Need help with print issue. random layers very bad quality

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Need help with print issue. random layers very bad quality

Postby yellow » 2016-Mar-Tue-09-Mar

Hi guys,
I upgraded my printrbot simple metal with the x-axis upgrade and heated bed. While printing items that were very short, things were working great. I have no clue why I waited so long to get a heated bed, even with PLA.
However, i was printing a much taller bracket and in some random layers, the print quality is horrible. Then it goes back to printing pretty decent. A picture is below. On the inside, i see the same issue but in different layers.

IMG_1393.JPG
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Need help with print issue. random layers very bad quality

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Re: Need help with print issue. random layers very bad qual

Postby yellow » 2016-Mar-Wed-14-Mar

no replies is usually a bad sign. Either it's obvious and i don't see it, or it's something new that no one has had to deal with. just thought i'd bump it once just in case.
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Re: Need help with print issue. random layers very bad qual

Postby RetireeJay » 2016-Mar-Wed-14-Mar

I have to say I haven't seen something like that before.
The widely-spaced and random nature of the problem layers, and the fact that the problem, when it occurs, seems to span several layers suggests maybe something to do with the way the feed filament is coming off the spool - like maybe it's pulling real hard some of the time and either causing an under-extrusion or else the tug of the filament is pulling the extruder position a little off (probably up) from where it's supposed to be.
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
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Re: Need help with print issue. random layers very bad qual

Postby olendorf » 2016-Mar-Wed-14-Mar

Yup, that's almost horrible, but usable.

No replies is a good sign. I don't think anyone is going to tell you, "print at 212 degrees and it will work great" or "change infill to 22%". No replies means that you have 100 different things to experiment with and only experience will solve this one for you. You can't usually fix that with a forum reply.

Here is what you do;
Thoroughly check out your machine to make sure everything is running smoothly. Nothing loose, wobbly, creaky, etc.
Make sure your temperatures are staying in line. Maybe your hotend temp is fluctuating too much. Feeding filament too fast cools it off. You just did a heated bed so try it without heating the bed. Maybe your power supply can't keep the hotend hot and power the bed too.
Are the fan or fans running properly?
Is the filament drawing from the spool smoothly? There should be as little resistance as possible. It needs to unroll not lay flat on a table.
Are the software settings matching the hardware? Nozzle size mostly but temps and speeds for the various materials need to be in line.

When the hardware is checked out then you need to try experimenting with printing settings.
Try different speeds, temperatures, infills, etc. Make sure to try a fresh, different roll of PLA. Sometimes a roll will go bad or be bad out of the box.
Probably the most important, watch very closely as it prints to spot what is happening during the defects and what happens during the good parts. You should be able to spot an issue. Not sticking? Too fast? Too hot? Too cold? The spool got stuck. Hey. the hotend is wobbling.

I've printed hundreds of things and one print I couldn't get to lay down the first layer correctly. I was watching it fail time after time and my son comes in and says "Why is that first layer printing so fast?" Then I remembered the previous item I had to print the first layer fast and forgot to set it back to normal speed.

So "You're Welcome" :) for no one answering your post!! You need to do the time and build your experience. When you figure it out and that piece comes out great you will be so much more in control and that's when it gets to be fun.
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Re: Need help with print issue. random layers very bad qual

Postby frankv » 2016-Mar-Wed-15-Mar

All the above, plus I'd add:

Since you say it only happens in the X axis, and especially since you've just changed things on the X axis & bed, I'd focus on that first. Check your X axis for jamming/rubbing/interference/binding. Check the X belt, its drive gear and its pulleys for play. Make sure the X motor and its mount is screwed down tight. Nothing down there getting tangled in the belt? Wires to the heated bed have enough slack, and not getting tangled in anything?

I don't know why it only applies to tall items... maybe it doesn't, and you've just been lucky with the small items. Maybe it's a temperature thing, where the problem only occurs after a certain amount of time. Maybe you've got a bend in your Z lead screw?

Also look for how the infill associates with the bad layers... maybe you need thicker walls?

Try a different slicer, or different infill patterns... it may work around the immediate problem enough to get the part printed nicely enough, or give you an insight into actually solving the problem.
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Re: Need help with print issue. random layers very bad qual

Postby Mooselake » 2016-Mar-Wed-17-Mar

Does this happen in every print at the same height, at different heights, or was it a one time thing?

Kirk
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Re: Need help with print issue. random layers very bad qual

Postby yellow » 2016-Mar-Thu-07-Mar

Wow, thanks for all the replies. Fully understand now that I need to try/check a bunch of things at this point before being able to really find out what it is. At work now, but will be trying a bunch of suggestions you gave me tonight. Thanks so much, and I will report back with what I find!!
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Re: Need help with print issue. random layers very bad qual

Postby yellow » 2016-Mar-Thu-21-Mar

Finally an update! I checked all the settings suggested and watched as the printer ran a small print. Everything seemed fine. Ran another small print. Everything seemed fine. Then finally on the third print i heard a clicking. just a few clicks, but i couldn't make out what it was. Was watching the X as that is what was changed, but the clicking didn't' line up with the X moves. Watched the Z, but still didn't make sense. Made sure everything was tight again as far as motors and that the belts had good tension. I guess luckily the clicking got worse as i continued printing so i could more easily watch what was happening. It turns out the motor on my extruder was clicking. I loosened up the tensioner, the clicking stopped, and my prints now look better than ever. More testing tomorrow to verify that was the only issue, but so far so good! Thanks for all the suggestions guys.
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