Joris print repeatable misprint

[morsch 0]

Hi guys,

I keep having an issue with this part: http://www.thingiverse.com/thing:20730

It's a joris (aka spiralize outer) print. The lower 80% come out fine, but things always turn into a mess at the right side at top of the print. The left side is fine.

The issue is exactly reproducible, i.e. repeated prints look identical. I've tried a couple of different print speeds and temperatures. I'm using PLA. Can anybody tell anything from the images?

Two more at: http://imgur.com/a/JD0AZ

I don't really have any issues with other stuff I've printed.

TIA

Moritz

 

[IRobertI 514]

I'd say it's a cooling issue, especially since you say that one side is fine. I don't know which printer you have but on the UM1 there's only a fan on the left side so the right side can get a bit warmer. On the UM2 the right fan is blocked a bit by the metal shroud so on small parts it can't quite reach the right side of the print.

You might be better off printing several at the same time normally instead of as a Joris. By printing several of them at the same time the head will leave one copy of the object for a while to let it cool down a bit while it's printing the next layer on another copy.

 

[lohiaprateek 0]

You need a better cooling shroud, this mostly happens due to excess heat build up, alternately you could also reduce print speed, such that the parts cool down a fair bit till the next layer start.

 

[morsch 0]

That makes sense! I'll try working on the issue from that angle.

Thanks for the advice.

 

[gr5 2,000]

In the expert "cool" settings there is a "minimum layer time". This should be 5 seconds which will cause upper layers to print slower so that other areas have time to cool. I don't know if the "spiralize" overrides this setting. 5 or even just 3 seconds should be enough with fan on. 5-7 seconds are needed with fan off.

 

[yellowshark 153]

Yup it is cooling. Once you get to the thinner top portion the individual layer times are too short so the deposited layer has not cooled before the next layer is extruded. What does intrigue me though is that you seem to have three goods sides and one duff side – I cannot explain that.

Usually the only way around it is to print two of them, or something else, in parallel; setting minimum layer time can sort it but the printer can only print so slow and anything with a point or a very thin structure above the main structure will need parallel printing in my experience.

 

 

[morsch 0]

I tried increasing the minimum layer time -- maybe 20s was overboard --, the good news is same issue didn't come up, the bad news is, well:

Guess I'll try printing multiple parts. I'll also look into improving the cooling, maybe add a shroud or a fan. Got plenty of 80 and 120mm fans lying around from computer projects.

 

[IRobertI 514]

Yeah, increased layer time means the head stays over the plastic for longer and transfers heat into it even deeper. It can work on some pieces but in my experience there's a very narrow window that actually works well.

 

[gr5 2,000]

You can try cool head lift also. That works. But I really love printing two. Or putting a tower next to it.