Extruded filament diameter
Posted by nophead
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Re: Extruded filament diameter August 11, 2007 06:06PM |
Hmm, reviewing your data against mine on the face of it there is not a lot in common. You have are getting a much lower temperature for an equivalent power but a much higher flow rate. My thoughts of possible reasons why your temperature is less: -
1)I think your barrel is a bit longer, mine has only 30mm exposed.
2)You have a plate at the top with a large surface area acting as a heatsink.
3)Yours is matt black whereas mine is shiny brass so less emissive.
If you are running at a lower temperature then its even more odd that I get the lower flow rate. Assuming we both have 0.5mm apertures the only other difference I can think of is the depth of the hole. Not the easiest thing to measure in my case but in your case it's just the thickness of the copper. Possibly if my hole is deeper then there is more friction so the flow rate lower and the pressure is higher so the expansion greater? Odd that you don't see any change at all in diameter though.
Other odd things are that you can vary the flow rate from 2 to 11 with the same heater power giving the same temperature. When I increase the flow rate then the temperature drops significantly for the same power. I need around 8 watts for thermal equilibrium but when extruding I think I need about another watt to maintain the same temp. Perhaps it is because you have so much more power going in and being lost to the environment that the cold filament has less influence.
I am changing the motor voltage at the moment from about 4v to 8v. My GM3's box is marked 5V but I am sure it was sold as 6V. You are using PWM which will explain why you can go down to lower speeds. Am I right in thinking 100% is 12V into a 6V motor? That would probably go some way to explaining the higher rate.
So we are left with the fact you can use a much lower temperatures and your flow rate does not affect diameter but mine does.
I will wait until I have build a controller so I can fix the temperature and flow rate independently and then I will do some more detailed measurements.
I now have about 10m of 1mm filament. Perhaps I should build a 1/3 scale extruder to use it up
[www.hydraraptor.blogspot.com]
1)I think your barrel is a bit longer, mine has only 30mm exposed.
2)You have a plate at the top with a large surface area acting as a heatsink.
3)Yours is matt black whereas mine is shiny brass so less emissive.
If you are running at a lower temperature then its even more odd that I get the lower flow rate. Assuming we both have 0.5mm apertures the only other difference I can think of is the depth of the hole. Not the easiest thing to measure in my case but in your case it's just the thickness of the copper. Possibly if my hole is deeper then there is more friction so the flow rate lower and the pressure is higher so the expansion greater? Odd that you don't see any change at all in diameter though.
Other odd things are that you can vary the flow rate from 2 to 11 with the same heater power giving the same temperature. When I increase the flow rate then the temperature drops significantly for the same power. I need around 8 watts for thermal equilibrium but when extruding I think I need about another watt to maintain the same temp. Perhaps it is because you have so much more power going in and being lost to the environment that the cold filament has less influence.
I am changing the motor voltage at the moment from about 4v to 8v. My GM3's box is marked 5V but I am sure it was sold as 6V. You are using PWM which will explain why you can go down to lower speeds. Am I right in thinking 100% is 12V into a 6V motor? That would probably go some way to explaining the higher rate.
So we are left with the fact you can use a much lower temperatures and your flow rate does not affect diameter but mine does.
I will wait until I have build a controller so I can fix the temperature and flow rate independently and then I will do some more detailed measurements.
I now have about 10m of 1mm filament. Perhaps I should build a 1/3 scale extruder to use it up
[www.hydraraptor.blogspot.com]
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Re: Extruded filament diameter September 01, 2007 06:41PM |
I'm a very new newcomer to the RepRap world... I just got here today 
But it occurred to me to wonder why you're using the acorn nuts rather than something with a long, thin tube the same diameter as the exit orifice to allow the medium to smooth out its flow before exiting.
What came to my mind was the removable screw-on metal (chrome-plated brass?) tips from Pentel mechanical pencils.
These pencils use graphite rods of various sizes including 0.7mm, 0.5mm and 0.3mm. These sizes seem to me ideal for beginning to investigate this kind of orifice.
It seems to me that a longer cylinder of the exit diameter would allow the plastic medium to adjust itself into a smooth stream before it has to exit, and might reduce the "die swell" effect.
I also wonder if the media being used contain dissolved gasses or volatile compounds that might be causing the media to foam up slightly when released from pressure. Has anyone investigated this?
~Rick
But it occurred to me to wonder why you're using the acorn nuts rather than something with a long, thin tube the same diameter as the exit orifice to allow the medium to smooth out its flow before exiting.
What came to my mind was the removable screw-on metal (chrome-plated brass?) tips from Pentel mechanical pencils.
These pencils use graphite rods of various sizes including 0.7mm, 0.5mm and 0.3mm. These sizes seem to me ideal for beginning to investigate this kind of orifice.
It seems to me that a longer cylinder of the exit diameter would allow the plastic medium to adjust itself into a smooth stream before it has to exit, and might reduce the "die swell" effect.
I also wonder if the media being used contain dissolved gasses or volatile compounds that might be causing the media to foam up slightly when released from pressure. Has anyone investigated this?
~Rick
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Re: Extruded filament diameter September 02, 2007 01:23PM |
Rick.Berry Wrote:
-------------------------------------------------------
> I'm a very new newcomer to the RepRap world... I
> just got here today
welcome rick!
> But it occurred to me to wonder why you're using
> the acorn nuts rather than something with a long,
> thin tube the same diameter as the exit orifice to
> allow the medium to smooth out its flow before
> exiting.
well, the acorn nuts are a pretty good solution for a few reasons:
1. easy to get. they are cheap too.
2. easy to drill. the wall between the end is usually very thin < 1mm
3. easy to remove/reattach because they are threaded. useful for a research project like this.
if we have a long thin tube that was 0.5mm you wouldn't get anything to extrude out of it... it would be nearly impossible.
> What came to my mind was the removable screw-on
> metal (chrome-plated brass?) tips from Pentel
> mechanical pencils.
> These pencils use graphite rods of various sizes
> including 0.7mm, 0.5mm and 0.3mm. These sizes seem
> to me ideal for beginning to investigate this kind
> of orifice.
we actually tried those once. there are a couple major problems.
1. they screw on to 10-24 or 10-32 threads. which means our 1/8" hole is nearly the size of the bolt to screw them onto. this means its *really* hard to drill that hole.
2. they are more expensive than an acorn nut, and a bit harder to find.
i like where you're heads at though... you'll fit in well here =)
> It seems to me that a longer cylinder of the exit
> diameter would allow the plastic medium to adjust
> itself into a smooth stream before it has to exit,
> and might reduce the "die swell" effect.
> I also wonder if the media being used contain
> dissolved gasses or volatile compounds that might
> be causing the media to foam up slightly when
> released from pressure. Has anyone investigated
> this?
i dont know much of the physics behind it, but i do know that the exit hole must be very short. if its long, it becomes very hard to extrude. a good example of this is blowing through a short length of tubing vs a long length of tubing. the longer length is *much* harder.
-------------------------------------------------------
> I'm a very new newcomer to the RepRap world... I
> just got here today
welcome rick!
> But it occurred to me to wonder why you're using
> the acorn nuts rather than something with a long,
> thin tube the same diameter as the exit orifice to
> allow the medium to smooth out its flow before
> exiting.
well, the acorn nuts are a pretty good solution for a few reasons:
1. easy to get. they are cheap too.
2. easy to drill. the wall between the end is usually very thin < 1mm
3. easy to remove/reattach because they are threaded. useful for a research project like this.
if we have a long thin tube that was 0.5mm you wouldn't get anything to extrude out of it... it would be nearly impossible.
> What came to my mind was the removable screw-on
> metal (chrome-plated brass?) tips from Pentel
> mechanical pencils.
> These pencils use graphite rods of various sizes
> including 0.7mm, 0.5mm and 0.3mm. These sizes seem
> to me ideal for beginning to investigate this kind
> of orifice.
we actually tried those once. there are a couple major problems.
1. they screw on to 10-24 or 10-32 threads. which means our 1/8" hole is nearly the size of the bolt to screw them onto. this means its *really* hard to drill that hole.
2. they are more expensive than an acorn nut, and a bit harder to find.
i like where you're heads at though... you'll fit in well here =)
> It seems to me that a longer cylinder of the exit
> diameter would allow the plastic medium to adjust
> itself into a smooth stream before it has to exit,
> and might reduce the "die swell" effect.
> I also wonder if the media being used contain
> dissolved gasses or volatile compounds that might
> be causing the media to foam up slightly when
> released from pressure. Has anyone investigated
> this?
i dont know much of the physics behind it, but i do know that the exit hole must be very short. if its long, it becomes very hard to extrude. a good example of this is blowing through a short length of tubing vs a long length of tubing. the longer length is *much* harder.
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