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densohax

Teflon spacer replacement

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First post, so a little background first: ;)

I am quite new with the ultimaker 2, I had it for 2 months now. I do have a lot of experience with the makerbot thing-o-matic.

Ok, so my teflon spacer scored from the inside and is brown from burning in the hot end. I did print with the provided PLA roll at first but switched to ABS right after that and printed some ninja flex in between.

My hot end was at 240 celsius and I use the Robert's feeder since the original one wasn't up to the task with ninja flex.

Everything was fine for a while, really didn't have any major problems, but then with retraction, the hot end would jam up.. So there are some deep grooves and scoring marks in the teflon part.

I submitted a ticket, and ultimaker replied quite fast.. I don't know yet if they will send me a replacement teflon spacer, but I believe I will have more problems with it in the end..

SO, I was wondering if someone made a ceramic replacement Spacer? I was going to try and make one, but machining ceramic on the cheap is going to be quite challenging I fear!

I know there is the e3d all metal hot end, from my quick search on the forums, it looks like it would be a great replacement .. However, I do feel a bit foolish to have put all that money in a printer and change everything after 2 months!

With my thing-o-matic, I NEVER had to disassemble the hot end and it definitely NEVER jammed up on me.. I'd like my ultimaker2 to have that same reliability ;)

 

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SO, I was wondering if someone made a ceramic replacement Spacer? I was going to try and make one, but machining ceramic on the cheap is going to be quite challenging I fear!

 

I don't have experience on ceramic replacement, but I have seen Ultimaker employees writing that PLA sticks to ceramic materials _very_ efficiently. Besides friction, I would be concerned about tightness of the fit between (ceramic) isolator and the actual nozzle unit. As PTFE is slightly elastic, it makes a tight fit with the nozzle unit.

My solution was to improve airflow towards the Teflon isolator:

http://umforum.ultimaker.com/index.php?/topic/6307-um2-twin-tornadoes/

It helped a lot. As I have also built a closed chamber for my UM2, my need for cooling the PTFE isolator was accented.

 

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Stainless steel would be good as it's not very heat conductive.

UM has a "new" glass infused teflon isolator but if you got the printer less than 3 months ago (you said 2 months) then I suspect you might already have it.

There is a spring pushing on that isolator from the top - very obvious when you look at it. You can reduce deformation by reducing the pressure of that spring by lowering the nozzle as low as you can. That's all I got.

I usually print at 220C and the isolator withstands 220C MUCH better than 240C.

 

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I don't have experience on ceramic replacement, but I have seen Ultimaker employees writing that PLA sticks to ceramic materials _very_ efficiently. Besides friction, I would be concerned about tightness of the fit between (ceramic) isolator and the actual nozzle unit. As PTFE is slightly elastic, it makes a tight fit with the nozzle unit.

My solution was to improve airflow towards the Teflon isolator:

http://umforum.ultimaker.com/index.php?/topic/6307-um2-twin-tornadoes/

It helped a lot. As I have also built a closed chamber for my UM2, my need for cooling the PTFE isolator was accented.

 

This is impressive! I will add more airflow to the isolator as well, I'm sure it will help, since I also print mainly in ABS.

 

Stainless steel would be good as it's not very heat conductive.

UM has a "new" glass infused teflon isolator but if you got the printer less than 3 months ago (you said 2 months) then I suspect you might already have it.

 

I do have a recent printer, I'm not sure how to identify that my teflon part is the new material or not, but it's all brown and scored inside.. I'm not sure what happened exactly, maybe it did sit down a long time while heating the heatbed with the head at operating temperature.. I will probably need to preheat the head bed first, but in the end, I feel that the teflon part must go and be replaced with something better. I'm open to new materials!

One thing is sure, I'm going to add airflow to this part!

 

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I have one of the first versions of the U2, and I have been having issues with printing under extrusion. I so far have been able to correct this by simply printing a bit slower. I was meaning to order a new one and or call ultimaker to have one shipped.

One issue with the PTFE is its compressive and tensile strength, especially near heat.

I have access to a lot of scrap peek, so I decided to create a PEEK replacement.

The comparisons are as follows:

Tensile Strength: PTFE = 25-35MPa, Peek = 90-100MPa

Compressive Strength PTFE = 30-40MPa, Peek 140MPa

Thermal expansion is approx 1/3 lower for Peek.

The machine ability of PEEK is better than PTFE and it is easier to have a smoother polished surface.

With the constant movement of the filament wire through the PTFE the higher strength PEEK should maintain its structure better than the PTFE allowing it to avoid possible friction issues.

I conducted the flow test cyclinder to 10mm3/s and noticed an improvement of two levels. I was able to complete the cyclinder with the new PEEK spacer.

peek1.jpg

peek2.jpg

 

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I have one of the first versions of the U2, and I have been having issues with printing under extrusion. I so far have been able to correct this by simply printing a bit slower. I was meaning to order a new one and or call ultimaker to have one shipped.

One issue with the PTFE is its compressive and tensile strength, especially near heat.

I have access to a lot of scrap peek, so I decided to create a PEEK replacement.

The comparisons are as follows:

Tensile Strength: PTFE = 25-35MPa, Peek = 90-100MPa

Compressive Strength PTFE = 30-40MPa, Peek 140MPa

Thermal expansion is approx 1/3 lower for Peek.

The machine ability of PEEK is better than PTFE and it is easier to have a smoother polished surface.

With the constant movement of the filament wire through the PTFE the higher strength PEEK should maintain its structure better than the PTFE allowing it to avoid possible friction issues.

I conducted the flow test cyclinder to 10mm3/s and noticed an improvement of two levels. I was able to complete the cyclinder with the new PEEK spacer.

 

Do you sell those? I'd like to buy one ;)

 

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I'm actually on a mission to see if i can get one made from WC(tungsten carbide). It is one of the least heat conductive metals on the planet and as you may know, it is virtually indestructible as they can even cut diamonds with it.

Only problem is to find a milling company that can actually mill it.

 

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Update, I wanted to see if I could fix the PTFE design.

I acquired some high quality PTFE bar stock (we have as leftovers at work). I made some small changes to the design of the original spacer.

Added a 0.5 mm chamfer to the opening to allow for easier entrance and for retraction, also increased the hole size to 3.97. Rounded the exit area slightly. I tested this first had no issues.noticed a drastic improvement similar to my peek one.

After this test I modified the original PTFE part to match; instant improvement also.

peek.jpg

 

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Update, I wanted to see if I could fix the PTFE design.

I acquired some high quality PTFE bar stock (we have as leftovers at work). I made some small changes to the design of the original spacer.

Added a 0.5 mm chamfer to the opening to allow for easier entrance and for retraction, also increased the hole size to 3.97. Rounded the exit area slightly. I tested this first had no issues.noticed a drastic improvement similar to my peek one.

After this test I modified the original PTFE part to match; instant improvement also.

 

I'm still interested in buying one of your PEEK spacer :)

With the bigger hole, wouldn't your filament hit the metal hot end flat part when retracting too far and going back in the metal tip from the PTFE spacer ? I do understand tho that the filament would be thinner at the tip, thus it might be "self-centering" ..

I received a diamond blade I ordered. I will improvise and try to machine a ceramic rod in a spacer. I will try with a larger hole, as you did, maybe this will prevent the PLA from glueing to the ceramic spacer.. Or else, I will try to create a spacer in which the PTFE spacer will sit..

 

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If I can find the barstock of peek that was laying around it would be easier. Currently I have to create the bar using an irregular shaped piece of scrap. It takes a long time to cut it down to round. Otherwise I wouldnt have an issue with sending you one.

 

I wouldn't mind getting one as well if you decide to make a couple :)

 

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Update, I wanted to see if I could fix the PTFE design.

I acquired some high quality PTFE bar stock (we have as leftovers at work). I made some small changes to the design of the original spacer.

Added a 0.5 mm chamfer to the opening to allow for easier entrance and for retraction, also increased the hole size to 3.97. Rounded the exit area slightly. I tested this first had no issues.noticed a drastic improvement similar to my peek one.

After this test I modified the original PTFE part to match; instant improvement also.

 

I think adding the chamfer at the bottom is not such a good idea, during a print it might help but when it cools down it will create a lip on the pla which will cause it to jam.

here at HQ we tested with ceramic but the pla just stuck to the inside walls and after cooling down we had no luck of getting it started again.

a new PFTE part will always increase the improvement of the machine. Because the deformation takes place after a +80 hours of printing (@210c)

Here you can see the machine we use to test all the different variations of the PTFE part... (don't pay attention to me on the photo :p, it was the best photo i could find cause the machine is half appart for the next series of tests atm)

IMG-20140804-WA0000.small.jpg

and then this one to measure the amount of force needed to just push it through the nozzle.

3EIeRv.jpgNEvlsw.jpg

 

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The chamfer at the end of the feed tube (top of the ptfe)`? (note I modified the feed tube to match the chamfer edge so once out of the PTFE it is somewhat seamless. These tests improved my machine, maybe another it can have a different effect)

If you mean at the bottom of the ptfe It isnt a chamber, it is rounding the edge. as it is currently a sharp edge. I basically broke the edge slightly to avoid the small burr (possibly not even seen by the eye) that is created from machining. I modeled the round just for reference. The round actually improved material removal as there isnt a straight edge to grab. I tested all options and this was the best in printing flow, no issues with removal on really any of the designs.

This as you say is the reason is why I created a few variances. One had a chamfer, it worked but there wasnt much of a difference compared to the straight 90, the second was just an edge 90 similar to the current Ultimaker design, and the third was just breaking the edge slightly with a small roundish profile to remove the 90 point. If you look you may not even notice that there is a round, basically smoothing out any sharpness.

The thought is, that at higher temperatures there is a visible deformation of the PTFE. This deformation can cause a narrowing profile from the compression on the bottom edge. This narrowing is due to it is the only place the material can "flow". The round profile at temp and pressure from the spring should be virtually non present and would absorb any deformation from the pressure. Or at least that is my theory :D.

Tests ive done on other products but similar materials.

Ceramic vs Peek vs PTFE vs Torlon. I have conducted long term temperature tests with Ceramic, peek, ptfe and torlon. Torlon is king in this dept relative to machining and cost as it holds up to temperatures in the 275-300c range. i'm searching through scrap now to see if i can test the Torlon. Each have varying properties some good some bad :)

 

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I printed with it for around 20 hrs made a large model for work overnight with it. It kept going strong no issues. I switched to a ptfe part since I had nice bar stock and I wanted to conduct some testing. I was able to create a higher precision part with my ptfe stock part compared to my irregular peek stock I have.

The main benefit of the PTFE is a reduced friction coefficient, but I am able to create a much smoother machined surface with Peek compared to the PTFE. I also noticed vast improvements when I opened up the hole by 0,4mm. I am currently testing on 3.00mm +/- 0.1. It has been running now for 5 hrs no issues very good quality with the updated PTFE part.

The improvements I have made on the machine and the quality of the prints I have done for work has actually turned into a sale for Ultimaker and as well paid off my machine and given me vast amounts of printing material :), they are in the works of ordering the ultimaker due to the low costs relative to returned savings. I print PLA models of our designed peek/torlon parts to fit before we send/order for machining. These torlon and peek parts no matter how small they are cost on average more than the machine. Having printed test parts to verify saves a lot o cash and time :)

 

PEEK isn't a great choice, we tested that with PLA and it jammed within an hour.

 

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Does anyone know how far up the teflon hole the PLA/ABS is still molten? I know from experience that if the head overheats then it melts right up to the bowden tube (and makes a lip there). But what about normally?

I'm wondering if a wider bore would reduce the pressure, provide a larger reservoir, reduce underextrusion issues.

OTOH, the larger the diameter of the molten end, the more likely there will be problems removing filament for material changes?

 

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I am currently trying a little hack I made to the hotend..

 

I cut off a portion of the PFTE white spacer and reversed it, put it on the top aluminum plate, I then inserted the PFTE red tube that came with my thing-o-matic MK6 head in the white spacer and cut it so it's flush with the hotend.

 

It seems to work pretty well for now, I didn't do any exhaustive printing with it yet, but at least it works and retraction works too!

 

The red PTFE tube of the thing-o-matic is more slippery and seems more durable than the PTFE white spacer of ultimaker.. I don't know why tho.. But it served me well in my TOM and it endured 3 years of non-stop printing..

*And I also removed the spring since it became obsolete...

** And I've put thermal paste on the aluminum heatsink where it contacts the plates

IMG 20140822 222442

 

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Ok it looks like it didn't work..

At 240 it didn't work, at 260 it does work, and it does print VERY GOOD!

Ok I might trigger the gun too fast here, but the ultimaker robot passed the retraction layers and it's the most beautiful I printed as of yet; and it's printed in ABS..

Let's see how this goes...

** Best robot I have to date while printing ABS. I guess 260 degrees helped a lot to reduce the forces needed to push the filament and retract.

IMG 20140823 000619

 

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260c... Maxed out. You are reducing friction with heat, yes but there are other material issues!. This temperature is where the ptfe will start to break down. This may make things worse over time.

I'd order a new one and then

Since you cut it. Maybe Try re drilling out the hole slightly making sure it is clean inside and all edges are smooth. Slide the filament before and after, you should notice a drastic improvement with friction.

Also

Have you modified the feeder yet?

Print Irobertls feeder it allows you to Better adjust the pressure on the filament. Make sure you make all the parts where the filament can touch smooth. :) also ensure your Bowden tube is secure and not moving with the retraction.

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