the use of vacuum or back pressure when printing with two nozzles

[ivan.akapulko]

Hi gang!

I go back to the painful subject of printing with two nozzles, it was said so many over the years that it seems worth to throw the subject, and not to remember. But yesterday, watching videos on YouTube for home-made food products, I came across the idea of using vacuum. Actually, the idea is simple in the extreme: the servo that controls the syringe with a nipple attached to the bowden tube. When using the following nozzle servo moves the plunger of the syringe, provides a reduced pressure in the bowden pipe and thereby eliminate leakage from the nozzle. Given that the flow of hot plastic is small, it can help if not get rid of the leak completely, then dramatically reduce them.

In the video, the author degas liquid silicone using similar system (but without the servo, by hands)

[Meduza]

You could also use a solenoid and a vacuum pump or a vacuum ejector and pressured air to create a underpressure in the bowden tube at will.

[LePaul]

Your idea sucks

(See what I did there?)

[ivan.akapulko]

Your idea sucks

(See what I did there?)

Well, maybe. I do not exclude that the gap between the filament and the bowden tube in the area of the feeder will reduce the effect of the reduced pressure. But this design defect is easy to fix a simple rubber gasket. Otherwise, the next tests will show how viable the idea itself.

[Amedee]

(See what I did there?)

I have to confess it took me some time to get it

[LePaul]

More coffee!

[ivan.akapulko]

More coffee!

12.03 pm and you need more coffee? You need to take care of yourself, Paul ))))

[LePaul]

A suggestion for Amedee

[MTVDNA]

Your idea sucks

(See what I did there?)

Well, maybe. I do not exclude that the gap between the filament and the bowden tube in the area of the feeder will reduce the effect of the reduced pressure. But this design defect is easy to fix a simple rubber gasket. Otherwise, the next tests will show how viable the idea itself.

Honestly, I don't think this is a viable solution. The whole hot end is not designed to be air tight, and I think it will be quite a challenge to make it so (especially if you want to be able to replace parts like the ptfe coupler). Also, adding a rubber gasket in the bowden tube will add a lot of friction, which I think will give you much more trouble than the reduced stringing is worth.

[drayson]

Honestly, I´m not sure that it will work on the long run...
There si a development shown at the UM forum where a German guy managed to implement a water chiller to keep the heated area controlled and an active nozzle lift on a dual UM2. His attemt looks promising, but the additional water hoses may put additional load onto the head. nevertheless, it works good as fas as the tests of his testers show...

[jonnybischof]

Not to forget that a water cooling system (without cooling blocks) easily costs 200+ bucks and most tubing / fitting systems are not suitable for prolonged use in a moving system.