Got any pointers on the Bowden Extruder?

[fredini]

Hi all,
I have my machine assembled and wired, now just working on getting it calibrated and printing. Its very close but I'm having some issues with the extruder. I've not got any experience with the Bowden extruder before and have a couple questions:

Question # 1:
When tuning the hotend as indicated in the Wiki, I get this feedback. I have averaged the 3 Kp,Ki and Kd values and entered that in the firmware config and re-uploaded it. However, you will also see that it is returning an error below that. Any idea why?

< 5:33:25 AM: PID Autotune start
< 5:36:41 AM: bias: 68 d: 68 min: 198.36 max: 205.89
< 5:37:36 AM: bias: 68 d: 68 min: 197.86 max: 202.81
< 5:38:24 AM: bias: 64 d: 64 min: 198.49 max: 202.23
< 5:38:24 AM: Ku: 43.51 Tu: 48.24
< 5:38:24 AM: Clasic PID
< 5:38:24 AM: Kp: 26.11
< 5:38:24 AM: Ki: 1.08
< 5:38:24 AM: Kd: 157.42
< 5:39:13 AM: bias: 64 d: 64 min: 198.39 max: 202.10
< 5:39:13 AM: Ku: 43.93 Tu: 48.63
< 5:39:13 AM: Clasic PID
< 5:39:13 AM: Kp: 26.36
< 5:39:13 AM: Ki: 1.08
< 5:39:13 AM: Kd: 160.21
< 5:39:59 AM: bias: 64 d: 64 min: 198.82 max: 202.10
< 5:39:59 AM: Ku: 49.65 Tu: 46.53
< 5:39:59 AM: Clasic PID
< 5:39:59 AM: Kp: 29.79
< 5:39:59 AM: Ki: 1.28
< 5:39:59 AM: Kd: 173.27
< 5:39:59 AM: PID Autotune finished ! Place the Kp, Ki and Kd constants in the configuration.h
< 5:39:59 AM: Error:Line Number is not Last Line Number+1, Last Line:2154
< 5:39:59 AM: Resend:2155
< 5:40:00 AM: Error:Line Number is not Last Line Number+1, Last Line:2154
< 5:40:00 AM: Resend:2155
< 5:40:01 AM: Error:Line Number is not Last Line Number+1, Last Line:2154
< 5:40:01 AM: Resend:2155
< 5:40:02 AM: Error:Line Number is not Last Line Number+1, Last Line:2154
< 5:40:02 AM: Resend:2155
< 5:40:03 AM: Error:Line Number is not Last Line Number+1, Last Line:2154
< 5:40:03 AM: Resend:2155

Question #2
Can someone give any advice on technique for loading the filament into the extruder? I have it but was having issues with filament kinking up between the extruder motor's rollers and the metal piece that connects the tube to the motor. My technique was to remove the motor and get the filament started through the rollers, then feed it into the tube and carefully slide the motor back into place so that I could send the filament all the way up the tube to the extruder. It worked but took a few tries as the filament would often kink up and jam between the rollers and the metal piece.

Question #3
I can't seem to get the extruder flow going. I can get a tiny trickle coming out but there's either not enough pressure pushing the filament into the extruder OR its not getting hot enough (sure feels hot enough!), It seems to be jamming up in the hot end. I tried a calibration print and the machine moves flawlessly, but doesn't extrude.

Since the extruder wasn't working, I removed the hot end tip. It seems like the filament is maybe fusing to the inside of the teflon tube? Unfortunately, now I seem to have a chunk of filament stuck inside the tube.

Other questions I have are about how much tension is needed on the set screws with the rubber gaskets to push the filament rollers together. THey do a fine job of pushing the filament up to the extruder, but no mater how much or how little tension I apply, I can't seem to get it to go through the tip.

Any tips or pointers are greatly appreciated!

[fredini]

So I just ripped this all apart and put it back together again.
I now better understand how the assembly held in place by the tension/set screws in the extruder gears comes out to load the filament in there. Once assembled, the gears push the filament through the tube, but the moment it hits the extruder, it stops moving. The tip is definitely hot! I'm running it up to as high as 250 degrees and I can get a dribble of filament to come through, but that's all. Feels to me like its jamming in the teflon tube? I've played with the tension on the set screws and filament seems to be feeding well, just jamming up in the extruder somehow. Any advice what to try next?

[kometen]

Be carefull. If you raise the temperature further, the teflon will be damaged!

Are you sure that your NTC resistor is correct type?
Can you feed the filament through the hot end with your hand?

[fredini]

I'm definitely using the thermisters that came with the kit.

I've mainly been running the extruder at 230, which is what I run my other printer at for ABS. I cannot push the filament through manually with my fingers. However, I just was able to use a thin stainless steel rod as a plunger to ream out the teflon and get the filament clog through the extruder. Am cooling it and then will try again....

[Polygonhell]

So I just ripped this all apart and put it back together again.
I now better understand how the assembly held in place by the tension/set screws in the extruder gears comes out to load the filament in there. Once assembled, the gears push the filament through the tube, but the moment it hits the extruder, it stops moving. The tip is definitely hot! I'm running it up to as high as 250 degrees and I can get a dribble of filament to come through, but that's all. Feels to me like its jamming in the teflon tube? I've played with the tension on the set screws and filament seems to be feeding well, just jamming up in the extruder somehow. Any advice what to try next?

disconnect the Bowden tube at the Hotend, set the temperature and try feeding the filament by hand, if that works, ensure that plastic is trying to feed into the extruder.
IME where it jams is at the exit to the extruder, between the drive roller and the entry to the Bowden tube.
The seemecnc Hotend seems to require a lot of force to extrude, as far as I can see, the Bowden tube doesn't really make things any worse.

[Polygonhell]

I'm definitely using the thermisters that came with the kit.

I've mainly been running the extruder at 230, which is what I run my other printer at for ABS. I cannot push the filament through manually with my fingers. However, I just was able to use a thin stainless steel rod as a plunger to ream out the teflon and get the filament clog through the extruder. Am cooling it and then will try again....

I can't reliably feed ultimachine ABS through the machine at 230, 240 seems to work though.

[fredini]

disconnect the Bowden tube at the Hotend, set the temperature and try feeding the filament by hand, if that works, ensure that plastic is trying to feed into the extruder.

I am definitely able to push filament through here by hand, but as soon as I reattach the Bowden tube, I get nothing. Before connecting the tube I played with the amount of tension on the screws and it feels like the filament has a decent amount of force to it.

[Polygonhell]

disconnect the Bowden tube at the Hotend, set the temperature and try feeding the filament by hand, if that works, ensure that plastic is trying to feed into the extruder.

I am definitely able to push filament through here by hand, but as soon as I reattach the Bowden tube, I get nothing. Before connecting the tube I played with the amount of tension on the screws and it feels like the filament has a decent amount of force to it.

Detach it at the extruder end and try pushing from there, again at 240 I can exit it to extrude by hand.
You're experiencing pretty much what I did and it turned out to be the filament bucking at the entrance to the Bowden tube, it's really hard to see when it happens.
Some times the filament just stops feeding, sometimes it will continue to feed and pop out of the side of the extruder.

[fredini]

First time around I was definitely getting the filament bucking at the entrance to the Bowden tube, but now I think its really fine there. The bottleneck now seems to be right at the extruder itself. When sending the filament up the Bowden tube, it pushes through fine until the moment it reaches the hotend, at which point I can feel it stop moving. I pulled the tip off several times to clear out the teflon insert tube, but it keeps jamming up there. When I remove the tube from the hotend and manually push the filament in, it goes though fine, but not from the force of the rollers by the extruder motor. I have played will all kinds of different levels of tension on the setscrews against the Orings, but no luck thus far. How much tension should be on those set screws?

[fredini]

Success.. Sort of. I've finally gotten my Rostock Max to print!

With the extruder at 240 degrees I was actually able to get the extruder working, but its really still limping along. After many failed first attempts I ditched the polycarbonate sheet as a print plate- it was warping and the ABS was not sticking to it. Instead I put Kapton tape directly on the heated bed and went for another attempt and was able to get an extremely blobby looking calibration object completed. My extruder flow was still so light that I used Repetier's Flow Multiply feature to bump the flow to 150%, then even 200%. The results were still very spotty- and the default flow turned out to be better than multiplied flow part of the print:
http://fredini.posterous.com/rostock-ma ... still-lots

That print had only 10% infill. Measuring the 40-20-10mm calibration object, I'm quite impressed- all sides actually measure within half a millimeter of the desired size. Now if I can only get the extruder flow to keep up. I also tried another print with 20% infill at 250 degrees, but dropped the temp back down to 240 halfway through. If anything, the other print was more swiss cheesy than the first.

I'm also having another issue at completion of prints- the machine returns to the home position up top, then sends the extruder over to the Z axis and starts making a bad grinding noise until I cut the power off. In Repetier's printer settings I have the "Printer has Dump Area" left unchecked. Any idea why this is happening and how to just have the machine just home itself upon job completion?

And a prize to anyone who can point me in the right direction to calibrate the extruder flow!

[kometen]

I am glad that the NTC's was included in your set. It wasn't in mine so I have to experiment with different types and found in the end some from Farnell.

The homing problem is solved by removing the X0 in this line : G28 X0 ; home X axis, in the printer setup Custom End Code in the Slicer configuration.
For the extruder flow: Is the teflon tube placed so it is attached with the nozzle head? I believe it should be. Also, do not tighten the extruder roller to much in the 3mm filament side as this will disturb the feeding too.
Are you sure that both heating resistors are working?
Check the temperature curves to see that it is steady.
Good luck.

[Polygonhell]

The print looks like either the filament is slippingin the roller, or the extruder is skipping steps.
The former is usually apparent if you rest a finger on the incoming filament. I.e. not filament motion while the gears are turning.
You can usually see and hear the latter, it can be caused by the pots being set too high or too low, I've adjusted my digipots down slightly from John's settings just based on the temperatures of the drivers while the machine was running.

The flow rate is about right, I think if anything it's maybe slightly high.

[fredini]

I am glad that the NTC's was included in your set. It wasn't in mine so I have to experiment with different types and found in the end some from Farnell.

I'm sure they would have sent you some if you emailed support

The homing problem is solved by removing the X0 in this line : G28 X0 ; home X axis, in the printer setup Custom End Code in the Slicer configuration.

I don't have this line in my custom gcode. In Slic3r, my custom gCode is:
M104 S0 ; turn off temperature
M140 S0 ; turn off bed
G28 ; home X axis
M84 ; disable motors

I was thinking this has to do with the printer settings in Repetier?
In printer settings on the behavior tab, I just noticed that "Go to Dispose after job/job kill" is checked. Could this be causing it?

For the extruder flow: Is the teflon tube placed so it is attached with the nozzle head? I believe it should be. Also, do not tighten the extruder roller to much in the 3mm filament side as this will disturb the feeding too.

Yes, I have definitely played with the tension on the rollers a LOT! Putting my fingers against the filament as it comes out of the tube near the hot end it feels like I have the best setting as far as tension and force on the filament.

Are you sure that both heating resistors are working?
Check the temperature curves to see that it is steady.

Temperature curves seem good in Repetier. How can I tell if both resistors are heating? Tap both sides and see if I am getting burned? It definitely seems to be getting hot enough.

In regards to the heated bed, I don't think the thermister position on the side is the best positioning. I can't seem to get a temperature reading to go higher than 90 degrees, but using my IR thermometer I see much higher than that in the venter of the plate. My other printer uses a thermister underneath the center of the plate and I think that is more accurate.

[fredini]

To confirm, the apeture on the extruder tips should be set to .5mm?

Does anyone know where there's some documentation on calibrating the extruder? Can I edit the config values in the Configuration.h file to affect feedrate:
#define DEFAULT_AXIS_STEPS_PER_UNIT {53.333, 53.333, 53.333, 292.0} // default steps per unit for rostockmax

Is the 292 value what I should adjust?
Is it the same as with a regular extruder where I would extrude something like 50mm, and measure exactly how much filament was actually used and use that to calculate what the 292 should be set to?

[Polygonhell]

Yes the 292 should be what you adjust, the easier way to do this is to change the extrusion multiplier in the slicer.
Once it's correct, you can then edit the firmware and just set it to currentValue * extrusionMultiplier, and set the extrusion multiplier in the slicer back to 1.
Yes you should do the same thing as a regular extruder, the measurement is input filament, 292 was really close to spot on, and the way SeeMeCNC makes it's rollers, there should not be a lot of variation machine to machine.

The extruder tip in the kits 0.5mm.

[fredini]

Yes the 292 should be what you adjust, the easier way to do this is to change the extrusion multiplier in the slicer.

Where do I set the extrusion multiplier in slic3r? Under the custom Gcode?

[geneb]

Fredini, for Slic3r, it's on the Filament Settings tab as "Extrusion multiplier".

g.

[fredini]

The rollers in the extruder gearbox are definitely slowing up and pausing as they turn. I'm not sure why.

[fredini]

Latest test print is a huge improvement:
http://fredini.posterous.com/rostock-max-first-3dprints
[img]http://s3.amazonaws.com/files.posterous ... SZh6jPI%3D[/img]

[fredini]

Some print results! I still seem to be having some issues with the extruder, but I am printing at least!

Issue #1: Adjusting the flow
I'm getting a steady flow in the extruder now- I don't seem to see the rollers binding anymore. However, there's some areas of the prints where the flow seems too low. My Katie full body scan print is noticeably swiss cheesy in the ankles

Issue #2: Blobbing
The prints have little blobs everywhere the print head sets down. This is especially noticable on the Pink Panther woman torso files.
I have retraction set to 10mm, Z lift 1mm, 55mm/sec speed, Minimum travel after retraction 3mm

Issue #3: Jumping out of alignment
Occasionally, the machine will "jump" out of alignment- most often in the Z axis.
In the first print, you see this as a ~10mm "jump" in the knees and again a few layers below where the print was stopped (this jump was in the Y axis).
On the second Pink Panther woman torso print the machine again jumped ~10mm in the Z axis at the beginning of the neck.

[img]http://farm9.staticflickr.com/8497/8335976080_3843f32080.jpg[/img]
Katie print attempts by fredini, on Flickr

[img]http://farm9.staticflickr.com/8214/8334873027_f7ca367a76.jpg[/img]
Katie prints by fredini, on Flickr *(note the slightly larger orange print from my Printerbot+ is for comparison)

[img]http://farm9.staticflickr.com/8219/8335926888_99f2ff395c.jpg[/img]
Katie prints by fredini, on Flickr (note the slightly larger orange print from my Printerbot+ is for comparison)

[img]http://farm9.staticflickr.com/8495/8335894960_b7d5b2b173.jpg[/img]
Rostock Max by fredini, on Flickr

[img]http://farm9.staticflickr.com/8500/8335887858_ba60f4b201.jpg[/img]
Early Rostock Max print by fredini, on Flickr Note the lower leg on the left has many holes, then there are tiny holes and blobs all over the place. Plus the webbing in the crotch.

[Polygonhell]

The Jump out of alignment is missed steps by one or more of the XYZ motors, it can be caused by either a mechanical issue, binding, digipots set too low or more likely by the digipots set too high and the stepper drivers going into thermal shutdown temporarily. When the settings are borderline, sometimes it just takes a while for the drivers to reach the cutoff temperature, then they cut out for very short periods often separated by minutes.
I've turned mine down to 160 (default is 195) in configuration_adv.h.
You can also try pointing a fan at the Rambo board to help them cool.

[Polygonhell]

On the blobbing issue, I'm still seeing some, though nothing like as bad as the print you have.
There will be a point where you have too much retraction, because the head is stationary during the retract, the time it takes to retract will be enough to cause a blob.
Also I'm currently running ZLift as well (0.3mm), but I'm not actually sure it's a help, I need to print a few more test parts to verify.
My pink panther lady came out close to perfect on the front, with no stringing between the legs, but the large overhang in back didn't have enough cooling, so she has some celulite.

I'm currently running Ultimachine White ABS @240C, 0.2mm layer height, 5 prime/suck @55 mm/s, 10mm wipe (this is a kisslicer feature), 1.5mm Min jump and 100mm trigger and 0.3mm Z-lift.

I'll probably increase the prime/suck slightly, and try losing the ZLift since I think it's doing more harm than good.

On the flow point, I don't have an issue with consistent flow, at the end of the day volume in = volume out, if you're getting swiss cheesy something is slipping or skipping.

[fredini]

First thing I'm doing next is to recalibrate the extrusion multiplier value in the config again.

Re: Blobbing I will play with lowering the retraction some.

Re: Jump out of alignment

The Jump out of alignment is missed steps by one or more of the XYZ motors, it can be caused by either a mechanical issue, binding, digipots set too low or more likely by the digipots set too high and the stepper drivers going into thermal shutdown temporarily. When the settings are borderline, sometimes it just takes a while for the drivers to reach the cutoff temperature, then they cut out for very short periods often separated by minutes.
I've turned mine down to 160 (default is 195) in configuration_adv.h.
You can also try pointing a fan at the Rambo board to help them cool.

When I wired the machine I had crimped on the wire extensions. I'm going to go back through and solder everything so I can rule out anything mechanical before before I play with the pots. None of the motors feel too hot at all so I'm guessing some of the connections can be improved upon and hopefully that is my issue.

[fredini]

This video shows the issue I'm having- the filament seems to pause periodically as its going into the rollers.
[youtube]http://www.youtube.com/watch?v=8q9huhK3EA0[/youtube]

[v8tony]

I had a really similar problem with my extruder when I first put it together... Try tightening the main drive axle more. The inner gear is only connected to the roller shaft by friction, so, I found that mine slipped there until I tightened it up a bunch...

As for the dust, my seems to leave dust like that as well... especially after a long print (2+ hours)...

That's my 2 cents...

Tony