Anyone seen this color change behavior before?

[iceman1979]

I am printing on an UM2 and recently when printing some tubes I noticed a color change in the part. The point at which it does it is different on each print and this happens on both my colorfabb and colorfabb_xt.

Colorfabb: printed at 200C, speed = 50in/40out, fan on 100% at 1mm

Colorfabb_xt: printed at 245C, speed = 50in/40out, fan on 50% at 1mm

Any ideas why this might happen all of a sudden?

[pmsimard]

Are they all the same tube?

Some material like the silver metallic from Ultimaker often change color even with just a few degrees of difference.

I would say speed or temp change. Speed can be affected by minimum layer time.

[IzzySID]

interesting,

were they all build using the same G-code file? and is it a parallel tube or tappered tube?

The four on the right all seam to have the effect at the same level, it looks like there could be either a difference in the nozzle temperature and/or a slight change in print speed at that level, the effect from the photos looks like there is a slight alteration in the print that is effecting the external surface which may effect its surface reflection properties and giving a change of hue.

Have you tried a different colour to see if the same happens,

I usually print at 205 - 210 for ColorFabb PLA, it may be worth trying a slightly higher temperature to see if the same happens.

Please keep us informed of your findings, Izzy

[iceman1979]

One XT set has a slightly different inside diameter but the other XT and PLA/PHA were from the same gcode. The regular colorfabb was printed with my saved settings I print all my colorfabb PLA/PHA stuff with. Those settings didn’t change and the fact that it did it on two different materials leads me to believe it is something with the printer.

[iceman1979]

two were from the same gcode (one xt and one pla/pha). I don’t use the tweek at Z plugin so i’m not sure how the speed would have changed, not intentionally anyway. I thought about temp but dismissed that when I thought about the temp for the xt being 245 and the temp for the PLA being 200. I’ll try it with a different color too and see what happens there.

Thanks for the input.

[MB3D]

Make sure, to have an absolutely clean hotend and extrude a.e. 10cm of filament before starting the print, to make sure, that there’s no residue from earlier prints.

What layer height and nozzle diameter are you using?

Can you tell me, how hot your bed is running ?

(in the following i refer to the pipe on the right hand side as there the issue is very obvious)

It could be, that the bed heats the material or at least keeps it warm, up to a few centimeters of build height.

Due to the low surface contact and tall model, only the bottom is kept warm, while the middle and top part are cooling down to room temperature. This may cause the color change.

I’d advise you to print with 50-60C for PLA/PHA and 70C for XT, both times bed temperature.

You can also go a little bit hotter with both nozzle temperatures. 255-260C works fine for me, when printing XT.

The material has to have enough time to heat up properly so you might want to print slower or with smaller layers/thinner nozzle.

All these 3 factors influcence the volume per second, that the printer extrudes. I’ve made the experience, that especially XT needs a little bit slower printing temperatures compared to PLA/PHA. You should have no issue with 50mm/s and average nozzle sizes at 0,1-0,15mm layer height, but maybe your printer doesn’t handle XT that well, I don’t know.

Cheers,

Marius Breuer

[iceman1979]

Layer height is .1

Hot end is original so something slightly over .4 I would imagine at this point.

Bed temp is 60C for PLA and 70C for XT

I took the hot end apart last night and gave it a good cleaning. Here is what all I found…

There was a residue built up on the heating element and temp sensor so I took some 0000 steel wool to it and shined them back up. The PTFE coupler had cavity ring near the hot end (again!, I go through these like crazy) so I replaced it.

There was some hardened material built up around the threads between the nozzle and the steel piece that the nozzle screws into and the PTFE coupler goes into (don’t recall the proper name of this part), I cleaned this out as well.

The nozzle cavity had a lot of hardened material stuck to the walls so I took some time cleaning that out. It was bad enough that I had to take some drill bits of varying sizes just to get that out. Once I had the majority of that out I took a bamboo skewer and wrapped some 0000 steel wool around the sharp end and chucked that into a drill and polished the inside. I had to take a torch lighter and heat up the nozzle a little bit followed by running the steel wool wrapped bamboo skewer inside it again to get some of that out.

I can tell I didn’t get it all out because there I still don’t get a clean plug using the Atomic cleaning method but it is 100 times better. Lesson here is to do a full hot end cleaning each time I replace the PTFE coupler.