Replaced hotend on brand new printer after jam. Now it clicks.
 
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rachel.s5
(@rachel-s5)
Active Member
Replaced hotend on brand new printer after jam. Now it clicks.

Hi All, 

Printer with only a few hours of prints. Prusa had me replace the entire hot-end to fix a jam. After the hot-end replacement extruder started to click/shift. I find it hard that they aren't related, I assume I made a mistake or knocked something out of place, but support was having me look at z-level and firmware. Firmware is up to date, and z-level is well its variable...let me explain. 

I found a video on Prusa's that claimed that the issue was caused by a dowel in between two gears on the feeder door. I took it out, and didn't notice anything knocked out of place, but made sure it was dead center and put it back. When reassembling I got the most results with the spring loaded screw on the side that attaches to the feeder. If its loose the skipping seems to stop, but then extrusion halts or is just a drip. If its tighter it will extrude more but starts skipping. I tried for hours to find the sweet spot between z-level, tightness of this spring, and extrusion amount and I can not for the life of me. Which is making me believe there is still something out of wack, too lose, or too tight from my hotend replacement or what. 

 

Anyone have any ideas. I just want to play with my printer =(

Posted : 21/06/2019 4:00 pm
Dave Avery
(@dave-avery)
Honorable Member
RE: Replaced hotend on brand new printer after jam. Now it clicks.

hot end too cold?

Posted : 21/06/2019 4:02 pm
rachel.s5
(@rachel-s5)
Active Member
Topic starter answered:
RE: Replaced hotend on brand new printer after jam. Now it clicks.

How would I check? All fans are go, and everything gets up to 215/60 

 

 

Posted : 21/06/2019 4:14 pm
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(@)
Illustrious Member
RE: Replaced hotend on brand new printer after jam. Now it clicks.

Rachel - a photo of a bad print really helps to narrow down suspect reasons.  Simply drag an image into the text box, a bluish background appears and when you drop the image a media dialog opens.  In the dialog is a Link To option, make sure you Link To Media File. Then press the Insert button to get back to the text box.

First, an observation that you replaced the entire hot end for a jam; that seems a bit excessive. Not unheard of, but not common.

The tension screw has quite a wide range of normal operation. If you are having trouble there, I'd look first at the idler axle to verify it is "centered", which it seems you have done; then at whether or not the Bondtech gears are properly aligned with the filament path.  These are pretty simple to look at and fix.  While looking at the gear, make sure the set screw is aligned and perpendicular with the flat area on the motor shaft. 

Next I'd look at the nozzle.  I'm presuming it's a standard 0.4 mm brass nozzle. I also assume it is new and this is the first roll of filament you've tried.  What is the filament? Brand & type?  In all cases, when extrusion just isn't working as expected, it never hurts to try printing hotter.  Raise the print temp 20c and try extruding 50 or 100 mm of filament manually.  Basically, what you want to do is go into settings, move the X-Axis up towards the top of the printer, preheat the nozzle temp to 230c, then using the Move Axis - Extruder to roll the number +100 counts (if it's at +54, roll it to +154). Rolling -, or negative, will unload the filament, you don't want to do that right now.  Only go +, positive, and don't worry if you overshoot. Just let it run.  This process will make the extruder push 100 mm of filament, creating a small pile of filament on the bed.  But it should flow evenly and without clicking.  Then lower the nozzle temp to 210c and repeat the +100 process. Filament should still flow evenly.

During this process, if you hear clicking and the filament above the extruder is "jumping" - try adjusting the idler door tension screw with more or less tension to see if it has any effect. If no, then try to center the tension range and we can try something else.

With the nozzle at 180c, take a piece of PLA filament and try pushing it against the nozzle.  It should melt pretty easily.  Don't worry about making a mess, the plastic comes off pretty easily, but keep the melting to one side of the cone area.  If the plastic isn't melting easily, try raising the nozzle temp to 230c and try again.  What you're looking for is a ballpark calibration of the nozzle temperature range. At 230c, the PLA should readily melt, and may even drip off.

If the above steps don't reveal any problems, then a deeper dive is required.  

This post was modified 5 years ago by --
Posted : 21/06/2019 5:07 pm
rachel.s5
(@rachel-s5)
Active Member
Topic starter answered:
RE: Replaced hotend on brand new printer after jam. Now it clicks.

Thank you for your detailed explanation, and info that will probably help in the future. 

 

Still too early to tell, but I finally found the sweet spot of LOOSING the screw off to the left (what is this called?) and then on then TIGHTING the two screws on the back (which were removed for hotend replacement) it was extruding and no longer clicking -- but it still WOULDN'T get a good print. No matter what zlevel I set it to (probably did damage to my plate and nozzle) 

 

Finally decided since it was so random and everything else seemed accounted for, to hit the build plate with some rubbing alcohol and viola. About an hour into a good looking print. Fingers crossed!

 

Posted : 21/06/2019 6:34 pm
rachel.s5
(@rachel-s5)
Active Member
Topic starter answered:
RE: Replaced hotend on brand new printer after jam. Now it clicks.

First successful print i weeks, but pretty big seperation between the layers any idea?

 

Posted : 21/06/2019 7:30 pm
rachel.s5
(@rachel-s5)
Active Member
Topic starter answered:
RE: Replaced hotend on brand new printer after jam. Now it clicks.

It still has an issue of that left screw spring. Too tight and it clicks, too loose and not enough filament to make a good firstlayer. 

Posted : 21/06/2019 7:57 pm
rachel.s5
(@rachel-s5)
Active Member
Topic starter answered:
RE: Replaced hotend on brand new printer after jam. Now it clicks.

Will do as you advise with manual extrusion this afternoon. 

Posted : 21/06/2019 7:58 pm
rachel.s5
(@rachel-s5)
Active Member
Topic starter answered:
RE: Replaced hotend on brand new printer after jam. Now it clicks.

Heres an example of first layer calibration. Everything is so inconsisntat. Sometimes it will be perfect all the way tight, others it'll be clicking like mad. 

 

 

 

Attachment removed
Posted : 21/06/2019 9:26 pm
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(@)
Illustrious Member
RE: Replaced hotend on brand new printer after jam. Now it clicks.

Okay - not sure which screws you mention. 

There is a right side back to front screw that holds the idler gear door on - that screw must not be too tight, the idler door must be able to swing freely (when not being held closed with the tension screw).  The idler door tension screw, goes left to right, needs to be several turns in once the spring is engaged. This is part skill, part art-form; but too loose or too tight will cause filament feed problems.

The built in Z-calibration test is too short to really help dial in Z-offset.  I use this cal circle (STL's are attached).  The result should be a welded disk of plastic similar to this image.

Cal Circles

Generate a gcode using the 0.15 mm default profile, Prusa filament.  

The bed surface is easily fouled with fingerprints. One is more than enough to ruin a print. Soap and hot water work best to clean and ensure good adhesion.  Here are my recipes for bed maintenance.

Alcohol rinse: every few prints

  • Gloves recommended.
  • Once in a while, an alcohol rinse is helpful to remove PLA residue. It does not remove finger oils well.
  • Pour a 5 cm puddle of 91%+ alcohol in the middle of the bed, with clean hands use a fresh paper towel to scrub the bed. Wipe up all the alcohol.

Acetone wash: infrequent

  • Pour a 2 cm puddle of acetone on the bed, scrub it around with a fresh paper towel. It will evaporate fast as you clean. This step removes PEI oxides that form over time and with heat, and improves PLA adhesion to a like new state.

 

Hot Water wash: often, as needed, and after any of the above

  • Handle the bed only by the edges.
  • Wash the bed in hot water, use a fresh paper towel as a wash cloth, with a few drops of plain dish soap (Dawn, unscented, no anti-bacterial, etc.).
  • Rinse well in hot water - if you have very soft water, rinse a bit longer.
  • Dry the bed with a fresh paper towel.
  • Handle the bed only by the edges.
  • Place bed on printer.

 

Streak test: when contamination is suspected

  • With a fresh piece of paper towel, and very clean fingers or gloves, dampen the towel with 91%+ alcohol, and wipe the bed side to side moving back to front, like you're painting it with alcohol. The alcohol should be thin enough on the towel it quickly evaporates. If you see any streaks, the bed is dirty and needs a wash.

 

 

Posted : 21/06/2019 11:06 pm
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(@)
Illustrious Member
RE: Replaced hotend on brand new printer after jam. Now it clicks.

As for the frog; it's a bit fuzzy, but I don't really see any major issues with it.  Here's one of my frogs for comparison. He has a coat of water color paint, but otherwise normal default print.

This post was modified 5 years ago by --
Posted : 21/06/2019 11:09 pm
rachel.s5
(@rachel-s5)
Active Member
Topic starter answered:
RE: Replaced hotend on brand new printer after jam. Now it clicks.

No the frog was real off. I could feel him breaking in between two fingers. The layers had visable gaps in them. Thanks for the two cents on the soap&water not good on oil! Ill give it another clean later.

After testing the art form of the idler spring, and different filaments. I noticed that the initial grab of a new material, didn't skip but it started to skip once the new material was nearing the nozzle. Just for laughs I stuck up a acupuncture stick. Didn't feel anything major and didn't go in that far, but seemed to help. Printing the gear/bearing now and its flawless. No noise, perfect first layer, I could see the issues as the frog printed - this I see none. 

 

Either I'm getting really lucky or the combination of all the little things is adding up. How often do you find yourself cleaning the inside of the nozzle? Is this done hot or cold?

 

I'm also super nervous about getting another jam, mine was bad and it was only like the 5th print. 

 

Posted : 21/06/2019 11:25 pm
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(@)
Illustrious Member
RE: Replaced hotend on brand new printer after jam. Now it clicks.

I've never had the needle do anything of value.  And if there is something in the orifice that is plugging the flow, pushing it back up into the nozzle sure doesn't seem like a long term solution.  Cold pulls remove debris that gets into the nozzle. The needle just moves it around.  But Prusa ships the needle for a reason; perhaps there are things I haven't experienced yet, like a burr on the nozzle? 

That said, if it's working, then run with it until it starts happening again.  The "Don't fix what isn't broken" mantra.  Keep an eye for small "why did it do that?" moments, they may lend insight into what is causing the plugging in the first place. 

Cold pulls are done whenever you suspect something is plugging the nozzle.  It is a really simple and easy process.

Start with the printer cold, below 30c is best.

  • Open the idler door completely.
  • Set nozzle temp to 100c then go to the next step - don't wait for the temp to hit 100c.
  • Immediately start pulling up on the filament (pull from above the extruder).  Some use pliers to lever off the extruder so they aren't lifting the printer;  I use bare fingers and pull just hard enough I'm not quite lifting the printer off the table.  
  • At some point you'll feel the filament start to give, keep pulling, and after a few seconds it will come loose and you can pull the end up out of the extruder.
  • Turn off the nozzle heat.

The tip of a good cold pull will have a nice looking rocket nose cone shape. A great pull has the 0.40 mm orifice, too.

For reference, a nozzle is about 12 mm long, and the melt zone continues into the heat break another 5 mm ... that's about how far a needle can make it before hitting cold plastic.  A jam is usually in the first mm. 

Posted : 23/06/2019 12:25 am
rachel.s5
(@rachel-s5)
Active Member
Topic starter answered:
RE: Replaced hotend on brand new printer after jam. Now it clicks.

Still absolutely hit or miss. Tried 210 to 230 prints. Loose, tight, or medium on the side screw. Multiple filaments. Cold pull. Cleaning my bed. The first layer usually seems decent but than it starts to crap out. Seriously i've had an absolutely flawless Benchy, followed by an atrocious batman.

With the idlear door open, I've ensured that one gear is in good shape, what about the other gear in the feeder? The one that isn't attached to the door. Should I be ensuring the dowel in that one is in good placement. Any guide on how to get at it? I'm running out of ideas. 

 

See print =( 

 

Posted : 23/06/2019 10:23 pm
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(@)
Illustrious Member
RE: Replaced hotend on brand new printer after jam. Now it clicks.

Two gears - a set - one is attached to the E-axis motor shaft, the other spins on an axle shaft that is held by two ears on the door.   This gear on the door is the idler. If you press on it with your finger, it should be solid and not give or flex.  The axle, a stainless pin that should be centered in the two ears. This video is for a MK3, but it applies to the MK3S.

https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-hardware-firmware-and-software-help/prusa-needs-to-fix-the-bondtech-idler-shaft/#post-130443

A loose gear on the E-axis motor shouldn't cause "clicking", but at this point it's worth checking if it is installed right. Check that the set screw is centered on the motor shaft flat.  Anywhere else and you can have extrusion problems.  The set screw should not extend out above the gear - it must be inset or at worst flush.

This brings me to one other question:  which spool holder are you using?

Posted : 23/06/2019 11:05 pm
GregB
(@gregb)
Trusted Member
RE: Replaced hotend on brand new printer after jam. Now it clicks.

Are we still having this problem?  Have you checked to make sure the Bondtech set screw is tight?

Mine fell out and disappeared.  It is the world's smallest screw and since the extruder assembly is also black you'll never see if it's hidden  inside somewhere.

Posted : 27/06/2019 12:18 pm
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