Some Calibration, 2 good prints, then spagetti

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Some Calibration, 2 good prints, then spagetti

Postby Cantrell » 2015-Jan-Thu-01-Jan

So I built my Simple Metal today.

During phase 3 (Setting Up Your Auto-Leveling Probe and Your First Print) I started out with clear z-index issues, stringy prints.

Then I had a few prints curve up at the edges part-way through the base and catch the extruder, knocking them off the base.

Finally, I succeeded, and got my fan shroud.

I noticed that I'd gotten a few settings wrong, so I fixed them, and printed another fan shroud. After 1 detached early in the print (same as before), I had another success, with about the same quality as the first.

Then I started phase 4 (Loading a Configuration File and Printing an STL On Your Printrbot Simple), and I load all the settings.

I download the cube STL, slice it, and print ... and all of a sudden the extruded plastic won't stick and I get spagetti.

I've fooled around with the z-index, by .2mm increments, and either it won't stick, but by Z-.6 it seems too close as it just forms a ball of goo around the extruder.

I'm using blue painter's tape on my bed (the normal metal one, I didn't get the heated bed, yet).

I'm not sure what I did wrong, or what to try next.

I'm using a Simple Metal with repetier on Windows 8.1
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Some Calibration, 2 good prints, then spagetti

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Re: Some Calibration, 2 good prints, then spagetti

Postby musk » 2015-Jan-Thu-02-Jan

What layer height are you using? If you're printing with smaller (.1mm) layers you'll usually want to have the slicer create a thicker first layer to help bed adhesion. This makes perfect bed leveling less important and helps increase your margin of error. It's a setting in slic3r and other slicers.
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Re: Some Calibration, 2 good prints, then spagetti

Postby RetireeJay » 2015-Jan-Thu-10-Jan

Getting that first layer to stick is key. And no matter how good your bed preparation, it's not going to stick if you don't have the first layer height right. The plastic needs to be squished between the hot end and the bed. In other words, a round thread coming out of the hot end has to be squished into an oval shape lying on the bed. If no plastic at all is coming out, your clearance is insufficient. If the plastic thread is round, and not stuck well to the bed, your clearance is too much. Adjust in increments of 0.2 or 0.1mm to get it right.
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
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Print on glass with Scotch Craft Stick or other glue stick
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Re: Some Calibration, 2 good prints, then spagetti

Postby Cantrell » 2015-Jan-Thu-12-Jan

The round vs oval explanation RetireeJay gave is very helpful to understanding the ideal, and both your explanations on the first layer helped as well, thank you!

I had a .1 layer height with a .3 first layer. Tried .5 but it mentioned that I cannot set first layer height larger than the .4 nozzle, which makes sense. So I went with the full .4

Definite improvement, but still no joy.

Understanding that the first layer was important, I compared all of the default settings to the defaults for my first print, and under speed the first layer speed was set to 75% (compared to the 30% from my successful print).

So I've also changed my first layer speed down to 30%, and I got a few layers down (of the cube print) when I noticed the corners were warping upwards significantly. By the 3rd or so layer, it broke free from the bed.

I'm wondering if this is an issue with my z index (which was -.5), so I tried going back to 0 (which was definitely too high, as I was seeing the plastic drip down to the bed). It looks like -.6 is my best. Closer to 0 and the first layer is round, and at -.7 it folds over the corners of the cube and I can't make it past the first layer.

Unfortunately, I still can't get this cube to stick. I start to notice the corners pulling free by the 2nd layer, and by layer 3 it keeps breaking free. So, the good news is that I think I've moved on from my first problem to my 2nd. :D

Side note: Oh, does the nozzle require any cleaning? After bad prints I tend to see goop on it that gets caught on the skirt at the beginning of the next print. Not sure how / if to clean it. Will have to look into that.

Second side note: How finely do you do tune your z index? The guide mentions using .1 or .2 increments but I've even seen people mention .05 as an increment.
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Re: Some Calibration, 2 good prints, then spagetti

Postby Cantrell » 2015-Jan-Thu-12-Jan

musk mentioned bed leveling, so I thought I'd post what the console shows when I hit play

Bed x: 10 y: 142.40 z: 0.56
Bed x: 10 y: 10 z: 0.77
Bed x: 142.40 y: 10 z: 0.88
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Re: Some Calibration, 2 good prints, then spagetti

Postby Cantrell » 2015-Jan-Thu-12-Jan

One more quick note, every time, when it starts printing the outer skirt loops, the very first time it puts the extruder down to extrude, it's extremely messy and tends to leave a strand connecting the start point to the head, which if left, will interfere with the print.

I've been snagging that each time and pulling it off, but I imagine it's not supposed to do that, and I'm not sure what's causing that.
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Re: Some Calibration, 2 good prints, then spagetti

Postby RetireeJay » 2015-Jan-Thu-12-Jan

Here's a compilation of posts about bed clearance and bed materials and bed preparation: viewtopic.php?f=16&t=7033
Also look at viewtopic.php?f=113&t=3757 and viewtopic.php?f=113&t=4454
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
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Re: Some Calibration, 2 good prints, then spagetti

Postby Cantrell » 2015-Jan-Thu-12-Jan

Excellent, will give them a read, thanks!
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Re: Some Calibration, 2 good prints, then spagetti

Postby Cantrell » 2015-Jan-Thu-14-Jan

So I'd used the same bed of tape for like 20 tries, and it may have been a source of error. Based on the treads you linked, I cleaned the bed of tape with 91% IPA, and started a new print. I have some hairspray for a future test, but I only want to vary one thing per try. :D

Currently at layer 19 of 294 and all corners appear to be adhering solidly, so this is looking like my best print yet; much nicer than the first two I made (and not spaghetti like the next few dozen :D ).

Thanks for the links, and comments; it's helping me foster an understanding of how the whole thing works, which helps me troubleshoot in general!
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Re: Some Calibration, 2 good prints, then spagetti

Postby Mooselake » 2015-Jan-Thu-14-Jan

Give the hairspray to your SO (or use it on your own hair if so inclined), and try gluestick instead. Hairspray can make a mess, and gluestick's a good way to get started.

I've been through Kapton, PET, blue tape, plain glass, sandblasted glass, acrylic floor finish, hairspray, things I've probably forgotten, and gluestick has been the most convenient so far. Plus it's cheap and easy, and like the name says it washes off without any problems.

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Re: Some Calibration, 2 good prints, then spagetti

Postby Cantrell » 2015-Jan-Thu-19-Jan

Does the glue stick go directly on the bare bed with no tape, or on top of the tape?

If it goes on the bare bed, how tough/involved is clean-up and how easy are parts to get off the bed afterwards? (edit: after re-reading you did mention cleanup was easy)

Quick update on the printout, not only did it not curl up on the edges after I cleaned the blue painter's tape with 91% IPA, but the shroud was REALLY firmly attached, and very tough to get up even with the tape (though I did manage). I'm anxious to try out something different, so the glue stick sounds great, I'm just curious as to the details.
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Re: Some Calibration, 2 good prints, then spagetti

Postby RetireeJay » 2015-Jan-Thu-21-Jan

I'm using glass on top of the bed, and it's held on by clips so it's easily removable. One treatment of glue can be re-used many times, and then refreshed in-place... but eventually the buildup of crud gets to be too much. A few swipes of the rag under running water cleans it up. You don't have to use glass, but I think for easy clean-up you would want some surface that's easily removed from the Printrbot (that would include tape).
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
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Re: Some Calibration, 2 good prints, then spagetti

Postby Cantrell » 2015-Jan-Fri-10-Jan

Gotcha; I've seen picture glass mentioned a few times in the posts you linked. I assume that's just the glass out of a cheap store bought picture frame, which I should be able to find in the right size. Heck I may have one already.

I assume I'll need to re-do my z-index (by the thickness of the glass), since I've changed the distance to the metal bed, which is the part the inductive z-stop works on? I've seen people mention the head 'crashing' into the glass when they tried it.
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Re: Some Calibration, 2 good prints, then spagetti

Postby Mooselake » 2015-Jan-Fri-11-Jan

I use double strength window glass, had a local shop cut 4 pieces so I could swap them (which, as it turns out, I've never done). I tried single strength, but my heated bed PCB is a bit warped and single strength would warp a bit with it. Double strength is flat within the tolerance of my dial gauge.

The real advantage of printing on glass is that it's flat, unless you warp it by pressing on it (in my case with the warped PCB). Single strength or thinner has worked for others, so maybe the warp was a moosecave thing. Try the thinner glass first, as it's less likely to interfere with your Z probe - a device that's not used here in the great white north.

You can put the gluestick directly on your bed, or on a blue taped bed, if you want. I'd recommend the tape, easier to clean than trying to wash plywood.

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Re: Some Calibration, 2 good prints, then spagetti

Postby Snowbound » 2015-Jan-Fri-17-Jan

It sounds like you're pretty close with -.5. Once you're close try small .02 adjustments, dropping to -.52 or -54.

Start the extruder heating before you start printing and let it sit hot for a few minutes to allow the nozzle to fully expand. This effects the Z height for the first layer.

If you're having sticking trouble and you're using tape, wipe the tape off with rubbing alcohol. It removes the waxy coating and then the print sticks very well.

Also, if you're getting ribbed sides try reducing the Extrusion Multiplier in the Filament settings. With the gray Printrbot 1.75mm I found that 0.85 is good.
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Re: Some Calibration, 2 good prints, then spagetti

Postby subether » 2015-Jan-Mon-00-Jan

FWIW, I've had good luck with Blue painter's tape, a light scrub with a chunk of paper towel with a good squirt of 70% IPA on it, followed with the purple glue stick. (the reason for the painter's tape is to give the plastic something to stick to that is also reasonably easy to remove; the IPA is to remove any oils or stuff off the tape, and the glue stick is to really hold down the plastic. )

You'll also want to turn off any fans in the room if you are going to do a largeish print to keep the curling down to a minimum; I was running a really large print and it lifted off the bed, tape and all from the curl.
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Re: Some Calibration, 2 good prints, then spagetti

Postby Cantrell » 2015-Feb-Sat-21-Feb

I haven't gotten glass yet, as I've been getting better and better with the tape. I use IPA for smaller prints only, and I've got a few settings files that I use for different situations (my Rough prints are 0.4 for all layers, middle ground is 0.4 for the first layer and 0.2 for the rest, and my 'high res' prints are 0.15 first layer and 0.1 for the rest).

Curling on the edges is something I'm still figuring out; a colleague of mine just bought one just like mine but with the heated bed, so I'm curious to see if he has fewer problems with curling. He's also thinking about trying glass to start.

I actually haven't had problems with the plastic pulling free from the tape, but I HAVE had problems with the plastic pulling the tape up from the bed too! I'm making some adjustments there; no fans in this room to turn off though.

I've got my first layer print speed back up to a respectable level (around 60% for 0.4mm, and 30% for 0.15). I could probably go a bit faster but I can't imagine it'd impact print times immensely.

At Snowbound's suggestion I've played with extrusion multiplier a little; I did a few test prints and I'm not sure what to think yet. The edges don't look terribly different but it's using less plastic to make the objects, which is a win itself. Curious what the downsides will be.

I also just played with my stepper motor current settings from another thread and am extremely pleased with the reduction in noise.

These forums have been a huge help to get me started, and I really appreciate everybody's feedback.
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