Trouble with Messy, Globby Layers

[oatfoundryprinting 0]

Hey All!

My name is Luc, and my company is a proud new Ultimaker owner. So far, I've been reading tons of posts about how to fine tune your machine, and have been having some pretty awesome results out of the gate. Still, it is very clear that I have much to learn about getting the best quality prints possible.

One of the first problems I identified with the stock Ultimaker was the way the fan functioned. I was getting too much cooling on the left side of the part, and not nearly enough on the right. So I found a new fan cover on Thingiverse to fix the problem.

http://www.thingiverse.com/thing:17768

So I've been playing around with speeds and temp settings to try and get good finishes, with varying results. This most recent fan part is a bit baffling to me, because in certain over hang parts, I get a PHENOMENAL finish, and in others, the layers become all globby and messy. From my own limited experimentation, I am pretty sure that this "globbiness" is caused by the print head moving over edges that have "curled up," and thus are not leaving enough room for the print head to extrude properly. The result is a messy layer that gets worse and worse.

I was able to overcome some of these problems by slowing down the machine to 50% speed, but I'd like to keep my speed up throughout the entire part. Here is an album with multiple pics of the part.

http://imgur.com/a/ZNfLR#1

My settings:

Layer Thickness = 0.06 mm

Shell Thickness = 0.8 mm

Retraction on, Speed = 40 mm/s, Distance = 4.5 mm

Bottom/Top Thickness = 0.6 mm

Fill Density = 100%

Print Speed = 60 mm/s

Print Temp = 200C

Cooling Fan on, Fan Speed = 255

Minimum Layer time = 5 seconds

2.80 mm filament that is calibrated in Cura

Heated Print Bed = 80C

Now, for this print, I ran it at 200C because I felt that the material began to mess up when it was still too hot for the next layer to be placed, so I tried to overcome this by bringing it down from 230C. I also noticed that even though the minimum layer time was set to 5 seconds, the piece (bc it is so small) seemed to start the new layer well before 5 seconds was up.

So here is my question to the community: Do you have any ideas why most of my curved surfaces come out great, while a small portion of the sections (like the fan ring hole at the top, or the angled feet on the bottom) have terrible quality? I'm all out of ideas, so I was hoping the community may be able to shed some light.

Thanks for reading guys! I've been going through so much of this community and it's been so helpful. You guys are awesome!

Luc

 

[gr5 2,173]

the minimum layer time was set to 5 seconds, the piece (bc it is so small) seemed to start the new layer well before 5 seconds was up.

 

What? Did you time it? This feature works quite well. Make sure you set the minimum feedrate to 0 as this setting can override the min layer time.

This is a difficult print because of the steep overhang and the cooling shrinking effect on steep edges that warp upwards. Not sure what to do about it other than adding some support. A heated chamber might help.

Anyway I recommend you do not make this at all. For one thing, it is bound to get too close to the nozzle and melt/droop onto your print. For another, restricting the air flow this much is not a good idea as the fan isn't designed for this small a nozzle and won't create much pressure and you will basically just drastically reduce the cooling.

 

[oatfoundryprinting 0]

Thanks for your response!

 

I could be mistaken about the timing issue, perhaps the layers were completing inside-to-outside wall paths that merely seemed to be starting new layers too early. Where is the minimum feedrate setting? I'm looking for it and cannot seem to locate it.

I agree this is a rather tough print, but I felt I should try the more difficult prints to give a sort of torture test for my machine. I've seen people print those super high resolution Yoda Heads with great success, and a lot of those surfaces are similar in slope and layering to what I was trying to print with this fan.

I have installed the printed fan after cleaning it up, and honestly, it rests perfectly around the print head without touching it, and with the fan blowing cool air through it, I did not notice any drooping down onto my part. It was also a concern of mine, but I thought it did quite well. Maybe I'm too inexperienced to make that call though.

I am really interested in what you said about airflow though. I had not thought about the fan's power, and reducing the nozzle size. It seemed to cool my other parts just great, but again, I probably don't have the best feel for this kind of thing yet. Still, the fan guide NEEDED to be replaced. The stock one was giving me too many problems. Is there another fan cover you might recommend?

Again, thanks for your response gr5! I truly appreciate the feedback

 

[gr5 2,173]

Where is the minimum feedrate setting?

 

Under expert settings/Cool/"Minimum speed"

 

[gr5 2,173]

I'm not a fan expert. I'm just repeating what other's have said. Daid (who wrote Cura) recommends this one which is as close to the stock one as possible:

https://www.youmagine.com/designs/ultimaker-fanduct-replacement

 

 

[oatfoundryprinting 0]

You were totally right gr5! My minimum feedrate was set to 10 mm/s, so it definitely was overriding the minimum cooling layer time. Is it best to set the minimum feedrate to 0 in order to achieve the 7 second minimum cooling layer time? What happens as the program begins to realize it will start its new layer before 7 seconds is up? Does it simply stop where it is, and will this cause new blobbing issues I was not experiencing before?

Again, thanks for the feedback!

 

[gr5 2,173]

As long as you have a relatively new Ultimaker (with the newer hotend - when did they switch to V2 hotend? A year ago?) then you can set the min cooling time to zero. Mine is at zero.

There's not going to be a minimum feedrate issue if your layers are .2 or .1 or even .05mm thick.

 

[oatfoundryprinting 0]

Just for clarification, you have your Minimum layer time set to 0? I feel that I Need this parameter on some of my prints due to a small section of the print being finished last very quickly, because that spot is vertically taller than any other part of my print. In these situations, I have noticed a MASSIVE difference in print quality, especially in curved surfaces, when the layers were not given enough time to cool.

My company bought this ultimaker about 2 months ago.

 

[gr5 2,173]

No.

Set minimum *feedrate* to zero. Anything but 0, it can end up printing too fast.

Set minimum *layer time* to at least 5 seconds.

I've done experiments but they aren't conclusive. My tests found 2 seconds to give good results, but 6 seconds noticeably better with fan at 100% (4 seconds probably would have been fine but didn't do that test). With fan off, 3 seconds was horrible, 5 seconds was quite good, and 7 seconds was noticeably better than 5 seconds.

This test was without heated bed (which would need longer times). My nozzle was at 230C for this test (wanted to find the min times for hot nozzle).

My results probably vary depending on the exact distances that the head is traveling and how much airflow the part gets when the head is farther away and how thick the layers are and temp of nozzle. Also the part itself matters as some parts don't care as much (like cylinders) and some parts care more (like overhangs). My test was with overhangs. I think my layer height was .2mm but that isn't in my notes.