Cool head lift feature

[Dim3nsioneer 471]

This post is mainly directed to Daid but may be also of some general interest.

I just tested the cool head lift of feature in Cura for the first time when printing some very small structure with very short layer time.

First of all, I was positively surprised to see not only the z stage to move but also the print head moving away from the object and back after the delay.

However, as the G4 command is used, the temperature of the hotend is kept stable while the filament still has some pressure inside the hotend. The result is terrible oozing.

My question: Is there any reason not to do some retraction before the delay? I think it would significantly improve this otherwise clever feature!

 

[jonnybischof 59]

I have an idea that could maybe solve this problem:

Imagine a small diameter cone next to the object being printed (the cone is of course being built up by the printer along with the printed object).

Now if the hotend moves away from the object, it goes behind this cone, and when it goes back to the object, it moves over the cone, stripping any oozed plastic off the hotend. So the hotend arrives at the object cleaned. The cone gets all the excess material, but as it is just a disposable item, it doesn't matter. I don't know how long the wait time is, I've never thested this feature, but why not just go over the cone several times if necessary and "clean" the hotend whenever necessary?

Also, the mere fact that the printer has to do more work per layer will already increase layer time.

Drawbacks:

- You waste some material for printing the cone (best keep it always hollow, ignoring infill settings, and note that oozing is also wasting material...)

- If you have stringing problems, you will have more stringing problems than before

/edit:

You could position the hotend "inside" the hollow cone in order to get all oozing material inside it. Then you could name the feature "trash bin".

 

[Daid 290]

It should do retraction before lifting the head...

I'm currently working on dual-extrusion stuff. One of the things is a wipe tower, which is a bit of the same as the trash bin. One of the issues I have with it right now is that it can topple over when your prints get high.

 

[Dim3nsioneer 471]

It should do retraction before lifting the head...

I'm currently working on dual-extrusion stuff. One of the things is a wipe tower, which is a bit of the same as the trash bin. One of the issues I have with it right now is that it can topple over when your prints get high.

 

At some layers it actually retracts, but just maybe 5 times out of 50...

I'm looking forward to your 'dual-extrusion stuff'... :wink:

 

[Daid 290]

Could be that the minimal-extrusion-between-retractions is kicking in.

 

[3dcase 37]

It should do retraction before lifting the head...

I'm currently working on dual-extrusion stuff. One of the things is a wipe tower, which is a bit of the same as the trash bin. One of the issues I have with it right now is that it can topple over when your prints get high.

 

Ohhhhh, can't wait :cool:

 

[Dim3nsioneer 471]

Daid, what shall I say... I see, you know your code... :grin:

I had the minimal-extrusion-between-retractions set to 0.5mm. Doing a cylinder with 2mm diameter was interestingly not enough for retraction (is there an additional factor?).

When I set the m-e-b-r to 0 I got retraction on each layer... :cool:

However, the result still looks awful... there are certainly anti-oozing-measures needed here as well... thanks anyway!

 

[lars86 36]

Yup, I just lost a print to this too. Even with minimal extrusion to the default 0.1mm, it rarely retracts on cool head lift.