Inconsistent Print Quality During Print

[perlguy 0]

My Ultimaker is acting a bit strange now during prints.

Note: I've added a heated glass bed to my printer, but that should not affect the prints like I am now seeing.

I am printing a simple structure using PLA and not heating the bed during this print.

As you can see from the photo, the bottom 1cm of the print looks nice and solid (but it is curling on the edges).

The layers above around the 1cm mark though have many small holes visible in them.

I am printing right now with 80% fill density.

Why am I getting inconsistent outer walls?

Bonus question, is the PLA curling because of the glass? It even curls if I print it on raft (like I am in the photo).

Thanks!

 

[illuminarti 18]

What are you using to slice it?

The poor quality seems to start when the holes in the sides start... Do you have retraction enabled, and what are your retraction settings?

More generally, what temperature, speed and layer height are you printing at?

 

[perlguy 0]

Using Cura right now...

After I posted, I noticed that it was around the hole layers as well.

Here are the settings I used...

Quality

Layer Height: 0.2

Wall Thickness: .8

Enable Retraction: Yes

Fill

Bottom/Top thickness: .8

Fill Density (%): 80

Speed & Temp

Speed: 100

Temp: 220

Filament

Diameter: 2.89

Density: 1

Retraction

Minimum Travel: 4.0

Speed: 40.0

Distance: 4.5

Extra Length on Start: 0.0

 

[billdempsey 0]

I got a texture with a lot of air in it at one point during a print and it turned out to be a bad extrusion rate because the filament size had suddenly changed quite drastically partway through a print. It dropped from 3.1 down to 2.7. It took me a few to figure that out. Another time I had this sort of print, the black clip had popped off of the axle on the extruder, so the filament was contacting the wrong part of the axle, which caused slippage. The top surface in both cases was covered with tiny plastic blobs sticking up.

It also appears that your holes are oval, rather than circular. So, I'm wondering if your z movement is a little off. Perhaps somebody else could tell you how to check that. I haven't had to do that yet, so I'm not familiar with the change.

 

[illuminarti 18]

Do you have support enabled? Is any support being printed alongside the layers that are failing?

Also, if you want to send me the gcode, I'd be interested to take a look and see if anything seems off about those layers.

 

Using Cura right now...

After I posted, I noticed that it was around the hole layers as well.

 

 

[cora111 0]

Your speed is very high compared to the print temp. Have your tried to print at lower speed, e.g. 25 mm/s? If that works, than increase the temperature for printing at higher speeds. I don't think your problems comes from retraction.

 

[illuminarti 18]

Yes, to Cora's point, printing at 100mm/s with a 0.4mm bead and 0.2mm layer gives an extrusion volume of 8mm³/second. Depending on the plastic that you're using, that might be a bit marginal... it could cause under extrusion, and possible head blocks, leading to more under extrusion, and then grinding, and a downward spiral of bad things.

220ºC seems to be a reasonable temperature for most PLA - you might try going a little higher - maybe 230ºC to reduce the viscosity a bit, but I'd definitely try a little slower... 25 is probably a bit excessively slow, but 50 or 75 would definitely help. And/or reduce the layer height, to also lower the volume per second.

 

[gr5 2,268]

You have 2 issues.

The holey pattern is typical under extrusion. Not enough plastic is flowing. Not sure why but I would try increasing temp by 10C or slowing down quite a bit as illuminarti said. More visual examples of underextrusion here:

http://umforum.ultimaker.com/index.php?/topic/1763-bad-surface-on-printed-parts/?p=12318

Your other problem is very common with large parts and is caused by upper layers contracting and pulling on the bottom layer. There are a ton of fixes for this problem. I notice your infill is 80% which is the opposite of what you want to reduce the upper layers from pulling the bottom up.

You probably won't like this advice but this will help greatly and is easy to do: put a layer of blue tape over the glass. Clean the blue tape with isopropyl alcohol (this is critical!). Your curling issue will probably go away. (don't forget to re-level). This will work better than anything else you can do.

If that's not enough or if you don't like that idea, you can consider adding vertical holes in your part if that works for it's purpose.

Also round the corners of your part - sharp corners lift more easily than rounded corners because all the force is on the tip of the corner.

Also use that heated bed if you have one. Heat the glass to 70C and print the first layer at 240C, no fan, 40mm/sec then dial the temp down with cura or ulticontroller after it finishes the first layer of the part (not the bed) (this improves the stickiness).

 

[perlguy 0]

Thank you for all of the tips!

I think tip #1 for me is: "Be Patient". I tend to want to try and print things out as fast as possible, and end up with poor results.

Although, all of the other tips are great too. Thanks!

 

[illuminarti 18]

Brent -

Did you have 'Joris' enabled in that print, by any chance?

In looking at some other gcodes today, I've been seeing that it screws things up when you are printing separate islands of thin-but-not-single-width walls. Basically some of the layers get printed too high, so they don't extrude or stick properly, so then the next layer doesn't have anything to stick to either... and you can end up with honeycombing like this...

Just a thought - wanted to see if it might account for what happened here, too?

 

Why am I getting inconsistent outer walls?

 

 

[gr5 2,268]

Here is more details of what illuminarti is talking about. From his other post:

http://umforum.ultimaker.com/index.php?/topic/1746-lack-of-extrusion-in-certain-part-of-a-part/?p=13006