1 Topic by mdrVB6

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Topic: Why did my prints suddenly drop in quality so badly?

Okay everyone, my print quality has gone to crap in the last few days and I'm trying to figure out why.  I am running SD2 with upgraded power supply and RUMBA, all else is stock.  Full enclosure.  Pictures:

Good print from a couple months ago.  Just a little banding.  0.3mm layers:
http://imgur.com/Q4rFFlm

Bad print from right now.  0.2mm layers. 
http://imgur.com/vOZDPbC

You can actually pull the bottom few layers off the print by hand, which suggest I might not be getting hot enough.  I print at 210C on the SD2 stock hot end, which is known to read about 30 degrees low, so I'm really at about 240 which is right in the middle of the ABS temp ranges.  I have always printed in this range but just now started seeing these issues. 

However, the even spacing of defects suggests a Z axis issue, potentially backlash.  I did get a little aggressive separating a few prints that used ABS slurry from the bed, so it is possible I damaged the Z axis, although I can't see any damage. 

I can eliminate bed leveling and distance from the hot end as potential problems because I'm getting a good stick to the bed and a smooth finish due to the glass bed and glue stick.

Where you you suggest starting to get my print quality back up?  Is it time to replace my hot end that might just have bit the dust?  I'm the second owner and I've put the better part of 4 kg of plastic thru this hot end.  The first owner did less than 1 kg.  Or should I start with a Z-axis M3 or M5 fine threaded rod upgrade?  I don't have enough spare rod when the bed is at home to install any of the anti backlash nuts that I have seen, so I would have to replace the entire rod and do one of the anti backlash mods at the same time.

I'd appreciate any feedback.  Thanks.

SD4 w/ RUMBA, E3D Volcano, all bearings, glass bed

2 Reply by AZERATE

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Re: Why did my prints suddenly drop in quality so badly?

I printed that part successfully several times. A few tips:
*Lifting and separating are more likely at higher infill settings
*Print with a good brim
*Keep an eye on the print. If the outer ridge of the brim begins to separate from the surface, you can salvage the print by applying some Krazy glue along the edge of each area lifting. This should be used with caution, though, if you are using Kapton over glass as it may tear.
*Check your extrusion multiplier and do a VREF tuning. This will help resolution.
*If you have not yet, print and install some sort of backlash bracket. 2n2r5 uploaded http://www.thingiverse.com/thing:101308  this is the best design for a 5/16" Z rod I have come across personally and helps banding.

Hope this helps.

Printit Mason and Printit Horizon printers
Multiple SD2s- Bulldog XL, E3D v5/v6/Lite6, Volcano, Hobb Goblin, Titan, .9 motor, Lawsy carriages, direct Y drive, fishing line...the list goes on
Filawinder and Filastruder #1870.....worth every penny!

3 Reply by AZERATE

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Re: Why did my prints suddenly drop in quality so badly?

Also, are you using a case? When I was between cases, I had great adhesion, but separation like in your 2nd pic since other layers were cooling too fast.

Printit Mason and Printit Horizon printers
Multiple SD2s- Bulldog XL, E3D v5/v6/Lite6, Volcano, Hobb Goblin, Titan, .9 motor, Lawsy carriages, direct Y drive, fishing line...the list goes on
Filawinder and Filastruder #1870.....worth every penny!

4 Reply by mdrVB6

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Re: Why did my prints suddenly drop in quality so badly?

Thanks for the reply.  I have a full enclosure.  I am actually not getting any lifting at all, I have excellent adhesion using a glass bed and a purple glue stick, so I don't really think a brim would improve anything.

I would like to put an anti backlash nut on it, but I think the manufacturer gave me a short rod.  When it is at the end stop, I have only 12 mm remaining above the top of the aluminum platform, and I haven't seen any design that would fit in this narrow space.  I'm pretty sure the one you posted is too big.  If I get multiple opinions that this is my biggest issue, I will upgrade to a fine threaded M3 or M5 rod, but I'm not sure that is the issue that I'm having.

As for VREF tuning, I would really like to find out a good way to do this on the RUMBA board with the better drivers that I have.  Wardjr has said to do it by ear, so that's what I did.  However, it is fairly hard to tune the extruder by ear.  I would like to find out where on the drivers to hold my multimeter probes, but I have searched high and low online and have not found good instructions on how to do this, including what voltages I am looking for on each axis.  Any suggestions?

Basically, I want to prioritize my repairs to the machine.  I think tomorrow I will try to get better info on multi meter calibration of the RUMBA drivers.  If that does not get my quality back, I will have to decide whether the next step is a full Z rod replacement or a new E3D hot end.  All input is welcome, of course.  Thanks.

SD4 w/ RUMBA, E3D Volcano, all bearings, glass bed

5 Reply by rvanee

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Re: Why did my prints suddenly drop in quality so badly?

I definitely remember that pattern of "pulsing" defects from my past. Basically, your extruded filament looks like it is changing volume cyclically in time as it is laid down affecting the perimeter quality/pattern and overall adhesion between layers. 

Unfortunately, my memory sucks at this age, so I can't definitively say what cured it for me. But, with the remants of brain I have left, I can still guess along with everyone else.

My best guess is that it may be the result of periodic temperature fluctuations at your extruder. There are a number of threads here that show how to calibrate the temperature controls to get a flat response. It would be good to look at/publish your typical temperature profile over time.

My not so best guess is that it may be caused by periodic drive fluctuations of the filament (contamination of drive rollers, etc.), which might help explain why it may have changed over time.

I'm sorry to be guessing, as I know I had this problem at some time and fixed it somehow. Have pity on an old man.

"Merely corroborative detail, intended to give artistic verisimilitude to an otherwise bald and
unconvincing narrative." Pooh in "The Mikado", Gilbert and Sullivan

6 Reply by adrian

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Re: Why did my prints suddenly drop in quality so badly?

1st suggestion: All filament has different filament widths and flow rates based on its thermal properties... there is no such thing as 'one setting for all' - you haven't elaborated on if you've adjusted filament width and flow multipliers between each 1kg of filament, since its unlikely to be perfectly the same.

then check your tension arm is tight. poor tension on the filament presents the same as extrusion underflow.

On several earlier SD2/3's, there have been issues with the threaded rod loosing its friction lock against the Z-motors drive-arm - even microslipping here can cause quality issues. Again, draw a black line from the drive-arm up onto the threaded rod - if the 'one' line becomes 'two' that are offset - then your drive rod is slipping. Reapply some thread lock and hope for the best or switch to a coupled solution.

and as for tuning by ear... you can do it just as easily visually - put a black sharpie line on the drive-arm, and then adjust it till you that line rotating smoothly... if its 'ticking' at all, back off the VREF - but do this only with the extruder at the appropriate temp for the filament. On an E3D, there can be performance differences between even 230 and 235 (colder filament is harder to push than less viscous/better melted filament...)

Run PID tune again too if you haven't lately.

7 Reply by mdrVB6 (edited by mdrVB6 2014-07-07 23:25:26)

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Re: Why did my prints suddenly drop in quality so badly?

Thanks Adrian.  I'm pretty good about filament flow calibrations.  I have a profile set up for each of the 4 rolls that I currently have on hand and it takes care of filament widths, extrusion multipliers, etc.  So I'm confident those are right.  Tension arm is also good, I have just a faint tooth mark in the filament after the drive gear and before it enters the hot end and it is evenly spaced. 

I put a mark where my Z motor connects to the drive rod and ran it up a down a few times.  No movement.

Now here is when it gets interesting.  I made the mark on the extruder drive gear and confirmed that it is had a lot of "ticking" and was not moving smooth like you said it should.  Yes, I have also done a steps per mm calibration and that is good.  Well, I hit up google pretty hard at work today and found a delta printer discussion group where some people were talking about tuning VREF on their DRV8825 drivers.  I guess it doesn't matter what board you have, a driver is a driver, hopefully.  Here is the discussion:

https://groups.google.com/forum/#!topic … uyQhUN7cmc

From here, I learned that you can just hold your multimeter probes on the trim pot and on the board's grount and read the voltage.  I assumed the voltages from solidoodle's help page is still good with the RUMBA and the upgraded drivers, so I am looking for:

X= 0.443 (or 4.43, not sure what magnitude I really wanted my meter to be in)
Y= 0.520
Z= 0.500
E= 0.192

Well, I was reading:
X= 0.194
Y= 0.295
Z= 0.319
E= 0.330

Doh! So I have had half the required current going to my axis drivers and double going to the extruder!  I had previsouly tuned them by hand so that there was not a wine noise but it seems that I was way off if the solidoodle stock values are indeed what I am looking for.  It's amazing I was getting anything out of the printer at these values.  So I used my ceramic screw driver and tuned them all into the stock values.  I've got a 5mm calibration steps printing now and it already looks like one of the best objects I have printed!

I am getting a little bit of the high pitched wine coming from my motors (I think it is Y or Z) at these values.  But the part looks great.  I just hit each motor with an infrared thermometer about 20 minutes into printing and I'm getting something in the 50 degrees C range for Y, Z and E but about 72 C on my X motor.  So hopefully these are not running too hot.  I will see.

I will run PID auto tune next but I'm not really having temp stability issues, so I don't anticipate a problem there.  Tests prints will be running all night and I will update as I go...

I'm interested if anyone else with a RUMBA and/ or these drivers wants to take a multi meter to it and see what values they are getting.

SD4 w/ RUMBA, E3D Volcano, all bearings, glass bed

8 Reply by adrian

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Re: Why did my prints suddenly drop in quality so badly?

http://www.soliforum.com/topic/2817/ste … ref-chart/ Has the correct voltages for most carrier boards.

Note, its not the DRV8825/A4988 bit that matters, but rather what 'sense resistor' is in use. For example, Klimets CoolDrv 8825's uses different values compared to Pololou's 8825... Seems like you might have the Pololou ones or ones that have a 0.05 as well..

9 Reply by mdrVB6

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Re: Why did my prints suddenly drop in quality so badly?

I should have known that someone had already looked up the values or various drivers.  These are the drivers I have:

http://www.reprapdiscount.com/electroni … iver.html#

So if I am understanding correctly, I want to use the values in that chart on the second row for "Pololu 8825", right?  So the solidoodle stock values are still a lot closer to correct than what I was using, but I could still get better.

SD4 w/ RUMBA, E3D Volcano, all bearings, glass bed

10 Reply by adrian

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Re: Why did my prints suddenly drop in quality so badly?

If you got the CoolDrv, they used to use a 0.01 sense resistor and you need to use the first line.
If they have changed them to use a 0.05, then yes, use the second line.

Based on the figures you're talking you have set, it would appear they do have 0.05, since you can't reach much over 0.4 with the 0.01 sense.

So yeah - historically you need the top line - but if its changed recently the second line may be more appropriate

11 Reply by mdrVB6

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Re: Why did my prints suddenly drop in quality so badly?

Okay, apparently I do have the CoolDRV.  I tried it with the pololu settings and it over temped my Y motor, which shut off.  Luckily, I was here watching it and I killed the job right away.  My drivers also got to over 70 C with my large desktop cooling fan on it and my X motor was over 100C.  Luckily, I let it all cool and everything still worked fine. 

I tried the CoolDRV settings and it hummed along nicely, so I guess that is it. 

I'm considering this problem solved, thanks Adrian!  I am still interested in eventually doing some kind of Z axis upgrade and an E3D hot end replacement, but I've got very good print quality out of tuning VREF.  I'll post a picture tomorrow but I'm confident I am now past the crappy layer adhesion and spotty printing that prompted this post.

SD4 w/ RUMBA, E3D Volcano, all bearings, glass bed