Straight, tall, thin cylinder has "wobbles" in it when printed
I had this happen twice, once when I printed a tall cylinder, approximately 130 mm tall by a bit more than 4mm in diameter. It has a base about 28mm in diameter and 5 mm thick. It prints properly, then reaches a point where, for the rest of the height, it has "wobbles" in it and it looks more like a threaded screw than a straight cylinder.
This is the first time I tried printing it, with other objects being done in the same print. Note that when it goes bad, it shifts to the left, then gets weird. It appeared to me that the break where it gets bad is a bit above the tallest other object being printed.
And here is where I tried to reprint it by itself. It went bad rather quickly and it also shifted to the left here:
I was not in the room for the first print and was busy during the 2nd one, so I didn't get to see just what was happening as it went bad. I also realized I have my timelapse set for layers, so it's not going to be helpful for this. Also, I did check to make sure the bed and print head could move easily along each axis. It's not long at all, in print hours, since I lubed it all.
My first thought is that, due to the proportions of the cylinder, that it's wobbling and that it printed up to the level of the other objects because at least one of them was printed before the head moved to the cylinder to print it, so maybe, when the print gantry moves up a level, and the bed moves to start a new layer, maybe the movement is making the cylinder sway some, so when the printer starts printing, there isn't a good alignment with the head and the position of the cylinder. I can see several reasons this could be wrong, but I can also see why those reasons are wrong.
My thought was that if I had some supports to hold it still, it might help, but I have never seen supports to work horizontally, only to hold up parts of a print and work vertically.
A few notes on what I'm doing:
* It's part of a press mold I'm making for pottery work, which means I'll have to print this out in several different sizes because it has to work with different rates of clay shrinkage so, when done, the finished version will always be pretty close in size.
* I can't go and buy something like a long nail from Lowe's, because of the size difference mentioned in the point above.
* I need a cylinder, so I can't change it to a square or other shape. (It's part of the hole for a wick in an elaborate stopper in oil lamps. It needs to be large enough for the wick to be pushed through it without messing up the wick, but narrow enough that the flame at the top can't just move down along the wick until it is burning the oil in the lamp directly.
* If this can be properly printed horizontally, I'm worried about trimming and being able to trim it so it's round when I'm done.
I have considered, as a solution to split the piece in 2 parts, one is the long cylinder, the other is the handle, which would have a hole in it for the cylinder to fit in. My concern is whether something that size, when printed on a side, will come out properly circular.
4mm diameter? This will be fragile ... much stronger if printed horizontally; would a hex/octagonal shaft be OK? If it must be circular consider turning down a length of metal rod or even a wooden dowel. Consider repurposing a knitting needle.
The layers are so small that there is not enough time for them to cool and firm-up before the next layer is added. That's why the print is good while there are other parts being printed and taking time.
Set a minimum return time in: Filaments > Cooling > Cooling thresholds > Slow down if layer print time is below:
The best value will depend on the filament in use; experiment, 15 seconds is often enough.
Cheerio,
RE: Straight, tall, thin cylinder has "wobbles" in it when printed
4mm diameter? This will be fragile ... much stronger if printed horizontally; would a hex/octagonal shaft be OK? If it must be circular consider turning down a length of metal rod or even a wooden dowel. Consider repurposing a knitting needle.
I know it's fragile, but I can't use something else for the reasons I included at the end. I'll have to print different sizes, going up in diameter in as small a step as as I can in many cases, to print versions that work with different clay bodies with different shrinkage rates.
The layers are so small that there is not enough time for them to cool and firm-up before the next layer is added. That's why the print is good while there are other parts being printed and taking time.
Ah! So it does have something to do with the timing - although not a wobble as I guessed.
Set a minimum return time in: Filaments > Cooling > Cooling thresholds > Slow down if layer print time is below:
The best value will depend on the filament in use; experiment, 15 seconds is often enough.
Thanks!
This does give me an idea that might help and work in the same way. I will need multiple versions in multiple sizes. I can put markings on the handle on the end to indicate the size for each one. (Normally I indicate the size by the filament color when I print.) I could print all the different sized versions of this at once. That way each layer may take long enough that I don't have to add a delay or I might be able to print all the different sized needles and, say, one other item, and, instead of it taking the extra time to pause between layers, that time will be used printing the other needles or other objects.
RE: Straight, tall, thin cylinder has "wobbles" in it when printed
....and, instead of it taking the extra time to pause between layers, that time will be used printing the other needles or other objects.
This will probably solve the problem.
I have considered, as a solution to split the piece in 2 parts, one is the long cylinder, the other is the handle, which would have a hole in it for the cylinder to fit in. My concern is whether something that size, when printed on a side, will come out properly circular.
Indeed, a cylinder printed on its side would not print well. But if you were to split the piece across a diameter and then print two halves lying down, they'd print cleanly and you could glue them together.
RE: Straight, tall, thin cylinder has "wobbles" in it when printed
The best solution for this is usually to print multiple copies so each has time to cool down.
Formerly known on this forum as @fuchsr -- https://foxrun3d.com/
RE: Straight, tall, thin cylinder has "wobbles" in it when printed
Tango its purely cooling. The previous layer doesnt have time to cool before it deposits the next. Thats why when you print it with other objects it only 'goes bad' when its above the level they stop at.
Doing as FoxRun says and printing several in one go all at the same height will give it time to cool between layers. Also will work better if you space them out a bit on the build plate. You could also slow travel speeds down to give more time.
The filament cooling settings also have a 'slow down if layer time is below' setting. That can be adjusted in these cases but multiples at one usually works better.
RE: Straight, tall, thin cylinder has "wobbles" in it when printed
I tend to think in "upfront" cost - in terms of time, work, and so on. So the last thing that ever comes to my mind is something like gluing pieces together - unless it's necessary. I'm not trying to say gluing is a bad idea - it's just, pretty much, the last thing I think of - if I think of it at all. But that could be a solution.
I think I'll go with a multi-item print, though. I checked and it takes 34 seconds to print one layer of the thin rod on this piece, so even printing 2 of them at once should do it.
I'm curious - I get why this issue wouldn't appear until above the height of the tallest of the other objects I'm printing, but why didn't this start even lower, like 1-3 layers above the disk handle for this when I printed it alone? I'm asking because I'll be doing similar parts for other molds in the future and often it'll help to be able to test the sizing with a mated part the rod would go through. Knowing that I can print a short test version of this, with the rod only, say, 10-15 mm high would save time in the future.
RE: Straight, tall, thin cylinder has "wobbles" in it when printed
That’s a reasonable question, I don’t have a definitive answer but if I had to speculate I’d say that when it’s lower the air the fan is pushing through to cool the layers is being deflected back upwards from the bed giving you increased cooling. When it’s gets up higher that effect stops and you get the hotter layers.
It does appear to get progressively worse until it gets to a certain point and then it’s just consistently bad.
RE: Straight, tall, thin cylinder has "wobbles" in it when printed
Probably exacerbated by the residual higher temperature from previous layers.
Formerly known on this forum as @fuchsr -- https://foxrun3d.com/
RE: Straight, tall, thin cylinder has "wobbles" in it when printed
I thought I had posted my results on here, but maybe I wrote it up and closed the tab before I hit "Add Reply." Sorry for the delay - I know a resolution helps people with similar issues later.
I had to do more test printing on this and that included a frame for the mold I'm making and reprinting the rod. Since the rod was taller than everything else, I printed 2 rods. That worked fine - they both printed okay. Since OctoPrint reported a 34 second time per layer for just one rod, I figured an extra one would give it enough time to cool down. The only glitch was when it got to the top and the rod was tapered to a point, since the cross section got smaller and smaller and the delays weren't long enough.
I'm thinking I might make a part to help with that. It would be the same diameter as the other rods being printed and, at the top, when the other sections narrow to a tip, this one would spread out. It's not a big part of the rod, so I don't think it'll be too top heavy. This extra rod would be my "control" rod, since it would add enough print time to each level to let the filament cool off.
The one question I have is if I could make a rod as narrow as 4mm diameter stand up easily if I printed it with a brim?
RE: Straight, tall, thin cylinder has "wobbles" in it when printed
The one question I have is if I could make a rod as narrow as 4mm diameter stand up easily if I printed it with a brim?
Maybe. Depends on what the printer is, is it a bed slinger ? Print speed is also always going to be a factor. With a fixed bed design then yeah shouldn't be a problem.
Personally though I would model in 3-4 'fins' at the bottom. Think classic scifi rocket or missile silhouette. That would give much more lateral support.
RE: Straight, tall, thin cylinder has "wobbles" in it when printed
Personally though I would model in 3-4 'fins' at the bottom. Think classic scifi rocket or missile silhouette. That would give much more lateral support.
Here's an example of something like this I did for one of my designs. Distance between fins and main shaft is 0.2mm.
Formerly known on this forum as @fuchsr -- https://foxrun3d.com/
RE: Straight, tall, thin cylinder has "wobbles" in it when printed
I printed a similar object. It had a thread so could only be printed vertically. I designed it with a central bore and afterwards I screwed in a piece of threaded rod which made it strong enough to be used.
Mine was actually so tall I had to print it in two parts and glue them together, which would be so fragile as to be unusable without some form of reinforcement.