Improving print quality

[jesse]

I printed out the calibration cube and a few other objects this weekend.

What are some other objects in STL format that can be used for calibration and debugging?

I'd like to post the prints and the settings used in order to get troubleshooting advice.

[Polygonhell]

IMO a single walled test cube and a 100% filled cube are the two best ways to calibrate, I also print a single walled cylinder, and various things for setting up retraction.

[jesse]

Here are some of my test prints. They were printed using the default settings from the PDF instructions.

Calibration wall: http://www.thingiverse.com/thing:5573

[img]http://i.imgur.com/VqB8fo2.jpg[/img]

Thin tall cylinder cup: http://www.thingiverse.com/thing:49143

[img]http://i.imgur.com/XLv4S0q.png[/img]
[img]http://i.imgur.com/L8o9wgc.jpg[/img]
[img]http://i.imgur.com/WeYyKnr.jpg[/img]

Calibration cube: http://www.thingiverse.com/thing:5011

[img]http://i.imgur.com/ZSjaQ2X.jpg[/img]

[Polygonhell]

Firstly your filament is slipping intermittently, this could be because your temperature is slightly too low, or because of mechanical issues with the extruder. Possibly pinch roller to tight/loose, check the assembly of it, making sure everything that is supposed to be tight is.
You can tell this most clearly from the cylinder print, you have a layer where you have like dots instead of a solid line, that's caused because of filament starvation, causing the filament to thin and break.
It's probably the source of a lot of your quality issues.

The single wall test cube has uneven walls, IMO it looks like you were printing either too hot, too fast, or with insufficient cooling. If your temperature is good, you need to spend as much as 20s a layer to let it cool enough without a fan.

If you can get a single wall print with good alignment, then tune a 100% fill print so it retains that alignment, you're 99% of the way to a well calibrated printer.

I personally like to calibrate printers at what most would consider hideously slow speeds, 5-10mm/s, then increase the speeds later. It removes many causes of poor quality, which you can address later when you know they are speed related.

[mhackney]

I'm also going through the calibration process now. I have the newest nozzle design and a fair amount of printing experience with an H-1 and H-1.1.

I've been struggling to get good flow. My temps are MUCH higher for the same 1.75mm filament than I need on my H-1 or 1.1. This green filament is my go-to material, it flows like melted butter at 200°C on the other machines. On this machine I have cranked as high as 245 and still have issues. I am not convinced it is temperature related. I've disassembled and checked the Steve's extruder twice. I have it setup now so I can't stop it from pushing the filament (in air) but is not crushing it. Very similar to how the other 2 are set up.

I think I know why I'm having problems now but I am not sure why or what to do about it. Here is a photo:

[img]http://mhackney.zenfolio.com/img/s8/v75 ... 8760-4.jpg[/img]

The top is up towards the Bowden tube. You can see the filament is "locked" in the tube on the bottom 15mm. When I pull the filament out from the top I measure that section at a little over 2mm! So the filament has increased in diameter and locked in the teflon tube.

I have a theory on how this is happening:

The pressure to push the melt through the orifice seems quite high (when "measured" by pushing the filament through by hand). This may be a factor of this new nozzle but I have not actually looked at my other nozzles yet to compare and maybe try one on this machine. This new nozzle does have a 66mm long orifice (that is .5mm D for my nozzle). The extra pressure may be causing the soft filament above the nozzle to expand from the force from the extruder.

If this is the case, increasing the temp will likely worsen the problem. Decreasing it may cause issues pushing through the long nozzle bore. A catch 22. I have not tried a cooling fan on the upper barrel - I need to take one off my other machines to test since my new fan is on backorder.

I also notice that the outside of the teflon tube where it enters the nozzle is compressed. You can just make it out in the photo at the bottom. This may also be contributing to the back pressure. I have replaced this inner tube twice and this has happened on all 3 tubes. It definitely increases friction in this area too. However, you might be able to see in the photo that the filament is actually locked above this constriction.

cheers,
Michael

[Highcooley]

Interesting findings.

Always speaking about PLA, I did have the filament expanding and filling the whole diameter of the inner tubes for about 15 mm with every hot-end I ever possessed. So, I consider this as normal.
With Steve's bowden hot-end, it is sometimes hard to change filament, as the part with the larger diameter does not fit backwards through the push-fit. I always have to retract and advance the filament several times, until the thicker part is fully melted and can be squeezed through the bottle neck. This is the same with the old and the new nozzle.

I don't know, if the expansion of the filament inside the small tube against the hard metal orifice increases back pressure compared to the old nozzle with the double tube against the wider nozzle wall. As my other hot-ends of other printers are constructed a bit differently, I cannot compare.

Hmmm, I do have some white PTFE tube from reprapworld laying around, which feels a bit more stiff but also more slippery. Maybe I give it a shot.
I already had this tubing working successfully with the old nozzle by chance, as I cut the original tubing a bit too short for the old nozzle. I don't know why, but I changed back to the original tube for the new nozzle. I'll report on the difference, once I find time to test it.

[Polygonhell]

If that's PLA it's too hot.
I've never managed to print PLA on either of my Steve's (Mk1 or Mk2) extruders without a fan and not have it jam at some point.

I haven't installed the "new" nozzle yet, the older nozzle for the MK2 Steve's also took more force than I expected to manually push filament through even without the bowden cable connected. I assume you've tried pushing it through the nozzle without the bowden cable connected?

I do think the thermister is reading high, but not by a lot (maybe 10 degrees), I've checked with a thermocouple in the AL block and it's actually spot on, but I think the Al block is actually hotter than the brass nozzle (because of it's better conduction), I keep meaning to remove the inner liner and run a thermcouple into the hotend to verify, but it's a pain in the ass to do it now.

I have seen something similar to what you are seeing, do you by chance have retraction set to a largish value? I think there is an issue if you have frequent retraction where pulling the molten blob up and down the ptfe liner causes the PLA mushroom to creep up the hotend.

[mhackney]

I am printing ABS. So here is where I am now:

I set my hot end to 200°C and attempted to extrude (into air). I slowly cranked the temp up and extruded 10mm to see when I would get a good flow of the correct volume (see post on my build thread). That happens around 210°C.

Then, I resliced slowing everything down to 10 mm/sec (and 80% for 1st layer).

I replaced the 2mm ID teflon tube with stock I bought from McMaster.

I then rechecked my Z=0 and the nozzle just touches a .001" feeler. I then rechecked X, Y, Z MAX LENGTHS and again, just touches a .001 feeler.

I am running a print now but have some observations.

1. Firstly, even though I calibrated as above and Z=0 is dead nuts, the first layer is supposed to be .035mm (as set in slic3r) but it is significantly less than that. The 1st layer is extremely thin. I restarted several times and each restart had the same results.
2. I am also translating the part (calibration cube) to X = 50mm just so it isn't printing over the hot spot on the Onyx.
3. I noticed that the first layer, although very thin all around, is extremely thin on the side closest to the X and Y axis - this is in the X direction at the "front" of the cube.
4. The filament is flowing very nicely at 210°C. I think the hotter temps I was running caused more problems than they were supposed to be solving.
5. Overall, the print looks better. It is about 1/3 way through. The corner edges are not very straight and some little blobs on the corners.
6. I am doing .4 fill density, rectilinear at 0° - the infills all around don't seem to go to the perimeter all the way. It looks like the nozzle moves to the correct location but the molten filament is retracting or shrinking away a bit. Not noticed this on my other printers.

I did not adjust the retraction but that is a good pointer. I'm doing 8mm at 60 mm/s with 0 lift Z.

Cheers,
Michael

[Polygonhell]

Did you set Z=0 with the heated bed and the hotend warmed up? it can easilly make as much as a 0.2mm difference

is supposed to be .035mm (as set in slic3r)

I assume this means 0.35mm

I noticed that the first layer, although very thin all around, is extremely thin on the side closest to the X and Y axis - this is in the X direction at the "front" of the cube.

Then likely you need to adjust an endstop, or the DELTARADIUS in the firmware, it can also be a mechanical issue.
Try this do the calibration, but also check the mirrored coordinate after you have all 3 coordinates in a plane, i.e. if you are checking 0, -90 also check 0, 90 if there is a significant difference it can't be caused by the firmware calculation, and either the bed is not flat (unlikely for a piece of glass) or the tower is not entirely vertical.

[mhackney]

Thanks,

No, I set things cold - didn't want to burn myself! I'll redo it hot.

I did mean .35 mm thick layers.

Hmm, DELTARADIUS is new to me! I don't recall seeing that or setting it. Good suggestion on the mirrored coordinates, I'll try that. Should this be done "hot" too? Probably it sounds like.

cheers,
Michael

[Highcooley]

All right...maybe this is just a one hit and a lucky punch, but I changed to the white PTFE tube (although hard to say, if it is really a bit more slippery, I still think it is) and the two first prints work fabulous...almost no build up or drag at the nozzle, nothing...I have all the original temperatures set which I already used with the old nozzle. One thing, I did was cutting the tube 1mm longer than the one that came with the hot-end, is it was almost too short to clamp between the push fit and the nozzle.

I am printing @ 42/55 mm/min without any problem.

Measuring the diameters...the white tube is 0.1mm wider on both, inner and outher diameter. It's hard to tell, if this has any influence to print quality, but that's what I noticed?!? If you have some other PTFE tube laying around, why not give it a try. Of course I wouldn't already recommend to go PTFE shopping just because of this positive report

[mhackney]

My tubing is exactly the same dimension as what SMC sells. Where did you get your tubing. That extra .1mm larger ID could make a big difference.
regards,
Michael

[mhackney]

Pokygonhell, you are indeed correct, setting Z with a hot bed and nozzle results in a .05mm shorter Z distance! Very consistent and when I cool and measure with a feeler gauge, I can verify and reproduce the difference. So now I get to go back and recalibrate with everything hot.

I suppose it will be necessary to do one set of calibrations at 210°C nozzle/100°C bed for ABS and another at lower temps for PLA.

Thanks for the tip.

Cheers,
Michael

[Highcooley]

I thought it was from reprapworld.com. However, this is not the case. It was some broken (burst) tube, that was originally shiped with my sumpod by Richard Sum. Sorry, but I don't know where he was sourcing this tube. If I google for 2.1mm teflon tube, I find US suppliers of PTFE tube with 0.085 inch outher diameter. So you probably have to look for 0.085 inch inner diameter tubing in order to find the wider tubing.

If you don't manage to find such tubing at all, give me a shout and I send you some of the last cm I have.

Cheers
Andy

[mhackney]

Ok, I am now starting to make some good progress on improving print quality AND not wasting a lot of time or plastic.

First, some observations:

• The filament spool holder on the Rostock is a nice feature but I find that there is too much friction with the stock Spool Axel. I realized that some of me "filament starving" issues were due to the filament not coming off the spool easily. I've been keeping an eye on it and helping it manually for now. I think an axel with bearings will be much better and a good first "real print".
• I've been wasting too much time with the calibration cube and not really getting good feedback. I just downloaded The Essential Calibration Set from thingiverse and using the .5mm thin wall shell. It prints fast and provides great feedback. Once I am through with it, the other calibration objects also look interesting.
• Calibrating Z=0 and the tower lengths is essential to do hot! This made a big difference in my first layer thickness and, therefore, quality. Now I am putting down a first layer at the expected thickness.

Starting with the .5mm thin wall calibration object I started a print with these basic parameters:]

10mm/s for all speeds except first layer speed at 30%
200mm travel
.36mm layer and 1st layer height
3mm retraction
210°C nozzle 100°C bed
random starting points
2 skirt loops

I immediately discovered that the nozzle drags across the previous layer and causes problems (delamination for instance). Since a delta printer can move in any cartesian direction pretty quickly, I simply added a 3mm Lift Z (on the Printer Settings tab in slicer). This made a huge difference. I completed my first ever single wall print on the Rostock by adding the Lift Z. Here is a photo of that print (purposely unflattering - see below):

[img]http://mhackney.zenfolio.com/img/s3/v44 ... 1948-3.jpg[/img]

Note that the skirt loops stuck nicely and are even thickness and right on the money at .036mm! Only part of the first loop printed as the extruder was getting prepped. Also note that the single wall is nicely layered (although maybe a bit wavy from mechanical backlash) and complete all the way around. The blobby back wall is where the layer ends/starts were randomized. I'll need to fine tune the Retraction parameters on the Printer Settings tab.

I'll do a little more fine tuning on this part before trying one of the others. But, I am now starting to get somewhere!

cheers,
Michael

note: copying this post to my build thread too

[Polygonhell]

Thanks,

No, I set things cold - didn't want to burn myself! I'll redo it hot.

I did mean .35 mm thick layers.

Hmm, DELTARADIUS is new to me! I don't recall seeing that or setting it. Good suggestion on the mirrored coordinates, I'll try that. Should this be done "hot" too? Probably it sounds like.

cheers,
Michael

The guide I usually recomend for calibration is gone, however it's still in the google cache here
http://webcache.googleusercontent.com/s ... clnk&gl=us

The only thing you need to do hot is set the final ZHeight.
The process should be more or less
Set 3 equa-distant outside points to form a plane

• NOTE - changing one endstop screw will also change the Zoffset of the other two slightly, so always measure all 3 then adjust
• Change only 2 screws to make the plane or you'll chase level forever

Adjust the DELTARADIUS constant in the frimware to remove any convex/concaveness in the motion

• Just adjust it until the center is at the same height as the outside points you just set
• Again changing this will change all the measurements, so you have to remeasure at least one outside point for the comparison

Finally Set the Zheight

• Everything up to this point is just relative to other measurements
• This needs to be done hot

NOTE use M114 to get the ZHeight, DONOT believe the numbers Repetier Host is reporting.

[mhackney]

I am doing a set of very controlled experiments and keeping notes. Printing the .5mm shell object and have it basically nailed. Some observations:

I started with retract and Z Lift. I found that the nozzle design is a lot different than the earlier pointier design that it drags and sticks to the filament a bit. With a delta design, doing a quick Z lift at the end does the trick. I also saw little blobs at the start of a layer so I experimented with retract. Here is the sequence of tests:

10mm/s speeds, 220°C nozzle:
0mm retract, 3mm Z lift - blobs
10mm retract, 3mm Z lift - 2mm gaps in the layers
5mm retract, 3mm Z lift - smaller blobs than no retract

I also test 3mm retract (blobs) and 4mm (very slight blobs) so 5mm retract was optimal for this filament and other parameters.

I then started lowering the nozzle temp by 5°C. 210°C looked ever so slightly better (less stringing) but 205° was very bad - it wouldn't stick to the heated bed or previous layers.

I did a quick retest of retract with a 210°C nozzle. 5mm remained optimum.

I'll next lower Z lift, this is really just an optimization for speed. Then I'll start ramping up the print speed and fine tune as I go.

So far, looking pretty good.

cheers,
Michael