That offset seems awfully high, but if it’s working for you, I can’t fault it. I’m glad you’re getting a great first layer now.
Be extra vigilant over the next prints to make sure the printer doesn’t auto level oddly and then add that large offset and hit your print bed. Probably won’t, but it’s always a good rule to stick around your printer until the first layer is printed.
I don’t know of a way to have the print purge in the corner, however, another solution is to increase the skirt distance/count.
Go into Expert: Expert Settings and under the Skirt section. You can increase the line count so that the nozzle makes more circles around your part before going and starting to print. For small parts you may also want to increase the “minimal length” so that if the printer goes and makes 3 skirts, but the part is small, it will keep creating skirts until it reaches the specified length of filament.
Try doing 2-3 skirts and see if that primes it enough for you.
In your free time, you may want to contact shop@lulzbot.com and ask about your Z-offset even though it’s technically working. It still seems like a lot and maybe they have seen this before. They’re very responsive and very helpful.
Hey Jim! thank you for your help man!
Just an update lulzbot guys say even something around -1.35 is kind of average what they have seen.
I also realized I was squishing it more than needed because I was having issues removing the Brim, so I’ve backed off to about -0.8 and even tho the brim thickness isn’t in line, prints are going smooth.
My issue now is I think overextrusion on finer prints. Any suggestions on how to fix finer prints on the top layer? like this.
hey buddy, can you quantify ‘a little’ - i have no sense for this, as its hard me to reciprocate the effect and testing it accurately. I was able to test the first layer issue with a 20mm cube stl pretty easily. Those whole overextrusion/oozing thing I would find out on complicated print pretty late into the stage, so thats why I don’t have a feel for the number.
What I have under Expert config for retraction is the follow;
Minimal travel time (mm) = 1
Combing type = All
Minimal extrusion before retracting (mm) = 0.005
Z hop when retracting (mm) = 0.2 (this used to be 0.1 but I think 0.2 made it a little better)
To fix your flow rate, or at least get it close, here’s where you start.
Go to thingiverse and download a 20x20 calibration cube. Print it out wiht your current settings. Take your calipers and measure the width. If you’re overextruding, your 20mm width will print out something like 20.2mm or so. Back off the flow percentage from 100% to 98%. Print the cube again. Measure. Is it closer to 20mm? Good. Reduce flow until you’re super close to 20mm.
Before you do this test, make sure you use your calipers an measure the filament in about 4-5 different spots, get an average of the diameter of the filament and put that into the filament diameter box.
I see some stringing as well. Ngen can do that but you’ve got some major stringing going on. Here’s my suggestion.
You talked about zhop. Making this larger can keep from making marks on the top surface of your print when the nozzle fast travels across the surface, however, in my experience, too much can be bad. The best way I can describe it is imagine if you have a pile off slime or goo (molten filament) and while it’s still goo, you lift your nozzle up. There’s going to be a bit of goo that gets pulled away from the surface. Then, when the nozzle jumps to the next surface, it’s going to pull this goo string with it, giving you the defect you see there. If you don’t zhop, the goo gets wiped off the nozzle as it travels along the surface below it, reducing stringing. This applies to most cases.
HOWEVER, there is an exception. If you are printing sections with really small surface areas…say a post that’s 2mm in diameter, the nozzle is pretty much covering the entire surface and doesn’t allow the cooling fan to cool the part before transitioning to the next area. Because of this, the surface below the nozzle is still very hot and gooey. Without a zhop, the nozzle “smears” this gooey material and it comes out as stringing. The same thing happens when you zhop a small area as I described earlier. Small surface areas tend to string, especially with co-polyesters and materials that require heavy cooling.
Long story short. Fix your flow rate first, then go back and start with zero Zhop and just see what happens. I don’t promise miracles, but it actually might be an improvement. Sometimes there’s such a thing as too much zhop:)
