Strange brown residues when printing with provided white PLA

parax · 2017-05-23T11:16:30.000Z

Hi there,

I just mounted my Anet A8 printer and made the first models to improve it (filament guide, new nozzle fan adapter, etc). For these pieces I used the provided white PLA that comes with the printer. Everything is working great, at exception of a bunch of brown residues that appears in the middle of the printing here and there across the piece, and that given its size the nozzle moves it around during the printing since its height is greater than the current height of the layer being printed.

I’m not sure if I need to worry and perhaps there is something still wrong with my setup, or otherwise it’s due to just bad quality of the provided PLA. At the beginning I thought it was residues from the brown tape that was covering the hot bed from the manufacturer, but then I replaced that with a Buildtak cover and I still see the same issue.

I’m printing this PLA at 200C with the hot bed at 60C.

parax · 2017-05-23T11:18:01.000Z

A sample of the brown residues

img_7641_0.jpg3264×2448 932 KB

tabbott · 2017-05-24T05:53:38.000Z

This may be a problem with the gcode. What slicer are you using, and are you printing from your computer or sd card? Do you notice the print head pausing at any time during the print?

Lea3DPrint · 2017-05-24T06:06:14.000Z

Probably just bad PLA. Try some other PLA since your print looks great otherwise

astrojr1 · 2017-05-24T06:20:34.000Z

My white PLA turns brown like that when it stays hot too long e.g. perhaps hanging about for an excessive time in the hotend before getting extruded. However, I only observed this on the scale of preheating times, not on printing times.

parax · 2017-05-24T06:29:22.000Z

I’m using Cura as the software slicer, with the gcode file stored to the sd card and then mounting the sd card on the printer (the computer is on another room). I’ll pay more attention next time to see if the head stops, but until know I haven’t noticed that effect. I configured retraction for a minimum of 0.8mm, with a retraction speed of 25mm/s. The rest of the printing I did it at 50mm/s, at exception of the infill which was at 80mm/s, and the first layer which was at 25mm/s.

parax · 2017-05-24T06:31:41.000Z

My hypothesis is that some of the PLA got accumulated on the nozzle and that’s what got overheated and at some point dropped on the model. Could it be that I’m printing too slowly? I’ll try to print faster next time, although I only have about a meter of this PLA now.

tabbott · 2017-05-24T06:59:15.000Z

This all sounds good, perhaps the PLA is not adhering to itself. I would try a new roll of filament and if the problem persists, see if a new slicer helps.

Roberts_Kristin · 2017-05-24T08:10:49.000Z

Try change filament flow because I look there overflow.

cmorg789 · 2017-05-24T14:35:58.000Z

Does the residue wipe off or is it stuck on the part?

parax · 2017-05-24T15:58:55.000Z

It is stuck, sometimes becoming part of the piece, others quite stuck so I had to use a knife, and others can be removed easily. I’ve seen the head moving them along when hitting them back once it has to print again on that area, since the residue is typically taller than the height of the layer.

I think that I’ll order some new PLA, since I got rid of this one anyway, and see what happens. If the problem persists, perhaps it’s an excess of PLA getting accumulated at the nozzle and I need to reduce the flow to avoid it. Right now, I’m experimenting with ABS (which, man, it’s really difficult with all the warping / curling considerations), but given precisely to its difficulty I think I’ll switch to PLA again soon.

Roberts_Kristin · 2017-05-24T22:04:07.000Z

retraction => 3 - 5 mm

retraction speed => 80 - 150 mm/s

cmorg789 · 2017-05-25T02:51:09.000Z

Almost sounds like you might be scorching the filament, what temp are you using?

parax · 2017-05-25T14:45:56.000Z

I mentioned it at the original message:

I’m printing this PLA at 200C with the hot bed at 60C.

parax · 2017-05-25T14:46:54.000Z

I’ll try that, but that means that it won’t do any retraction if the movement is < 3 - 5 mm, correct?

Roberts_Kristin · 2017-05-25T19:42:28.000Z

no it’s a distance of retraction.

Roberts_Kristin · 2017-05-25T20:13:00.000Z

I recommend bed temperature 50 - 55 for PLA and print temp need test with temperature test tower but I printing on 210 - 215.

Ewokalvino · 2017-05-26T12:25:42.000Z

Pla = less than 200°, also no bed required. Thats your issue. Go lower temps

cmorg789 · 2017-05-26T21:17:09.000Z

That’s not nessasarily true. PLA can be run between 190-210. Also bed heating helps with adhesion, no point in turning it off completely.

Ewokalvino · 2017-05-27T11:52:36.000Z

First. Temperatures are just reference. it may change, Second. PLA doesnt need bed like many materials. it may help, true, but its NOT necesary

now going a bit deeper. All materials are diferent, even the same brand material have diferent temperature ranges, specially if are diferent colour even with same material. And somthing else you have to keep in mind. Your printer 190º maybe is 192 in real life, or 188. thats not 100% exact. if you have a printer that calculate 200º at 205 and you dont know it and u put 210 cause “pla can 210”, you may printing at 215? 220?. result of this?..

Temperature ranges are just reference and orientative, you have to check and do few tests and same material may will need little tweaks in other printers.

hope its good explained. im spanish and actually really sick to think/translate well