Lutzbot TAZ 6 Printer Nozzle Drags back through print

I am somewhat new to 3D printing giving that I "inherited’ a TAZ 6 from a previous teacher (I teach engineering at our local HS). I have printed several things without fail, then I started seeing the nozzle drag through the material at the start of the print. I have not been able to correct this.

You can see where the plastic was just bulldozed aside in the picture. What could be wrong here? This is consistent across the part so leveling should not be involved.

couple of things to look at.

you need to raise the offset a bit, the print is far too squished

what slicer are you using? in Cura there is a z hop and a setting to avoid printed parts with travel movements

start with those and let me know

I thought is was far too squished as well and that is what bothered me. Once you get past this initial problem, it prints quite well and clean. I will look at the offset and the hop. It may be a couple of days but I need to get this solved as I have a backlog of printing to do! lol

Okay, I have found the Hop settings in Cura. But I have not found the Z offset. Can someone point me in the right direction? That first layer I posted has a literal groove down the middle of the filament. So there is definitely a z-axis issue here.

You may want to first try manually cleaning off the nozzle. It’s likely there is material on the nozzle and that’s making the printer think the bed is lower than it actually is.

We recommend using a non conductive scotch brite pad as anything metal that comes in contact with the nozzle risks sending a static shock to the board.

If your first layer is still too high you can adjust the z-offset for you printer. The z-offset is the distance from the top of the leveling washer to the top of the PEI print surface and affects how tall your first layer is.

This can be done through the LCD menu by clicking the LCD knob in once to bring up the main menu then navigating to:

Configuration --> Advanced Settings --> Z-Offset

You can make your first layer less squished by turning the knob clockwise.

Once you have found a good setting for the z-offset, make sure to back up a screen and Store Settings.

The typical z-offset is a number somewhere close to -1.35mm. If you change the z-offset from -1.35 mm to -1.45mm this will make your first layer more squished. If you change the z-offset from -1.35 to -1.25 this will make your first layer less squished.

You can also adjust the Z offset live while the printer is printing. I like to do this while it’s printing the skirt. You can do that by selecting Tune --> Z offset while printing.

Okay, so the first thing I did was to use a dial caliper to measure the top of each washer to the PEI Surface.

Back Left: 1.43mm Back Right: 1.33mm

Front Left: 1.44mm Front Right:1.67mm

The current Z Offset is -1.20mm. The PEI surface is up against the underside of all the washers. However, the right side is soft in the downward direction while the left side is firm. I do know that the surface was replaced last year by another teacher and this could be the issue.

-1.13 look like it did the trick. However, my prints still have a small “ridge” where it came off the PEI surface. Is it normal to have to trim off these “edges”?

If the base (side touching the bed) is wider than the rest of the print, it means the nozzle is too close to the bed. Increase the z-offset or adjust the initial layer height settings of the slicing software. One or the other… by increments of .1mm.

got it. So I need to go up to -1.12mm on my Z offset.

So, I have changed the Z Offset a couple of times and now the initial “outline” around the part (not sure what you call it) is really good. It skips right at the beginning and then lays down a nice bead of material. The initial outline of the part looks good as well. But the issues with the “smushed” fill are still there and the nozzle still drags back through that first layer even with Z Hop set at 1 mm. I am going to change the Z Hop to 3mm this morning and see what happens.

Z Offset up to -1.02, 3mm Z Hop set and I still get that drag through the first fill layer. the squished part of the first fill layer is less and getting better. I need to print about 50 of these things so I have been moving the Z-Offset up with every print.