Sharp top edges  

RE: Sharp top edges

Your tip looks - stringy...

The tip is a very small surface area. It will get really hot... Try dropping your nozzle temp 10 degrees for the top 20 layers.

(don't blame me if your nozzle clogs at the tip...)

And maybe bump up your print fan in that area - same reason.

RE: Sharp top edges

I will try it.  Thanks.

RE: Sharp top edges

If you're interested in a hardware tweak, you can buy "adapter" nozzles that fit airbrush tips to reduce radiant heat from the heat block on fine details like this. I have one I bought for about $4... haven't tried it yet but can definitely understand how it would make a difference.

https://hackaday.com/2018/10/01/high-detail-3d-printing-with-an-airbrush-nozzle/

RE: Sharp top edges

Interesting!  

RE: Sharp top edges

Posted by: @vintagepc

If you're interested in a hardware tweak, you can buy "adapter" nozzles that fit airbrush tips to reduce radiant heat from the heat block on fine details like this. I have one I bought for about $4... haven't tried it yet but can definitely understand how it would make a difference.

I bought a set, but haven't thought of a way to get past the mesh bed leveling issue. You either need to do leveling, then swap nozzles, or do a manual adjustment of your 1st layer height afterwards. Have you read of anyone actually using these on a Prusa?

RE: Sharp top edges

Posted by: @robert-rmm200

[...] And maybe bump up your print fan in that area - same reason.

I believe you can use a modifier to bump fan speeds. Normally PETG doesn't like much fan. An upcoming PrusaSlicer release is supposed to let us determine fan speeds based on feature type (e.g. outer perimeter versus other types) which may come in handy for these sorts of issues.

RE: Sharp top edges

Along with the above suggestions on fan speed make sure the settings under filament>cooling for 'Slow down if layer print time is below' is set to something small like 2-3 seconds and set the Min print speed there to a faster value like 25-30mm/s

When it comes to those very small areas it does then so quickly that it triggers the layer time so slows right down, that leads to the nozzle staying in the same area too long and it ends up printing on top of layers that haven't cooled down.

RE: Sharp top edges

Thanks guys.  I will give it a try.  

RE: Sharp top edges

Posted by: @bobstro

Posted by: @vintagepc

If you're interested in a hardware tweak, you can buy "adapter" nozzles that fit airbrush tips to reduce radiant heat from the heat block on fine details like this. I have one I bought for about $4... haven't tried it yet but can definitely understand how it would make a difference.

I bought a set, but haven't thought of a way to get past the mesh bed leveling issue. You either need to do leveling, then swap nozzles, or do a manual adjustment of your 1st layer height afterwards. Have you read of anyone actually using these on a Prusa?

 

I'd just assumed that installing one would necessitate adjusting the PINDA as well to compensate for the increased nozzle length. 

RE: Sharp top edges

@vintagepc

Yes,  It should.  

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Certainly a lot easier with a skelestruder than stock since the PINDA is mounted with an M3 screw and a 5-detent thumbwheel...

RE: Sharp top edges

I tried slowing it down and lowering them-erasure.   It got worse on two successive printers.  I am going to try upping the fan speed and speeding the print up to like 40 mm/s. 

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This might be a waste of filament, but if you don't need to print two nose cones (to give one a chance to cool each layer while a layer is being put on the other), you could try a sacrificial cylinder. Try adding a (blind diameter guess) 1cm diameter cylinder of the same height as the nose cone with 3 perimeters, a couple bottom layers to help adhesion, no infill, no top layers. I think this might minimize waste while hopefully letting the small nosecone tip cool between layers.

Just for chuckles, I just sliced a 10mm dia x 200mm tall cylinder with 4 bottom layers, 3 perimeters, zero infill, zero top layers using the Prusament PETG filament profile and it uses 8.56g of filament for a waste of $0.21USD. I can't guarantee that it will work, but it might be worth trying once. (Lowering the diameter to 5mm reduces the waste to 3.64g/$0.09USD, but I'm not sure if something that thin will be stable and avoid falling over all the way up to 200mm...)

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@sembazuru

Great idea.  Will try it tonight.  

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I got it to print 15% infill, up the fan speed to cool the print, and sped up the print to 45mm/s.  It works. 

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Pictures! Without pictures it never happened!

And congrats on succeeding. We all learned from it.

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I am printing one last one this morning and will post pics tonight.  

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@ Bobstro

Any ideas now on how to get PETG to print better on this tip?

I set the fan on 80 min and 100 max.

I set the fan to come one when the level is 30 seconds or longer and slow down to 15mm/s.  Any other adjustments?

RE: Sharp top edges

Ok.  Here is a photo.  The tips are less than ideal.