Software anti-ooze

Isn't this nozzle wipe an annoying thing? The alternative is plugging the extruder orifice.

My solenoid for the anti-ooze is on order, but I couldn't find the .stl file for its holder nor would I know where to get piano wire (don't have a piano I can take apart, sadly). Also, I'd have to order a very small size drill and prey that I can drill my single extruder nozzle right at once... there's considerable risk to this. I'm not really a machine tool specialist as well as I master my Allen keys...

Then I thought of a very simple mechanism that would only require a change in the software:
"Software Anti-Ooze(TM)"

With ABS plastic, I noticed that after stopping the extruder motor, regardless of the temperature, plastic didn't keep leaking out. Instead, the speed the fillament was extruded slowed down exponentially after stopping the motor. If you would slow down print movements in sync with this, there would be no need for anti ooze, only a slow-down. It would require a one time measure of how much fillament comes out the extruder after the motor stops. When you stop the engine you just snip off the plastic and afterwards measure the length of what came out. Then, in a next run, you measure the time it took until the extrudate stops moving. The shape of this curve could be constant for each plastic or perhaps varies a bit per extruder. I guess with the length and time you could make an adequate slowdown to reduce the need of anti ooze.

You do need to 'plan ahead' in the software when a slowdown is needed and the motor should be stopped early, but this should be possible nevertheless.

The disadvantage is speed, but I guess for many this would be offset by the simplicity (re)gained in the mechanics.

What do you guys think?

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Regards,

Erik de Bruijn
[Ultimaker.com] - [blog.erikdebruijn.nl]

I think it would help but not cure the stringing completely.

There are too components to the stringing problem:

1) The extruder oozes after switch off.

2) Even when the ooze has stopped the filament is still molten and attached to the object. When the head moves off it drags molten plastic out of the nozzle leaving a string.

As well as stopping the flow you also need to break the filament.

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[www.hydraraptor.blogspot.com]

Yes, (only) the solenoid is better in this respect. But compared to traveling towards a wiping brush or V-blade the software solution would allow for the same quality. With ABS I didn't notice any leaking after the motor stops, only that the extrusion rate slows rapidly but doesn't stop instantly. An alternative would be to cool the extrudate to solidify and then leave the area. This would allow for the same quality as the solenoid. If you leave a small drop of water on the object, this would probably cool it enough.

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Regards,

Erik de Bruijn
[Ultimaker.com] - [blog.erikdebruijn.nl]

I only wipe the nozzle on a brush at the start of the raft and the start of the object so no big deal. I run a short length to establish the pressure and then wipe it off. I think I would do the same even if I had a valve. When the heater is off the plastic shrinks and air gets in so you have to run it a few seconds to prime it.

The anti-ooze is really to solve a different problem: stopping one thread and starting another.

I am not sure what you mean about leaving the extrudate to cool. The problem is the plastic that is still inside the nozzle and is liquid is attached to the solid object. When you move off it stretches and drags out more plastic. If you turned off the heater so that it went solid then you would have it welded to the object so would not be able to move off.

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[www.hydraraptor.blogspot.com]