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UM2 Aluminum Insulator - What Not To Do

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Like many others, My Teflon insulator is sadly deformed...

deformed And Sad insulator

I had ordered one 9 days ago, but somehow, they forgot to ship it out until I called, an honest mistake I'm sure, but I'm having soooo much trouble with it that I had to do something so I can continue printing!

Enter the hair-brained idea of turning a new insulator from aluminum :)

aluminum insulator

Simple enough. Turned it using open source files for dimensions. Fit nice, installed great.

New aluminum insulator

I knew that the aluminum was going to draw a lot of heat from the nozzle, so I added one of the "quick and dirty" fan flow redirects (in other words a little piece of metal that makes more air flow across insulator) I didn't want to spend a whole lot of time coming up with a cooling solution until I actually tried the aluminum insulator.

redirect

Now for the test.

Fed new filament...seemed to work great. Started a print...not so great. It laid down about 50mm of skirt before it just jammed.

Took it apart... This is what the filament looked like. It totally conformed to the entire length of the aluminum insulator. There is NO retracting or changing this filament!

conformed filament

While I did feel a little defeated that my pretty little aluminum insulator SUCKED, I had to press on to get the machine up and running. I decided to cut some material off the base of the Teflon insulator to get me through the week. Here is a shot of the Teflon insulator. You can't really tell from the photo, but the opening around the base is larger than it's supposed to be.

deformed insulator

I chucked it to the lathe and cut aprox 2mm off with a very sharp cutoff tool.

I reinstalled, and everything is working OK now.

short insulator

 

Obviously, it's still a screwed up little piece of Teflon, but it's working now, and should hold until my replacement comes.

 

 

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The ´Friction itself was probably not the problem.... atleast not the biggest one..... the aluminium if properly treated would also have a low friction.... not as low as teflon but still low enough. The biggest problem was that the aluminium insulator got to hot , allowing the material in it to get warm enough to get squished to the inner diameter of the insulator and through this increasing the friction manyfold.

 

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I was speaking to someone about this, it may have been in the other posting or not, but we discussed having the material aluminium/metal. We discussed the heat transfer differences. This heat transfer rate would cause the nozzle volume to increase as you increase the heat higher into the filament. Also ptfe has a very low friction coef, and is somewhat flexible and can force material through if an issue arrises.

I think any material which resists heat and heat transfer would be great :D

 

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Made one out of peek, works ok, but the friction is higher than PTFE.

See here;

http://umforum.ultimaker.com/index.php?/topic/7024-teflon-spacer-replacement/

I also made one out of Torlon. They all were relatively the same for me.

 

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I used the fins from an old heatpipe-based PSU heatsink and put them on an aluminum pipe which happened to have the right dimensions..

I had a spring that could be cut down to fit where the old spring was.

Here are two more photos:

2014 09 07 4314

2014 09 08 4321

 

The last photo is taken after five hours of printing. I thought it would be full of ABS by then, but it was absolutely clean.

 

There is no guide for the bowden tube to align it with the hole of the aluminum pipe and I think it draining most of the available heating power from the nozzle when running at 260C.

But it worked fine with ABS.

I will try to improve the design a bit today.

 

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I think I recall someone mentioning having a tungsten carbide spacer made? Any thoughts on that before I have one made?

My printer has the teflon one that came from the factory and the printer is about 2 moths old right now. I have almost 700 hours print time on it and from what I'm reading I'm way past due for a change. I don't want to have to buy one every 200 hours so paying to have a tungsten carbide one made would be worth it IMO if its slippery properties would hold true for PLA.

Thanks

John

 

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