Strange issue with fine resolution prints

[roykirk]

I have a Flash Forge printer utilizing Makerware. I use both PLA and ABS in the 1.75 mm size. It's been a great experience so far, but I've noted one minor issue that crops up at times. Since I use my prints for metal casting, I often want them printed in the highest detail possible, which would be .10 mm on my printer. Occasionally, however, the printer simply can't or won't print a model at .10 mm. It'll get about 5 minutes in to the print and then start spraying a random ball of filament all over the place. At first I thought it was a platform leveling issue, but multiple attempts at leveling and calibrating the nozzle did nothing. By chance, I discovered that if I set my print resolution to .20 mm or higher on these "problem" prints, the model prints perfectly. I seem to have solved the problem, but I'm wondering if anyone knows what is causing this and how to avoid it? As I said, it's only certain models that cause this, and I'm at a loss to figure out what common factor they all may have. It also happens with both ABS and PLA.

[CaptainObvious]

When you preview (if you do) the G-Code, do you see any problem? That way you'll know if it's a slicing issue or something with the printer firmware.

[roykirk]

When you preview (if you do) the G-Code, do you see any problem? That way you'll know if it's a slicing issue or something with the printer firmware.

I don't see anything obvious in the G-Code, but I'm not certain I'd know what a "problem" was even if I did see it. I forgot there is one commonality when this happens. Thus far it's only happened on models where I'm using a raft. Other than that, I can't pinpoint similar designs or features of models where this problem is happening. When it does happen I've just gotten in the habit of switching over to .20 mm resolution. It sure would be nice, however, to fix the problem or at the very least to know the model types that are going to cause issues so I can set the resolution lower from the beginning.

[CaptainObvious]

I don't see anything obvious in the G-Code, but I'm not certain I'd know what a "problem" was even if I did see it. I forgot there is one commonality when this happens. Thus far it's only happened on models where I'm using a raft. Other than that, I can't pinpoint similar designs or features of models where this problem is happening. When it does happen I've just gotten in the habit of switching over to .20 mm resolution. It sure would be nice, however, to fix the problem or at the very least to know the model types that are going to cause issues so I can set the resolution lower from the beginning.

By previewing the G-Code I meant using a probram like Repetier Host to actually see how the filament is laid down according to the G-Code, I haven't used Makerware so I don't know if it has that functionality.
From what you describe it seems to be a problem with the slicing software, some bug that appears when you use a raft, if you preview the code it should be fairly obvious if that is the case.

[3dkarma]

Are you printing things with any form of overhang? It may be that there's not enough surface area for the layers to fuse together. Maybe try playing with the extrusion width / layer height ratio.

Good thread here on reprap.org.

[roykirk]

Are you printing things with any form of overhang? It may be that there's not enough surface area for the layers to fuse together. Maybe try playing with the extrusion width / layer height ratio.

Good thread here on reprap.org.

No, it doesn't appear to have anything to do with overhangs. As noted in my original post, changing the layer height does fix the issue. I'm just hoping to find the source of the problem so I don't have to do that.

[Geoff]

Having the same printer and using Makerware and RepG, I can tell you it's Makerware.

I cannot print at 0.1 on Makerware. It just does not extrude correctly when I set it and it ends up not laying down properly, it appears to be an issue with the starting Z height which I can't see how to adjust that in Makerware.

In Replicator G, I have no issues using 0.1mm but yeah, the slicing is painfully slow. Also try 0.15 that seems to be pretty good on my Flashforge.

I printed this at 0.15 on my Flashforge, it has no sanding at all. It has 2 layers of very very thin paint, 1 undercoat of matte black and drybrushed green over the top, so really, at 0.15 the lines are pretty invisible still so for metal casting it would be ok. But Replicator G is the go mate for high detail prints.

Also, print slow! dont print fast at 0.1, our machine just doesn't like it. If you are printing 0.1 or 0.15, lower the print speed to 30ms feed and 70ms travel.

This is only 10cm high.

[roykirk]

Thanks for the awesome advice, Geoff! I also have Rep G, but I'd recently moved to using Makerware because it's just so much more pleasant an interface. I guess I may need to go back to Rep G for fine detail prints. I've never used 30/70 rates before, but it sounds painfully slow. Based on advice I'd read somewhere else, I typically use 65/95 for the rates. I'll try your recommended rates for .1 or .15 to see how it works.