first print on UM2 - some questions

[braddock 1]

Hi all... so I attempted to print one of my pendants on my new machine... I half expected it to fail, but to my surprise, it did pretty well, but there's some obvious issues I think can be made much better.

Firstly, the object is only 36mm wide, and I printed it at 0.04mm layer height.

I printed it with the back of the skull touching the bed, with teeth pointing up. I used support and raft.

I couldnt see any settings for temperature in cura? I'm wondering if the temp is too high?

Also, when the print finished, it kept extruding and made a blob on the detailed area it had just done such a nice job on, ruining the print.

Anywhere the support was attached did not print well.

Overall, amazed at the surface quality, but I want to improve the bad stuff.

 

 

[illuminarti 18]

With the UM2, you configure the temperature within the "Materials' menu on the printer itself.

Areas with support aren't going to print great, there's not a huge amount that you can do about that, really. I'd be inclined to print it as shown in the last picture, with the teeth pointing down, so that the support is under the print in it's natural orientation, and less visible.

You might also take a look at MeshMixer 2.0, and see what it can do for you in terms of generating more intelligent support, with smaller contact areas, and then not use Cura's support capability.

Make sure you update to the latest firmware, using Cura 13.11.2. There was a bug in some versions that might have caused the printer to not properly home when a print finished and/or was aborted. That might be what caused the blobbing at the end?

 

[nick-foley 5]

If you're going to be printing a lot of stuff that tiny you might want to consider a smaller nozzle.

 

[braddock 1]

thanks guys. This isn't my primary use for the printer, but I wanted to see how god a job it could do.

I'm modeling some of my own supports now in Maya, and will have a crack at that.

What is the ideal temp for PLA?

 

[illuminarti 18]

It varies by brand, color, and what you're trying to do with it, really. I generally print most things at 220 or 230 degrees. You could go colder if you print slowly. The main thing is going to be to make sure that you set a minimum layer time of a few seconds, so that you make sure the plastic is cool before you over print it. Especially on overhanging parts. You might also find you get better results printing several copies at one time, so that the plastic on one part can cool while the other is printing, without the head having to slow down so much that heat transfers and remelts the plastic under it. Load multiple copies of the STL in Cura, and then set the gantry height in prefs to '0', to force it to print the parts layer-for-layer, rather than sequentially.

 

[braddock 1]

Cool, thanks. I have the print speed set to 20mm per second, but it is a small print. I have a print running now at 210 degrees.

 

[braddock 1]

As a solution for the blob at the end of the print, I can model an extra shaft and small platform to be cut off once it's finished, that way, I can control where the final blobby extrusion will occur.

 

[nick-foley 5]

at 20mm/s and layers that thin you should probably be printing 190-195ish.

 

[gr5 2,004]

As a solution for the blob at the end of the print, I can model an extra shaft and small platform to be cut off once it's finished, that way, I can control where the final blobby extrusion will occur.

 

That won't help. Instead model a tower next to the part. Or just print 2. I recommend printing 2 because then you end up with two. lol.

It won't help because the problem is that the print is too small at the teeth - the nozzle never leaves the melted pla so the pla never has a chance to cool.

 

[billdempsey 0]

It varies by brand, color, and what you're trying to do with it, really. I generally print most things at 220 or 230 degrees. You could go colder if you print slowly. The main thing is going to be to make sure that you set a minimum layer time of a few seconds, so that you make sure the plastic is cool before you over print it. Especially on overhanging parts. You might also find you get better results printing several copies at one time, so that the plastic on one part can cool while the other is printing, without the head having to slow down so much that heat transfers and remelts the plastic under it. Load multiple copies of the STL in Cura, and then set the gantry height in prefs to '0', to force it to print the parts layer-for-layer, rather than sequentially.

 

The temperature also varies widely by the age of the filament and the moisture it has absorbed from the air. I have a few huge 5LB. spools of PLA that are about 10 months old. They have become so hardened (and I assume have absorbed so much moisture) that I have to print at 250C in order to get them to flow smoothly, even at 40mm/s. That's one drawback of getting 5LB spools in colors you don't use constantly. :-|

 

[lennart-bruggink 3]

A lot of people first get the problems with the last extruded blob ( including my nose in one of my scanned head prints:( ). The answer to this problem was as Illuminarti said printing multiple copies, and the cause being the printhead in its vicinity.

Is it possible for such problem to be incorporated in Cura's Slicer?

Maybe as optional setting that the extruder homes/ lifts etc when layer time becomes too small in the end?

I guess this also would make stringing an issue, but i'm not sure if that would be better or worse than a solution as proposed above.

Still, I'd like to see a sticky post, which describes several known issues.

Cheers!

Lennart

 

[illuminarti 18]

There is already 'cool head lift' option in Cura that moves the head off the print as a last resort when printing small layers.

 

[lennart-bruggink 3]

There is already 'cool head lift' option in Cura that moves the head off the print as a last resort when printing small layers.

 

Indeed I know the existence hereof, which I like

However If I understand it correctly this mean that it lifts/moves the head at any layer

(depending on your print of course).

I agree, the cool head head lift solution solves more than one problem, but perhaps at the cost of speed?

I do not have the evidence to back it or turn it measurable, however.

Cheers,

Lennart

 

[illuminarti 18]

Well yes, it can happen anywhere, but only when the layer print time is so small that it would need to go slower than the minimum speed to get the layer to take that long. That typically only happens in the final stages of a print. But if it was happening sooner, then it would still be equally necessary for those layers too, so I'm not sure I see your point?

 

[lennart-bruggink 3]

... but perhaps at the cost of speed?

 

Just thinking out loud here, that's all.

 

(You have probably done loads of prints, whereas I have no feeling (YET) for making an assumption if it would matter. Well anyway I have not been the one standing next to the printer with a stopwatch to measure time per layer)

 

 

 

..But if it was happening sooner, then it would still be equally necessary for those layers too,..

 

 

As I have learned from another post, it's beneficial against cupping too (iirc).

 

So all in all, I had a thought twist and off course didn't know enough of the current functions to be able to say anything decent about it. I like it that you (or anyone) answer though!

 

Cheers

 

Lennart

 

 

 

[illuminarti 18]

Hey, everyone's ideas are welcome. We're all mostly just making it up as we go along :-) Eventually ideas start to coalesce out of the murk when enough people start seeing and saying the same things. :-)

 

[alluvian 0]

... The main thing is going to be to make sure that you set a minimum layer time of a few seconds, so that you make sure the plastic is cool before you over print it. Especially on overhanging parts. You might also find you get better results printing several copies at one time, so that the plastic on one part can cool while the other is printing, without the head having to slow down so much that heat transfers and remelts the plastic under it.

 

This always seemed like a really silly solution to me.

I get the reason for min layer time, you don't want to keep printing the next layer until the first can cool a little, but why does cura lengthen the time by moving slower (which I would think would transfer more heat to the part which somewhat defeats the purpose).

Would it be possible for it to print the same speed, retract, then just move the head off print until the min time is reached and then resume? Or would it still drip even after a retraction if just hovering offprint?

I don't even have a printer yet, I am super newbie at this, so my apologies if I am missing something obvious.

 

[gr5 2,004]

Would it be possible for it to print the same speed, retract, then just move the head off print until the min time is reached and then resume?

 

This is called the "cool head lift" feature. It actually works pretty well. Some people don't like it because it can create a vertical string but it really isn't that bad.