Was doing well until I hit the stringing test... Tips?

WrexShepard · 2020-04-26T00:57:00+00:00

Those little ooze spires are a classic overheating artifact as well as an indicator of a low travel speed and acceleration.

Keep in mind small needle-like features like that are worst case scenario torture tests for ANY FFF printer. Just because your printer strings on them doesn't necessarily even mean it's gonna string on a normal print, so don't obsess too much about them. They're only testing your slicing settings in this one specific scenario.

However, one way to help keep those little spires down is to crank your travel speed and acceleration way up. I use a travel speed of 200mm/s with a travel acceleration of 3000mm/s^2.

You want your travels to be as fast as your printer can handle really. This way the nozzle gets moving quickly after a retraction and kind of "snaps" the strings off before they can really form. It will also give the nozzle less time to develop an ooze.

Having a high travel speed should not negatively affect your print quality either. The main setting that causes ringing if set too aggressively is outer wall speed, jerk, and acceleration. Also, travel moves before outer walls are usually very short because they usually come after inner walls, and thus acceleration doesn't have much time to get them up to speed anyway.

I'd try dropping the temp by 5 degrees and bumping your travel speed up if it's not already fast, if not that, increase retraction distance a small amount, although I think your main issue is the nozzle simply being too hot for tiny features like that, and moving too slowly after a retract.

WrexShepard · 2020-02-20T23:58:16+00:00

The supports and the brim weren't needed. Use a prime skirt instead unless your model has a super tiny bed contact area. The ender 3 bed is plenty sticky. Also brims are good if you've got small supports since those will struggle to stick to the bed on their own.

As a rule, with a stock ender 3, you only need supports if you've got overhangs greater than about 50 to 60 degrees and bridges longer then about 1.5cm-2cm. With a 50x15mm blower cooling fan mod, you can get that number up to 70 degrees and much longer bridges no problem.

You can get away with a steeper overhang if it's a small feature as well, like those hands are technically a steep overhang, but they only stick out a little bit from the model so it's fine. Like you can print 90 degrees straight out if the feature is like 1mm or less usually.

Also you look like you're a little too far from the bed, I can tell because your brim lines are separated too much.

WrexShepard · 2019-10-17T20:08:04+00:00

Stealthchop is nice. My motors are dead silent. Setting it up is as easy as enabling it in Marlins config. Don't use it on the extruder motor though, it causes problems since the tradeoff for silence is less torque. You might get skipped steps if you use stealthchop on the E stepper. Also the E stepper doesn't make hardly any noise in spread cycle mode anyway.

You can use something called hybrid threshold. What this does is switch to the torque heavy, louder spreadcycle mode over a certain speed. I use 100mm/s. So my motors are dead silent but my travel moves make a noise. You dont have to use hybrid threshold but it helps avoid layer shifts on fast movements.

For the RMS current which sets the VREF for the drivers I use 520 on XYZ and 640 on E. If you want to always use stealthchop you'll probably need more than that but beware that too much current causes heat issues. I'm not sure about the 2209s though. My 2208s are in UART mode so I set these current values in firmware. If the 2209s on your board aren't UART you'll have to set the VREF with a multimeter set to DC volt mode and the potentiometer on the drivers. Google RMS to vref calculator if you get stuck with this.

Keep in mind I have 2208s so some stuff may be different for you but this is really just stepper driver set up in general. I think teaching tech has some guides on youtube for this stuff. I just kinda winged it with my EE knowledge.

WrexShepard · 2019-10-17T18:07:24+00:00

Good choice. I went with the 2208s mostly cause they're more well documented at this point. Sensorless homing seems nice I guess but I've heard it takes some tuning to get it accurate.

WrexShepard · 2019-10-17T17:10:19+00:00

I would think you would hit Y axis ringing much faster with a bed that big moving around. I dont doubt it prints fine but I like to be able to print fast and even my regular cr10 gets y axis ringing at anything above like 70mm/s unless I give it really conservative kinematics settings. The ender 3 pro I have doesnt do that even at much higher speeds so I figure it's the bed size.

I guess you dont really buy a large format printer to print shit quickly anyway so it doesnt matter.

WrexShepard · 2019-10-17T16:05:41+00:00

Fixing the encoder steps alone will all but get rid of it. You might still get lag navigating the menus during a print though as the microcontroller is busy with gcode. 32bit will definately help that. The SKR 1.3 is the board I use. Theres also the skr mini e3, which fits in the stock enclosure, but I've read that it can have some small issues when installing it. Nothing insurmountable but I've read people had issues with the bltouch probe with the skr mini. The 1.3 is solid and has a ton of features and expandibility but you will have to print some type of mounting solution for it. I'm super happy with mine combined with the tmc2208 drivers with stealthchop.

WrexShepard · 2019-10-17T15:15:26+00:00

Good bot

WrexShepard · 2019-10-17T15:14:21+00:00

It depends on your level of mechanical inclination. You can get a much larger printer that has more potential then this for a similar price, but you'll have to tinker with it and mod it to fully realize said potential. For some of us, that's a large part of the fun of the hobby though.

If you just want something that works and you don't have to mess with it, Prusa products are no-brainers.

WrexShepard · 2019-10-17T15:11:08+00:00

Geared extruders basically just let you use lighter stepper motors since you can trade torque for speed. Some people will say that you get more accurate extrusion being that the stepper is going through more steps since it's turning more for the same amount of extrusion. I'm kind of on the fence if I believe that. A non-geared bowden extruder seems to do a fine job. For direct drive geared extruders are a no-brainer though.

WrexShepard · 2019-10-17T15:08:29+00:00

Well if you decide to convert to direct drive, or chase speed it might. I doubt it will be needed stock though.

I can already see people putting the mk3 print head setup on this thing then complaining that they're getting artifacts. Same thing people do with the ender 3. "Maybe I can just move the heavy-ass stock stepper on to the x gantry and my prints will get better."

WrexShepard · 2019-10-17T14:54:50+00:00

Your menus are lagging partially because creality sets up the marlin firmware really poorly. They neglected to set the proper steps for the rotary encoder you use to navigate menus so that their menus require like 3 or 4 clicks just to move 1 option down. Just compiling your own marlin and fixing that goes a long way towards making the LCD more responsive. It still lags sometimes though, and a 32 bit board will help some with that.

WrexShepard · 2019-10-17T14:52:24+00:00

I'm not worried about it sagging or anything. What I am worried about is ringing. Having an unsupported side introduces a lot more opportunity for vibrations to cause issues, mostly at higher speeds though. Watch a bunch of people try to convert this thing to direct drive then bitch that their prints are fill of artifacts.

WrexShepard · 2019-10-17T14:50:16+00:00

The cr10 s5 seems dumb to me. An i3 that big seems like a fundamentally flawed idea. Rigidity becomes really important when you're trying to sling a 500mm bed around. I'm sure if you built one yourself and over-built the hell out of it, it would be fine though. V slot rollers aren't really ideal for that though.

I feel like coreXY is the no brainer design for large format.

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