Can you detune the extruder to still use poor filament (Skip not shred)

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Lucidwolf
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Joined: Sat Aug 25, 2018 12:31 pm

Can you detune the extruder to still use poor filament (Skip not shred)

Post by Lucidwolf » Wed Aug 29, 2018 9:51 am

Full disclose this is probably a dumb post and maybe the answer is to "get gud at first layer noob".

I started printing a few bench marks with my PLA library, but when I used my admittedly not great and old natural PLA for first print prototypes the extruder started turning my filament into extruder snow if I over pressured the nozzle. See first picture. I don't even hear it grinding. If I don't catch it in time it just shears the filament off right at the nozzle entrance which requires me to tear the extruder apart to fix. (That is painful and probably another topic... I think there is room for improvement to make the field stripping time minimal.)

What this made me realize is my first printer (mini Kossel clone with a bowden) has a bug that I thought was a feature. Since it does not have that great of a level bed I would have to have a very thin first layer in the high spots of my bed. Instead of grinding this filament the extruder would instead skip when it got over pressure. That was perfect because it let me get a first layer down without turning my cheap filament into a snow cone when it reached those high spots. I now realize the motor on that clone is very weak, but perfect for the filament I use, because it skips not shreds. I can't imagine my frustration with printing back in the day not knowing how to really level the bed without this "bug-feature". It apparently really eased me into printing.

My Point:
Is it a crazy idea to try and de-tune the extruder motor down for 1.75mm PLA crap filament prints such that the motor skips at over pressure instead of tears. I'm thinking this might be possible by micro stepping the extruder to drop it torque rating by large amounts and then playing with current to get more detailed control torque skip. I like the big motor because i was thinking of going up to 3mm filament with this printer in the future, but I didn't realize how badly it can shred small cheap filament. This might also increase chances of success with flex filaments that can tear easy.

Anyways I just need someone to tell me this is a stupid idea or that it has already been tried and failed or tried and there is a whole forum somewhere dedicated to it that I just fail at Google. :lol:

Thanks,
Lucidwolf

Figure 1
let_it_snow.png

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mhackney
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Re: Can you detune the extruder to still use poor filament (Skip not shred)

Post by mhackney » Wed Aug 29, 2018 10:01 am

Yes, it is crazy to detune an extruder to compensate for inexperience, poor slicing, bad filament and all other issues. You apparently understand that microsteps come with a reduced holding torque so use your knowledge to fix the problem the right way.

There are no issues with using cheap filament of flexibles. You either did not assemble the extruder properly or doing something silly in slicing or some other place. Find and fix the issue and you will be fine. I print crap filament all the time. I also print TPU and other soft rubbery filaments. Never make snow, in fact I've never seen that before from any of the 1000s of people I've helped. That level of extruder grinding indicates something big is wrong. The good thing about "big" issues is, they are easy to find and fix.

3mm is "yesterday". There is no practical reason to use it and there are reasons for not using it.
www.SublimeLayers.com - Musings and Experiments on the Art and Technology of 3D Printing

Support me and my work at Patreon and get early access to my upcoming book 3D Printing Strategies - the art of perfecting your designs and prints

Lucidwolf
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Joined: Sat Aug 25, 2018 12:31 pm

Re: Can you detune the extruder to still use poor filament (Skip not shred)

Post by Lucidwolf » Wed Aug 29, 2018 11:44 am

Also I forgot to mention at the start of this post that I am trying to learn the machine inside and out what is happening here is not in any way shape or form an issue with the part quality. This printer has out right spoiled me with accurate bed probing, duet controller, these fancy trick arms that have no backlash, huge bed, beefy aluminum frame, direct extruder, and 24v power. If i started with this machine I wouldn't know near as much because it would have been too easy. :D

I am used to taking 100 dollar kits adding 50 dollars of linear rails and getting them dimensionally hardy that kids/parents can beat on them for STEM activities, but that took a good amount of time.

As for alignment i used the trick of running a guide down the assembly prior to setting the gear and assembly. It looked lined up. Everything went together beautifully. I unfortunately didn't have the bag of screws for the thicker attachment so maybe i missed a part I should have. I have gotten quite proficient at tearing down the hotend maybe i can find a way to see if there is a gap so I can look again. I kept the screws loose enough on the assembly so that i could spin the manual feed with my pinky, because it felt right. I will let you know if i did anything I shouldn't have. Well build wise anyways. :lol: Its well established at this point there is a lot wrong with my usage.

I didn't have to adjust the filament feed when i calibrated that, and I love that caliper tool btw. I wish i would have known that sooner so i don't think I am over or under extruding.

When I did this i was doing torture tests to see how hard i could stick it to the build plate I know i was over pressurizing the nozzle to see when it would back off thinking that was a feature. Turns out it will just shred the filament like Conan the barbarian. I just learned something. :lol: I thought maybe I just had too much power.

Also i might just attach the cheap extruder motor to see if it behaves the same on the Titan Aero. For science of course. :lol:
All this energy is because I have a new toy to break and rebuild. :D I will settle down and stop spamming the forum.
You just have an engineer that is going hog wild. I will try to keep my bag of crazy contained because I just realized you probably have to respond to every post as the support guy... Sorry

Thanks for the response,
Lucidwolf

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mhackney
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Re: Can you detune the extruder to still use poor filament (Skip not shred)

Post by mhackney » Wed Aug 29, 2018 11:48 am

Make sure your first layer height is dead on. If your layers are supposed to be .2mm a single layer print should measure .2±.03 mm. If your first layer is too low there is no where for the filament to go and it can cause extruder issues like skipped steps/grinding. I'd start there.

I'm actually a "user" and not a support guy. I don't get paid for this.
www.SublimeLayers.com - Musings and Experiments on the Art and Technology of 3D Printing

Support me and my work at Patreon and get early access to my upcoming book 3D Printing Strategies - the art of perfecting your designs and prints

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UltiBots
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Re: Can you detune the extruder to still use poor filament (Skip not shred)

Post by UltiBots » Wed Aug 29, 2018 11:58 am

@mhackney = super "user" and friend of UltiBots. His depth of knowledge and experience with Delta printers are detailed at http://http://www.sublimelayers.com.
Brad - UltiBots LLC

Lucidwolf
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Re: Can you detune the extruder to still use poor filament (Skip not shred)

Post by Lucidwolf » Fri Aug 31, 2018 10:16 am

(M82) extruder absolute is a super important command to have in your slicer if the configuration file sets extrusion up as relative (M83)... :lol:
The extruder is a bit more forgiving if you don't try to exponentially jam more and more down its gullet. :roll:

You wanted to know how i was shredding it so bad and you were right it was so bad it had to be super easy.
This probably also means i need to add a M83 on the end of my slicer code or find a way for config to do that automatically after a print.

Lucidwolf
Posts: 14
Joined: Sat Aug 25, 2018 12:31 pm

Re: Can you detune the extruder to still use poor filament (Skip not shred)

Post by Lucidwolf » Mon Oct 01, 2018 11:06 am

While the M82 command was a bad slicer setting that didn't help; I still could not reach fast speeds without the risk of the filament getting chewed up from the hob gear.

Just thought I would follow up to my final solution:
1.) I added an access hole to clean the hob if it started stripping
2.) I reamed the entrance hole to the hob that is thru the arm so that a piece of tube could reduce the diameter and align with the hob better.
3.) I used a larger diameter nozzle to reduce back pressure and resolved myself to sub 100 mm/s speeds.

Then I decided to order the hardened hob from E3D since i was going to start printing more exotic filaments with this printer.
:shock: WOW. Now its acting like I expected. The geometry was way better than the original hob. I am back up to ludicrous speed.
With the extruder on the healing bench minus the nozzle i could pull filament through it like a pull cord and it would just spin the extruder motor without stripping or binding. It also had the Goldilocks pattern of just enough bite but not so much the filament is deformed.

So if you are having issues grinding filament maybe you just got a lemon hob gear.

I don't know what was up with my Aero kit because i had a questionable 0.4mm nozzle, a poor hob gear, and it didn't come with the right bolts to assemble. At least the replacement order all the parts were high quality. I am surprised because E3D is the gold standard.

Here is hoping with a hardened hob gear and a tungsten carbide nozzle there will be no material I can't print. :lol:

I have been documenting what I did post build on thingiverse if anyone is interested.
https://www.thingiverse.com/thing:3089764

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