Extruder - suggestion

RepRappers,

I am currently trying to get my prints from Bowden type of extruder that I got along with the kit (3dstuffmaker). I am spending hours and hours but in no form or shape I am getting a consistant PLA flow; I want to try another type of extruder.

so do you thing Wade type is better than bowden? Or do you suggest any other extruder?
Where should i look for if I want to get one?

Please note I am very new to 3D printing and have not yet printed one good print

Thanks in advance for any suggestion/opinions/views



Regards,
Dinesh

I'm quite new to this but I had the same problem. After days of fun I found out it was the hobbed bolt.

But for you it could be the hobbed bolt, not enough tension on the springs or even the filament. I've had a couple of hobbed bolts now and the quality has been quite bad on a lot of them. I'd have a look at those before getting another extruder.

bowden is interesting. if you tighten down enough to grip the feedstock you risk deforming it so it does not move thru cable. .then if you use a larger cable than 3mm you risk swelling outside of extruder and having back flow issues, which when the extruder cools down it no longer works without changing the cable.

i would say try different feedstock. some feedstock crumbles when a hobbled bolt is used.

i almost think there should be separate hobbled bolts for pla and for abs. abs works great with deep tooth bolts, pla does not it tears apart, at least the cheap stuff does. a good size for hobbled bolts is 4 to 6mm threads, and 1-1.5 mm deep into a bolt. you want as much grip surface area as to put enough pressure to grip the feedstock, yet not so much to change the feedstock shape.


another thing i have done with cable is slicing a cut down the tubing until 50mm from where it goes into hot end. this gives you a little play in case feedstock side changes slighty. some modifications are to use 3.2mm tubing until hot end and switch the last 50mm with 3mm using a coupler.

Thank you for the insights.

After experimenting for a while, I found out that the extrusion from the extruder end is fine but the extrusion from the end of the tube is not fine. Please see two videos (1. 1. extrusion from the tube & 2. extrusion from the extruder-without tube2. extrusion from the extruder direct without tube)



I think I have nailed down the problem - An suggestions please

3eality, how u going with this?, roger

Edited 1 time(s). Last edit at 11/14/2012 05:57PM by rogerw.

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Prusa 'Explorer' (3dStuffMaker), GEN6, J-head Mk III-B, Bowden Extruder, Marlin 1.0.0 RC2, Repitier-Host V0.84 and Slic3r 0.9.8, PLA. Live at Victoria, Australia.

Hi Roger,

Hope you have got a chance to see my videos. I am still have the problem with my extruder. Now I have got herringbone parts. Will try to assemble it.

How abt you.

Regards,

3eality Wrote:
-------------------------------------------------------
> After experimenting for a while, I found out that
> the extrusion from the extruder end is fine but
> the extrusion from the end of the tube is not
> fine. Please see two videos (1. 1. extrusion from
> the tube & 2. extrusion from the extruder-without
> tube2. extrusion from the extruder direct without
> tube)

@3eality - interesting videos. The extrusion looks quite smooth without the tube present, but very jerky when it emerges from the end of the tube.
I agree with you that this is a problem. It seem as though there is some sort of friction that briefly impedes the movement of the filament until it jumps forward a step.
My Bowden tube is made of PTFE (eMaker Huxley kit from RepRapPro) and the filament slides nicely through it.

I suggest you take a sample of filament that has been through the extruder (the hobbed bolt will probably have left some tooth marks in it) and try feeding it through the plastic tube by hand. Does it slide smoothly, as it should, or does it seem to catch anywhere?

richgain

hi 3eality,
yes i spent all last night with my finger over the end of the tube felling it come out too.
i have seemed to inherited an extrusion problems too which I seemed to fix last night.
i was going to say that maybe it is a bad design to have the extruder a long way away from the nozzle like we have
but then from images it looks like richgain's type of machine has a simialr design.
(the other prusa's seem to have the xtruder right on the x carriage thus getting rid of the tube altogether).
Anyway I finally got mine to go again last night - not exactly sure what i did. Just broke it down into steps like you have been doing.
ie. does the filiment come out the extruder, is it coming out the tube ok, is it coming out the nozzle ok when i manually extrude.
i seem to every one in a while just get slippage and it will stop extruding a bit during the print but then it picks up again.

seems like yours must have some sort of friction problem if it is jerky when it comes out. what happens if you hold pressure on it with your finger (which i s what i was doing last night). Does it feel jerky still or smoother? Are there any burs on the tube that could be causing it to catch.

what are herringbone parts - seen me a picture.

roger.

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Prusa 'Explorer' (3dStuffMaker), GEN6, J-head Mk III-B, Bowden Extruder, Marlin 1.0.0 RC2, Repitier-Host V0.84 and Slic3r 0.9.8, PLA. Live at Victoria, Australia.

if you get sliping every once and a while it could be the pla material. i was having a lot of issues, then it randomly went away, it came back again when i recieved more of the same feedstock as before. different vendors sell different hardness of feedstock. if you cant byte deep into feedstock or ir crumbles, it may be the pla.

Think I have nailed down the problem. Below is my analysis and conclusion - a bit long but worth reading

What I have done:
1. Got two PLAs (no1 purchased from 3Dstuffmaker and no2 a sample from my mate a NZ maker - will confirm the supplier)
2. Chopped the end of my extruder tube as it was worn out a bit because I have removed and inserted a lot of times
3. Tested the extrusion with both PLAs with the tube attached to the extruder and without the tube attached
4. Manually pushed both the PLAs with hand to feel the friction and any difference

What I have observed and - what it means:
1. Consistent to my previous observation, both the PLAs extruded smoothly when I tested without the tube attached - so there is no issue with the hobbed bolt friction
2. When tested with tube attached, at the end of the tube PLA no1 continues to have a stepped output. However no2 is much smoother and almost close to extruding without the tube - so the issue seems to be to do with PLAs
3. When tested manually by pushing with my hand, I could notice the difference in the strength required to push and the flow attained between the PLAs - so the pressure points between the PLAs are different that are causing the problem. Also noticed that PLA no1 is more rigid than no2
4. So have stretched sections of PLA no1 manually to straighten it up and tested again. This time I could notice the difference of the flow from PLA no1. I needed lot lest pressure to push it out

Conclusion
PLA no1 is coiled with lesser diameter than PLA no2. Also no1 is less flexible than no2. These two differences played the major role in the problem. When combined with the design of the Bowden extruder, the problem exaggerated.

When we remove the rolled PLA to use in printing, it retains the shape of a spiral curvature. The more shorter the diameter it is rolled and packed the tighter the spirals are. The bowden extruder tube has shape of long inverted 'U'. Now when pushing the PLA into this shape (i.e. spiral into a U shape), it is bound to have some friction points with in the tube. The shorter the spiral of the PLA more the friction points within the tube. Adding to this if the PLA is rigid the pressure at each friction point between the PLA and tube is high. This demands more pressure from extruder. However the extruder is pushing the PLA with a constant pressure. This constant pushing pressure builds in the tube till it can over come the resistance at each friction point. Once it overcomes it pushes the PLA outside the tube. When this release happens, the momentum causes to leak some of the pressure and the cycle begins again.

The more closer the diameter of the PLA is to the tube the less the pushing pressure required. Also more the flexibility of the PLA is, less are the friction points and hence less pressure is required to push. Also the constant leakage and build out of the pressure is minimised and a smooth flow is attained.

The issue is not just with the PLA, it is inherent to the design of the extruder and amplifies with the quality of the PLA. We can minimise it by having a very perfect tube that matches the PLA diameter. However the problem may continue to exist. Also this whole equation made me to realise why there a lag in extrusion and PLA from from hot end. Because of the pressure build out in the tube the hot PLA flow is not responsive to the extruder action i.e. it doesnt start when extrusion starts and it doesnt stop when extrusion stops. This behaviour distorts the shapes where intricate on and off of the extrusion are required.

This does not happen in Wade extruder as the distance traveled by the PLA from extruder to hot end is less. The whole mess of pressure release build up is not there. This responsiveness to extruder movement and PLA flow from hot end is direct and synchronised. Attached is brief picture that tells the story.

Thank you for your patience in reading this and appreciate your feedback!

Edited 1 time(s). Last edit at 11/17/2012 06:54AM by 3eality.

I'm guessing that if your extruder is that sensitive to friction in the tube, then you probably won't be able to push the feed through the hot end with either PLA. You should show a photo and describe your extruder so that others here might be able to help you. That's probably where your problem is. How is your hobbed bolt? Is there enough pressure on the idler bearing?

Just a thought ... is your Bowden tube definitely made of PTFE? You may have to ask the supplier.
PTFE is a very soft plastic - cuts very easily with a craft knife with almost no force. Also very slippery - grip a length of it between finger and thumb of both hands as tightly as possible and then pull your hands apart. PTFE tube will slip between your fingers with very little friction.
PLA filament ought to slide the through the Bowden tube with little friction, whether it is straight or curved. It should also still fit into the tube even after it has been through the extruder. If it is crushed too flat by the pinch wheel to fit down the tube you may have the tension bolts done up too tight.

Edited 1 time(s). Last edit at 11/17/2012 10:31AM by richgain.

ptfe is slippery pfa is like ptfe but it can set into a mold, and has a slightly higher temp. it is less likely to deform when high temp is applied. Polyurethane tubing can be used as long as it is oversize in inner diameter, but the tubing does stretch under pressure. i would say it stretches above 3%


3eality is right about the u shape issue with bowden, this is one reason the cable is kept as short as possible. another issue is when the feedstock becomes deformed from too much pressure from the idler, a square feedstock trying to go thru a round hole.

@ richgain " made of PTFE? You may have to ask the supplier"
- I am waiting for the response from the supplier. However as you have described, my bowden tube doesn't seem to be PTFE. When I chopped of the end with craft knife, it took lot of effort and snapped. So i guess it is not PTFE. I will wait for the response anyway.

I have checked the extruded PLA and there is no de-formation of the shape. There is none. There are gripping marks but no change in the shape.

Also when I took a piece of PLA streched it to straighten a bit, the flow appears to be more smooth with less friction.

I think I have decided to give up the bowden and migrate to wade.

Happy to continue experimenting for the benefit of the RepRappers.

Thanks a heap for all the suggestions and support

hi 3eality,
as you know i have the same set up as u (with the extruder hanging on the side of the machine, pulling filament in from below, going up and over thru the inverted U shape tube and then into the hotend on the x carriage). - will post photo for others.
is this whole setup called the bowden or is that just the hotend? what does a wade look like - is that with the extruder directly on top of the hotend ie. all moving with x carriage. that seem to be how the 'real' prusas are designed - maybe due to this friction issue.
the whole inverted U thing design just seems to add a lot more friction/work for the extruder to do - in your case with bad results - most of my issues are based around the extruder too.
roger.

Edited 1 time(s). Last edit at 11/18/2012 05:42PM by rogerw.

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Prusa 'Explorer' (3dStuffMaker), GEN6, J-head Mk III-B, Bowden Extruder, Marlin 1.0.0 RC2, Repitier-Host V0.84 and Slic3r 0.9.8, PLA. Live at Victoria, Australia.

Roger,

Yes! yours is a Bowden extruder, and the one sits on X carriage is Wades extruder. No hot is not referred in the contest. it is the next component to extruder. The picture on the RepRap wiki is a bit confusing as the picture shown is primarily a hot end.

Technically Bowden is a good thought. It takes of the moving mass sitting on X carriage and avoids issues associated with moving mass (momentum etc). However it opens new issues like the ones we are facing (friction points, sensitive set up requirements etc).

Bowdens doesnt have to be ruled out. Because of their advantages (no moving mass and space efficient) it is a very good solution when planning multi hot ends. However they need a very fine set-up process and are very sensitive to any change.

I can also now express one more issue with the setting. When I extrude the PLA at +10mm of Z to ascertain a consistent flow etc. Once I am happy and move Z to home, the flow of PLA changes. A mere change in the height of the Z changes the angle or curvature of the inverted U tube and you can clearly see the difference in the PLA flow.

I am slowly mastering it, however I can say 'IT IS NOT FOR STARTERS' It takes time before you completely understand Bowden settings and a further time before you can get hold of it.

BTW, do you know if your U tube is made of ptfe? I am still waiting for a response from 3Dstuffmaker.

well i'm not sure what its made of now i wanted to get another length of it to set up to feed from the (yet to be built) filament spooler.
ie. saw a post where they run the filament straight into a piece of tube and then up to the bottom/start of the extruder ie. to stop it looping and tangling.
roger
have attached a picture of our beast (from the web site) for others to see. it shows the extruder on the right. it is make of clear perspex. and a close-up.

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Prusa 'Explorer' (3dStuffMaker), GEN6, J-head Mk III-B, Bowden Extruder, Marlin 1.0.0 RC2, Repitier-Host V0.84 and Slic3r 0.9.8, PLA. Live at Victoria, Australia.

Thanks for the pictures. If you are getting good prints with your bowden, then cheer up. I am struggling to get a consistent print. All except by bowden set up is working. However, I have learnt much from this exercise.

If you set up a rolling spool for the PLA sitting right below or sideways to your extruder, then it should solve tangling.

i printed the best one yet so far on sat night - tried to show my brothers yesterday and could even get one layer down - arrghhh

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Prusa 'Explorer' (3dStuffMaker), GEN6, J-head Mk III-B, Bowden Extruder, Marlin 1.0.0 RC2, Repitier-Host V0.84 and Slic3r 0.9.8, PLA. Live at Victoria, Australia.

hi 3eality,
found my problem . my hotend was too close to the bed (set z to .1 to raise it a bit in slic3r and fixed it). being too close then didn't
let any plastic out, put pressure on extruder and then it starter to slip. this then dug a hole in the filament. after i fixed it by manually pushin the filament along a bit the hole that had been dug seemed to be getting stuck
at the start of the tube and maybe even adding more friction to the whole bowden thing.
finally pulled all the filament out from the extrduer to the hotend and it had bumps and lumps all over the place.
is your filament like that too ie. bumps and lumps adding more friction to the tube.
roger.

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Prusa 'Explorer' (3dStuffMaker), GEN6, J-head Mk III-B, Bowden Extruder, Marlin 1.0.0 RC2, Repitier-Host V0.84 and Slic3r 0.9.8, PLA. Live at Victoria, Australia.