1 Topic by tedh98 (edited by tedh98 2015-02-19 17:15:20)

  • tedh98
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Topic: Printing problems after cleaning extruder head

I have a Da Vinci 1.0A, version 1.0.3.  I have had this about 2 months and have about 126 hours on it.  I have been running the XYZWare software (version 1.1.31.7)

When I first got the printer, I calibrated the bed using the "calibrate" feature (didn't even know about doing a manual calibration at that point) and was able to start printing right away with no problems.

One evening a print job lifted off the glass and made a mess around the extruder head. So I finally get around to removing the extruder head and cleaned everything up.  I put it back in the printer and use the "calibrate" feature again.  It worked the first time, should work this time.  Got a good calibration, within 7 on all the numbers.

I then attempted to print a small part that I've done successfully prior to the clean-up.  The extruder moved into place for the little test strip or prep strip.  I immediately noticed that the head is pretty far away from the glass.  Instead of being "smeared" on the glass, the filament is just dropping in place, resulting in a test strip that is just a line with tiny zig-zags.  I let the print continue and it quickly became obvious that the job wasn't going to print correctly.  I cancelled the job at that point.

I went back and checked the calibration and it was still fine.  Tried the print job again and the same thing happened. I turned off the printer and measured that the extruder head was about 2.24 mm off the glass bed.

I've recalibrated the bed several times, using widely different numbers but the end result is that the extruder head is always about 2.2X mm off the glass bed during a print job.

To rule out anything with the XYZware, I unplugged the computer from the printer and ran the "demo" sample and the same thing happened. 

Any ideas what would be causing this?   Thanks for any help or insight.

2 Reply by mpoffo

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Re: Printing problems after cleaning extruder head

A couple of thoughts.  It sounds like you took everything out.  I wonder if everything is seated correctly.  I may be worth it to take it out and reset it.

If it is seated properly try this technique for leveling and adjusting the bed by Carl:

http://www.soliforum.com/topic/8408/bed … beginners/

This has worked well for me.  Your spacing is obviously not correct so either the bed needs to come up or the extruder is somehow not in correctly and too high.

DaVinci 1.0A with Repetier .92
Simplify 3D
E3DV6

3 Reply by tedh98 (edited by tedh98 2015-02-20 02:36:04)

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Re: Printing problems after cleaning extruder head

mpoffo - thanks for the suggestions.

I've removed and re-installed the extruder assembly a handful of times to check to make sure I have it seated properly.  Once everything is lined up, it seems to snap right into place. 

When I took everything apart, I didn't see any shims or washers that I overlooked either.

If I manually calibrate the bed, I run into a new problem.  I used a .2mm feeler gauge to set the gap between the extruder and bed.  Since I'm having to raise the bed almost 2mm higher than what the system is expecting, the extruder carriage bangs into the bed (it actually hits the screw that holds down the glass in that back corner) during the cleaning process at the start of a print job.

I have done the auto calibration about 5 times now with different target figures.  I had a 190, a 230, 250, 280 and 350.  With all those different settings, the extruder head was consistently around 2.2X mm off the bed during a print job.

I interpret that as during the auto-calibration, the system is not only checking the position of the 3 corners for level, but it is also getting the height or position of the bed so it can adjust it properly during printing.

I am really stumped on this because I can't see what I may screwed up when putting it back together that would create such a large gap.

4 Reply by johnluksas

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Re: Printing problems after cleaning extruder head

What I would do is to start a print and adjust the bed to a height that you are sure that the extruder will clear the bed and not be below it. After that you need to do the old fashioned paper trick where you adjust you corners until a piece of printer paper will slide under the nozzle with a little resistance. You could try to clean the metal corner glass holdouts where the auto-calibrate sensor hits. When the auto-calibration runs I sometimes got various values that were much different than the last, but when I cleaned them they are consistent. Tip: When calibration the sensor "nub" should just touch the surface and then quickly back off. If you can not calibrate it after this You could maybe try the z-offset in OpenXYZWare.

5 Reply by rv.mike

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Re: Printing problems after cleaning extruder head

Obviously the bed is drawn down too much. I too encountered this yesterday after a cleaning.. I loosened the screws up a turn and re-calibrated it manually, then let DaVinci do it's thing and it passed. prints as good as new now.

6 Reply by tedh98

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Re: Printing problems after cleaning extruder head

The position of the bed doesn't make a difference.  I have tried a handful of different heights with the same end result.  The heights I've experimented with were 190, 230, 250, 280 and 320.  Those numbers where the average number provided after a successful calibration.

7 Reply by johnluksas

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Re: Printing problems after cleaning extruder head

I am just not understanding. So why can you not just calibrate the bed manually based on the last z-axis saved measurement that the printer took. The z-offset is only saved when a calibration is successful so you could just stop the printer in a print and adjust it

8 Reply by tedh98 (edited by tedh98 2015-02-20 19:48:03)

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Re: Printing problems after cleaning extruder head

After my auto-calibrate, the bed is nearly 2mm below the extruder.  If I shut off the printer after a job has started printing, I can easily slide(and still have room to spare) a credit card under the extruder.  From reading other posts, I get the impression that most people just manually fine tune a few tenths of a mm after an auto-calibrate.

If I manually raise and level the bed to get the extruder and bed within .2mm of each other, the bed is way too high.  During the extruder cleaning process at the very beginning of the print job, the carriage that the extruder rests in will hit the glass hold down screw in that back corner.

I hope that makes sense.

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9 Reply by johnluksas

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Re: Printing problems after cleaning extruder head

Oh so you can adjust all you want to get it close when you are printing but it still does not change the fact that the machine does not pull the bed down enough to clear the carriage and extruder because it recognizes the z axis as being below your manual adjustment. The only way to make the machine set a new z offset, it needs a "correct" and flat bed, but from your previous post you get various values that are different every time. I experienced this when my metal glass down hold down "contacts" were not clean. If they are clean I would check also to see if there are any of the contacts that are not quite touching the metal band around the bed. (if you did not know the calibration nub sends an electric pulse through the contact around the band and into the blue wire in the back, and when it received the signal it stops and calculates the value.) Just make sure the nub touches barley then jumps right back afterwards, that was why i was not getting accurate measurements. If you can not correct the measurements I believe yo u are able to change the z offset in OpenXYZWare or some other programs. I have no experience with this though.

10 Reply by cadarousse

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Re: Printing problems after cleaning extruder head

Your calibration problem probably has everything to do with the mess you cleaned off the hot end. The stainless steel screw that is the contact for auto-calibration is at a fixed distance from the nozzle, and so disassembling should not cause a 2+mm error.
I've found that a coating of plastic or even the plastic vapors from printing will make auto cal not work.
Do an auto cal and watch carefully what happens when the screw touches the corners of the bed. If it reverses IMMEDIATELY upon contact, that's good. If it does NOT, and the z-axis has to grind its way through contamination before it reverses, it will cause HUGE errors.
I have discovered a couple of things. First, the best way to clean the bed frame is with a piece of Scotchbrite green pad. Then, use the included brass cleaning brush on the nozzle screw, BUT IT MUST BE DONE WHILE HOT. If you try to clean it cold, nothing will happen, and your calibration will be off. ABS is tough to get off the metal. I've tried brushes, solvents and witchcraft to get those contacts clean. You might also try a little Caig D100 on those frame corners, as it will keep the vapors from sticking so much.
Best of luck!