I’m new to 3D printing, having just received my Lulzbot Mini last week. Before my printer arrived I had arbitrarily pre-ordered a roll of ABS as it seemed like that was one of the more popular 3D print materials. I am now learning that ABS takes quite a bit of tweaking to get a good print.
One of the issues I’m having is that my prints are aggressively sticking to the print plate. So mush so, that sometimes I damage my prints in the removal process, or am afraid I am causing some damage to my printer and/or print surface.
What do you guys recommend to help mitigate this issue?
I purchases some PET tape (1mil thickness), but haven’t tried it yet. Do you guys recommend using PET tape? If so, do I need to make any adjustments to my printer (i.e. adjust the Z etc. etc.) or in the Cura software to compensate for the PET tape?
Add a little positive z offset in the slicer. You are probably squishing the plastic onto the build surface a little too much. I adjust the z offset in 0.1mm steps when I am working with a new plastic. The PEI build surface on the mini is far better than PET tape so, stick with it.
One thing you will want to do is check the filament diameter. The stock Cura setting is 2.85mm but filaments vary in diameter even on a single roll so get a caliper and measure the diameter in 4 or 5 different places on the roll to get an average diameter size. Then click on the Expert tab in Cura and switch to Full Settings. In the Basic tab you will see Filament Diameter. Enter the average of the diameters you measured. This will help with many potential printing problems.
The Lulzbot recommended temperature for part removal if 50° C. If you are still having issues with parts sticking too well, apply a very thin layer of Elmer’s purple school glue stick to the bed before printing. It will allow easy removal and cleans up with a damp cloth.
Couple points that are regularly brought up here, and that I have learned as well…
Make sure your initial layer height is dialed in and that your head clearance is good. If you are squishing your first layer too hard against the plate, you will have A) potentially degraded quality in the remainder of your print, B) a hard time getting the print to release.
Cool the bed to +/-50c. If you cool below that, prints stick MORE. I find that I can pull smaller prints at higher temps. Just be careful you are not removing when the print is still pliable.
Print at the lowest temp you can with your filament. What is that temp? Trial and error will tell you. I use Hatchbox, and it says 210-240 for ABS! Print some calibration disks @ 1 layer in height, and see how it is rendering (check for skips, overruns, bubbles, etc). Make sure the hobbled bolt is not digging into your filament and that you are tightening the filament lever to 8mm (print a jig to help). LISTEN for little popping/skipping sounds in the extruder.
These are a few of my favorite things. (Think Julie Andrews : )
When you say “add a little positive z offset in the Slicer,” can you explain exactly how to do that? What exact perimeters should I be adjusting in Cura?
The first layer height can be checked by printing something 1 layer thick and measuring with calipers. It can be thrown off a bit based on how hard you push the calipers together and if there are any other issues, but it’s a good place to start. I usually check in a few spots and average it. Make sure you are checking after the nozzle is primed and flowing well. Sometimes the very start will under extrude as plastic gets pushed into the nozzle.
The right temp for a filament depends on the filament, sometimes even the color. You have to experiment a bit. Too low, and it will under extrude, or even strip the filament. Too high, and it will usually get stringy or even scorch leaving a brownish area on lighter colors. Once I dial it in, it’s usually good for that roll. I tend to start a new roll with some basic test prints to get a feel for how it acts. Then try to destroy them to make sure layer bonds are good and such. These are little 5 minute calibration tests, so it doesn’t take a lot of time or material. Keep in mind, you need to adjust a little based on layer height as well. Taller layers will need a little more heat as you are moving more plastic and it doesn’t have as much time to melt. For example, on a roll of PETG I have on the printer right now, I print at 255 for 0.1mm layers. I need to move to about 260 for 0.3mm layers or it strips the filament on fast infill.
For Z-offset, go to the machine settings. There’s an option there. Positive numbers move the nozzle away from the bed, negative moves it closer. I find moving by 0.05mm or so at a time helps dial it in without taking forever. That’s one trick I like in Simplify3d, you can set each model to use a different “process”, so you can print a few copies changing something on each one. It saves some time dialing in settings. If you try that, make sure you know which one is which.
Examining the bottom “smoothness” is a tell-tale sign that the nozzle is too close to the PEI bed. Another tell-tale sign is the flaring of the sides touching the bed (again, the bottom of the print). If when you remove the print, and the bottom has white stress marks… you’re too close to the bed.
Nopick has you on the right track with the Z-offset. Increase by .1mm until you get a bottom that is smooth, consistent and with a little texture of the extruded filament. If you can achieve this, the print will easily remove from the bed at 50C… or cold. It will actually “snap, crackle” and eventually “pop” off the bed as the bed temp cools past 60C.
Personally, I find that to be not enough adhesion to the bed. My preference is an almost completely smooth bottom with no flaring of the sides. This means that the initial layer is “squashed” enough to produce an oval versus a cylinder. This will result in a part that’s difficult to remove from the bed. I find these tools help tremendously in getting under the part to remove the print. Cheaper if you buy them as “artist spatula” or painting knife sets.
The bigger problem which most folks fail to mention, is that if the auto-level procedure on your Mini is leaving the nozzle too close to the bed the root cause is usually a dirty nozzle tip, or contact points. Interference in conduction of the metal (nozzle to probe discs), will cause the nozzle to press to far into the bed corners. Examine the wiper pad and replace if necessary. Clean the nozzle and contact discs with acetone to dissolve ABS.
