Burns in prints

I'm facing a problem with ABS burning during print in particular points and leaving marks. The burns often happen near the top of overhangs, both when supports are present like not.

I printed the Zortrax's office organizer at 0.14mm 20% fan and 20° supports as well as the little Marvin for 3DHubs at 0.09mm, 100% fan no supports and here's what happens:

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I printed three of those little Marvins at the same time and with different rotation over the plate and all the three have the same burn in the same point, so it's a replicated problem and doesen't depend if the area is facing the fan or not. I noticed the problem also in other prints I've made and with various degrees of burns but I haven't shot images, it happens quite often though and all share the same situation: near the overhangs and near top of passing holes (with any shape) and most visible on left side of them.

The office organizer has been sanded too with 150 grit to try and remove the marks, but without luck. The burns extend inside the part deeper then the outer wall of the surface.

Anyone with the same problems? What could be the cause?

I see the same thing one in a while and it appears to come from filament residue that clings to the end of the nozzle.  I've had a little luck in reducing the burn marks by wiping the end of the nozzle with a Kimwipe (lint-free paper towel) just before the print starts when the extruder is at temperature.  It also helps a little to carefully scrape the residue off the nozzle when it is cold.  Someone mentioned using a brass brush on the cold residue too, I think.  Neither of these are much help for long print jobs, say 12 or more hours because the residue builds up gradually on the nozzle during the job.

I theory you could pause the printer part way through a job, wipe the nozzle down, then resume the job but that didn't work the last time I tried it.

Mike

I have the same problem after to week: just bought it no problem but after a spool of abs used I noticed some burns spot. I noticed that the nozzle gets dirty faster than before: cleanse after every print: it could be a problem caused by the material it is constructed? I've always cleaned with acetone and a cotton cloth: I removed all the debris that came out prior to printing and so on.

Now I am trying to print the same subjects with the fan at 60% (so far I have used 20%). Thanks for any advice.

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It is better to only print one part at the time imo. When printhead moves all over the plate traveltimes is longer and some ABS will leak out and then build up residues on to the nozzle. And after some time this burnt residue will drop off somewhere as the result in this pic above.

I have the same problem after to week: just bought it no problem but after a spool of abs used I noticed some burns spot.

:huh: Hum...

It’s very short to have less quality printing after bought a printer…

 

It is better to only print one part at the time imo.

It's also worse printing time.

We must have the choice to print one or more parts, it not normal to suffer such a tyrannisme  :angry:

ZORTRAX ! FREE OUR (their :wacko:) PRINTERS NOW !

:huh: Well may be is a bad quality serie of Z-ABS if it isn't observed by everyone or bad quality nozzle if only on new printers.

(I hope not I won't be too long to buy one -_-)

The strange thing is that, at least in my case, the burnt points and present only near overhangs. I think that is because in those cases the printed area bends upwards and when the hot nozzle touch it printing the next layer it burns the already deposited ABS. Neither 100% fan helps in those cases to prevent curls. Things are better in 0.19mm> layers, because more thick layers less curls happen.

Yesterday it also happened that the filament got stuck in the hotend due to a knot in the spool that stopped a print (I couldn't load a new filament anymore, since it loaded for about 10cm and then the traction pulley started clicking). I had to disassemble the whole thing to understand that the very small passage inside the hotend was obstructed by material that didn't melt anymore enough to let the new filament pass. I've been able to completely clean it by reassembling the hotend without the lower fan and the nozzle and then heating the extruder. So I gently inserted the 0.4mm nail from bottom into the exposed hotend and a bit a time completely removed residues without damaging anything or using more dangerous methods (acetone or drillings). 

While this is a boring thing to happen I really have to thank Zortrax for the excellent way the M200 is made. It is very easy and strightforward to disassemble and maintain the machine and tutorials are well done and really help a lot. I've been able to have my M200 in order again in less then one hour.

" :huh: Well may be is a bad quality serie of Z-ABS if it isn't observed by everyone or bad quality nozzle if only on new printers.

(I hope not I won't be too long to buy one -_-)"

The cause is not z-abs or the nozzle. The only parameter that can affect how much abs leaking is retraction. And mabey this retraction already is tweaked too the best it can bee or mabey it can be tweaked abit more. No real way too know. 

 mabey this retraction already is tweaked too the best it can bee or mabey it can be tweaked abit more

:huh: Hum... you may be right

I think retraction adjustement should be same for everyone by construction.

So it would affect all printers. I wonder if everyone had been concerned by this problem

Now I’m printing again with new setting (fan at 60%)…layer is always 0,19 mm.

I noticed that when then nozzles moves on flat surface, at the beginning of the Owl, I have no problem: when The nozzle is at the end of the work I have some spot burns.

A friendly have printed 48 marvin in the same surface and he has not problem!

I have the same problem.

First time, i thought i didn't clean the hotend enough, but after 100% cleaning (cloth & acetone) the problem is repeated.

It got dirty during auto-calibration - don't know why is heating extruder needed while this operation??? It also gets dirty every time while check-procedure before printing. The hotend touches surfaces with oozing material, it glues to hotend sides and got burned. Then I just wait (in negative way..) when dirties touches my print structure :(...

For no-artistic prints there's no problem.

But when u print i.e. face (top-directed) and after whole face idealy printed nose gets browny-dirted in last 2-3 surfaces, its really annoying.

When u print cristal, and it's 99% perfect, except its browny-dirted tip what - of course - makes your attention been focused only on it, its really annoying... and so on..

437

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Usually I pay a lot of attention to what happens during the leveling test before the print really starts. I check this phase continously and I'm ready to remove the excess filament coming out from the nozzle with the pliers that Zortrax provided and do it again and again until the first layer of the raft starts.

If your nozzle is clean the filament will come down quite stright so it's easy to remove, if it's already dirty it will curl and it will deposit on the sides of the nozzle, making removal almost impossibile. Anyway taking care of the excess filament in this part of the process can help you to prevent having a dirty nozzle at the begin of the print but it can't do much for long jobs, because if you have any overhang in the print the curls due to heat will deposit the ABS around the nozzle. Also in the very top of your second print I think the problem is that for some reasons movements are quite slow when you are at the end of a print that has a cone or a pyramid with a tip and those slow motions melts and ruin the top of the print.

Maybe the next release of the Z-Suite could address this issue, setting faster moves in such situations.

I have the same problem.

 

don’t know why is heating extruder needed while this operation???

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Simple thermodynamics actually. In a nut shell metal expands when heated and contracts when cooled. The nozzle is made of brass and expands a fair amount let's say up to .003 of an inch or roughly .1mm in metric. If your trying to lower a nozzle .09mm or .14mm close to the bed and the nozzle isn't heated first you will most likely smash into the bed or squish each additional layer causing a possible clogged nozzle or an ugly print. Now the first layer is generally higher than that due to the fact that rafts are common with the zortrax but none the less you will be pushing to much plastic into each layer as it doesn't know the correct value of the z axis depth.

All in all it is important that this be done and provides you with the most accurate z axis height (even better if you let the bed warm up as well)

You may say they can account for the thermal expansion in the software and you would be partially right however metals thermal expansion isn’t an exact science so the expansion is not always the same and metals thermal capabilities degrade over time especially copper and brass.

Yep, that sounds logic. Thx Techbuilder.

Maybe the way out is to make cold-nozzle and hot-nozzle check-procedure while auto-calibration, and save readings in M200's self-memory.

Then make only cold-nozzle check before every printing, and auto-calibration (with hot nozzle) only time to time..

but hot-nozzle check everytime seems to be the most safe and simple.

Yep, that sounds logic. Thx Techbuilder.

Maybe the way out is to make cold-nozzle and hot-nozzle check-procedure while auto-calibration, and save readings in M200's self-memory.

Then make only cold-nozzle check before every printing, and auto-calibration (with hot nozzle) only time to time..

but hot-nozzle check everytime seems to be the most safe and simple.

Can't do that the initial touch that it does before it starts printing is what distinguishes correct distance of the nozzle to the bed based n the layer height you selected in Z suite.

One thing they can do is set retraction to occur slightly before leveling but that can caused a clogged nozzle. Best solution is lay a small amount of filament before each peck but that will increase the amount of time the auto leveling takes

So I got my M200 yesterday and have done a few sample prints - everything has looked amazing! ...Except for sometimes seeing the same problem of burn marks in the prints. Usually near the end of the print. (Will update with photos).

It looks like there's a buildup of burned filament on the nozzle, but I don't think that even when a little pre-extrusion during auto calibration it would build up that much. It almost looks like something (if not the ABS) is seeping past the OD threads of the nozzle, but I would think that would be unlikely. I'll take a picture later - it just looks like there's too much material to have come from a little filament getting caught from "back-splash", plus the fact that the source seems to be the contact surface at the nozzle and heater block (could be my imagination).

I tightened the nozzle, which didn't solve the problem. I'll try cleaning it out, though it's a new unit so it's probably not too dirty yet.

I'm thinking about a possible solution and will update with results later: I want to coil a small metal wire around the nozzle at the base, near the hex pattern. I'm thinking this may help wick any melting material away from the nozzle hole, but the danger is that the coil may come loose during the print... I'll try to figure something our and see how it goes.

Simple thermodynamics actually. In a nut shell metal expands when heated and contracts when cooled. The nozzle is made of brass and expands a fair amount let's say up to .003 of an inch or roughly .1mm in metric. If your trying to lower a nozzle .09mm or .14mm close to the bed and the nozzle isn't heated first you will most likely smash into the bed or squish each additional layer causing a possible clogged nozzle or an ugly print. Now the first layer is generally higher than that due to the fact that rafts are common with the zortrax but none the less you will be pushing to much plastic into each layer as it doesn't know the correct value of the z axis depth.

All in all it is important that this be done and provides you with the most accurate z axis height (even better if you let the bed warm up as well)

You may say they can account for the thermal expansion in the software and you would be partially right however metals thermal expansion isn’t an exact science so the expansion is not always the same and metals thermal capabilities degrade over time especially copper and brass.

Not to mention that plastic is non-conductive, so if there's a plug or film of cold plastic at the tip of the nozzle, auto-sensing is not going to work. The nozzle has to be hot so that any plastic there is molten and the metal can push through it to make electrical contact.

But, yeah, to get back on topic, the burn marks are a drag. Anyone notice if it got worse after the 0.0.8 temp bump from 270 to 280C?

I have similar problem with the print of marvin.  I'am not able to achieve better results in upper part of Marvin :(

Bottom part is ok but upper part above eyes is not sharp and "slightly burnt".

See attached pictures.

I attached my z-suite settings and STL model too

Grey marvin was printed from Z-ABS without support

Green Marvin was printed from Z-ABS with support

Thank you for any idea how to improve print result