Kittaz build complete but have a few issues

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Zonyc
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Kittaz build complete but have a few issues

Post by Zonyc » Fri Nov 21, 2014 4:13 am

Hello

I've recently finished building my Kittaz and am in the process of calibrating it. Unfortunately, I've run into some issues which hopefully can be addressed here.

1. When testing the printer upon turning it on for the first time, I noticed that the Z axis motor on the lower left would rotate fine when no load was placed on it, however, when attached to the Z rods via couplers, it would not rotate, causing only the right side to rise. This resulted in a horrible grinding noise but fortunately the whole assembly is pretty robust. After some playing around, I finally tested the circuit for continuity and noticed that the black wire which powers the lower left z motor was broken. The wire appeared to have broken off from the pins located inside the CB YZ Harness. In a rush to fix this, I accidently crimped the wire to the wrong end of the pin (after pulling it out), basically rendering it useless. Ultimately I ended up pulling the black wire for the lower left Z motor from the YZ Harness and attaching the two directly to complete the circuit. After doing this, the motor worked great. This leads me to the problem: I need a new YZ wire harness and CB YZ wire harness or the appropriate pins to restore it. Where can I find these?

2. When calibrating esteps for the extruder, the instructions located at [1] say to enter m501 into pronterface to see the current esteps. Doing this returns no value in pronterface or repetier host. In order to update the esteps, I had to reflash the firmware. Currently its at ~746 but still appears to be slightly underextruding by 2mm when 100mm of filament is extruded at 100mm/min. When printing it looks like there is a bit of overextrusion which is strange (picture below). The bed is level as confirmed by printing the gcode located at [2] so the appearance of the print probably isn't caused by the nozzle touching the print. The left (blue) print is made on a calibrated printrbot simple and the right print (white) is printed on the Kittaz. The calibration cube printed on the Kittaz is much more blobby and stunted. Is this the result of miscalibrated esteps? Also is there any way to change the value of esteps via command rather than reflashing the firmware?

3. As you can see in the photo below, the calibration cube printed on the Kittaz is also much shorter than the blue one. It measures at 17.14mm in height rather than the 25mm it should be. The x and y axes are printing at the correct dimensions (each small cube should be 5mm X 5mm X 5mm). Is this the result of miscalibration on the z axis? I read here previously that only the extruder motor (esteps) required calibration and adjusting from the default 800 value.

4. Prints which require modest amounts of retraction cause the (3mm) filament to stop feeding resulting in a ruined print. I have tried retraction settings as low as 1mm at 10mm/s which has improved the problem a little bit, but not completely. I've attached a photo of what happens to the filament when this occurs below. There is no resistance felt when manually pushing the filament through the extruder into the hot end manually. I've also played around with the tension on the filament quite a bit but this didn't seem to help. Any ideas?

I am currently printing using slic3r and pronterface using the default slic3r settings located at [3] and printing with PLA, although the results are almost identical when printing with ABS using the recommended settings.

Please let me know if you need more info.

For 2 and 3
Image
Image

For 4
Image
[1]https://ohai-kit.alephobjects.com/proje ... libration/
[2] http://download.lulzbot.com/KITTAZ/cali ... tion.gcode
[3] https://www.lulzbot.com/support/taz-slic3r-profiles

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Orias
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Re: Kittaz build complete but have a few issues

Post by Orias » Fri Nov 21, 2014 9:37 am

Thanks for the details! I'll have a list of answers written up for you soon.

Thanks!

Zonyc
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Re: Kittaz build complete but have a few issues

Post by Zonyc » Sat Nov 29, 2014 3:52 am

Just an update to the issues I was having earlier:

1. Still have not heard anything from Lulzbot. Hopefully it was not forgotten?

2. To calibrate e-steps without flashing firmware, the command I used was m503 in order to see the E-steps. The rest of the commands outlined in the guide are correct. Currently my E step calibration is perfect with respect to the amount of extrusion desired.

3. In order to fix the Z height issue, I simply flashed the stock firmware provided by Lulzbot. Its pretty strange that this fixed the issue considering I did not make any modifications to it other than changing the E steps.

4. The retraction issue is still somewhat present. Disassembling the extruder and ensuring the holes for the filament lined up precisely helped quite a bit, but I am still having issues on longer prints with the stock retraction values provided in the default slic3r configs.

Here are some pics of my recent prints - the calibration cube is now the correct size.

Image
The left blue cube is from the printrbot simple (same one as last post). Right white cube is a recent print to confirm the z height issue was fixed.
Image
Basic tree frog print at 0.27mm layer height. Looks good.
Image
This gorgeous print unfortunately did not finish due to the retraction issue presented above. The print failed at ~17.5 hours and was due to be completed in 19 :(

Lotharyx
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Retraction is Problematic

Post by Lotharyx » Mon Feb 23, 2015 4:34 pm

Hi there. I don't have a KITTAZ yet, but I fight the same retraction gremlins with my MakerBot Thing-O-Matic.

What I suspect is happening is, with a lot of frequent retractions, gradually more and more of the filament begins to heat up (farther and farther away from the nozzle). Eventually it gets warm enough far enough back that the feed gear just chews it up easily trying to overcome the friction in the system. The farther back you retract, the more the problem is exacerbated, probably because the warm gooey end of the filament gets closer to the feed gear.

With my ToM, I can't retract more than 1mm before even small 1-hour prints start to misfeed. With the ToM, the feed gear is very close to the hot end, and there's not much in the way of isolation or cooling (such as Budaschnozzle's fins and PTFE insert).

I suspect that the farther away the feed gear is from the hot end, the better this issue gets. Some printers put the feed gear at the opposite end of the feed tube, and those probably don't suffer retraction problems at all. Of course, that distance comes at a cost of increasing friction and compression in the filament.

I'm mildly disheartened to learn that the TAZ has the same feed problem which I suppose is inherent to the printhead design.

As far as mitigation is concerned, here are a few ideas that may or may not help:
1) Minimize retractions. I'm not yet familiar with any slicers other than skeinforge, but if there are options not to retract sometimes (such as between layers), use them.
2) Increase airflow around the printhead to help keep it cool.
3) If possible, during long prints, pause the print and allow the printhead to cool off completely. The longer the hot end stays hot, the more parts that should stay cool start to get warm.

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mhackney
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Re: Kittaz build complete but have a few issues

Post by mhackney » Mon Feb 23, 2015 4:51 pm

Hello, I have been studying and discussing this issue with PLA for several years. It's too easy to jump to the wrong conclusion. Bottom line, PLA melt is thixotropic. If you retract fast (greater than 25m/s) you will experience what I call "micro plugging". The more retracts there are (like lots of short segment moves) the problem will appear. I have several parts that I can reproduce this phenomenon with almost every extruder and hot end combination UNLESS I slow retract down to 25mm/s.

Each type of plastic has different properties and many folks just use the same retract parameters for PLA as they do ABS. Try this experiment - slow down retract in your slicer to 25mm/s and print a problematic part. Of course, this presumes that you have eliminated most/all of the other sources of extrusion issues. But this one is a big contributor and I've helped nearly 100 people successfully print PLA by slowing down retract.

Interestingly, speeding up the accompanying prime produces better results than going slow in that direction. I retract at 25mm/s and prime at 50mm/s. This fast prime leverages the thixotropic properties to prevent an initial blob of filament coming out of the nozzle.

I'd love to have access to the lab test equipment I used to in order to collect hard data on this phenomenon. But I've set up a lot controlled tests to isolate and ultimately fix this problem.

Just to wrap up, one other big variable that affects PLA extrusion is the ratio of nozzle bore to length. Ideally you want a length to diameter ratio of about 1.5 - so a .4mm nozzle would have a .6mm bore. A long bore increases back pressure and increases the likelihood for "micro plugging" to occur.

I've been using a water cooled Kraken hot end for over a year. I print 6+ hours a day 7 days a week for my business. I have not had a single PLA plug in over year. Over Christmas we printed a 48 hour guitar body for my son and I've done 100s of prints over 12 hours.

cheers,
Michael
Sublime Layers - my blog on Musings and Experiments in 3D Printing Technology and Art

Start here:
A Strategy for Obtaining Great Prints

Strategies for Resolving Print Artifacts

The Eclectic Angler

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JonathanB
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Re: Kittaz build complete but have a few issues

Post by JonathanB » Thu Feb 26, 2015 1:04 am

Water cooled hot end, drool :D

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Orias
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Re: Kittaz build complete but have a few issues

Post by Orias » Fri Feb 27, 2015 8:57 am

Zonyc wrote:Just an update to the issues I was having earlier:

1. Still have not heard anything from Lulzbot. Hopefully it was not forgotten?

Not forgotten- but by the time I got back into the office, you were up and running and had great looking prints! Being part of the user forum- we let the community chime in as well- it's always helpful to have another view point, other experience and opinions.

Zonyc
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Joined: Fri Nov 21, 2014 2:56 am

Re: Kittaz build complete but have a few issues

Post by Zonyc » Sat Feb 28, 2015 2:22 am

mhackney wrote:Hello, I have been studying and discussing this issue with PLA for several years. It's too easy to jump to the wrong conclusion. Bottom line, PLA melt is thixotropic. If you retract fast (greater than 25m/s) you will experience what I call "micro plugging". The more retracts there are (like lots of short segment moves) the problem will appear. I have several parts that I can reproduce this phenomenon with almost every extruder and hot end combination UNLESS I slow retract down to 25mm/s.

Each type of plastic has different properties and many folks just use the same retract parameters for PLA as they do ABS. Try this experiment - slow down retract in your slicer to 25mm/s and print a problematic part. Of course, this presumes that you have eliminated most/all of the other sources of extrusion issues. But this one is a big contributor and I've helped nearly 100 people successfully print PLA by slowing down retract.

Interestingly, speeding up the accompanying prime produces better results than going slow in that direction. I retract at 25mm/s and prime at 50mm/s. This fast prime leverages the thixotropic properties to prevent an initial blob of filament coming out of the nozzle.

I'd love to have access to the lab test equipment I used to in order to collect hard data on this phenomenon. But I've set up a lot controlled tests to isolate and ultimately fix this problem.

Just to wrap up, one other big variable that affects PLA extrusion is the ratio of nozzle bore to length. Ideally you want a length to diameter ratio of about 1.5 - so a .4mm nozzle would have a .6mm bore. A long bore increases back pressure and increases the likelihood for "micro plugging" to occur.

I've been using a water cooled Kraken hot end for over a year. I print 6+ hours a day 7 days a week for my business. I have not had a single PLA plug in over year. Over Christmas we printed a 48 hour guitar body for my son and I've done 100s of prints over 12 hours.

cheers,
Michael
Thanks for the solid reply!

Its interesting that you have found that a max of 25mm/s was effective at stopping jamming when printing PLA. With the stock buda nozzle I have tried reducing the retraction speed to 1mm @ 10mm/s and still had jamming issues. If you have a look at the skull picture you can see that it stopped printing well into the print (17 hours) and was doing a circular perimeter with standard rectilinear infill (~40%) when it jammed. I think the issue was more related to heat creeping with the stock nozzle. I've since swapped out the buda for an e3d v6 and have had zero problems printing PLA with respect to issues with jamming even with retraction speeds of up to 1mm @ 40mm/s with this setup. The setup I use is a 0.4mm nozzle with the heat break bored out a little and tapered slightly. Just as an aside, colorfabb XT it turns out is much more finicky than PLA when it comes to not only retraction but print speeds as well.

When you say priming are you referring to before the print begins (i.e some start gcode)? How much filament to do you extrude at 50mm/s and what do you do with it before starting the print? Would doing a skirt (say 2-3 loops) at a relatively fast speed have the same effect?

Thanks again for your reply.

Zonyc
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Joined: Fri Nov 21, 2014 2:56 am

Re: Kittaz build complete but have a few issues

Post by Zonyc » Sat Feb 28, 2015 2:49 am

Orias wrote:
Zonyc wrote:Just an update to the issues I was having earlier:

1. Still have not heard anything from Lulzbot. Hopefully it was not forgotten?

Not forgotten- but by the time I got back into the office, you were up and running and had great looking prints! Being part of the user forum- we let the community chime in as well- it's always helpful to have another view point, other experience and opinions.
Unfortunately I am still having issues with the Z axis (prints shorter than they should be). This happens because the z axis will occasionally refuse to lift. The axis does not grind when moving up and down when given a gcode command (unless ridiculous speeds are tried). The issue starts when the x idler, motor mount and gt2 belt are added to the setup - especially when you tension the belt (even only slightly to remove slop).

I've taken multiple measurements from the top of the smooth rods down to the aluminum bed mount. I've also loosened the x idler and motor mount screws. I've replaced the x idler/motor mount and z axis mounts with these files: http://devel.lulzbot.com/TAZ/Kauri/prod ... est_parts/. This resulted in the exact same issue as with the stock idler/z axis mounts. The motors are in top notch shape, and I've tried almost everything I can think from new bearings to replacing the wiring to different materials for the idlers to reduce warp (pla, colorfabb xt, etc..).

Sometimes prints will turn out fine and be the correct height, while other times the z axis will fail to lift. All values with the exception of the e-steps are stock in the firmware.


Thanks.

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mhackney
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Re: Kittaz build complete but have a few issues

Post by mhackney » Sat Feb 28, 2015 7:53 am

Zonyc, firstly - terminology! Each slicer uses different words to describe the extruder action. I use KISSlicer and it's called "suck" and "prime" so I tend to go back to that (except I don't like to use "suck" so I use retract! But these refer to the motion of the extruder to retract and advance the filament between non-printing moves as a way to eliminate/minimize ooze and stringing.

If you are still having issues with low retract that indicates (to me) that there are other problem areas. It is a complex system and no one "fix" is a silver bullet. I have no Budhashnozzle experience but hopefully this weekend I'll get RazzMaTAZZ finished and can start using it (KITTAZ is basically the same as a TAZ4). I even bought some 3mm filament SOLEY to gain some experience that I might be able to use to help folks here. Otherwise, this machine is getting converted to 1.75mm and a Cyclops hotend and dual Bowden extruders asap.

I agree that heat creep is a big issue for these hot ends. That's why I love the Kraken water cooling. I have been running it in production for well over a year, 6+ hours a day nearly 7 days a week and I have not had a single PLA jam! That is spectacular in my book. I'm building water jackets for my E3D V6 hot ends and I want to test the Cyclops with air first but I'm prepared to move to H2O.

I think there needs to be a crisp separation of molten and solid filament in the hotend. Too long of a transition provides opportunity for creep, excess friction, stiction, the hydraulic plugging phenomenon I mentioned, etc. Just generally not good.
Sublime Layers - my blog on Musings and Experiments in 3D Printing Technology and Art

Start here:
A Strategy for Obtaining Great Prints

Strategies for Resolving Print Artifacts

The Eclectic Angler

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