Extruding Problems

I can't seem to complete any prints anymore on my 10in with hexagon hotend and PLA. I thought maybe it was an issue with moisture with my filament so I spent some time drying it out. Today I tried a test cube and as you can see from the results about iut 3/4 through it extruding all the way. http://m.imgur.com/TaGHP2b,jOWol0o I also have a picture of my filament after I pulled it out of the printer. It's been stripped so only I guess the outside of it remains.

I thought maybe this was from heat creep before but I have a fan on, all be it it's a strange configuration. Any ideas what I can do to solve this. It's been going on for some time now.

Is your filament getting chewed up when on retraction? I'm having an issue with that with some MakerGeeks PLA. Seems like everytime there are multiple retractions the filament gets chewed up by the hobbed bolt and there is nothing left to be gripped by the extruder.

Quote:

Originally Posted by untruehero

I can't seem to complete any prints anymore on my 10in with hexagon hotend and PLA. I thought maybe it was an issue with moisture with my filament so I spent some time drying it out. Today I tried a test cube and as you can see from the results about iut 3/4 through it extruding all the way. http://m.imgur.com/TaGHP2b,jOWol0o I also have a picture of my filament after I pulled it out of the printer. It's been stripped so only I guess the outside of it remains.

I thought maybe this was from heat creep before but I have a fan on, all be it it's a strange configuration. Any ideas what I can do to solve this. It's been going on for some time now.

Yes it's getting chewed up and this is makerfarm PLA. OK, that's really interesting. I'll have to try a different filament and see what the results are.

Any of a number of things can lead to extrusion stopping. All you can do is minimize the likelihood from each cause. One way to go about it is a divide-and-conquer approach based on whether or not the filament has a notch cut into it during the extrusion stoppage. The following assumes a stock Greg's accessible Wade extruder.

FILAMENT HAS A NOTCH CUT INTO IT BY THE HOBBED BOLT

Having a notch carved into the hobbed bolt suggests the problem is at or after the hobbed bolt drive. If there were issues with the extruder motor drive setting, the gearing, or the fit of the hobbed bolt in the extruder, the extruder motor would skip steps or stop rotating. Since this wouldn't put any stress on the filament at the hobbed bolt, there'd be no notch carved into the filament.

Make sure the teeth of the hobbed bolt are clean. Material cut or shaved from the filament during prior feed issues, or material caught on the teeth when removing hot filament could affect how well the teeth can bite into fresh filament. Consider hitting the hobbed bolt with a blast of compressed air before prints to remove anything loose. For cleaning stuff out of the hobbed bolt, a dental pick is a good start; if any filament was hard to remove with the dental pick I'll usually give the hobbed bolt a more thorough inspection/cleaning by removing it or at least removing the guidler block, using a stick pin (sharper point than my dental pick) for a final cleaning. Flush debris from the hobbed bolt area with compressed air before feeding new filament.

If the printer is a Pegasus or is using some other form of direct drive on the extruder, make sure the stepper motor mounting screws are tight. If they are loose, the motor can shift can make considerable difference in how the hobbed bolt is gripping the filament.

It could be the filament. I have one spool of filament that is thin, oval, and brittle. I'm lucky to complete any print with it. The hexagon hot end has been argued by many as undersized and overly sensitive to oversized filament OD issues. I've had filament with bumps in it that couldn't pass into the top of the 1.75mm hexagon hot end - I could often see rings around the filament where it caught on the top of the hot end. Some have suggested that moisture absorbing into long-unused filament can enlarge the filament, leading to issues with it fitting into the hot end. A few have drilled the hex hot end feed to a larger ID in order to minimize problems with the sensitivity to oversized filament.

Look down the filament path and make sure the cut of the hobbed bolt is properly aligned with the filament feed. Extruders like Greg's Wade with filament guide should have the cut in the hobbed bolt centered with the filament guide. Misalignment can lead to the filament rocking back and forth on the hobbed bolt, changing how the hobbed bolt grabs the filament as the filament moves around; some have argued the misalignment can lead to the filament twisting as it feeds.

If you're using 1.75mm filament in the stock wades extruder, the feed of the filament is already less than ideal since the extruder parts are sized to also handle the larger 3mm filament. Some have added a short length of 2mm ID aluminum tube, Bowden tubing, or empty ink tube from a Bic pen into the feed hole at the top of the extruder body to help with this. The feed tube extension can also help with some filaments that might flex or bow between the hobbed bolt and the extruder body; a few have had the filament actually fold over in this gap. I can't speak to it, but some have been told to lubricate the hot end with vegetable oil or olive oil to season a metal hot end with a lubricating surface. That might also help with cases where the sloppy 1.75mm filament fit causes the filament to be entering the hot end misaligned, rubbing against the wall of the feed hole.

Retraction can do it, caused by any combination of print design, retraction length and distance between retractions that causes the hobbed bolt to pass over the filament more than once. Each subsequent pass will weaken the filament more. Retract enough times over the same portion of filament and the hobbed bolt can simply start slicing away at the filament.

Likewise, don't get overzealous in retracting filament in the ending gcode after a print completes. Retracting hot filament up into the body of the hot end and allowing it to cool is asking for the filament to get stuck in the hot end or the hot end to get plugged up.

Extruder springs adjusted too tight might cause more cut into the filament than necessary. Springs too loose could lead to the hobbed bolt shaving off a thin layer of the filament instead of pushing the filament along. Personally though, I have never found the springs to make much difference when I'm having problems with the extrusion stopping.

The filament spool needs to unwind very smoothly. If it catches or sticks as it unrolls, that adds to the risk of problems. The stock MakerFarm spool holder that mounts to the top of the printer has been a problem for multiple users.

Make sure the bearing in the guidler arm spins freely. This is the bearing that presses the filament against the hobbed bolt. Printed Greg's Wade parts shipped by MakerFarm usually need to be cleaned up quite a bit in order to prevent the bearing from rubbing on the square hole in the guidler.

Marginally low hot end temperature could lead to problems, especially when combined with print cooling airflow that inadvertently cools the filament in the nozzle tip and/or print speeds that are too high for the print temperature.

Melted filament has to have somewhere to go in order for fresh filament to be able to feed into the hot end. Extrusion stoppage could suggest the nozzle tip is too close to the print surface on the first layer or not being raised properly between subsequent layers. Only in rare cases have people reported finding contaminants that were plugging up the nozzle and forcing the extrusion to stop, but it does happen. Some add a felt disk (like a Dremel buffer wheel) to the top of the extruder to wipe dust and other loose contaminants off the filament as it is pulled into the extruder.

NO NOTCH IS CUT INTO THE FILAMENT

When no notch is cut into the filament, there's a chance that the bite of the hobbed bolt into the filament is so perfect that the extruder motor is forced to stop rotating, but there's more likely to be an issue with the hobbed bolt drive.

With the filament removed from the extruder and motors disabled or the printer off, manually rotate the large gear through an entire rotation. There'll be cogging from the extruder motor, but the gear should rotate with a consistent feel. Watch for the large gear being hard to rotate or the rotation feeling rough or tending to catch at times, indicating a mechanical problem that needs attention.

Make sure the small gear is tight on the extruder motor shaft. I wouldn't bother to try using a motor without a flat for the set screw on a printed gear that can't withstand overtightening, but there are round-shaft motors out there.

For a Greg's Wade extruder, if the extrusion issue started after installation of new printed gears, perhaps the gears didn't print cleanly. The teeth on the 9-tooth gear can be especially challenging to print without a good handle on print thermal management. Improperly shaped teeth might not be easy to see, but they could lead to problems meshing with the large gear.

Is the current limit on the stepper motor driver adjusted properly? Are the extruder motor firmware settings for acceleration and feed rate suitable for your setup? As diagnostic insight, you could always try a higher current limit on the driver, less acceleration and/or lower feed rate.

If using the herringbone gears like Greg's Wade, recheck proper gear alignment. I usually do this by loosening the small gear on the extruder motor and repositioning the small gear on the shaft for smoothest gear mesh when manually rotating the large gear. You can't just check alignment visually, since the herringbone teeth will somewhat "pull" the teeth into alignment but still leave the gears meshing roughly. Check for proper spacing between the extruder motor and extruder body while you're at it. It's not unusual to have to elongate the motor mount holes in the Greg's Wade body provided by MakerFarm in order to obtain proper mesh.

Make sure the nuts on the hobbed bolt haven't tightened to the point that the hobbed bolt can't spin freely in the extruder body. Don't try to use a nylon lock nut on the hobbed bolt - I found that the repeated start/stop motion of the hobbed bolt tended to tighten the locknut over time. Two nuts need to be used, with the nuts wrench-tight against each other.

IMPROVEMENTS TO THE GREG'S ACCESSIBLE WADES EXTRUDER

FWIW, I have an updated Greg's Wade extruder with improvements over the stock MakerFarm parts that might help with some of these possible issues.

A shim washer is provided for use with the bearing on the large gear side. The shim washer helps prevent the inner race of the bearing from binding up on the extruder body.
The guidler arm has been tweaked to improve the clearance around the guidler bearing.
Spacing of the motor mount holes has been improved for the 9/47 gears. I believe the extruder body MakerFarm uses is based on an older Greg's Wade design intended to be used with 11/45 gears, which would require a slightly different optimal hole spacing.
A small block is provided for use on the exposed spring bolt. The small block can be used for mounting an LED that illuminates the hobbed bolt area for inspection/cleaning.
The revamped openSCAD source simplifies what it takes to optimize the parts for use with 3mm vs 1.75mm filament.
The revamped openSCAD source also simplifies what it takes to change hole sizing, like the motor shaft hole in the 9-tooth extruder gear. Resizing the hole design is better than pounding the gear onto the shaft, drilling it out, or trying to use a gear with a too-large shaft hole.