Strategies for Resolving Print Artifacts

[mhackney]

When presented with any problem, a time tested approach is to break it down into it's smallest components and determine what you know and don't know about each. This can eliminate a lot of unnecessary effort and help you focus on finding the root issue. If you are seeing odd print artifacts in your parts and have worked through and are an ardent practitioner of my guide A Strategy for Successful (and Great) Prints , you can use the following strategies to track down and erradicate print artifacts. In this case, you can break the problem down into six categories:

1) first layer problems
2) >first layer problems
3) perimeter problems
4) top layer problems
5) fill problems
6) overhang problems

and for each of these there can be:

A) slicing problems
B) mechanical problems

(of course I've simplified this, the model itself (see #6) could be a problem as could electrical issues, etc. But for the majority of the cases, these two will suffice.)

You can attack 1 through 6 in order - and, of course, you might not experience all of these. Here are some strategies:

1) First Layer Problems - follow the recommendations in my Guide and use the single layer object until you can print it reliable and perfectly. If slowing down, adjusting extrusion, using the lowest filament melt temperature, etc don't work to eliminate the artifacts you are observing or if you see artifacts that indicate a mechanical problem, then you need to turn your attention to the mechanical aspects of the machine and work through those until you find and resolve the problem. You can use the recommendations in #2 below to solve these first layer issues too.

2) Greater than First Layer Problems - if you nail the first layer, it goes down nice and smooth without significant artifacts predictably and reliably but are seeing issues in the second or higher layers, this is almost always related to a mechanical problem and not a slicing problem. Think about it, once the first layer is down it has created a "raft" for the next layer and the top surface of that raft should be precisely parallel at any point on the surface to the nozzle tip's motion. In other words, the next bead should go down perfectly. If not, start with the nozzle itself. Polish the tip, check the bore to make sure it is round and has no burrs or significant scratches in it (hold up to light and look through). If you have a spare nozzle, polish it up and try it. Once the nozzle has been eliminated (and nozzle issues would also be prime suspects for #3, #4 and possibly #5) next check the hot end itself. Make sure it is tight with NO WIGGLE whatsoever. One easy test is to re-orient the hot end in the effector (rotate it 90° or 120°) and test print. Does the issue show up in exactly the same place? If so, it is not the hot end, if not, then you have narrowed it down a bit. Don't forget to use the slicer rotate feature to rotate the part, say 90°, and test. The results of this can help determine which tower/s might be contributors.

Think about the delta to cartesian geometry mapping - the Delta Z tower is precisely aligned with the Cartesian Y axis. This is a powerful realization as it allows you to start thinking about the relationship of the tower movements to the part geometry. For instance, if you have print artifacts that are precisely aligned with the Cartesian Y axis no matter how you rotate the part or hot end, that should be screaming "There is a problem along the Z tower mechanical path from the effector up through the arms to the carriage - including the track the carriage rollers ride in". Don't forget the belt, stepper pulley and idler pull at the top. A small piece of debris on the parts can cause the belt to stretch slightly as it goes around the pulley and this can result in a print artifact. A good thing to do is to clean everything carefully (I use windex and clean lint free paper towels) and re-test. It is also a good idea to tighten the pulley grub screws - I can't tell you how many times that has been the issue (especially on the X and Y towers where delta-to-Cartesion coordinate translation is a little less intuitive to figure out).

Next check to see if there is a relationship with the print artifact and either the X or Y towers. If so, try rotating the part in your slicer and rechecking. Move the part closer and further away from a suspect tower and reprint and check. This is why I like a simple, small part to test - you might be making a lot of prints and you want to get the data as quickly as possible.

If you discover a relationship, work on the suspect tower as per the Z tower suggestions above. One technique I use is to apply pressure from my finger on the effector aligned with the direction of the suspect tower while it is printing. First towards the tower, then on the other side away from the tower. This eliminates backlash in the system and can help identify issues. You can do both directions on a single print so you get a twofer on this test!

3) Perimeter Problems - these could be caused by either slicing or mechanical problems. Here it is important to think about what could cause the observed artifact. Is it a blob? If so, that is most likely a slicing issue and you should turn your attention to tuning the slicing parameters. Is it a dislocation, i.e. corners or long edges are not completely aligned one on top of each other? If so, that is a mechanical issue and you can use the strategies in #2 above to identify which axis is contributing to the problem.

4) Top Layer Problems - these are somewhat related to #2 in that the top layer is being laid down on what should be a near perfect base. Nozzle imperfections are a prime suspect as is a loose hot end - see the tests and recommendations in #2.

5) Fill Problems - fill problems are more unusual and almost always a slicing issue. Once you have the first layer and perimeters nailed, squirting the plastic inside to fill the part is usually not a problem. Overfilling that causes bulges in higher layers can be an issue. This can be addressed with calibrating the extruder, filament extrusion temperature, infill extrusion width and even infill density.

6) Overhang Problems - firstly, realize there are geometry limitations on what can be printed with a FFF printer! The laws of physics still apply to 3D printing. Overhang issues are almost always related to slicing. There are many different types of overhangs and bridges so I'm not going to attempt them all here. However, a common one is worth discussing. Think about an inverted pyramid - the sides slope up and out creating an overhang. Most slicers default to printing perimeters outside-in. Think about that. What is that outside perimeter going to adhere to? Depending on the slope of the wall, there may be very little plastic underneath from the previous layer. I like to print these inside-out. Think about that. Now, the first inner perimeter will be printed securely on a solid base. The outermost layer will have the advantage of a neighboring layer to stick to, helping prevent it from sagging.

[Tincho85]

Great as always. I learn a lot from your threads.
Thanks for sharing Michael.

Martin.

[mhackney]

Thanks Martin!

[Eaglezsoar]

Thanks for another great guide Michael.

[XpresoAdct]

Thank you!

[626Pilot]

mhackney, is there a thread where you talk about your Kraken setup, what arms you use, etc.? I'm looking to move from the Cyclops to the Kraken, but I need a printer with a FLAT effector.

[mhackney]

In my build and Kraken threads. At the time I did the change I was running the stock V1 arms and stock V1 carriages, etc. That might have been part of the consistency issues with printing I had. I finally gave up on multi-extruders with individual nozzles per filament after three attempts. No matter how good the retract, etc I would get drag marks on the surface of my parts - where they are most visible in my reels. Most people would have been happy with the results I was getting but it wasn't sufficient. You've seen the work I've done with the Cyclops of the tree logo encapsulated in clear PLA? I could never do that with a cult-nozzle extruder to this level. All that said, I love the Kraken. It is water cooled and was my intro to water cooling.

With the water tubing and 4 sets of thermistor/hot end wires and part cooling fans I don't know if magnetic arms could handle it. I have Trick Laser CF ball end arms now and I think they would work well.

Why are you moving from Cyclops?

[626Pilot]

The cyclops is nice, but it suffers from four problems.

• Colors tend to bleed, even if you use a prime pillar/short wall.
• Different materials (PLA, HIPS) might need to have significantly different temps to run properly.
• Questionable for use with carbon fiber and metal filaments. Krakens can use the hardened steel nozzles. The melt chamber in the Cyclops is all-aluminum and could easily be destroyed by a SINGLE spool.
• Awful overhang performance. If you use part cooling fans, the enormous heater block will lose heat so fast that the cartridge heater won't be able to keep up. (If you have a solution for this, let me know!)

I could use the Chimera, I guess, but I would still need a perfectly tram effector.

There's a dual-extrusion setup that puts the hot ends on a yoke driven by a servo. When one nozzle is deployed, the other is lifted, and vice versa. That seems a little crazy to me, and it only has two nozzles.

I have a Palette filament splicer coming next year, but it's probably going to force me to use Cura with a plugin (BLECH!!!!!!) - I need something that will run off an SD card. Running prints over USB is like a bomb waiting to go off, but instead of an explosion you just get really annoyed because the print has inexplicably hung.

If the Kraken doesn't work out, I might just build a CoreXY printer with all the heavy BS on a gantry, use that for 4-extrusion, and use delta printers only for 1- and 2-material work. Does anyone actually have good luck with the Kraken not drooling all over a print?

[blackrabt]

Really helpful information here, thank you.

[626Pilot]

mhackney, what retract settings do you use with your Cyclops with PLA, and how well do they work? I'm getting better retracts with a velocity of 10mm/sec, but it's still oozy.

[TwoTone]

"6) Overhang Problems - firstly, realize there are geometry limitations on what can be printed with a FFF printer! The laws of physics still apply to 3D printing. Overhang issues are almost always related to slicing. There are many different types of overhangs and bridges so I'm not going to attempt them all here. However, a common one is worth discussing. Think about an inverted pyramid - the sides slope up and out creating an overhang. Most slicers default to printing perimeters outside-in. Think about that. What is that outside perimeter going to adhere to? Depending on the slope of the wall, there may be very little plastic underneath from the previous layer. I like to print these inside-out. Think about that. Now, the first inner perimeter will be printed securely on a solid base. The outermost layer will have the advantage of a neighboring layer to stick to, helping prevent it from sagging."

Still being new to these, where/how do I change it from outside-in to inside-out?

[IMBoring25]

It depends. What slicer are you using?

[TwoTone]

Cura that came loaded in MatterControl.

[mechg]

I had a z-banding issue recently with my Orion. It was really noticeable on white material when printing a cylinder. It was worse on the side opposite one particular tower.
It turned out that tower's cheapskate had too much play. Using the cams to tighten the roller wheels eliminated the problem.

I guess this falls under the #3 - Perimeter Problems - Mechanical

[jarekdadej]

that falls under PID bed heater problem. Tune you PID for bed heater and those will go away.