Can't get rid of "zits" on Marvin at 0.1mm

[2CNK]

I printed A-OK with 0.1mm on larger models on my Raise3D N2, but Marvin is giving me trouble I can’t seem to zero in on (I had never printed something this small though.)

At first best I could do was this - note the “eyebrow” and the zits at the edge of the mask, and the drooping loop on the head.

Then I read here about how to lower heat and increase cooling because it’s such a small model and only 0.1mm.

I did that, which eliminated the sag and the most of the stringing. However, the zits remain:

I have played with making retraction more aggressive (20mm/s -> 40mm/s and 1.0mm retract to 2.0mm retract… 3.0 and I get air prints with this filament) but I just can’t seem to get any obvious change in those zits.

I’m thinking maybe try lowering print temperature again, and also lower print speed. I’m grasping at straws though. Any suggestions for me?

[Perry_1]

So, these zits are caused by either under retraction or over extruding, printing too fast, or not cooling enough.

I know thats not too helpful, but thats where you need to experiment.

Since you are not getting zits on the rest of the print, I would lean towards printing too fast/not cooling enough.

[DroneWorks]

I was just having the same problem and I’m getting very close to completely fixing it can you contact me somewhere like Instagram I have three things that you can check out @droneworksnewyork

[Zettlinger]

try printing multiples of the small marvin (group of 4 or so)

[2CNK]

Interesting, that’s not something I would have thought of doing. I’m game to try it and see; do you have any advice on what I should watch out for?

[2CNK]

Actually that’s very helpful! I’m keeping a spreadsheet of data and changing only one variable at a time, but that’s a slow process and it’s better if it’s guided in some way. It helps to have someone with experience say where to look, otherwise it’s hard to know whether to get more aggressive with changes, or move on.

[Zettlinger]

i would start slow (30mm/s) and in 4 pieces (so each piece gets some cooling time without the hotend hovering above it)

Dont retract too much, the N2 hotend doesnt like hot plastic to be pulled up too far (max 1,5 should do with pla. i often leave it on 1 except for very soft flexible or fluid plastics) and increase the retraction speed to 40 or 50 mm/s

Goodluck (won’t answer the post on the forum now )

[2CNK]

I went down to 190C and extremely slow like 10mm/s for all printing (infill as well as both exterior walls). Stringing is almost entirely gone, and the zits are slightly better - but most of them can pop right off with fingernail pressure.

I feel it should be and can be better, but low and slow seems to be one of the first tangible (but slight) improvements so far.

[2CNK]

Thanks for the tips and I’m just starting a print trying this next.

My last print with an extremely low printing speed of 10mm/s and 190C with a small external blower fan yielded some slight improvement. I’m interested to see what happens with this approach.

(Yup, that’s me - I’ll share my results on the forum when I have a solution.)

[2CNK]

My last two attempts had one of the Marvins detach from the bed (raft and all). I think I’ll try again but widen the raft so that it covers all four units instead of four separate ones.

[2CNK]

For the benefit of anyone watching, I solved the bed adhesion by upping to 60C and letting it warm up for 10 or so minutes before printing anything.

I got slightly better results printing multiples, but nothing earth shattering. I might just be getting pretty much as good as it’ll get on those sharp corners on a little model with a 0.4mm nozzle.

[2CNK]

For anyone who might be reading and finding it useful, here’s what I settled on.

After a lot of testing and tweaking, I decided that some zits (at the sharp corners of some facial areas) were unavoidable on such a small model and with a 0.4 nozzle.

Not sure how this will show up, but I have attached a BEFORE and AFTER photo.

Before is the results I settled on. After is after removing the zits with a fingernail and tweezers.

I think this is the best I can really get on such a small item (2.5cm tall) and 0.1mm with the N2’s 0.4mm nozzle.

Here’s what ended up working for me with Raise3D PLA and an N2 printer:

* Bed temp to 60C (I had troubles with models popping off the bed at 40C, but the jury’s still out on this)
\* Retract speed change from 20mm/s -> 40mm/s
\* Retract Extra Restart -0.02mm (note the minus sign: -0.05mm works but it’s too much, you get really sparse infill. -0.1mm gets air prints.)

I printed 3 models on one big raft, chose the best looking one. Printing 3 models gives the tiny things time to cool more between nozzle passes, as another poster suggested.

I preheated the bed manually for 10 mins or so at 60C before firing up the print (otherwise the bed doesn’t have time to warm through - the heater is at target temp but the bed itself isn’t.)

I manually adjusted extrusion temperature up to 215C during the raft printing, dropped it back down to target 205C after raft was done. The raft uses a lot of plastic in constant flow, and at 205C or lower the extruder didn’t quite keep up.

I played a lot with extra fan, lower printing temperatures, different retract settings, etc. I never got any improvement I would consider super significant. The best and simplest results for me so far seem to be the above for printing this particular model.

[Edward_1]

my advise would be is to get handy with a scalpel and lighter
also using a high quality fillement, for example colorfabb ngen help a great deal!

[Raise3DShanghai]

Hi, have you tried to adjust the flow rate yet?

Please update the motion controller board to version 1.1.1 and then adjust the flow rate from default 94% to 90% and see if that helps.

[2CNK]

Thanks for the suggestion! I didn’t try the flow rate down to 90% but I did have success with doing more retraction.

I noticed the zits are all at the retraction points. I increased retraction amount and I also set “extra retract amount” to a negative (-0.02mm) which helped.

[Raise3DShanghai]

Glad to hear that!

Higher retraction speed is also helpful to minimize the zits.