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Teflon spacer replacement

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Posted · Teflon spacer replacement

OK, I have GOT to try this. Turn an aluminum insulator with heat fins (like an E3D) and coat the inside with this

http://www.brownells.com/gunsmith-tools-supplies/metal-prep-coloring/paint-finishes/bake-on-aerosol-paints/teflon-moly-oven-cure-gun-finish-prod1145.aspx

Then use dual fans if I have still have problems with PLA prints... Or just have one of my machines ABS only with this insulator.

 

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Posted · Teflon spacer replacement

Another aspect; if the print head was more tolerant for high temperatures, it might help to sort some of the problems now facing dual extrusion. Also, this would allow us to use broader range of materials - see for instance this thread:

 

I totally agree. The design needs to be updated. Having to change the Teflon bushing on an arbitrary basis is not satisfying.

 

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Posted · Teflon spacer replacement

OK, I have GOT to try this. Turn an aluminum insulator with heat fins (like an E3D) and coat the inside with this

http://www.brownells.com/gunsmith-tools-supplies/metal-prep-coloring/paint-finishes/bake-on-aerosol-paints/teflon-moly-oven-cure-gun-finish-prod1145.aspx

Then use dual fans if I have still have problems with PLA prints... Or just have one of my machines ABS only with this insulator.

 

That's an interesting product! Thanks a lot for the heads up!

 

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Posted · Teflon spacer replacement

If I understand the heat dispersion in the nozzle unit correctly - and referring to simulations made by Kris - I think the temperature of the Teflon isolator drops pretty quickly (vertically, from bottom upwards). In other words, only the first couple of millimeters are really vulnerable. Two ideas for brainstorming:

 

I think you are correct. Trouble is, the nozzle needs the heat, the PTFE bushing doesn't. Thus heat needs to be drawn away from the bushing. I do not believe that the problem can be solved by using a different material, they all have their drawbacks (e.g. added friction, thermal expansion etc).

Instead it should be possible the improve the current design, hopefully to the point were is functions reliably and parts do not have to be exchanged frequently.

After countless iterations, here are the things that work the best according to the analysis :

1. One added heat sink close to 1310-Z2P-A

2. Heat breake integrated in nozzle

3. Added ventilation holes to 1310-Z2P-A

P2

 

The results are shown down below. There still is a heat accumulation at the bottom of the bushing. But it is smaller and the overall temperature is lower.

 

P1

 

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Posted · Teflon spacer replacement
Thus heat needs to be drawn away from the bushing.

 

Yes - and your draft seems to tackle that really well - it looks great!

 

 

I do not believe that the problem can be solved by using a different material, they all have their drawbacks (e.g. added friction, thermal expansion etc).

Instead it should be possible the improve the current design...

 

Here, I don't see the situation so black/white. There is obviously room (and need) to improve the original design. At the same time, I wouldn't turn down help offered by different materials. Keeping the current PTFE isolator "as is" by its shape and just changing its material doesn't seem to be easy. Attempts to use ceramic materials or aluminium have failed. Until proven wrong, I still believe in the washer approach. If the washer is thin enough, the negative properties of its material (like added friction) will be manageable - but it can reduce the temperature at the tip of the actual isolator.

About the simulations - there's one factor which is tricky to simulate but might also have an impact: retraction. When 260C filament is pulled up and pushed back (in some cases almost immediately after), it certainly warms up the inner surface of the isolator. Maybe retraction settings need to be tried, hmm...

Maybe the solution will be a combination of new materials, new design and new isolator pricing by Ultimaker ;)

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Posted · Teflon spacer replacement

About the simulations - there's one factor which is tricky to simulate but might also have an impact: retraction. When 260C filament is pulled up and pushed back (in some cases almost immediately after), it certainly warms up the inner surface of the isolator. Maybe retraction settings need to be tried, hmm...

 

Yes, any settings would have to be changed to account for the new temperature gradients.

About the washer: I have tried that as well.

1. I used ceramics. I figured it would withstand the temperature and it also has low thermal conductivity. ZrO2 seemed like a feasibly option. The problem is, ZrO2 is a better thermal insulator compared to e.g. steel, but it is 10 times more conductive then PTFE. The analysis seems to indicate that this in fact eases heat transfer to the PTFE bushing.

P3

 

In addition it is unknown what the material does when it gets in touch with PLA/ ABS. It might increase friction. If you decrease thickness, you need to cool it. Otherwise it will saturate quickly.

 

2. I then optimized a steel heat break which later was incorporated into the nozzle.

P4

 

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Posted · Teflon spacer replacement

Interesting!

As I said previously, I was planning to do further tests with metal spacers.

Time has been limited though since I need my printer up and running for my business too.

However, I tried another cooled metal spacer which looks like this:

2014 09 14 4328

Suprisingly, it worked fine with PLA from start.

Then I realized the reason why it worked was that the spacer was pushed up because the spring I used was to weak.

This meant a thermal barrier of PLA had formed between the spacer and the nozzle, helping to keep my metal spacer cool.

Not the kind of solution I was looking for :smile:

With a stronger spring the thermal load on the spacer was too much and PLA was softening inside it.

I was actually thinking of adding a stainless U-shaped heat break like the one in Kris post but that did not happen yet.

The main problem I would say is that the fan is so tiny, which puts extreme requirements on heat sinks if you want to stay below the softening temprature of PLA.

I can only imagine what the Ultimaker-team has been going through trying make it work with two heated nozzles...

 

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Posted · Teflon spacer replacement

Yeah, I basically have the same problem. I need my printer operational so I can only incorporate small changes. Baby steps...

After reading on the forum about what parts usually break down first, I have even ordered spar parts in advance. I.e. a spare nozzle, a new temp. sensor and PTFE bushings. Since then nothing has happened, it just prints & prints. I guess it is scared now ;-)

I guess the extruder is a good basic design, but there is room for improvement.

 

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Posted · Teflon spacer replacement

Yes, any settings would have to be changed to account for the new temperature gradients.

About the washer: I have tried that as well.

1. I used ceramics. I figured it would withstand the temperature and it also has low thermal conductivity. ZrO2 seemed like a feasibly option. The problem is, ZrO2 is a better thermal insulator compared to e.g. steel, but it is 10 times more conductive then PTFE. The analysis seems to indicate that this in fact eases heat transfer to the PTFE bushing.

 

I've been on holiday for the past couple of weeks. Right before my holiday, I lost yet another PTFE isolator. I got fairly furious. Gloves off - and other gloves on.

Kris, I actually didn't get the last sentence in your message above. It looks like there is much more heat in the upper parts of the PTFE isolator after an extra isolator washer is added. As you stated, the washer conducts heat better than PTFE - but not as well as stainless steel does. The nozzle block is made out of brass, so it conducts heat better than any of those materials. I actually don't understand how the washer could act as a catalytic substance for heat transfer?

As I don't know how to make proper simulations to challenge yours, I decided to try my luck in real life instead... I don't know about the results yet, I'm making the first tests now as I'm writing this message... So, here's my attempt:

PTFE+Vespel

The brown washer (or short tube, rather) is Vespel. I used the Ultimaker's original PTFE isolator as the main body, as I thought it would give tighter fit with the washer than the glass-impregnated one would. I shortened the PTFE isolator by about 3mm, the washer is about 3.5mm thick. I'm hoping the temperature of the PTFE isolator's lowermost point stays lower - and that the hot retracted material would stay inside the Vespel tube and not raise all the way into the PTFE tube.

Let's see, I'll update with the results later...

*** UPDATE, October 10 ***

I can't yet claim I would have solved the problem due to having used the new isolator for few days only. However, I have been successfully printing both with ABS and PLA, also some retraction intensive prints like these:

https://www.youmagine.com/designs/3d-anniversary-roses

So - it looks as if friction wouldn't be a big issue. Maybe I should try with 100% Vespel isolator? On the other hand, if the hybrid isolator works and passes the durability test, I'll probably avoid fixing something which works :)

 

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Posted · Teflon spacer replacement

Based on my experiments I would probably keep the PTFE insulator as in the photo.

PTFE has several very interesting properties.

It has low friction and things does not stick to it easily, but even more interersting is that the coefficient of friction decreases with increased load (!)

I think those properties is the key to why it is so difficult for any other material to compete with PTFE when it comes to handling molten PLA. The plug of molten PLA that forms when you have backpressure from the nozzle will not only be unable to stick to the PTFE, if you push harder the PTFE will actually become more slippery (!).

(At least in general, I can not find any data for PTFE - molten PLA friction)

You might get away with a short piece of Vespel like this and that might very well be a permanent solution. But as I said removing the PTFE completely might not improve things.

 

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Posted · Teflon spacer replacement

Any idea where we can get Vespel ? It looks like a very specialized material.

I have three burnt PTFE I could cut in order to beta-test.

 

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Posted · Teflon spacer replacement

Any idea where we can get Vespel ? It looks like a very specialized material.

I have three burnt PTFE I could cut in order to beta-test.

 

I bought Vespel from Goodfellow (http://www.goodfellow.com), but there are probably cheaper sources... In the US, Vespel can even be ordered from Amazon with quite reasonable cost:

http://www.amazon.com/Vespel-Round-Opaque-Diameter-Length/dp/B00FKK36LU

I'm wondering when Ultimaker will announce something based on Vespel. When people have proposed Aerogel, ceramics and metals, Ultimaker engineers have made comments on those materials. Vespel has also been proposed, but there's been complete silence from Ultimaker's side. I'm drawing conclusions and wearing a folio hat.

 

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Posted · Teflon spacer replacement

@3Poro

There are other materials that can be very interesting.

Celazole PBI is also an excellent thermal insulator. Other plastics in melt do not stick to PBI. These characteristics make it ideal for contact seals and insulator bushings in plastic production and molding equipment.

 

  • Highest mechanical properties of any plastic above 400°F (204°C)
  • Highest heat deflection temperature 800°F (427°C), with a continuous service capability of 750°F (399°C) in inert environments, or 650°F (343°C) in air with short term exposure potential to 1,000°F (538°C)
  • Lowest coefficient of thermal expansion and highest compressive strength of all unfilled plastics

 

With a more affordable price.

12.70mm Celazone Pbi Rod,305mm Length, Duratron Pbi Rod > £129.18 or 161 euro

http://www.plasticstockist.com/Duratron-PBI.aspx

With this you can make 14 coupler > 11.5 euro per coupler !!! :)

 

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Posted · Teflon spacer replacement

That stuff is highly interesting! I wish I had the skills to find this kind of material.

I have been spending quite some time looking for plastics but my google skills are apparently not good enough :sad:

The Celazole Pbi appears to be exactly the kind of material you would like for the thermal insulator.

The non-stick properties might even mean you can get away with the whole insulator made in this material even for printing PLA.

As for the Vespel, I was reading a bit about it an it worries me a bit is that it basically is a polyimide, just as Kapton, and ABS is well known to stick very well to kapton. But maybe Vespel is different somehow (?).

Anyway, I am seriously considering ordering a piece of Celazole Pbi now.. :smile:

 

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Posted · Teflon spacer replacement

There are some vendors in Sweden for some rare plastics. I think that is where I get mine. Though could be in Norge instead, last time I ordered some Torlon stock and some high temp plastic for injection. I haven't had to look in a while. If I can remember I'll check with my purchasing group tomorrow.

 

That stuff is highly interesting! I wish I had the skills to find this kind of material.

I have been spending quite some time looking for plastics but my google skills are apparently not good enough :sad:

The Celazole Pbi appears to be [/size]exactly the kind of material you would like for the thermal insulator.

The non-stick properties might even mean you can get away with the whole insulator made in this material even for printing PLA.

 

As for the Vespel, I was reading a bit about it an it worries me a bit is that it basically is a polyimide, just as Kapton, and ABS is well known to stick very well to kapton. But maybe Vespel is different somehow (?).

 

Anyway, I am seriously considering ordering a piece of Celazole Pbi now.. :smile:[/size]

 

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Posted · Teflon spacer replacement

I agree - Celazole Pbi looks very interesting. Over the next few weeks I'll be testing my Vespel+PTFE isolator, so I won't be trying other materials - but I'm all ears about them.

Regarding my findings so far... I have made prints both with ABS and PLA; some of them very retraction intensive. So far I haven't found any issues. However, I'm using fairly slow print speed (20-40mm/s) due to another test I'm running on parallel - I'm testing MK8 wheel with IRobertI's feeder. Yes, I know it's not optimal to test 2 changes at once - but I didn't have a choice due to unrelated reasons.

Right now I'm in the middle of an ABS print which shall take another 48 hours to finish - but the first half is very promising.

 

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Posted · Teflon spacer replacement

a 96 hour print?! My hat's off to you man

 

Hmm... It looks like it will be closer to 110-120 hours :smile:

So far the print looks very promising - better than my previous prints of the same design. As there are lots of retractions involved, I'm afraid these long prints are to blame for my bad luck with the PTFE isolators. With such long prints, there are many things to take care of:

 

  1. Filament path. When you use most of a full reel of filament, the path better work pretty well. At least I've been surprised by the number of ways filament can get tangled/stuck somewhere. When a print takes several days, there's no way to keep an eye on it frequently enough.

     

  2. Temperature management. As I'm printing ABS, I couldn't imagine trying very long prints without some sort of closed chamber. Over the course of several days, temperature and humidity in the room are not constant.

     

  3. Power supply. UPS is a must, at least in my location.

     

  4. Surprises. My previous very long print was interrupted after about 3 days into printing by my 2-year-old son. He just pressed the memory card - causing it to get ejected. To avoid this from happening again, I made a shield for the front panel controls:

 

UM2 child shield

Let's see what my UM2 (and my son) will figure out next to surprise me :wink:

 

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Posted · Teflon spacer replacement

hi,

I'll try to make a Celazole PBI coupler.

Does anyone have the technical scheme of the UM2 PTFE coupler?

Thanks!

 

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Posted · Teflon spacer replacement

OK, time for a more detailed update... First of all, I apologize for lack of "before" and "after" photos. However, I didn't see the point for posting them as I can't see any change in either of the isolator parts (Teflon or Vespel). The bottom end of the PTFE isolator is bright white - it doesn't show any sign of being exposed to high temperatures.

I have been printing quite a lot with ABS at 260C, having my chamber closed and print bed temperature at 110C. With very long prints, the bottom of the raft gets slightly yellow (in case of white ABS), but the actual print remains as white as the filament is. Shortly put, I believe the environment has been as hot as it gets without going beyond 260C.

My tests have been with Ultimaker's ABS, PLA and Flex PLA. I have some other filaments as well, but I haven't yet had the time to test with them. My biggest concern was ABS due to the point Anders Olsson brought up - what if it would stick to Vespel, as it could stick to Kapton in high temperatures? When I opened the print head, I made sure I had made a retraction intensive print with ABS just before that. However, I didn't see any ABS (or any other) residue on Vespel. The inner wall of the short Vespel tube was as if nothing would have touched it.

After using the new isolator for a few weeks only, I'm not yet ready to declare it to be the solution to my problem - but I feel increasingly confident about its potential. After opening the print head for a few times for inspections, I feel increasingly confident about the need to update its design. Opening it is too tricky. If there were 2 extruders, it would only get worse - at the same time, there would be increased need for opening it every now and then.

Here's one of my latest prints, with Ultimaker's Flex PLA:

http://umforum.ultimaker.com/index.php?/topic/467-post-your-latest-print/?p=73900

Thank you all for brainstorming; I'm back to printing!

 

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