LulzBot MINI and nGEN (print object lifts off even with glue)

Hi guys
I am printing with Colorfabb nGen with the recommended settings for my lulzbot mini (that come with the pre-built profiles with the software)
What ends up happening is over time the corners of some objects end up warping upwards…
I mean it will be hours into a print and then the base starts warping up. what does that mean?

Like so;

Just to add, I am printing with applying glue stick on the PEI before I print.
and the image attached is like half way through the print job when this starts happening so it hurts more haha
I’ve read about the sandpaper / 2000 grit + isopropyl thing on another Thread however if you notice carefully it isn’t to the PEI that its listing! its the layers beyond that that end up doing it !
I’ve never had this issue with PLA, only nGen

Kinda looks like you are printing on a raft…are you? Maybe it’s just the angle of the photo

Hey buddy
I’m not printing with a raft, but I did increase my bed Temp and added a “Brim” and so it sticks better.
However I think another issue is my first layer is very stringy, like poor. I was on a makebot website and it showed me what a bad first layer is… and thats what mine looks like. I always have to peel away at it just to try and get to some semi good layers.
How do you figure I avoid this issue?
Is that in the Advanced Tab in the expert settings?

I’ve not had this issue, but I can give you a few tips on getting a good first layer. I’m just very confused with what you’re seeing because normally NGEN is known for not warping much at all. When in doubt, if you contact support@colorfabb.com they do an amazing job troubleshooting issues with you, so considering contacting them as well.

  1. If you’re having problems with bed adhesion: Take 1500 to 2000 grit wet/dry sandpaper, wet it down with water and liiiiightly sand your entire PEI sheet. You usually won’t see much visually but it helps make your bed “sticker”. Since you’re using a glue stick, I’m not sure if it will help, but on parts without glue stick this works wonders.

  2. Most of the time a bad first layer is due to initial nozzle height or a flow rate issue. First thing to try is to print a small dummy part with Ngen. Make sure your part prints a skirt around it. When the part completes, take the skirt and measure the thickness of the skirt using a set of calipers. If you’re using the standard NGEN profile under expert settings, your first layer should be about 0.425mm thick. If yours is not close to 0.425, go under expert mode, Machine (toolbar), Machine Settings.

Inside that window you should see a setting called “Z- offset”. If the actual printed skirt thickness was, say 0.3mm, and cura is trying to print 0.425mm (initial layer thickness under the advanced tab), then you need to put .425-.3 = 0.125 into the Z-offset window.
Note: A POSITIVE z offset moves the nozzle away from the bed, a negative number moves the nozzle towards the bed. Print the test part again, measure the skirt thickness. Repeat this until you get pretty close to 0.425… 0.4-0.45 is close enough from my experience.

Caution, if you find out your z offset needs to be a negative number, err on the side of caution and take smaller steps adjusting your layer thickness. If you use too big a negative number, your nozzle will gouge into your bed so be careful if you use negative numbers.


3. After you get the z height dialed in, take a picture of your first layer and post it here.

  1. You might also consider posting your Gcode here so we can take a look at your print settings.


    Jim

Hey Jim

first of all thanks for helping me out.

The first layer is never ever looking good for me.

I’m going to send you a link to a quick video I made. PMed

Hey lulz,

here is the Gcode for the Z offset through Cura.
you can adjust your Printers Z offset through Cura. Go ahead and connect to your printer, and bring up the control box. In the lower right hand corner you will notice a text entry box.(Gcode bar) Within the box you are going to need to enter some manual commands to update the offset. Make small adjustments when changing, as large ones can cause your printhead to be dug into the bed or print in mid air. (as the gentleman told you)

M851 -> Reports current Z offset in mm

M851 ZXXX -> Changes offset to XXX in mm

M500 -> Saves settings

Here is an example:
If your M851 is -1.35 and you want to move the nozzle away from the bed, Then make the number closer to 0.
Make a M851 Z-1.25 enter
This will move the the nozzle .1 farther from the bed.
Then do M500 enter to store the change, or it will go back to the previous setting.
If you want to move the nozzle closer then go .1 at a time until you achieve the desired results. Remember the M500 or it wont be stored.

When first testing this new offset, keep a careful eye on that first layer. If it appears the nozzle is being dug into the bed, turn off the printer and adjust the offset until it no longer does that.

Hope it helps

David,

How is this different than just changing the Z offset under cura Machine: Machine settings: Z offset?

The biggest difference is that you don’t have to remember to change it in the slicer every time you switch software. If you only use Cura on one computer, it’s about the same. Kind of like adjusting the E-steps for the extruder. You can adjust it using the flow% in the slicer, or set it in the firmware. When you change the firmware though, those settings can get reset, so there’s that to remember as well…

I kind of like using the slicer for Z-Offset, that way I can adjust it a little based on filament etc… For example, ABS tends to do better for me if I let it “squish” on the bed a little more. While PLA, PETG, and HIPS don’t mind being up a little bit. They still stick well, but come off a lot easier when the bed cools.

Just to make sure it’s not forgotten, make sure to watch that first layer after changing the settings. Make sure the auto-leveling probe works well, and that the nozzle isn’t digging into the PEI.

Issue keeps happening here are some changes I have made and some more information to share.

Here is a 20mm hollow cube print I printed:
http://imgur.com/a/jrxCZ

You can see how the first layer is always messed up.

The brim is about 6.08mm with a digital caliper (assuming I take the thickest point). My brim always gets messed up because the printer doesn’t extrude immediately and after a bit prints a blob and it moved around and sometimes even ruins prints as you can see by the image.

The 20mm cube turns out to be 20.06 to 20.12mm around those ranges.
The first layer is always the worst. its Stringy, never adheres, there is always a lift off type area. the later layers always are ok.

Here are my Printer settings
http://imgur.com/a/scIxR

What is the thickness of your brim? Not the width. The thickness of your brim will tell you your 1st layer thickness. You’re shooting for 0.425 if you’re dialed in correctly and you used the standard profiles. Looking at your image, I’d say you’re nozzle is too far away and I’ll be it’s thicker than .425mm

Measure the thickness of the brim layer and let us know!

-Jim

Hey Jim
you must be a psychic
the brim thickness (sorry my misunderstanding)
is 0.6 mm
even tho my setting is set to 0.425

Now that’s established, what are my next steps to get er fixed. thanks so much guys.

p.s. I did the 1500? grit sandpaper thing prior to the print. didn’t help.

I’m afraid my old eyes couldn’t quite make out your settings in the screen shot, but here’s my take. From the photos of your cube print, the first layer of filament doesn’t appear to be touch the bed well enough to be able to adhere well. Your Z setting needs to be lowered a bit. Also, I’d clean the bed with alcohol. I print a lot with nGen on my Mini and it doesn’t need glue stick to adhere. The glue stick may actually be preventing the filament from sticking in this case. If I could see your settings better, I might have some other ideas to help.

This probably is your issue.

Here’s what you do. Your skirt thickness is 0.6mm, your initial layer thickness is set for 0.425mm. The difference here is 0.6-.425 = 0.175mm.

In cura under expert mode, click in the toolbar under Machine : Machine settings. You will see an item called “Z-offset”. Change that value from 0 to -.15mm (note negative sign…this means move the nozzle towards the bed). Normally you can put in -0.175mm directly but since the negative value moves the nozzle towards the bed, I like to “sneak” up on the value so I don’t accidentally go too far and have the nozzle plunge into the PEI surface. It makes for a bad day :slight_smile:

Remember when using expert mode that you need to load the correct material profile from the lulzbot website before printing.

Print a small sample with another skirt. Measure the skirt again. It should be closer to 0.425mm. Say the new skirt is 0.5mm, 0.5mm - 0.425mm = 0.075mm. So the next time around I’d put (-.15 - 0.05 = -.2mm). Again, note that I don’t use the exact calculated values (-0.175 or -0.075) because I just want to be conservative and avoid bed damage. Keep making the Z-offset a more negative value in small increments until your skirt thickness is 0.425 …or 0.42 - 0.44mm range…close enough.

Try running your print again and see if that helps with your fist layer issues.

REMEMBER! YOU MUST LOAD A LULZBOT MATERIAL PROFILE FIRST IN EXPERT MODE BEFORE PRINTING. Profiles can be found here: https://www.lulzbot.com/mini-cura-profiles


Hope this helps!
Jim

Ok first print again, I copied over default nGen settings to expert/full settings and just changed the machine z offset. Then I printed

my brim thickness is 0.524 mm

here is the code that spits out after printing

Print started at 10:16:16
< Bed x: 0.00 y: 0.00 z: -1.28
< Bed x: 160.00 y: 0.00 z: -0.93
< Bed x: 160.00 y: 160.00 z: -0.92
< Bed x: 0.00 y: 160.00 z: -1.27
< Eqn coefficients: a: 0.00 b: 0.00 d: -1.28
< planeNormal x: -0.00 y: -0.00 z: 1.00
< Probing done!
< echo:endstops hit: X:0.01 Z:-1.27
Print finished at 10:53:53
Total print time : 0:37:36

going to adjust one more time here and send some photos . and reupload setting photos.

i feel like the machine adjustments aren’t making a difference.

Width I am getting is 0.55 now even tho I’m at -0.3 now.
The first time it levels the front left corner it even touches the silver circle pressing it down, but then corrects itself later.

Print:
Print started at 11:43:33
< Bed x: 0.00 y: 0.00 z: -0.98
< Bed x: 160.00 y: 0.00 z: -0.75
< Bed x: 160.00 y: 160.00 z: -0.83
< Bed x: 0.00 y: 160.00 z: -1.11
< Eqn coefficients: a: 0.00 b: -0.00 d: -0.99
< planeNormal x: -0.00 y: 0.00 z: 1.00
< Probing done!
< echo:endstops hit: X:0.12 Z:-1.11
Print finished at 12:20:53
Total print time : 0:37:19

The nozzle should touch each corner washer twice. Once quickly to get a rough estimate, the second time much slower. Can you post a video of a close up when your nozzle is hitting the washers? That would tell us if something is wonky with the leveling process.

Will shoot video now.
I’m at -0.5 offset on z on machine settings and my brim is still about 0.5mm
no difference since -0.3 probably
will post a video here soon

Print started at 15:08:29
< Bed x: 0.00 y: 0.00 z: -0.93
< Bed x: 160.00 y: 0.00 z: -0.78
< Bed x: 160.00 y: 160.00 z: -0.91
< Bed x: 0.00 y: 160.00 z: -1.12
< Eqn coefficients: a: 0.00 b: -0.00 d: -0.95
< planeNormal x: -0.00 y: 0.00 z: 1.00
< Probing done!
< echo:endstops hit: X:0.12 Z:-1.12
Print finished at 15:45:04
Total print time : 0:36:35

Humor me. Try adding a large positive number to the Z - offset, see if your skirt prints in the air. If you get no change, you have software/firmware issues I think. If you are changing the Z-offset by a large positive number and nothing happens, you may need to contact support and see what would cause that. Z-offset is a very important feature to have working.

-Jim

I am at 0.48mm (target being 0.425mm) with a -0.8 offset.
Before I keep doing this. Is this OK ? have you seen people with such large offsets?

Update1: hey guys ok at a -1.0 offset I get the brim to be around 0.4 to 0.44 mm and printing the first layer is phenomenal.
To save you all the trouble follow jim’s suggestion. The best investment you can make is get a digital caliper off Amazon or something in your calculations.

Jim/everyone else. Do you guys have a suggestion to still somehow fix my printing initially. Is there a way to make the printer blurp out some filament in a corner before moving onto the main print, that way I can wipe it off and the nozzle is prepped to do the printing. Know what I mean?