Over extrusion during bottom layers

[aceware 0]

 

I'm getting a "Foot" equal to the height of the bottom layer on every print. I've calibrated the extruder and all the axes without affect. I carefully watch the print during the first 8-10 layers and it looks as if the nozzle is pushing material beyond where it's supposed to. This only occurs during the bottom layer. The part dimensions return to their proper dimensions once the floor is complete. I've also inspected the g-code and the X and Y coordinates are not changing from beginning to end. Any suggestions on how to make this behave?

[Slashee_the_Cow 620]

It would help to know what printer you have, and if you can provide an example Cura project (.3mf, in Cura go to File > Save Project) then we can look at your settings to see if anything looks of.

 

Make sure you've properly levelled the bed and set the Z offset correctly. If it's trying to print a little too low, it'll squish.

If you have automatic bed levelling make sure to run that (I put it in my startup gcode... better to take a minute levelling the bed for a good print than getting a bad print... after the line that says G28 add one that says G29). ABL adjustments slowly go back to normal after the first 10 or so layers (depending on your printer).

[gr5 2,333]

Short answer: initial layer horizontal expansion is your friend here.  It's a setting in cura.  Set it to a negative number.  Typically half the width of your nozzle so try -.2 as a first value.

 

Also maybe increase the distance very slightly between nozzle and bed using whatever leveling procedure you use.

 

Longer answer: squishing the bottom layer is critical to get your part to stick.  Having the part come loose during printing (what people often call warping as the corners come loose first) is a much worse problem than the "elephants foot" issue you describe (it's often called "elephant's foot").

 

In addition! Because of the heated bed, and because PLA softens at 52C and because the bed is above that (as it should be for other important reasons), the layers starting around layer 3 or 4 tend to be *inward* a bit.  Which accentuates the "elephants foot".  This is fixed by keeping the bed no hotter than around 60C.  If you raise the bed to 70C this will be quite obvious.  Your bed temp sensor may read a bit low meaning your bed may be a bit hot.  You can test with an IR non contact temp sensor pointed vertically (glass reflects a lot of light at an angle so it will see the temp of whatever is reflected at the same time and average it somewhat so aim straight down.