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bruce

Modified filament feeder idea

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I don't own a printer, so please forgive me if this sounds stupid...

How much force does it take to push filament into an extruder? If actual grams force numbers aren't available, is it effortless like pushing solder onto a hot iron, or annoyingly hard like shoving dough through a pasta machine?

It is my understanding that the Ultimaker is fast and accurate because of it's light weight extruder, but that this creates some issues with things like strings because the stepper is too far from the extruder to quickly stop flow on command.

Assuming that is an accurate assessment, I was wondering if it would be possible to modify the filament control system using a small, light stepper on the extruder head; perhaps something like a NEMA 8 or NEMA 11, or maybe one of these common printer type steppers, depending on how much force is required. I'm imagining keeping the NEMA 17 stepper at the fixed end of the bowden cable to haul filament off of the reel, followed by some sort of microswitch-based filament tension detector, and then the small and light stepper just managing the feed right on top of the extruder.

Obviously that adds complexity and weight, but if it could add better control it might pay for itself. Does that sound at all plausible, or am I trying to solve a non-problem?

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I don't own a printer, so please forgive me if this sounds stupid...

How much force does it take to push filament into an extruder? If actual grams force numbers aren't available, is it effortless like pushing solder onto a hot iron, or annoyingly hard like shoving dough through a pasta machine?

It is my understanding that the Ultimaker is fast and accurate because of it's light weight extruder, but that this creates some issues with things like strings because the stepper is too far from the extruder to quickly stop flow on command.

Assuming that is an accurate assessment, I was wondering if it would be possible to modify the filament control system using a small, light stepper on the extruder head; perhaps something like a NEMA 8 or NEMA 11, or maybe one of these common printer type steppers, depending on how much force is required. I'm imagining keeping the NEMA 17 stepper at the fixed end of the bowden cable to haul filament off of the reel, followed by some sort of microswitch-based filament tension detector, and then the small and light stepper just managing the feed right on top of the extruder.

Obviously that adds complexity and weight, but if it could add better control it might pay for itself. Does that sound at all plausible, or am I trying to solve a non-problem?

It sounds like a reasonable idea but at times all the power of the current Nema 17 motors is required. and performance can be improved by fitting a more powerful Nema 17 motor. The extra weight would slow down the XY jerk speed too, though I'm sure if someone came up with a strong enough and light enough motor they would go that way. I guess you are always stuck with the force required to push filament through a small 0.4mm hole.

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It sounds like a reasonable idea but at times all the power of the current Nema 17 motors is required. and performance can be improved by fitting a more powerful Nema 17 motor.

Ah, that would be a bit of a killer for a NEMA 8/11 primary feeder motor then.

The extra weight would slow down the XY jerk speed too, though I'm sure if someone came up with a strong enough and light enough motor they would go that way.

Well that NEMA 8 is all of 60g, which should be a bit easier to jerk around than a 350g NEMA 17. Certainly you couldn't hit the same top speeds with 60g to 100g extra riding the extruder as you could without it.

One reason for the high speed jerks is to reduce stringing, is it not? Perhaps a small stepper could still be useful for applying a bit of back force to stop the oozing?

I guess you are always stuck with the force required to push filament through a small 0.4mm hole.

Yeah, it sounds like a small secondary stepper would be pushing forward just to not get in the way of the main stepper, and would only justify its existence if it could help hold the filament back during those moments when you don't want any flow. If it isn't capable of doing that, it would be a totally useless expense.

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Instead of a stepper, why not some sort of valve on the nozzle that can be quickly closed and opened?

I'm still waiting for my ultimaker kit to be shipped so i'm not really familiar with the mechanism, but it makes more sense to me to leave the main feeding mechanism where it is and add a small solenoid or servo to the print head that could either block the nozzle with a tiny metal pin or maybe even operate some sort of scissor or knife mechanism to cut the plastic string at the start of a fast jump.

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Instead of a stepper, why not some sort of valve on the nozzle that can be quickly closed and opened?

I'm still waiting for my ultimaker kit to be shipped so i'm not really familiar with the mechanism, but it makes more sense to me to leave the main feeding mechanism where it is and add a small solenoid or servo to the print head that could either block the nozzle with a tiny metal pin or maybe even operate some sort of scissor or knife mechanism to cut the plastic string at the start of a fast jump.

Personally, I like the idea of a Archimedes\screw drive as that would enable different types of feed stocks. You can buy a 5lb bag of pellets a lot cheaper than you can buy a 5lb spool of filament. That and you can (in theory) worry a lot less that the stock is consistantly sized.

It probably wouldn't work well with the bowden setup, though.. :(

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What happens if you mixed a nema 17 at the extruder gear and a light weight stepper or servo at the nozzle? The nozzle disengages when fully extruding and engages for retraction or assisting in fine control at the head?

Just a thought.

Anyone seen what the Cube extruder looks like? (its encapsulated in a plastic shroud) I have seen plenty of video of the thing and it looks pretty small.... and no stringing.

 

Chuck

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Small? From the first angle yes, from the front angle you can see it's a lot larger then you think. It could easily hide an NEMA17

I'm all for the "plugging the nozzle with a pin" idea, as this should work even better then retraction (also works at high temperatures), but it must be very hard to build...

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yeah your right... just dug up some pics on their parts site

 

interesting...looks like they used to use aluminum in the head and switched to a copper heater block.

Also of note... they use a "build platform adhesive" to coat their build plates. Wonder what that is.

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