Backpressure Issue

[javiercordero20]

Hello All,


I keep having an issue with my V3 with Backpressure. I have rebuilt the hotend three times and made sure the filament can pass through to the nozzle without much issues. Yesterday I managed to get 2 prints done but today the problem is back. I could use some advice and help to solve this issue once and for all.

Preferably over something like Skype so I can show the issue and diagnose it together.

Things I have tried:
- Check Extruder gear tension
- Clean hobbed bolt and checked alignment.
- cleaned and rebuilt Hotend
- checked for clogs (hockey puck)

Sincerely,
J.D. Corero

[mhackney]

Javier, the original problem we diagnosed on Saturday was due to having way too high retract speed (110mm/s). You changed that to 25mm/s and printed 2 parts successfully. Did you switch slicers from Cura to S3D? Did you inadvertently change the retract or other settings? The BandAid print that I saw photos of was quite good. I assert you do not have a hotend or extruder problem (with the caveat that the hob gear needs to be cleaned, the Bowden inserted completely on both ends, etc).

[javiercordero20]

Javier, the original problem we diagnosed on Saturday was due to having way too high retract speed (110mm/s). You changed that to 25mm/s and printed 2 parts successfully. Did you switch slicers from Cura to S3D? Did you inadvertently change the retract or other settings? The BandAid print that I saw photos of was quite good. I assert you do not have a hotend or extruder problem (with the caveat that the hob gear needs to be cleaned, the Bowden inserted completely on both ends, etc).

Hello Again,

As I stated in messenger, I have decided to try Octoprint as you mentioned in your build log in hopes of solving my issues. I installed octoprint and added the configured and files you linked in your buildlog. I then tried to print a 20mm cube. First I tried printing it on my Buildtak but immediatly got an issue with the nozzle printing to deep into the buildtak to the point it might become impossible to remove. I could not find a Z-Offset in octoprint so I flipped my buildplate to the glass side and added a little gluestick to allow the PLA to stick to it. I noticed that the print time was extremely quick.

In MC with MatterSlice it took 1hr~
in S3D its 25min
In Octoprint its 12-15min

I have a suspicion that speed is not the solution.

When the print started it printed at a blazing speed and about half way through the print I heard it start to skip. I concluded that it skipped while putting down the infill for the cube.

Here is a picture of the cube after I canceled the print.

I hope this information is helpful to finding the cause of my problems.

Sincerely,
J.D. Cordero

[mhackney]

I'm sorry if you misunderstood, at no point did I ever offer that OctoPrint (or any control program for that matter) would solve your problem. OctoPrint is a nice web based control program and does have some advantageous when run from a RaspberryPi over using your PC as a controller but you are just spinning your wheels as far as solving your printing problem is concerned.

Are you using the V3 auto calibration script? It not only calibrates your printer but will set the Z height properly too. I run it several times a day as my printer changes with use, temperature, humidity, etc. You run the script, it takes care of the rest.

How are you slicing this part? You mention MatterSlicer and then S3D. Are you generating gcode from those slicers and uploading the gcode to OctoPrint? You likely got filament starvation because you are printing at ridiculously fast speeds due to not setting slicer parameters.

The solution is to 1) understand what is going on and 2) make careful observations and 3) be consistent and only change ONE THING at a time and 4) repeat. And as I've recommended, read the link in my signature. 10 minutes will save you hours of frustration.

[javiercordero20]

I'm sorry if you misunderstood, at no point did I ever offer that OctoPrint (or any control program for that matter) would solve your problem. OctoPrint is a nice web based control program and does have some advantageous when run from a RaspberryPi over using your PC as a controller but you are just spinning your wheels as far as solving your printing problem is concerned.

Are you using the V3 auto calibration script? It not only calibrates your printer but will set the Z height properly too. I run it several times a day as my printer changes with use, temperature, humidity, etc. You run the script, it takes care of the rest.

How are you slicing this part? You mention MatterSlicer and then S3D. Are you generating gcode from those slicers and uploading the gcode to OctoPrint? You likely got filament starvation because you are printing at ridiculously fast speeds due to not setting slicer parameters.

The solution is to 1) understand what is going on and 2) make careful observations and 3) be consistent and only change ONE THING at a time and 4) repeat. And as I've recommended, read the link in my signature. 10 minutes will save you hours of frustration.

Hello,

Whenever I move or touch the bed plate I run the calibration script which is on a SD card in the printer.

I am slicing the files on Octoprint Itself using the Cura Engine and the Cura config file mentioned in your Build Log.

[mhackney]

Post the gcode please. That way we can verify that the settings are all correct. If you observed it printing that fast, something is very wrong.

[mhackney]

Oh, and you do not have to message me with a link to this thread in Facebook. I'll see updates when I am have the time.
Thanks.

[javiercordero20]

Post the gcode please. That way we can verify that the settings are all correct. If you observed it printing that fast, something is very wrong.

Here's the file (sliced with Cura Engine on octoprint):

20mm_Cube.gco

(162.22 KiB) Downloaded 206 times

[javiercordero20]

Hello,

Extruding with the Effector homed skips..

[mhackney]

The speeds in the gcode look reasonable. I can't tell what the extrusion width/orifice diameter is though. If it is too small (<.5mm) then you could neb attempting to push too much filament through a small opening.

My recommendation, read the link in my signature. Print the single layer test object starting at a very slow 20mm/s (pay attention to items 3, 4, 5 and 8).

When I have time later I'll print the gcode you posted just to see if there is anything amiss.

At this point you could have some subtle issue that manifests itself under certain conditions. A burr or debris in the nozzle, a slipping cog on the extruder, a misaligned cog in the extruder, etc.

[mhackney]

We call that "extruding into air". How fast and how many mm of filament were you extruding into air?

Let's start with this then since it is the simples way to reproduce your problem. I am asking that you not attempt to print anything until we can successfully extrude several hundred mm of filament into air at a reasonable speed without skipping.

Start slow, extrude 50 mm at 10mm/s and let's see what happens. To do this, you are not going to use the jog controls on the Control tab - not this:

Instead, you are going to use the console input field on the Terminal tab - this:

This will let you explicitly state ho much and how fast to extrude. You will enter gcode directly into this field. Here is the first extrusion you are going to enter:

M83 ; set extruder to relative mode

G1 F300 E100

This says extrude 100mm of filament at 300 mm/min. G1 is the move gcode, F is the speed and E is the length of filament to extrude. I can't test this right this because I'm in the middle of a print. But give it a try and report back what happens.

Make sure that the filament is not chewed up and that the extruder cog is not filled with plastic.

[mhackney]

Note, you do not have to enter the comment, just enter

M83

to set the extruder to relative mode

[javiercordero20]

We call that "extruding into air". How fast and how many mm of filament were you extruding into air?

Let's start with this then since it is the simples way to reproduce your problem. I am asking that you not attempt to print anything until we can successfully extrude several hundred mm of filament into air at a reasonable speed without skipping.

Start slow, extrude 50 mm at 10mm/s and let's see what happens. To do this, you are not going to use the jog controls on the Control tab - not this:
Screen Shot 2016-10-10 at 9.41.41 PM.png

Instead, you are going to use the console input field on the Terminal tab - this:
Screen Shot 2016-10-10 at 9.37.26 PM.png

This will let you explicitly state ho much and how fast to extrude. You will enter gcode directly into this field. Here is the first extrusion you are going to enter:

M83 ; set extruder to relative mode

G1 F300 E100

This says extrude 100mm of filament at 300 mm/min. G1 is the move gcode, F is the speed and E is the length of filament to extrude. I can't test this right this because I'm in the middle of a print. But give it a try and report back what happens.

Make sure that the filament is not chewed up and that the extruder cog is not filled with plastic.

Hello,

While you were writing this post I removed the nozzle inorder to see if it was clogged. I then tried something silly. I heated the block and told it to extrude. With no nozzle you would expect it to extrude cleanly and easily as its not forcing the filament through a small opening but.. it skips..

Sincerely,
J.D. Cordero

[mhackney]

Yikes! That's not a good thing to do as you get molten filament in the threads where the nozzle screws in and makes it very difficult to assemble correctly. But the good news is, at least you now know it isn't the heater/nozzle. You could still have a snag in the cold zone or there could be a problem with the extruder (the items I listed in the earlier post).

[mhackney]

Since you've gone this far with removing the nozzle, try this:

leave the nozzle off and heat up. Then push some filament through the bowden by hand - disconnect the bowden from the extruder to do this. This will let you test everything below the extruder.

[javiercordero20]

Yikes! That's not a good thing to do as you get molten filament in the threads where the nozzle screws in and makes it very difficult to assemble correctly. But the good news is, at least you now know it isn't the heater/nozzle. You could still have a snag in the cold zone or there could be a problem with the extruder (the items I listed in the earlier post).

Hello,

Before doing this silly test I removed, cleaned, and rebuilt the extruder. I happened to have two other ones of the same type/model. So I can easily swap hobbed bolts or complete assemblies but as mentioned above it still skips even with this new/fresh hobbed bolt and rebuilt extruder. I can try another but this extruder assembly came from a printer and it worked.

Sincerely,
J.D. Cordero

[javiercordero20]

Since you've gone this far with removing the nozzle, try this:

leave the nozzle off and heat up. Then push some filament through the bowden by hand - disconnect the bowden from the extruder to do this. This will let you test everything below the extruder.

Will Do.

[mhackney]

Given everything you've said and done it really seems like there is some silly thing happening. It should not be this difficult to get good extrusion. Although not trivial, there aren't that many things that can be problematic and you seemingly have isolated each of those and verified no problem, yet when they are all together, you have a problem.

It could still be related to the bowden insertion in the cold end forming the plug you had over the weekend. Have you checked for a plug in that area again?

[javiercordero20]

Since you've gone this far with removing the nozzle, try this:

leave the nozzle off and heat up. Then push some filament through the bowden by hand - disconnect the bowden from the extruder to do this. This will let you test everything below the extruder.

Will Do.

Hello,

First try - It didn't go through. It was hard as a rock.
Second try (with short tube) - went through easily. possibly was partially clogged.
Third Try - Went through easily

Sincerely,
J.D. Cordero

[mhackney]

I don't understand how you tested. What do you mean by "short tube"? What was third try, short tube (whatever that is) or the standard bowden. Maybe some photos would help.

[javiercordero20]

I don't understand how you tested. What do you mean by "short tube"? What was third try, short tube (whatever that is) or the standard bowden. Maybe some photos would help.

Hello,

Let me explain.

For the first attempt I just disconnected the Bowden tube from the Extruder and left it connected to the hotend and tried to manually feed filament through it. It didn't work. The filament ended up getting stuck in the hotend somewhere. Once that didn't work I used a second bowden tube I had which I cut down to about 5-8cm. This is what I refer to as the short tube. I used the short tube to figure out if maybe the long bowden tube wasn't properly pushed in all the way..

Short tube:

I hope this clarifies my explanation.

Sincerely,
J.D. Cordero

[mhackney]

Yes, that clarifies, thank you.

Have you checked for that plug?

Also, have you checked that filament can be easily pushed the full length of the bowden, there might be a kink or something?

The one thing that changed in your 3 tests was the removal and reinsertion of the bowden into the hot end. Ad the second and third tests were good - i.e. the path was not obstructed in any way.

[mhackney]

By the way, using a short tube like that is a good idea for testing things.

[javiercordero20]

Yes, that clarifies, thank you.

Have you checked for that plug?

Also, have you checked that filament can be easily pushed the full length of the bowden, there might be a kink or something?

The one thing that changed in your 3 tests was the removal and reinsertion of the bowden into the hot end. Ad the second and third tests were good - i.e. the path was not obstructed in any way.

Hello,

With the full length bowden tube and the hotend without a nozzle I can push it through with no resistance.. What are the chances the nozzle could be the issue? If so.. I have a Hardened 0.4mm Nozzle I can try. What do you think?

Sincerely,
J.D. Cordero

[mhackney]

Nozzles can be defective or clogged with debris. Can you check with the nozzle installed again now?