Why does the first layer only adhere to bed if I increase the temperature by 10 °C and drop the speed by 75 %

Question

I'm running a stock Ender 5 pro with the filament that came with it, and using Creality Slicer 4.8.2, but I'm only able to get reliable bed adhesion if I increase the bed temperature from 50 to 60 °C for the bottom layer and decrease the print head speed by about 75 % from the default profile for the Ender 5.

The machine is absolutely stock, and is fresh out of the box except for bed levelling.

I used the default bed leveling print and that came out well, so I'm reasonably certain that it's not a bed leveling issue. The problem seems to be with models that I've made myself in blender and exported as STL files.

In all cases the raft that was generated by the Creality software has printed out perfectly, but the print has only partially gone down when it came to the model itself.

Answer 1

Your bed is too low - raise it by turning the knobs underneath.

The first layer should not look like strings sitting on the bed as per your photo. Instead it should be a wider strip that looks somewhat like an electronic circuit trace, or like someone has pushed wet paint out of a tube that is being wiped across the surface.

My method is to head the bed with "preheat" in the menu, and let it sit at printing temp for at least 5 minutes. This avoids the heater being at temp but the top of the glass bed being cool.

Then start your job. As the brim or skirt is printed, actively watch it in person and twiddle the height knobs a quarter turn at a time. You want the "end view" or cross sectional view of the printed filament to be like this:

 _____<==>_____

and not like this

 ______0______

and definitely not like this

       0
_______________

If the head starts scratching the bed, you've gone too far so lower the bed back down again (effectively raising the print head a little)

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Here's a print in progress trying to show a better brim. Notice eachgstrand is ovalised and mushed down. That brim will come off in one piece afterward.

Answer 2

Assuming Creality's stock firmware still doesn't have Linear Advance enabled, there's a fairly hard requirement to go slow on the first layer. This is because, as the toolhead accelerates up to higher speed without advancing the extruder extra to compensate for the backpressure in the filament-path/nozzle, you'll have an interval of underextrusion, giving less contact area for the extruded material to cling to the bed at the same time there's added force pulling it in a direction parallel to the bed surface. This becomes less critical to adhesion starting with the second layer, since the new material is bonding to itself rather than just trying to stick to a bed.

Having the bed hot will help it stick better and maybe even help reduce the pressure at the nozzle by reducing the heat loss, so it might work around the problem. But in general, you don't want to be in a situation where a few degrees of temperature difference are the cutoff between a failed print and a successful one.

Anyway, do all the usual stuff to improve bed adhesion, and especially make sure your bed height is as close to perfect as you can get it, if you want moderately fast printing to work. But don't be surprised if you need to upgrade to a version of Marlin with Linear Advance (or to Klipper) to get successful high-speed first layers.

Answer 3

Looking at the image, the deposited filament lines do not connect. If we consider that you have the correct filament width in your slicer and the correct amount of steps per millimeter for the extruder or no problem with extruding is present, your initial bed to nozzle gap might be too large, level with a thinner piece of paper or subtract a few tenths, see this answer for redefining the Z-height. Alternatively use a slicer option called “Z offset setting”, see this answer.

Why does the first layer only adhere to bed if I increase the temperature by 10 °C and drop the speed by 75 %

If the nozzle gap is a little too large, the filament doesn't get squished enough for proper adhesion. This is seen as non-connecting filament lines. It looks as if the nozzle is under-extruding, but if that has been checked, a larger initial gap has the same effect. If you increase bed and or hot end temperature and slow down, the filament gets time to adhere properly, even when the gap is larger.