Extruder keeps slipping

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jimc
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Re: Extruder keeps slipping

Post by jimc » Thu May 22, 2014 7:00 pm

Well if thats the case then the filament isnt making it all the way into the hot end. Its probably going just past the drive gear and not making it into the lower hole so it will continue on to feed into the hot end.

Toby
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Re: Extruder keeps slipping

Post by Toby » Thu May 22, 2014 8:07 pm

I've had cases where the filament did not make it into the hot end and the gear started skipping because the filament drive hole (in the ABS) wasn't perfectly lined up with the hot end hole (in the peek). The tip of the filament would catch on an edge and back up into the gear, causing it to start skipping.

But this was with some flexible filament, not PLA or ABS. In that case I was able to get it working in two ways:

1.) Take the filament drive apart, thread the filament all the way through to the hot end, then remount it on the gear with the filament already in the hot end. It's a little tricky working around the metal cylinder that holds the filament against the gear, but not hard. I used some dental floss to loop around the filament from the hole where the cylinder sits. That allowed me to pull the filament out of the way when I remounted the drive on the gear, then remove the dental floss and put the cylinder back in.

This at least would allow you to determine if the problem is in something before the filament reaches the hot end, or if it's just not getting channeled into it in the first place.

2. The other method was to pare the filament to a sharp end on all sides so that it had a better chance of being channeled into the hot end.

slamma
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Re: Extruder keeps slipping

Post by slamma » Thu May 22, 2014 9:23 pm

Ok thanks guys. This is the why this problem has been challenging: The filament is making all the way through the hot end. However, when extruding only about 50%-75% of the amount of filament that should be extruded is extruded because of the popping & clicking similar to what is shown in the video on this thread.

I've going to try and do some debugging using the unused E1 extruder driver on the controller board and see if that this able to push without the clicking.

Dale Reed
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Re: Extruder keeps slipping

Post by Dale Reed » Thu May 22, 2014 10:54 pm

From MY experience, the clicking usually indicates that the drive gear is turning good and hard and trying to push the filament, but it's skipping because of excess friction in the path or insufficient force from the idler holding the filament against the gear drive gear.

Please excuse me if you've covered this.... but have you adjusted the idler wheel pressure against the filament and gear using the M4 screw at the top of the ABS filament drive? I assume you have.... If you have it pretty snug and it's skipping, you'll see the filament pretty chewed up and bits of filament in the gear when you back the filament out.

I assume from what you've said above that you have a new stepper motor, new gearbox and new drive gear that is not clogged with shredded filament.

Have you tried temporarily mounting the spool above the printer and feeding without the PTFE tube? Some folks have reported issues with the filament friction in the tubing or catching at the printed plastic part near the spool in which the tubing sits. Get an appropriate size drill and drill out the filament guide just larger than the filament, and while you're at it, get a bit the size of the tubing and put a short recess for it in the filament guide, and maybe even in the top of the filament drive (but be careful here!!!). Someone posted a part number for replacement tubing (from Amazon or McMaster-Carr or somebody like that where you can order online) that is "slipperier".

Does it skip at all when you feed through the filament drive WITHOUT the hot end mounted below it? Not a definitive test, but if it does, it's NOT a hot end clog!

I assume the stepper motor connections are snug on both the motor and at the RAMBo board.

That's all I've got. I'll stop typing and let those who know what to do help you!
Dale

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jimc
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Re: Extruder keeps slipping

Post by jimc » Thu May 22, 2014 11:37 pm

i dont remember if you said this already but what is the filament you are using and the brand? i assume you have the temp on the hot end up to the appropriate setting for the plastic? have you taken the filament drive off and looked through the hole where the filament goes in? you should be able to clearly see through the plastic drive and the hole should be nice, smooth and round. is the filament diameter within spec. too large a dia and it will be tight. i have to agree with dale, the clicking happens when there is too much resistance in the path. something is forcing the motor to stop.

slamma
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Re: Extruder keeps slipping

Post by slamma » Tue Jun 10, 2014 6:39 pm

Hey guys, I finally had a chance to take another crack at this issue over the weekend.

In my case I was able to solve this by recompiling the M2 firmware and boosting the digipot value for the extruder current. I bumped the value from 165 to 255 after trying several different values. In addition to bumping the values I've bumped the hot end temperature a few degrees higher. The combination of these two things has my machine extruding without clicking.

A couple follow-up observations. It would be great if there was a documented G-code command that allow you to adjust the digipots without recompiling the firmware. I did some googling which turned up a few possible gcode commands that presumably would change the digipot values but testing those gcode commands made it clear the digipot values weren't changing.

Another thing is I have both the new V3b heaterblock style extruder as well as the classic ceramic style extuder head. Is the thermocouple in the new V3b heaterblock different than the one used in conjunction with the ceramic style hotend? For some reason for the same filament the old style I would set my PLA temp around 185c as compared to 215c.

Thx for the help guys.

Dale Reed
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Re: Extruder keeps slipping

Post by Dale Reed » Tue Jun 10, 2014 9:37 pm

slamma,

The difference isn't in the type of thermistor (temperature sensor) but its location. In the V3 (wound / ceramic heater core) hot end, the thermistor is taped to the brass nozzle with Kapton tape and reads very close to actual nozzle temperature. In the V3B (aluminum heater block) hot end, the thermistor is near the heating element (cartridge resistor) but "relatively far" from the nozzle tip, and there's a pretty good temperature gradient from the heater down to the nozzle. Basically, you need to heat the block at the thermistor to about 215 C to get about 190 C at the nozzle.

Dale

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Tim
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Re: Extruder keeps slipping

Post by Tim » Wed Jun 11, 2014 1:41 am

Well, interestingly, since I've been collecting all the different firmware versions recently and comparing them, the original MakerGear firmware source has this in the digipot section:

Code: Select all

#define E0_CURRENT 165 //For MakerGear M2, 185 is a good starting point (~1A)
While this is a far cry from 255, it is not at all clear to me why somebody wrote the comment that 185 was a good starting point and then set the value to 165.

It should be pretty easy to add a routine to the firmware that attaches some unused M code to a call to digipot_current() to manually adjust the current drives.

Still, one has to wonder why you need to bump your current drive up so much compared to the value that works for everybody else. Although solid-state problems are extremely rare, it's looking an awful lot like you might have a bad power transistor, or digipot, or something in that path on the RAMBo, that is forcing you to have to jack up the value on the digipot to compensate for it. It would be a very rare thing, but then, you seem to be the only person still experiencing this problem after dispensing with all the usual suspects.

Claus
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Re: Extruder keeps slipping

Post by Claus » Wed Jun 11, 2014 10:29 am

I just wanted to add that I have experienced problems with a slipping extruder too. When it began I started pushing the temperature in my V3B hot end. But not to 215C, rather 200C. At that time I didnt know that the V3B is supposed to be set at 215. But the problem was a loose screw in the drive gear pulley. The screw gets loose after a few hours of printing so I have to keep tightening it - but - the prints were excellent. I recently ordered a new pulley with 3 screws. Maybe that helps. Right now I am having the slip thing again so I set the temp to 215 and higher. It stops the slipping but the prints don't come out the way they did before. So I am not at the end here, I might try to modify E0-current.

terrymcc
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Re: Extruder keeps slipping

Post by terrymcc » Sat Jul 05, 2014 3:22 pm

I only run PLA from 190-200 but I don't think high temp would cause what you are seeing.

Are others running PLA this high? I am getting decent prints but on occasion have had some delamination. Maybe I'm not hot enough. (I don't mean to derail the thread)

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