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Extruding shredded bottle caps HDPE - Inconsistent 2 and 3mm dia.

Adrian
(@adrian)
Active Member

Hi All, 

I am an Australian based in Indonesia and am helping an Australian couple that has donated a new Precision 350, to a community to convert collected shredded bottle caps that are all HDPE, into filament (not for 3d Printing) but to use the filament to produce arts and crafts for sale. They aim for 2mm and 3 mm dia filament for their customer, with reasonable consistency but not high tolerance needed. 

The operator that was shown what to do by their angel investors, he started having issues about 6 months ago, the issue relates to filament consistency  - so it's got worse over time. As I was not able to visit him due to travel restrictions we sent the unit to my house and have been playing over the weekend.

I happily volunteered to help locally, I am active in 3d printing and have some engineering skills. Also how lucky is it to play with a Precision 350. I did extrude some 1.75mm and tried to print it, but as you all know it's hard to get HDPE to bond to its self and not warp - I digress. 

Below are a number of issues I am facing and have done some research on, any help and guidance would help heaps;

  1. The feed wheel was completely worn and have replaced it - Also saw some ideas to rebuild the worn one with TPE/TPU onto a GT@ Geared pully. Also to try the silicone into a mold. 
  2. There seems to be little bits every 50 to 100mm, like little pimples on the surface of the filament.
    1. I am thinking the nozzles is dirty - so plan to replace it
    2. Also worry that there is dried -crystallised burnt material in the screw or in the nozzle - So plan to do a devo purge 2 - 108c to 320c - Should I do that in through the old Nozzles to clean that out or just use the new nozzle? See Picture from around the nozzle
    3. Contaminates in the shred - I looked visually and looks fine but I have no idea really.
    4. Also could shred size be a factor? I plan for the operator to double shred and see if that helps. Any thoughts?
  3. I am also struggling with Spooling - I will read more forums.
    1. with the DEVO reel with an internal dia of 105, and I note all the pre-sets are set at 75mm. When using 75mm, it works fine - I thought it would have to match the Reel. ? Please help on this point - What is the Devo reel internal dia ? Should the pre-set match that dia. 
    2. So when I tried using a ex 3d Reel and I adjust the Dia to the internal dia of the reel, I can never get the right tension. Am I missing some relationship? 
    3. I am still confused on the tension wheel and again more trial and error. 
  4. I am also getting ovalisation in both 2mm and even more in 3 mm -
    1. I read that the fans have a big impact. - so need to play around also
    2. I saw some shrouds for the two fans that redirect air away from the nozzle
    3. Also saw the 3d Printed cylinder that uses one of the fans to help circulate the air evenly around the extrusion - Is that worth the effort? I realise the example was for PLA - would it help for HDPE?
    4. I also note that with the new feed wheel and that the roller wheel has the tensions screw could be putting too much pressure on the filament - I find it very hard to reach the nut to hold it tight to tighten and thus release some pressure on the filament - Any help on this?
  5. I also worry about the shredded materials - It has been sun-dried and put into plastic tubes, but i assume as it is hygroscopic that it's moisture has increased - However I do not hear or see any bubbling or hissing during extruding. 
    1. I am thinking about a way to add silica beads to a larger tub and put the smaller tub in to help dry out. 
    2. I will try the oven trick - but as this is a community-based project it may not work in the field.
  6. Finally, the current Temp setup that was made through the first trial runs did make good filaments.
    1. For 2mm. 
      1. Rpm 5, H 4- 165, 3-170, 2- 170, 1- 165.
    2. For 3mm worked in the past but I cannot seem to get the dia consistent and severe ovalisation.

RPM 5 H4 -165, 3-170, 2- 170, 1- 165.

Just trying to work out all the moving parts. So any advice on what should be the priority to reduce variations is most appreciated.

Thanks, Adrian

1634612218-Dirty-nozzle-suroundings.jpeg
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Topic starter Posted : 19/10/2021 2:56 am
Adrian
(@adrian)
Active Member

Sorry I forgot to added in the Fan speed. It was set at 33% for both 2mm and 3mm. 

Regards

Adrian 

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Topic starter Posted : 19/10/2021 3:54 am
louis
(@louis)
Member Admin

Dear @adrian ,

Thank you very much for this detailed explanation. I will do my very best to assist you in this nice adventure. 

Given your list of issues/thoughts, we sure have a lot to discuss 😉 

1. Puller wheel
To ensure good gripping of the output, the silicon wheel should have a relatively flat surface.
A 'trench' dug in the silicon wheel will cause major pulling issues, with an impact on the texture and diameter.

2. Surface issues 
2.0. Thank you for including a picture. I can immediately comment on the thermal insulation. Normally, the glass wool (wrapped around the barrel under the panels) should be wrapped more tightly around the knee/nozzle. I recommend lifting the top panel : https://support.3devo.com/remove-top-hood/ . Then you can carefully use pliers and gloves to insulate the knee/nozzle as much as you can. 
In addition to this, the hole around the nozzle should be covered by a small magnetic plate (picture attached).
With the glass wool, the magnetic plate, sufficient temperature set on H1, and having the fans angled 'downward' (not straight toward the nozzle), you should be able to improve the texture of your filament a lot. 
2.1. Dirty nozzle It is a little hard to tell. The nozzle does look dirty on the outside, but I cannot see the inside or how much solid plastic builds up at the tip over time https://support.3devo.com/nozzlebuildup/
2.2. Contamination inside Purging the machine is always a good plan. I would recommend using Devoclean MidTemp EZ, approx 15min at 15RPM. As a matter of fact, I would recommend purging the machine quickly at the end of each session. https://support.3devo.com/purging-your-filament-maker/
2.3. Contamination in the batch Any small particle of contaminant that does not melt during the process, ends up in the final filament, often in the form of a little bump on the surface. 
Little bumps on the surface could be these, or unmelted HDPE particles, or melted HDPE particles that re-solidified in the nozzle
2.4. Particle size Yes, this can have an effect. I would recommend shredding twice, just to be sure. So long as all particles are smaller than 4mm, you should be fine.

1634906646-magnetic-plate.jpg

Best regards,
Louis

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Posted : 22/10/2021 12:44 pm
louis
(@louis)
Member Admin

3. Spooling 
This step is a little difficult to explain with written words.

- yes, the 'empty spool diameter' in the menu should match the actual spool. See picture below. In the case of 3devo spools, 105mm should be the correct value.

- prepare the slipper clutch mechanism by tightening the black knob at the back of the Filament Maker (center of the largest panel) : screw it in, all the way, minus 2 full turns. That should give you good results.

- the material flow should be quite stable. If not, the spooling process will be disturbed and feed back the turbulence in the puller. I recommend spooling only once you are satisfied with the quality of your filament

- start extrusion, let the process stabilize 

- tighten the spool holder strongly on the spool

- go to the Spooling menu (wizard of 4 steps)

- during step 2/4, cut the filament just beneath the puller, guide it through the positioner, then through the hole of the spool. Keep pulling on it manually to maintain tension

- before moving to step 3, the filament should be fully tense. Keep pulling manually to ensure this

- as soon as step 3 starts, the spool will spin. Quickly bend the filament into a U-turn, so that it does not slip out of the hole. Then, let the spool complete 3 rotations without disturbing it. Do not skip through that step too fast

- continue to step then press 'done' (no waiting needed). The tension should be optimal.

https://youtu.be/uxp2iuypDAo?t=704

1634907244-spool-dimensions.png

Best regards,
Louis

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Posted : 22/10/2021 12:54 pm
louis
(@louis)
Member Admin

4. Ovality 

https://support.3devo.com/why-is-hdpe-difficult-to-extrude/

This does not necessarily have to do with the compression of the puller. 

By nature, HDPE crystallizes a lot --> it makes it warp during printing, and shrink unevenly during extrusion. 

You can experiment with the temperatures, cooling, fan configurations/add-ons.

There is another 'exotic' solution : adding additives that help it maintain its shape. 

We recently achieved promising results with Carbon Fiber (80 microns), and are currently studying the use of talc.

It is normal that the phenomenon gets worse for 3mm filament, because there is more room for shrinking. 

5. Drying 

I do not think that drying HDPE is essential/mandatory, especially since you have not witnessed any bubbles. 

If you can, it could be interesting to run a quick drying test (80°C, maybe 1h ?) and measure the moisture before/after, using a moisture analyzer. If you do not have access to that technology, I think you can simply keep experimenting without being too worried about the moisture.

6. Settings 

These look very reasonable to me. Among other things, the settings will influence : 

- output texture, ovality --> the nozzle temperature is critical here. Increasing it will prevent nozzle build-up, but decreasing it could limit the shrinkage. Either way, insulating the nozzle is key. https://support.3devo.com/oval-flat-shaped-filament/

- flow stability --> https://support.3devo.com/filament-thickness-deviation-inconsistent-diameter/

7. Conclusion 

Does that help ? 

Please let me know how your next trials go, if I can do anything to assist...

Please always feel free to participate, send me videos, pictures, comments, or datalogs https://support.3devo.com/devovision-guide/

Best regards,
Louis

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Posted : 22/10/2021 1:05 pm
Adrian
(@adrian)
Active Member

@louis Fantastic Help! - I am making this week for a high school project 6 cloured rolls. For this little project thee consistency is not a key factor. See pic for fun. 

So once I am done I will work through all your points starting with the nozzle and Devo clean first. 

 

Thanks Heaps. 

1635399449-Completed-Spools.jpeg
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Topic starter Posted : 28/10/2021 5:37 am
louis
(@louis)
Member Admin

Hi @adrian

Looking good ! Minus a few issues on the green one I see, but those are rather neat spools overall. 

Thanks a lot for sharign that picture. 

I wish you good luck for that project then, and am looking forward to assisting you when you start experimenting again.

Have a great weekend ! 

Best regards,
Louis

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Posted : 29/10/2021 10:55 am
Adrian
(@adrian)
Active Member

@louis Getting there. Later next week I can really play. 

BTW the charity I am helping link is here.

  https://www.youtube.com/watch?v=mKRiQx_2YQ0   

Ignore the ask for money as this was a few years ago for a student program. Now funded and hopefully after I have ironed out the maintenance issues I can give back to the community with some maintenance schedules.  

Still can only use the DEVO roll and can't get my 3d Rolls to work. But one issue is we are trying to keep the cost clearly low and I just do not have enough old 3d Rolls, even with donations from other heavy printers.

I came up with a free stockholder see pic, it is just scrapped Bamboo. Yes it does require a transfer from the Devo roll, but I have to do that anyway, but I made an easy-to-use jig, that can do it in 10 mins or so. 

Kinda kool if I say so.

Regards

Adrian 

 

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Topic starter Posted : 29/10/2021 4:48 pm
Adrian
(@adrian)
Active Member

Sorry I was having issues with the image upload. I bet you have not seen this before?

Adrian 

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Topic starter Posted : 29/10/2021 4:55 pm
Adrian
(@adrian)
Active Member

@louis Hi Louis, I was just reading over old posts and found this image that Timo loaded a few years back to reply for lumps issues. 

Can you confirm once I pull the top off and clean out the hardened plastic you expect (ideal) that the nozzles should be fully covered with insulating wool? 

Can you confirm the max temp of your standard fibre wool? 

Thanks, Adrian

1635563943-Orginal-insulating-wool.jpg
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Topic starter Posted : 30/10/2021 3:19 am
louis
(@louis)
Member Admin

Dear @adrian

Thank you for sharing. Our team liked the video very much : it tells the whole recycling story nicely (collecting, sorting, cleaning,....). 

Spooling :

I am sorry, I do not think I fully understand your situation with the spools. 

You do manage to spool on the 3devo spool, then transfer the filament onto the bamboo roll (nice process, by the way 😉 ), correct ? 

"can't get my 3d Rolls to work." --> do you mean that the spooling step fails when using other spool brands/models ? Can you please describe the symptoms ? This most likely has to do with the spool dimensions calibration. 

Nozzle insulation : 

The glass wool can withstand 1200°C, well above the max temperature of the Filament Maker (350 or 450°C, depending). 

The nozzle does not necessarily need to be fully covered in glass wool all the way to its very tip. Of course this can help preserve the heat, which is super important, but placing glass wool to close to the tip can result in small glass bits 'grabbed' by the filament and stuck on its surface (causing printing issues, obviously). 

Does that answer your questions ? 
Please let me know how I can help

Best regards,
Louis

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Posted : 02/11/2021 9:19 am
Adrian
(@adrian)
Active Member

Hi Louis,

Thank you for so much info. Today I managed to the the first DevoClean and you can see in the picture the journey and process. Actually it was kinda kool how it worked.

As per all the post before and yours I still have a lot to do to "clean up" the output filament. I will over the next month, particularly the glass wool, new nozzle, and maintenance plans. 

Would you mind emailing me. I have something to share offline. 

Regards

Adrian 

1637481639-After-DevoClean.jpg
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Topic starter Posted : 21/11/2021 8:00 am
louis
(@louis)
Member Admin

Dear @adrian ,

Thank you for that nice picture 😊 

As far as I can tell, I think there might still be a small amount of contamination inside the barrel (still a few dark spots). This is not necessarily an issue because Devoclean MidTemp has a 'sealing' effect : when left inside the barrel during shutdown, it tends to stick to impurities very well, and will carry them out next time you start extruding. 

Yes, I will send you a private email in just a moment ! 

 

Please feel free to publish your next questions/results 

Best regards,
Louis

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Posted : 24/11/2021 9:45 am
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