Questions about the nozzle
Posted by Marius
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Questions about the nozzle October 28, 2009 03:47AM |
Hi
I was looking at the nozzle design, and couldn't quite understand some parts of it:
- What use is the copper jacket? I don't see it serving any purpose, except looking nicer.
- Wouldn't it be best to keep the brass barrel as short as possible, and put the heater wire as near to the end as possible, to keep the molten part as small as possible? I see no mention of this.
I was looking at the nozzle design, and couldn't quite understand some parts of it:
- What use is the copper jacket? I don't see it serving any purpose, except looking nicer.
- Wouldn't it be best to keep the brass barrel as short as possible, and put the heater wire as near to the end as possible, to keep the molten part as small as possible? I see no mention of this.
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Re: Questions about the nozzle October 28, 2009 07:03AM |
Admin Registered: 17 years ago Posts: 7,879 |
The tab on the copper jacket engages with a screw that stops it from turning. That stops the cement turning which in turn stops the nozzle unscrewing itself. It tends to do that because of the force on it and the fact that PTFE is very slippery.
As you can see in the picture the heater is as close as you can get to the end and still have some room for cement.
The other end of the barrel has to overlap some way into the PTFE to prevent the thread simply being pushed out. So I think the barrel is as short as it can be with that design.
[www.hydraraptor.blogspot.com]
As you can see in the picture the heater is as close as you can get to the end and still have some room for cement.
The other end of the barrel has to overlap some way into the PTFE to prevent the thread simply being pushed out. So I think the barrel is as short as it can be with that design.
[www.hydraraptor.blogspot.com]
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Re: Questions about the nozzle October 28, 2009 07:35AM |
Right, that makes sense.
I read your blog (Nearly all of it), and you seem to have tried a lot of different extruders. As far as I can tell, you seem to have settled on the steel one, with a resistor for heating.
My dorm mate and I are modifying his homemade mill to a repstrap, and we're going to buy these to serve as a nozzle (with some modifications). It looks similar to your welding tips, so perhaps a similar design would work. Which extruder you made would you say works best?
(For extruding ABS, if that is relevant)
The tapering might be hard to do (no tools). Does your recommendation change, if we don't use tapering?
I read your blog (Nearly all of it), and you seem to have tried a lot of different extruders. As far as I can tell, you seem to have settled on the steel one, with a resistor for heating.
My dorm mate and I are modifying his homemade mill to a repstrap, and we're going to buy these to serve as a nozzle (with some modifications). It looks similar to your welding tips, so perhaps a similar design would work. Which extruder you made would you say works best?
(For extruding ABS, if that is relevant)
The tapering might be hard to do (no tools). Does your recommendation change, if we don't use tapering?
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Re: Questions about the nozzle October 28, 2009 07:35AM |
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Re: Questions about the nozzle October 28, 2009 06:27PM |
Registered: 14 years ago Posts: 21 |
We have decided to use a kapton tape based design. It seems everyone who tries it is positive about it, and I haven't seen any reports of failure.
We'll also be using Isotan wire instead of nichrome, simply because only the former is available in coated (enamelled).
Using kapton tape probably means we'll be using a retainer washer concept, like the makerbot. This seems like a sensible design: It solves the unscrewing in a simple way, whilst fastening the PTFE at the same time. Why is this design not used in the reprap? Is the conventional design deemed simpler?
Edit:
We're looking for some high temperature solder. The nozzle size we have is 0.8mm, and we'd like to reduce that with the solder. It's hard to find though... is it known by any other names?
Edited 1 time(s). Last edit at 10/28/2009 07:25PM by M.qrius.
We'll also be using Isotan wire instead of nichrome, simply because only the former is available in coated (enamelled).
Using kapton tape probably means we'll be using a retainer washer concept, like the makerbot. This seems like a sensible design: It solves the unscrewing in a simple way, whilst fastening the PTFE at the same time. Why is this design not used in the reprap? Is the conventional design deemed simpler?
Edit:
We're looking for some high temperature solder. The nozzle size we have is 0.8mm, and we'd like to reduce that with the solder. It's hard to find though... is it known by any other names?
Edited 1 time(s). Last edit at 10/28/2009 07:25PM by M.qrius.
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Re: Questions about the nozzle October 28, 2009 08:33PM |
Admin Registered: 17 years ago Posts: 7,879 |
HMP solder is sometimes called silver solder. It is a mixture of tin lead and silver. [uk.farnell.com]
The taper in the inlet of the SS extruder reduces the force needed to extrude by a factor of three. Without it you would struggle to extrude unless you keep the transition zone very short. It only needs a cheap hand tool to make the taper.
I have settled on SS because PTFE does not stand up to the temperatures and pressures that I use. Adrian seems to be the only one who gets away with it in the simple design. Most people find the thread pops out unless they support the nozzle, or add pipe clips, etc.
I use slightly higher temperatures and more pressure because I do HDPE and because I do my first layer of ABS at a low temperature where it is incredably viscous.
I have no experience of the Kapton version but it does seem that one down side is that you need PID control rather than bang-bang with it.
[www.hydraraptor.blogspot.com]
The taper in the inlet of the SS extruder reduces the force needed to extrude by a factor of three. Without it you would struggle to extrude unless you keep the transition zone very short. It only needs a cheap hand tool to make the taper.
I have settled on SS because PTFE does not stand up to the temperatures and pressures that I use. Adrian seems to be the only one who gets away with it in the simple design. Most people find the thread pops out unless they support the nozzle, or add pipe clips, etc.
I use slightly higher temperatures and more pressure because I do HDPE and because I do my first layer of ABS at a low temperature where it is incredably viscous.
I have no experience of the Kapton version but it does seem that one down side is that you need PID control rather than bang-bang with it.
[www.hydraraptor.blogspot.com]
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Re: Questions about the nozzle October 28, 2009 09:27PM |
Registered: 15 years ago Posts: 478 |
@Nophead
> I have no experience of the Kapton version but it does seem that one down side is that you need PID control rather than bang-bang with it.
I think I have missed the part regarding the need for PID control if using Kapton tape can you point me to that part pls...
Bodge It [reprap.org]
=======================================
My rep strap: [repstrapbertha.blogspot.com]
Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]
> I have no experience of the Kapton version but it does seem that one down side is that you need PID control rather than bang-bang with it.
I think I have missed the part regarding the need for PID control if using Kapton tape can you point me to that part pls...
Bodge It [reprap.org]
=======================================
My rep strap: [repstrapbertha.blogspot.com]
Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]
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Re: Questions about the nozzle October 29, 2009 02:38AM |
Registered: 14 years ago Posts: 21 |
> > I have no experience of the Kapton version but
> it does seem that one down side is that you need
> PID control rather than bang-bang with it.
>
> I think I have missed the part regarding the need
> for PID control if using Kapton tape can you point
> me to that part pls...
I didn't see that either, but I think he's referring to the low temperature limit of kapton: 300 degrees (although some mention 460). When using simple bang, the heater will probably be hotter than that.
Does the makerbot have PID temperature control?
> Adrian seems to be the only one who gets away with it in the simple design. Most people find the thread pops out unless they support the nozzle, or add pipe clips, etc.
I see I misunderstood the makerbot instructions. I thought the retainer was screwed on, thus it would keep the nozzle in place, without relying on the PTFE.
> it does seem that one down side is that you need
> PID control rather than bang-bang with it.
>
> I think I have missed the part regarding the need
> for PID control if using Kapton tape can you point
> me to that part pls...
I didn't see that either, but I think he's referring to the low temperature limit of kapton: 300 degrees (although some mention 460). When using simple bang, the heater will probably be hotter than that.
Does the makerbot have PID temperature control?
> Adrian seems to be the only one who gets away with it in the simple design. Most people find the thread pops out unless they support the nozzle, or add pipe clips, etc.
I see I misunderstood the makerbot instructions. I thought the retainer was screwed on, thus it would keep the nozzle in place, without relying on the PTFE.
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Re: Questions about the nozzle October 29, 2009 05:40AM |
Admin Registered: 17 years ago Posts: 7,879 |
PID discused here:
[dev.forums.reprap.org]
[blog.makerbot.com]
It seems that Kapton heaters only take about 10s to get up to temperature and have massive overshoot if you use bang-bang. Not a problem now that both the RepRap firmware and the MakerBot firmware support it. You might have to tune it though if not using the standard designs.
In contrast the heaters I have used take about 100 seconds to get to temperature with only a degree or two of overshoot.
Yes I think the MakerBot extruder supports the nozzle with the washer. It is only Adrian's RepRap extruder that still relies on PTFE for mechanical strength.
[www.hydraraptor.blogspot.com]
[dev.forums.reprap.org]
[blog.makerbot.com]
It seems that Kapton heaters only take about 10s to get up to temperature and have massive overshoot if you use bang-bang. Not a problem now that both the RepRap firmware and the MakerBot firmware support it. You might have to tune it though if not using the standard designs.
In contrast the heaters I have used take about 100 seconds to get to temperature with only a degree or two of overshoot.
Yes I think the MakerBot extruder supports the nozzle with the washer. It is only Adrian's RepRap extruder that still relies on PTFE for mechanical strength.
[www.hydraraptor.blogspot.com]
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Re: Questions about the nozzle October 29, 2009 06:49AM |
Registered: 15 years ago Posts: 478 |
Great thanks m qrius & Nophead I have not powerd any of my heater elements yet.
One is fire cement the other two Kapton.
I'd asumed that the original A temprature control was more acurate than it appears to be.
So I now need to build one of my extruder controllers first this explains the need for the extruder controller with its secondary CPU.
Bodge It [reprap.org]
=======================================
My rep strap: [repstrapbertha.blogspot.com]
Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]
One is fire cement the other two Kapton.
I'd asumed that the original A temprature control was more acurate than it appears to be.
So I now need to build one of my extruder controllers first this explains the need for the extruder controller with its secondary CPU.
Bodge It [reprap.org]
=======================================
My rep strap: [repstrapbertha.blogspot.com]
Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]
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Re: Questions about the nozzle October 29, 2009 09:00AM |
Registered: 15 years ago Posts: 264 |
I have a kapton heater that only gets a couple degrees of overshoot using bang-bang. I filed off the threads so that the thermistor has good contact with the barrel.
I'm running ABS at 220 C. I have had problems in the past with the kapton tape breaking down. The nichrome wire gets hotter than the barrel and is only cooled on the inside where it contacts the barrel.
In my last rebuild, I bent a piece of aluminum sheet (0.032 inch thick, I think) around the tape after everything was built. The idea being it would transfer heat away from the wires faster than when they are only cooled from the inside. I haven't had any shorts since then so it is either cooling like I hoped or it provides enough mechanical stability to prevent a short even with all the insulation charred.
From inside out I have: Brass barrel, single layer of kapton tape, 8 Ohm nichrome wire, approximately 2 layers of kapton tape to provide stability, aluminum sheet (extends above and below nichrome wire to dump off heat) and finally fiberglass insulation.
10 second heating time doesn't seem typical to me. I have built 6 Ohm 4 Ohm and 8 Ohm heaters and they all take a minute or two to get up to temperature. I could not cool the 4 Ohm heater fast enough to prevent smoke and fire so I had to limit it to 75% duty cycle.
I'm running ABS at 220 C. I have had problems in the past with the kapton tape breaking down. The nichrome wire gets hotter than the barrel and is only cooled on the inside where it contacts the barrel.
In my last rebuild, I bent a piece of aluminum sheet (0.032 inch thick, I think) around the tape after everything was built. The idea being it would transfer heat away from the wires faster than when they are only cooled from the inside. I haven't had any shorts since then so it is either cooling like I hoped or it provides enough mechanical stability to prevent a short even with all the insulation charred.
From inside out I have: Brass barrel, single layer of kapton tape, 8 Ohm nichrome wire, approximately 2 layers of kapton tape to provide stability, aluminum sheet (extends above and below nichrome wire to dump off heat) and finally fiberglass insulation.
10 second heating time doesn't seem typical to me. I have built 6 Ohm 4 Ohm and 8 Ohm heaters and they all take a minute or two to get up to temperature. I could not cool the 4 Ohm heater fast enough to prevent smoke and fire so I had to limit it to 75% duty cycle.
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Re: Questions about the nozzle October 29, 2009 09:31AM |
Admin Registered: 17 years ago Posts: 7,879 |
Yes I was surprised when Adrian said his heated up in ten seconds but I did the maths with the mass of the brass nozzle and its specific heat capacity and it makes sense.
I estimated the volume of the drilled out and threaded brass to be 0.46cc. Brass has a density of about 8.5g / cc so approximately 4g of brass. The specific heat capacity is 0.377 KJ / Kg K. So to heat 0.004Kg by 170C we need 0.256KJ. The heater is 24W, so indeed just over 10 seconds will do it.
[www.hydraraptor.blogspot.com]
I estimated the volume of the drilled out and threaded brass to be 0.46cc. Brass has a density of about 8.5g / cc so approximately 4g of brass. The specific heat capacity is 0.377 KJ / Kg K. So to heat 0.004Kg by 170C we need 0.256KJ. The heater is 24W, so indeed just over 10 seconds will do it.
[www.hydraraptor.blogspot.com]
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Re: Questions about the nozzle October 30, 2009 05:51AM |
Registered: 15 years ago Posts: 478 |
@Mccoyn
What is the Length of your barrel..
The Welding tips I have are 25mm long 5.89mm diamiter.
Which gives 19.5 mm of barrell sticking out from the peek insulator, 14.5mm for the heater element with a 3.5mm flat for the K-Type Wire Thermocouple with a 2.5mm cone shape tip. with a 0.6mm hole Drilled out to a depth of 23.5mm with 3.5mm drill.
Note: The flat area overlaps the cone by 1mm.
The Peek insulator is as per Adrians drawing for the The thermal barrier as defined in Thermoplast Extruder Version 2.0
Edited 3 time(s). Last edit at 10/30/2009 06:24AM by BodgeIt.
Bodge It [reprap.org]
=======================================
My rep strap: [repstrapbertha.blogspot.com]
Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]
What is the Length of your barrel..
The Welding tips I have are 25mm long 5.89mm diamiter.
Which gives 19.5 mm of barrell sticking out from the peek insulator, 14.5mm for the heater element with a 3.5mm flat for the K-Type Wire Thermocouple with a 2.5mm cone shape tip. with a 0.6mm hole Drilled out to a depth of 23.5mm with 3.5mm drill.
Note: The flat area overlaps the cone by 1mm.
The Peek insulator is as per Adrians drawing for the The thermal barrier as defined in Thermoplast Extruder Version 2.0
Edited 3 time(s). Last edit at 10/30/2009 06:24AM by BodgeIt.
Bodge It [reprap.org]
=======================================
My rep strap: [repstrapbertha.blogspot.com]
Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]
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Re: Questions about the nozzle October 30, 2009 06:01AM |
Registered: 15 years ago Posts: 478 |
Deleted
Edited 1 time(s). Last edit at 10/30/2009 06:25AM by BodgeIt.
Bodge It [reprap.org]
=======================================
My rep strap: [repstrapbertha.blogspot.com]
Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]
Edited 1 time(s). Last edit at 10/30/2009 06:25AM by BodgeIt.
Bodge It [reprap.org]
=======================================
My rep strap: [repstrapbertha.blogspot.com]
Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]
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Re: Questions about the nozzle October 30, 2009 02:43PM |
Registered: 14 years ago Posts: 1 |
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Re: Questions about the nozzle October 30, 2009 06:50PM |
Registered: 14 years ago Posts: 21 |
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Re: Questions about the nozzle October 31, 2009 07:03PM |
Registered: 15 years ago Posts: 264 |
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