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Printing large prints

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Hey everyone,

I purchased an UM2 about 4 months ago and have usually been able to solve any issues by just searching the forums, that is until now. I'm attempting to print something that is rather large, almost the entire bed and wondered if there were any special 'tricks' I should know about.

5a330d0536e2a_IMG_20150423_1541521.thumb.jpg.a0bb3d10b834221f9724ad7642b138cf.jpg

Although the print is only 3mm high is has a lot of surface area, but I start to see issues when it starts the infill on the first layer, like this:

5a330d0577ad2_IMG_20150423_1542351.thumb.jpg.f446d00ff84ef6a6eed470835c54479d.jpg

The lines rarely touch, most of the issues seem to happen towards the back so I have played with adjusting the bed screw but making it any looser gives me really, really, flat lines and I'm worried about causing a jam. Would it be possible that when the printhead reaches the back the tube is bent as such a sharp angle that underextrusion is happening?

I've downloaded IrobertsI feeder but haven't installed it yet, I can't afford the downtime yet (this is a work printer). I switched filaments recently so here are the settings of my machine:

printer filament is 3mm PLA from here:http://www.voxelfactory.com/

layer height: 0.1mm

shell thickness: 0.8mm

retraction enabled

bottom/top thickness: 1mm

fill density: 25%

print speed: 60mm/s

Initial layer thickness: 0.15mm

Initial layer line width: 125%

travel speed: 100mm/s

bottom layer speed: 30mm/s

infill speed: 60mm/s

top/bottom speed: 40mm/s

outer shell speed: 50mm/s

inner shell speed: 50mm/s

combing: OFF

z hop: 0.15mm

Infill overlap: 25%

machine settings

filament: 3mm black PLA, I measured with a calliper in 4 different places and got the average of 2.96mm

print temp: 225C

total print speed: 25% for first layer, 75% for rest

fan:100%

bed temp: 60C

I've noticed that this filament is more powdery than the stuff that came with the printer, it's A LOT softer so the UM2 will not hesitate for a second to start grinding. Since it's so soft I've noticed that I can't get my printer to go faster than 60% total speed of the above settings without causing the knurled wheel to start chewing into the filament.

5a330d0536e2a_IMG_20150423_1541521.thumb.jpg.a0bb3d10b834221f9724ad7642b138cf.jpg

5a330d0577ad2_IMG_20150423_1542351.thumb.jpg.f446d00ff84ef6a6eed470835c54479d.jpg

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Check to make sure your glass is flat. In some cases (like mine) the glass plate isn't flat in some areas and you get gaps on the bottom layer. This normally goes away on the next layer or 2. You could also try adjusting the initial layer height.

Did you enter the actual filament diameter into the material Settings?

Also you should try and stick to 2.85 filament as you can get issues with 3mm especially if the tolerance changes and goes higher then 3mm.

softer material normally needs to be printed at lower speeds, you may also want to try increasing the temp a little to see if that helps.

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I just noticed you have z - hop turned on. Some Cura versions have under extrusion issues with this especially if it's set higher then the layer height. This can be seen in layer View where the lines won't be touching each other.

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.15 for initial layer height is extra difficult to level the bed perfectly. The default is .3 and you should consider sticking with that value.

Also, better to get extra flat lines as you mentioned than to have the lines not touch.

If you get issues with corners lifting off the bed switch to brim mode instead of skirt mode as you have it now.

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Also you should try and stick to 2.85 filament as you can get issues with 3mm especially if the tolerance changes and goes higher then 3mm.

When I did my initial search for 2.85mm I kept getting hits on google for 3mm, I then found a thread (not here) where someone called 2.85mm and 3mm the same thing, that mixed with my inability to find a candian supplier for 2.85mm for the color I needed I ended up just going with 3mm. It is irritating how soft it is but I'll just chalk it up to another lesson learned.

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.15 for initial layer height is extra difficult to level the bed perfectly.  The default is .3 and you should consider sticking with that value.

I will adjust that and post some pictures of my new print

 

If you get issues with corners lifting off the bed switch to brim mode instead of skirt mode as you have it now.

Actually the one good thing about this soft filament is I've noticed next to no lifting what so ever, even on a print this big. That actually reminds me, before this filament I was using the filament that came with the printer which stuck nicely just on the glass, I've only just recently been forced to cover the bed with kapton tape to get this new filament to stick

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Hey everyone I just thought I would give a little update. The above mentioned print, although having a beautifully printed first layer, failed yet again. This new material I got fails after a few hours, usually after I've left work. I printed something smaller that would take just as long and it failed too.

I've narrowed the issue down to either:

1. I'm printing at too high of a temperature (225C) and the nozzle is slowly getting clogged with burnt plastic. I say this because I've noticed that it has a lower melting point and when it first extrudes to clean itself out I see some smoke.

2. My stock feeder is failing me. One of the first things I did with this printer once I had it calibrated was print roberts feeder. I installed it yesterday and ran it for a test drive when I got into work this morning. I noticed right away that I was able to print at higher speeds where the stock feeder would click.

I will see if these solutions fix my overall problem with printing large objects, hopefully this doesn't stray from the topic too much.

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5a330d3a5216e_IMG_20150430_1450071.thumb.jpg.1a4370bc7b815201077ba34e3a94f4b0.jpg

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So another update:

Turns out temperature was the main problem with all this. The PLA that came stock with the UM2 was being printed @225C and this new filament had a significantly lower temp of 200C.

Looks like it wasn't the size of the print but rather the temperature I was running it at, the constant high temp would eventually clog the nozzle with burnt bits of plastic and I couldn't see it since I was using black PLA. I've attached a few photos of a piece I'm printing to prove this point.

5a330d4f4473d_IMG_20150504_1410271.thumb.jpg.8d85fdfcdb273cb777f0ff30984051c3.jpg

5a330d4f8f499_IMG_20150504_1410551.thumb.jpg.2d4f81e677f4c742efe92905f58c7b11.jpg

The above picture is the furthest I've gotten with this print and you can see that it starts to clog near the top where the print head is sitting in a small surface area for a long time. I aborted this print when I saw this, used the atomic method to clean it, and saw some darkened spots on the pulled filament.

Here is a view of the bottom, you can see all of the charred bits in the first layer and brim.

5a330d4fd31b8_IMG_20150504_1411101.thumb.jpg.c5ebb1d1d01eecefffe0432ef6f78b3d.jpg

5a330d4f4473d_IMG_20150504_1410271.thumb.jpg.8d85fdfcdb273cb777f0ff30984051c3.jpg

5a330d4f8f499_IMG_20150504_1410551.thumb.jpg.2d4f81e677f4c742efe92905f58c7b11.jpg

5a330d4fd31b8_IMG_20150504_1411101.thumb.jpg.c5ebb1d1d01eecefffe0432ef6f78b3d.jpg

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Hi everyone. I have a similar issue with large prints I do at the moment. Every time the print head gets to the far left corner I get underextrusion. Walls do not touch and I get the "tweet" sound of the feederstepper when it snaps back due to high resistance. In the front area where the bowden tube isn't bent that much it is no problem at all.

I print at 220°C and 55mm/s. Layer hight 0.2mm.

Any suggestions how to fix this problem? When I am home I will post some pictures.

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It could be that your filament is square or oversized. Is this more of a problem at the end f the filament (it is more curved)?

Quick fix: Slightly lubricate teflon tube inside with thin oil. Blow away as muxh as you can.

At 3dSolex there is a slightly oversized transparent Bowden Tube which has removed similar problems before.

Also MAYBE your Bowden tube is too short, so the bend-stretch is very intense and hindres the moving of the filament.This would help explaining why it is worse in the corner.

The Tube should be around 70cm long

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There is a good chance that the filament you have is poor quality. I have bought a variety of filament, both ABS and PLA. It's a hit-and-miss affair.

Some PLA turned out to be OK for printing, i.e. 210C - 220C, 0.1mm layer height at 50mm/sec, but quite brittle. Also, at 0.2mm I had to drop the speed to around 25mm/sec.

Some simply was useless, and I use it for pinning, head-cleaning and little else.

My current favourite (despite it's awful smell) is some cheap ABS I bought of ebay, followed by the black PLA from 3dfilaprint.com which can be pushed quite hard. The ABS manages 60mm/sec at 0.25 at 260C with no hassle, and the black PLA can manage 40mm/sec at 0.25 at 220C. By far the best results I have had so far are with ABS.

So, I suggest you try a different supplier and see what they offer.

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