I'm trying to print a simple 4x4mm hollow square column with Cura.

I’m trying to print a simple 4x4mm hollow square column with Cura. Starts out fine, but then holes appear in the walls (0.6mm thickness, 0.1mm layer height). Apparently not enough PLA from the feeder?
Any tips on how to achieve a better print? I already raised the temp 10 degrees and lowered speed and the filament thickness a bit in Cura to increase extrusion (I think). How would you prevent holes in the walls?

Is your extruder skipping or biting far enough into the filament that your gear/hobbed bolt/whatever grabs the filament is becoming full of filament dust?

That will cause inadequate extrusion like this, since at that point the extruder has lost its grip on the filament.

@Stephen_Baird I see the filament in the bowden tube (it’s an @Ultimaker ) has teethmarks on it, so that seems okay. But the feeder wheel hardly turns (I can see it turn when I watch closely), probably because it has so little PLA to feed to the extruder. I increased the wall thickness in Cura to 0.8mm, the preview shows it takes two times to draw a wall with a 0.4mm nozzle. With 0.8 the print starts out really massive, but after about 5mm height the holes appear again.

It might be that your extruder motor driver is overheating and cutting out. I had this problem with my printer until I switched to a geared extruder motor.

@Andrew_Lindsey I can easily touch the motor itself, can’t be more than 50C. The driver would be on the Arduino board, right? Is there an easy way to check? (Maybe this subject would be better on the @Ultimaker forum…)
Even with complete infill (Cura Quickprint mode, high quality setting) the print turns out horrible.

https://lh3.googleusercontent.com/-2uOQ3dwDXLQ/UPbOW0vx-PI/AAAAAAAACzc/JphZfd5xELo/s956/failed+prints+4x4mm.jpg The third one with Cura’s hollow-vase setting is the least horrible print…

What controller are you using? The motor driver is either on your controller board, or on a servo driver module plugged into your controller board. Whichever it is, it should have a heatsink and a fan blowing air on it. It should also have a pot to adjust the current limit, try seeing if changing that has any effect.

@Andrew_Lindsey Okay, thanks for the suggestion! I’ll check at the Ultimaker forum first before I start touching stuff on the board :stuck_out_tongue: http://forum.ultimaker.com/viewtopic.php?f=19&t=2364

It’s heat. there is not enough time for the layers below to cool and thus they are slumping. When the head pases over for the next layer the gap gets bigger and bigger. You will need to drop the heat to 185 for PLA (use a bit hotter on base layer) and have a fan blowing on the part. Also slow the speed to 10mm or less.

A short (low quality, sorry) webcam clip showing the hollow column to fail at the top, after it can’t deposit plastic on starting gaps. Also it starts out at 4x4mm and gradually starts to shrink at every layer it seems.

layer height 0.2
wall thickness 0.6
fill 0
printspeed 50 mm/s
temp 190
fil.diameter 2.89
nozzle 0.4
min. layer time 3s
fan 100%
no Joris

And here’s at 185 C http://www.youtube.com/watch?v=G9w8rsH4U7c

Add some cooling to increase the strength of the previously deposited plastic, slow down to let the previously deposited plastic cool and strengthen. Maybe reduce the temperature to deposit a firmer layer, especially if there are hairy, liquid threads drifting around.

Would you get the same gapping with a larger 8x8mm less wobbly column?

@David_Forrest Ah, good idea, I hadn’t thought of a 8x8mm one to test it. I did try printing 3 columns at once though, giving each column more time to cool. Which produces results that are a lot better. Printed at 185C, speed 20mm/s, and layer 0.2mm:

I had to turn off retraction in Cura, because of the many retraction blobs that occurred. So, lots of threads now.

Tried it with 3 columns at the far corners of the printing bed (so the threads would maybe break?) at 0.1mm layer height, but that was horrible again, holes, not enough extrusion…

@Jan-Pieter , as long as you have v2 hotend, v3 bolt and the new extruder clamp you should be ready to go for a massive load of retraction.

You need to find the right speed, full cooling and accurately measure the diameter of your filament (forget about all the cheating). What you need to keep in mind: As soon as you have so much stringing (by disabling retraction) you’re loosing material in your equation! The printer won’t magically compensate for it. So enable retraction, don’t loose material on the way and provide the printer with the best possible filament and its diameter.

This print should really work with your printer! Keep us in the loop on your progress :slight_smile:

@Florian_Horsch_flouS Ah, interesting. I usually have retraction speed at 90 mm/s over a distance of 4,5mm with 0 extra lenght on start. So then I just keep increasing the filament diameter until there’s no more stringing? :slight_smile:
How would you print a (hollow) 4x4mm column?

No, sounds like a misunderstanding here. Let’s try again:

Try 70 mm/s over 4.5mm (NO EXTRA LENGTH EVER! That would be the parameter to compensate for lost material, which you’re trying to prevent in the first place… so no extra length please!). Min. distance must be shorter than the minimum distance you want to see retraction at. So if your pillars are 10mm away from each other you should at least insert 9 mm (or just leave it at a sane value of 2mm for all prints!).

So back to the question how I would print it:
0.1 mm layers, also possibly printing multiple of them to escape any cooling issues. But before that I would try a single one. Depending on your desired wall thickness I would go for one to three perimeter lines (e.g. 3 * 0.4 mm = 1.2 wall thickness). If you’re in for just one perimeter line you should definitely try the “Joris the outer edge mode” in the expert settings (up in the top navigation bar), because then you have a continuous Z travel - very nice!

Fan: Full speed! Possibly I would add another ventilation device next to the printer - that could fix all your troubles.

Speed: Try to find a speed where it doesn’t end up in a big molten mess. It shouldn’t be too slow (or the nozzle will remelt everything) and shouldn’t be too fast (or the new material doesn’t have time to cool down).

Temperature: Go as low as you can comfortably print. This really depends on your filament. I’ve seen good PLA which was still coming out great at 185 °C, but first I would try 190 °C or something more “secure” (in terms of not risking that there’s too much pressure in the nozzle).

Hope that helps! I’m in the middle of a print, otherwise I would give it a shot. Try single walled (0.4mm nozzle setting + 0.4 wall thickness + Joris mode on) - that could be perfect!

Btw: @Jan-Pieter please make sure that you’re printer is really retracting, instead of just faking it. Please check that by looking at the videos of slide #20 and #21 within my blog post: http://techwall.net/ultievening-protospace#more

If you’re seeing crippled retraction on your machine please upgrade to a newer version of the firmware through Cura (http://software.ultimaker.com)

@Florian_Horsch_flouS Right, I’ll try three columns (for cooling) at 0.1 height, 0.4 wall, 185C, 20 mm/s speed, 2.90 diameter, 70 mm/s retraction of 4,5 mm and 3s min. layer time. Have the latest firmware via Cura (nov 2012 ultimaker). Printing… nów! :slight_smile:

And cancelling because the first layer didn’t stick at 185C. Will do first layer(s) at 200C, then go down to 185C.

@Florian_Horsch_flouS Looking better already :slight_smile:

Changes: lower speed, increased diameter from 2.89 -> 2.90, retraction turned on.

Ok… probably still a bit too much material (try 2.91 or 2.92 ?!), also I had sometimes better retraction results with highter temperatures (not really intuitive… so you could also try 200 C for the whole print).

And probably the best tip: I would arrange those pillar not in a row. Otherwise you wipe the middle one too often, right?

Also check the retraction as discussed above (I don’t like the tiny stringing on your pillars. That shouldn’t be the case.

Do you have “joris” on?

Good progress!