Welcome to the SeeMeCNC Community

looking for some help here.

Small prints work just fine, large prints always run into this same problem of the extruder starting to skip pretty regularly after the first few hours of printing. the bottom half of the prints look great, but the farther up, the worse they get. (see picture)

This is a V2 Max and I have the E3D V6 hot end. ( I had a V5, and stock hot end on it before with the same problem) I'm running Seemecnc's version of repetier firmware .91. The only things I have adjusted in the firmware are the motor currents, because I have the kysan motors, and the type of thermistor for the E3d hot end.

I have tried everything I can possibly think of to try and fix this, but it never seems to go away. I have adjusted temperatures, currents, speeds and types/brands/colors of filament. I have checked the temperature of the extruder motor when it starts to skip and its not overly hot. the Rambo board and the hot end both have working cooling fans as they should. I have replaced the nozzle, bowden tube and hobbed drive gear (same size just more bite on the teeth)
I do print almost exclusively with pla as I use it to burn out for investment casting (which works wonderfully well by the way) but abs prints exhibit similar behavior.

after its skipping badly like in the photo, I can stop it, and immediately start a new print and it will print just fine for the first few inches, and then start with the same behavior again.

I have two other V1 Rostocks and they are set up almost identical to this one with the exception that they are running an older version of firmware. They both print flawlessly with pla no matter how many hours the prints are. I have ran over 100lbs of pla through one of these printers alone. They are incredibly reliable and I have almost never had a jam or problem with them. most prints I do are 10-20 hours.

ever since I got this new V2 I have never been able to get consistent reliable prints from it. its frustrating because its older counterpart is sitting right next to it and runs flawlessly

Anyone out there have any additional ideas for me to try? I really need this printer up and working reliably. It has a pretty big backlog of work waiting for it.

Thanks,

Mechneering

If the skipping is only occurs above a certain height, it must be caused by an increase in friction in the filament path as the head rises. You've eliminated an overly hot extruder based on other details.

It could be increased friction in bowden tube like Earthbound said.
You could try using the bowden tube from the reliable printer.

Does the reliable v1 have the old side mounted extruder or top mount?
"Steves" extruder or EzStruder?


You could also use a geared stepper motor on your v2 ezStruder to get more torque.


Try dipping end of filament in canola oil before feeding in printer. Recently in another post by nitewatchman he claims it works wonders to eliminate his PLA jams.

What hot end and nozzle size?

I had to cut down the tube about 7-8 inches because it would bind when the arms approached the top. Now it's basically pulled tight when all the way on the outer edges of the build plate and much better at the top. I also don't route it through the plastic mesh, it just does it's own thing swinging in the wind.

I have replaced the bowden tube once thinking it was the problem and also shortened it. But to no avail. Adding a bit of lube to the inside of the tube sounds like something worth trying.

My older V1 has the upgraded trick laser top mount ezstruder setup. And the V2 has the stock top mount. I'm also running a .4 nozzle.

The reason I figured it wasn't the bowden tube is because in Repetier host I can home the towers where the carrier is all the way to the top and the bowden tube is most bent/looped and it will extrude manually just fine.

Thanks for your ideas, I will continue to experiment.

Would there be any benefit to having the PTFE tube come out of the ezstruder and after about an inch put a coupler to a large size tube? Then down near the hotend use another coupler to bring it in to its normal size?
that would eliminate any friction for about 9/10 of the length of the tube, and the biggest part of your friction equation?

dunginhawk wrote:Would there be any benefit to having the PTFE tube come out of the ezstruder and after about an inch put a coupler to a large size tube? Then down near the hotend use another coupler to bring it in to its normal size?
that would eliminate any friction for about 9/10 of the length of the tube, and the biggest part of your friction equation?

This would be a bad idea because of hysteresis of the filament through the tube during retracts. The tube needs to be as tight as possible around the filament without it binding to provide consistent filament feed and good retracts.

EDIT: Here's a good explanation of it... http://reprap.org/wiki/Erik's_Bowden_Extruder#Drawback

The Bowden cable system has one major drawback: Hysteresis. The plastic filament will compress in any extruder, but putting pressure on such a long length of filament will multiply the effects of this compression, leading to springiness. The flexibility of the PFTE tube exacerbates this problem.

dunginhawk wrote:Would there be any benefit to having the PTFE tube come out of the ezstruder and after about an inch put a coupler to a large size tube? Then down near the hotend use another coupler to bring it in to its normal size?
that would eliminate any friction for about 9/10 of the length of the tube, and the biggest part of your friction equation?

I don't think that would work. The basis of how a bowden tube works is by constraining the filament inside the tube as its pushed from above. if the tube gets larger, the filament has more play and slop, and will more likely bend or fold inside the larger tube. And the retracts would have to be much larger to account for the extra play of the filament inside the tube.

thanks for clearing that up... i didnt think about the retracts... I may work something like that up for ninja or copperfil that doesnt require retracts... i like to tinker

I personally would like to see a lightweight micro cold end sitting an inch above the hot end and do away with the bowden tube for the most part. I'm sure the swinging mass would be a problem though.

Let's see, put the drive gear down at the print head and run a rotating Bowden up to the frame where the motor is. Spin the Bowden like a spedo cable and turn the gear down at the head.

jdurand wrote:Let's see, put the drive gear down at the print head and run a rotating Bowden up to the frame where the motor is. Spin the Bowden like a spedo cable and turn the gear down at the head.

That idea is crazy enough it just might work! the trouble is getting a flexible drive shaft that will effectively transfer the torque to the drive gear without too much rotational flex. Not sure if rotational flex it the right term, but something along the lines of rotational built up energy or springiness, due to the construction of the flexible drive shaft.


And back to my original issue, I took the bowden tube out of the plastic sheath and added a bit of oil to the inside of the tube. I did one tall test print and it seems at the moment to be working better. So you guys were right, it appears that the friction inside the tube was causing the problem.

THIS is NOT my rostock
[youtube]http://www.youtube.com/watch?v=_ZEVGcxJ0Qg[/youtube]

It is filament starving. My best (educated) guess based on 1) you are printing PLA 2) the description that you can stop, restart and it prints fine, 3) it's a new machine 4) an E3D v6 hotend is that a) your retract setting is too fast (what is it?) and/or b) have you measured the bore length in your nozzle? If so, what was it? Also, make sure the nozzle is clear with no machining burrs.

I had an issue once where end of the filament went under an adjacent loop because I didnt pay attention when i set it up. So as it pulled it would frequently get stuck and snap. But at first it worked pretty well probably because of the larger diameter of the curl in the filament. I didn't notice it for a long time. I thought I had bad filament.

Having similar issues with my prints. Stock hotend. Appears to be a soldering issue on my resistors. Still looking into.

So after a lot of troubleshooting and frustration, I think I have finally figured out what the issue was with my printer. My thermistor temperature reading has been way off. (I thought I checked that) not sure why, perhaps its just a bad thermistor, but ether way it was reading about 30 deg. hotter than the hot end actually was. Thus I have been trying to print pla with a hot end around 160-170 deg C. much to cold to work reliably, and that was what has been causing my extruder motor to skip so much. The force required to push the cold filament through the nozzle was just to much for it.

I haven't changed out the thermistor yet, but if I print pla at a software setting temp of 230, and an actual temp of closer to 200, the prints are working great.

I have also checked and rechecked the firmware to make sure I have the right thermistor type selected so I'm pretty sure that's not the issue, but maybe...

the canola oil helped a bit, but not a long term fix. Freeing the bowden tube from the wire bundle going to the hot end also helped.

I've had a lot of trouble recently. It's revolving around the hotend. I really want a drop in solution as that thermistor in the hotend is the bane of my existence in 3d printing. I think Seemecnc is creating this.

netdefilr wrote:Having similar issues with my prints. Stock hotend. Appears to be a soldering issue on my resistors. Still looking into.

I do hope that you did not solder the wires going to the resistors, these must be crimped, not soldered...the heat is too great in this area and
solder will melt. You can purchase a screw-in thermistor on Ebay at this link:
http://www.ebay.com/itm/Modular-Screw-o ... 4ad175c679

The other thing is those thermistors are sensitive. I have my iron on at least 350C normally, they defect at 300C. Its pretty easy to damage them with an iron and some clumsiness.