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cecilievf

Top edges curling up

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Hi everybody!

I've had some trouble with my UM2 and I finally got it up and running today so I was very excited to finally be able to print with ABS (my Ultimaker Orignal only prints PLA properly). But I've run into an issue now.

During the print some of the edges would start curling upwards and the printer has to print on top of this curve on every layer and the material builds up. It looks super crappy and eventually I'm pretty sure the print will fail. (I had a power outage so I didn't get to finish it)

Pictures of the issue is here.

http://imgur.com/a/CdVZ4

Settings:

Ultimaker Red ABS

Temp: 245 deg

Bed temp: 90 deg

Print speed: 50 mm/s

Layer height 0.15 mm

Fans OFF

Fill density 20%

Hope somebody's got a clue what's going on..

Thanks!

Cecilie

 

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try printing multiple objects at once to give the layers time to cool. Try using a little thicker shell. Try using fan 10~50%. Are you using an enclosed chamber? Try using thinner layers.

After a while, you'll be able to predict how parts will print, and you'll be able to adjust settings to get it to print right the first time. Hang in there

 

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This is a common problem with PLA. I've only printed 10 or so ABS prints and none with overhang. There is extensive discussion and some solutions here:

http://umforum.ultimaker.com/index.php?/topic/4094-raised-edges/

The first page or 2 of posts don't get to the root cause but eventually they do. The quick answer is use more fan. I know on ABS it's usually best to have zero fan or very little fan, but for overhangs you do need some fan. I haven't tried it myself but 30% fan is probably about right. There are some older slicers that are more ABS oriented (not Cura) that will turn the fan on for only those traces that are the outer edge of an overhang! Pretty cool. I've watched printers print with these slicers. The fan comes on an off maybe 10 times on just one given layer.

Because you have a heated enclosure you should be okay with more fan than most people who print ABS. The downside of fan with ABS is you can wreck layer adhesion. If this happens it will be obvious as the part will easily break apart on layer boundaries which tells you that you need to do less fan or more nozzle temp or hotter enclosure. It happens when the current layer isn't remelting the layer below for a good bond.

Multiple objects at once won't help. It's about the INSTANT cooling as the outer edge overhang is being laid down.

 

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Another solution is to print amazingly slow (5mm/sec) for a layer which remelts the layers below into the proper position. You can do this every N layers or every layer or whatever. I don't like this solution myself and haven't tried it.

 

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multiple objects will help. Especially if the part is small. Trust me, I have 1000's of ABS prints under my belt, and multiple objects help. I think it has to do with the radiant heat being expelled by the nozzle. at 250 ~ 260 , it helps getting that heat away from thin lip overhangs for a second so the fan can do there work, ALSO, if you set your second object up so that one of the fans on the print head are moving directly over the problem area, you get much better and quicker cooling in that problem are. Often times, I custom make a ring, about 25mm in diameter and put it to the left of the part. This places the right fan over the part you want whiles it's printing the ring. In an enclosed chamber, this can really help becasue you need to get the radiant heat away from your print and a nice fresh source of open air flow over it.

I've also found that it's not always necessary to enclose the chamber for smaller prints. Smaller prints, as long as they are adhered to the bed sufficiently, don't warp nearly as bad as large prints.

 

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I tried another print with the fan on 45% about halfway through the print and the top half looks great but I'm not too pleased with the bottom that had about 15-20%. It's still better than my first print without the fans but not perfect. I suppose I'll play around with the fan settings a bit more and find the right combination.

I'm just worried that too much fan in the beginning of the print might ruin the adhesion?

 

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That's definitely a possibility. I've had prints where I had fans come on 100% becasue I had a tweak at Z from another project I forgot to delete in Cura. Anyways, layer 3 rolls around, Fans come screaming on at 100% and the part buckles like crazy and pops free.

If you use a good brim with a 30 line count, and a nice ABS slurry bonding agent, you can play around with dropping the bed temp in cura so you don't have so much radiant heat in the print. Drop it after layer 5-10, depending on your layer thickness. How much you can drop will depend on your ABS slurry skills :p I tend to drop my ABS temps gradually, so I would have 3 tweak at Z settings, dropping a couple of degrees each time.

Have you played around with minimum extrusion temps? You might be printing hotter than you need to? Keep playing around with settings, and take notes when you get it dialed in.

 

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That sounds like something I should try. The problem is that the company I work for (and where the printer are) are seriously strict about chemicals in the production area and I will not be able to use acetone in this setting before it has been approved. This always takes a really long time. Would it be possible for me to acheive proper adhesion for dropping the bed temp if I use glue or hairspray or something similar?

 

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not sure....

I have used all manner of bonding agents, but the slurry has worked best for me. Maybe search around for what people in Denmark are using for a bonding agent. You guys might have a killer glue over there that works just right....who knows.

The acetone smell isn't bad, my daughters work on their nails, and that smells 10x worse. I don't use that much acetone when I prep my bed. I pour a teaspoon of acetone on the bed and I rub a hockey puck-like block on the glass that is printed in abs. The acetone dissolves just enough of the puck to create a film on the glass. Not much acetone is used, and it evaporates quickly. If you're going to be printing in ABS a lot, it's worth trying, at least once.

 

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For hairspray it's best to remove the glass anyway to keep the rest of the printer clean. Therefore, why not remove the glass from the UM2, take it into another room somewhere and apply the acetone/abs slurry and wait for it to dry, then bring the glass back to the printer.

Always remove clips using a tool such as a screwdriver as they are very sharp and will cut you if you aren't careful.

 

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Thanks guys! The company I work for is pretty large and getting chemicals approved for use (even just for a one time test) is a major pain as it has to go through a couple of different departments. There is a paint room (for mixing paint for the decoration machines) not too far from the printers, I might try and ask them if acetone is allowed in there.

I will probably be printing quite a bit in ABS so I'll have to find something that works.

 

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