Print head knocking over prints

I have an Ender 3 S1 Pro…

Often, after several layers the print nozzle start rubbing against the top-most layer, extrusion gets messed up, and either the print head knocks over the print or drags it across the bed.

I have a print job going right now, where I increased the layer height from .2 to .3 mm, in the hope that that will work. But I shouldn’t have to do that, right? Seems like that would mess up the appearance and structural integrity of the final product.

Is there a physical test of the printer that I can perform to determine if the Z axis is functioning properly?

I would recommend reducing your flow/extrusion rate, usually prints being knocked by the nozzle is a sign of over extrusion. When previous layers are over extruded they end up being slightly thicker than they should be often resulting in collisions with the nozzle.

Try reducing your flow rate and see if that improves things. You might also find using different infill patterns may help, the standard cubic style infill has small overlaps which can create small bumps so you may find a different infill pattern works better.

Good luck and hope you get it solved.

Thanks, Nikoli, for the quick reply.

I forgot to mention that I replaced the .4mm nozzle with a .6mm. Maybe I should have reduced the extrusion rate at the same time? Would a .6mm nozzle by default flow faster than a .4mm?

You’re welcome :slight_smile:

Yes if you have changed nozzle then the extrusion rate would be different to how it was with the 0.4 nozzle. Usually you can adjust the settings within your slicer so that they match with the 0.6 nozzle, most slicers have profiles for different nozzle sizes so have a look around your slicer software to see if there is one already setup that you can use.

Usually the main differences between the 0.4 and 0.6 config wise will be line widths. I have just had a look in my slicer at the Ender 3 S1 Pro profiles for both nozzle sizes and there is a considerable difference in line widths between nozzles. Hopefully this might help you dial in the right settings.

I would also recommend re-leveling the bed if you haven’t already done so since changing nozzles as not all nozzles are perfectly identical. If you still find your having issues with possible over extrusion there is a calibration test you can do to fine tune the extrusion rate. Here is a link to a e-steps calibration guide if you need it…
How to Calibrate an Ender 3 (Pro/V2/S1) Properly

Hope some of the above helps and hope you get the printer printing perfectly soon.

Thanks again, Nikoli. You’re too kind.

I changed the flow rate from 100% to 85% on a print that previously failed, and this time it worked perfectly. Maybe I’m underextruding now… who knows.

I’m about to embark on a print that’s 200mm high, so I’m keeping my fingers crossed.

You’re very welcome @Goodheart :slight_smile: always happy to help out a fellow maker.

I am glad to hear that reducing the extrusion rate has helped, I would definitely recommend doing the calibration test I linked in my previous post as it will ensure you are extruding the exact amount and should also help with dimensional accuracy when it comes to printing objects with lids or screw on parts.

Depending on which slicer you use you can adjust the extrusion rate. A good way to calculate the extrusion rate needed in slicers is to print a simple test cube in spiral vase mode, measure the wall width to check if it matches the line width specified in the slicer. If it doesn’t match then you just take the measurements from the printed test cube and calculate the extrusion multiplier required for the slicer but this is more for advanced users who want precision control over each individual filament or want to fully verify their extrusion widths are accurate :slight_smile:

Let us know how you get on as would love to help get this solved for you. I would definitely recommend calibrating your e-steps though as mentioned in my previous post as this will definitely help you ensure good accuracy across all prints. If you then wish to do so you can always go one step further with the cube calibration steps but this shouldn’t be necessary if the e-steps are calibrated correctly.