Extruder problem

[Roger Woollett]

I have a round 2 printer which has served me well but is now giving me a problem. When I make it extrude the filament comes out "tangled" rather than as a steady stream. I can sometimes clear it briefly by putting a 0.4mm "pricker" into the nozzle but the problem quickly comes back. I suspect there is a particle of dirt in there.

The thermocuple and heater resistor are held in with (Klepton?) tape. I think I could probably get it apart if I do it hot but am nervous of damaging them. The problem then is to clear the blockage - is there an easily obtainable solvent for PLA? Alternatively are replacement nozzles still available?

Any help would be most welcome.

[Alex Gibson]

Hi Roger

 

There are a few possibilities.

 

Clearly you have a blockage in the nozzle.  This is either a bit of foreign material that’s stuck in the nozzle itself, or as you’ve been running for a long time it could be that the PTFE lining has degraded and a bit of it is now coming out of the nozzle.

 

Both are fixable. 

 

Yes, new nozzles can be bought if necessary, and new PTFE lining can be obtained too.

 

Solvent for PLA is not going to be helpful – it takes horrible chemicals to dissolve PLA, and its melting point being low, a better first effort is to try to flush it clean using a higher melting point material.

 

We can’t go too high (can I check you haven’t already as this could explain the failure?) – over 240 degrees and this will cause the PTFE liner to begin to break down.  230 degrees is a safe maximum (I am sure these printers under-report their temperature in original TVRRUG configuration!

 

I would start by using these instructions to do what Ultimaker call an ‘atomic pull’ and everyone else calls a ‘cold pull’:

https://all3dp.com/2/3d-printer-clogged-nozzle-how-to-perform-a-cold-atomic-pull/#:~:text=Also%20called%20the%20atomic%20pull,clog%20and%20debris%20with%20it.

The idea is to use a higher melting point material to encapsulate and when just barely melted, pull out the debris.

 

Don’t use nylon and the high temperatures you might see elsewhere – use ABS or better, PETG, and 230 degrees on a TVRR.  If you need some scrap 2.85 PETG I can help with that in Reading…

 

Do it several times – either it will work, or be a useful diagnostic.

 

The other thing is to use acupuncture needles (again I can provide spares in Reading) to poke through – maybe alternating.

 

If that all doesn’t achieve at least a partial fix, either you have degrading PTFE liner or a blocked  or damaged nozzle.  For the latter, has the nozzle been dragged along the print surface hard at any point recently?  This can cause the tip to deform.

 

Good luck, try the cold pull and let us know how you get on, pics if you can!

 

Cheers,

 

Alex Gibson

 

+44 7813 810 765    @alexgibson3d    37 Royal Avenue, Reading RG31 4UR

 

admg consulting

 

edumaker limited

 

·         Project management

·         Operations & Process improvement

·         3D Printing

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[Malcolm Napier]

Hi Roger,

Alex's advice is about as good as it gets for "fixing" your hotend. I have stripped them down before now and replaced the PTFE - even though Brian Reifsnyder advised against it. The parts lists for the various versions of J-head hotend are here. That contains the spec of the PTFE tube that you need.

HOWEVER, I believe that I have some spare nozzles left over from Round 3 if you want to drop in a replacement J-head. I need to inspect the darker reaches of my storage space. I will do that and get back to you. And, failing that, an E3D nozzle is a drop in replacement (maybe needing an aluminium mounting plate if you don't have one of those) which increases the capability of the printer considerably (in terms of materials).

When you say, "I have a round 2 printer which has served me well", can you elaborate please? How much printing have you done over the years and of what nature?  You use PLA presumably - but what sort of objects and how many? I ask because Alex has used the Beta build Mendel90 - that was planned to be the Round 4 reference design for new build kits (as opposed to upgrades) - as part of the "face shield for the NHS" print farm that he operated for a good few weeks recently. He reckoned that it compared very favourably with the newer models it was operating alongside. And I know of at least one other person who is chugging along quite happily with a TVRRUG machine. So, I am alway interested to hear of machines that have stood the test of time.

Regards,

Malcolm

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[Bob Dunlop]

Hi,

On Sun, Jul 12 at 08:51, Roger Woollett wrote:
> Alternatively are replacement nozzles
> still available?

I have a virgin replacement complete with heating resistor and thermister
immediatly to hand. Spotted it last week, so no need for Malcom to go
digging. Drop me your address offline and I'll stick it in the post.

--
Bob Dunlop

[Roger Woollett]

Many thanks for all your very quick replies.

Alex - Thanks for all the background. I will try the cold pull method which sounds quite promising. I know that I sometimes get a clean extrude so I am hopeful that nothing is too damaged.

Malcolm - I am afraid my use of the printer has been pretty spasmodic compared to many. It has produced a variety of things - Raspberry Pi cases, Vacuum cleaner hose adapters, playing card boxes, various brackets etc. It can go several months without use but then proves its usefulness. Designs are done on a PC using DesignSpark Mechanical. Then Slic3r and Pronterface on a Raspberry PI. The latest job is a stand for a Raspberry Pi 4B so that it can be vertical to improve natural cooling.

Bob - thanks for the offer. Perhaps I could hold that in reserve until I have tried to clear the blockage.

I will post again to let you know how I have got on. Not sure if I can get to it today but soon.

Thanks again everyone.

[daprigoo]

Another thing you might want to check is the extruder's hobbed bolt is clear of debris. It's effectiveness decreases as it accumulates stripped PLA and over-cooked plastic can also cause blockages.

david

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[Roger Woollett]

Good point David. In fact as part of my investgations I had stripped the head down. I did not find much debris on the hobbed bolt but I did find and cure considerable backlash between the gears. I think the mechanical side should be OK now.

[Roger Woollett]

On Sunday, July 12, 2020 at 4:51:50 PM UTC+1, Roger Woollett wrote:

[Roger Woollett]

Sorry about the empty post I seem to be having finger trouble.

Many thanks for the help - the cold pull seems to have worked so I am now back to getting a better print.

My test piece is a 15 x  20 mm rectangle 3mm high. It prints fine except that at one end the infill separates from the perimeter. The poblem end is towards y = 0. I cannot detect any backlash on the y axis and I have tried slowing things down but nothing seems to work. Anyideas?

[Malcolm Napier]

By "separates", do you mean that the infill does not meet up with the perimeter on any given plane in x-y?

If so, the first two things that I would try are to rotate the print through 90 degrees, re-slice and do a print. Then I would try a different slicer. These are quick tests and I would expect the problem to stay where it is. However, the tests would serve to eliminate slicing as a cause of the problem. Better that way than to spend days chasing a mechanical problem that is really a slicing problem.

I would then try moving the test print around the bed to see if the problem gets better or worse at different locations.(or maybe do several prints of the test object in one go).

 

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[Roger Woollett]

Yes that is right mostly in the y directiion but less so in x. It could be that there is a miscalculation and the sum of the infill does not add up to the distance from one perimeter to the next.

I had not really considered it to be a slicer problem but that makes sense. My main aim is to get the print parameters (temperatures, speeds etc) right. I now think the separation may be a distraction.

Thanks again for the help.

On Tuesday, July 14, 2020 at 9:02:48 AM UTC+1, Malcolm Napier wrote:

By "separates", do you mean that the infill does not meet up with the perimeter on any given plane in x-y?

If so, the first two things that I would try are to rotate the print through 90 degrees, re-slice and do a print. Then I would try a different slicer. These are quick tests and I would expect the problem to stay where it is. However, the tests would serve to eliminate slicing as a cause of the problem. Better that way than to spend days chasing a mechanical problem that is really a slicing problem.

I would then try moving the test print around the bed to see if the problem gets better or worse at different locations.(or maybe do several prints of the test object in one go).

 

On Mon, 13 Jul 2020 at 18:04, Roger Woollett <ro...@woollett.org.uk> wrote:

Sorry about the empty post I seem to be having finger trouble.

Many thanks for the help - the cold pull seems to have worked so I am now back to getting a better print.

My test piece is a 15 x  20 mm rectangle 3mm high. It prints fine except that at one end the infill separates from the perimeter. The poblem end is towards y = 0. I cannot detect any backlash on the y axis and I have tried slowing things down but nothing seems to work. Anyideas?

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[Roger Woollett]

Last night it worked fine but today I cannot get a consistent result. I have sent you a private message.

[Malcolm Napier]

Triffid Hunter's Calibration Guide is my starting point for anything like this (assuming that I can't live with what is being produced).

For something a bit more modern, I would probably turn to Teaching Tech on YouTube. He has several videos on calibration of different kinds. This is one.

I have however, found that the basic TVRRUG configuration is pretty good as a baseline.

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[Roger Woollett]

Thanks for reminding me about that.

Bob Dunlop is very kindly sending me a new hot end so when that is fitted I must settle down to some proper testing.

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[Roger Woollett]

Back in business - thank you everyone. The first print with the new extruder was a total success  - using  Slic3r defaults. Then disaster - the tape holding the thermistor in came adrift and the head got way too hot - white smoke. I put the thermistor back adding binding wire to avoid further problems but the nozzle was clearly blocked. Fortunately I manage to clear things and it is now performing at least as well as ever.

In the course of getting things going I found a number of faults and had to replace the bracket for the Z axis microswitch. I have attached a PDF of my design which uses two 20mm M3 screws to give a more positive grip. The slot allows the bracket to be replaced with the microswitch still wired in.

[Alex Gibson]

Nice one, glad it worked out!

 

Cheers,

 

Alex Gibson

 

+44 7813 810 765    @alexgibson3d    37 Royal Avenue, Reading RG31 4UR

 

admg consulting

 

edumaker limited

 

·         Project management

·         Operations & Process improvement

·         3D Printing

 

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