Globs, chunks, and uneven pla flow.

Hi all,
I've been playing with different temperatures and setting and have been getting some near perfect calibration cubes, but when I print anything larger, I get chunks in the first layer then blobs later on in the print. The blobs eventually grow sow large they hit the print head and ruin the print. Has anyone experienced this?

I am printing PLA (tried two different kinds) at 205 on glass with hairspray. Upgraded the hobbed bolt and use a top feeder for the filament. Using Cura engine in Matter Control with various settings.

 

Hi Mark. Thanks for the quick reply! I'll try lower temps. Please excuse my noobness... I've gone through every setting in Matter Control and the only setting that refers to an extrusion rate is Min Extrusion. Is this where I change it? I've also been reading in the forums that retraction can be an issue. Here's the settings i found:

 

I would also recommend printing a file from thingiverse that can be compared with anther printer. Sometimes I notice that that certain prints look ugly and others look good. I guess it's all in the way you model the part and what software used. It's technique!

Try printing the magnet box and see if it looks good or not. That way we can see what the difference is. Here's mine

One printed with a raft - left side. Right side printed straight onto the bed.




Sent from my iPhone using Tapatalk

 

Do you have z-lift (z-hop) on retraction turned on? I'd be curious what your retractions settings were too. That could be one explanation for the blobbing

 

Thanks for all your replies.
Mark: I'm considering purchasing that software.
PrintedSolid: I checked and the bed was pretty far from level. I ran the auto-bed-leveling and it seems level now, but it now prints a centimeter or so off the glass. Any ideas? Does the Z-offset apply when using auto-leveling?
Peter: Nice box I'll try that once I get this going.
Donhuevo: Yes, Z-Lift is set to 1 mm

Thanks again. I've spent countless hours this week in the forums and appreciate the help.

 

Depending on the part and software settings, your retractions could very well be happening in exactly the same place layer after layer. With the z lift on retraction you could be leaving a little bit of extra plastic above the plane of the current level you're on. Think Dairy Queen soft serve ice cream. You may want to disable the z-lift on retraction and if you're using the Slic3r engine inside MatterControl, there's a setting in there where you can wipe on retraction. This is normally good to cut down on stringing but may help to 'hide' your blobs in the spaces in your infill. Lastly, spray a paper towel with your hair spray and use that to apply to the bed. You'll get more even coverage and only where you want it.

 

Thanks for that. I've been curious on how retraction works. I don't mind blobs being hidden in the infill, but the print head eventually clogs up and jams. I will try your retraction settings as soon as I get this bed level.

Update: if I do not use Automatic Print Leveling, the first layer prints at a good initial height, but the bed is not level (checked visually and ran a bed level check test print). With Automatic Print Leveling on, the bed seems to be level (visually checked), but the first layer prints a centimeter off the glass.

Is there a way to manually level the bed? Or with Automatic Leveling on, is there a way to set the initial nozzle height?

Thanks

 

Do you have an R1 or an older model with drawer slides.

 

I believe it is an R1...it has the smooth rods under the bed.

 

Ok then you need to define a Z offset

Easiest way is to use the Slic3r engine and define it there

Otherwise I like this command sequence

After G28 to home all

G1 Z0.5 ;Move Z 0.5mm to reach true 0 point
G92 Z0 ; Force define new Z0 point


Then run G29

 

Great. Thanks Mike. I will give that a try.

 

Did you ever solve your blob problem?

 

Hey Cosber. Yes, I manually leveled the bed and replaced the hotend with an E3D v5 and now there are no more blobs.