture looks underextruded, there shouldn't be any gaps between the traces. Did you double check that you're getting a good nozzle clearance?

Kirk

[Jivix]

This could be caused by filament that has a high amount of shrinkage. You might be able to counter this by using a different infill method than circular/rectilinear, as those allow the shrinkage to compound in the same direction.

It could also be from excessive cooling, I recommend keeping the fan off for the first 2 layers, first layer at a bare minimum. You want to minimize physical forces on your filament until the second layer can come across and bond to the first layer, removing any strain built up in the plastic.