Messy When Printing Multiple Objects

When I try to print multiple objects on the same bed, the print quality starts to drop. It looks like it either extrudes too much or too little when it transitions from object to object. Any tips on fixing this?

Is it oozing when travelling from one object to another? If so increase the extruder retract a little on the Dimension tab.

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[www.hydraraptor.blogspot.com]

I have seen a similar situation when moving between separate, parallel, bridged areas on their first layer. You often get a hanging loop of filament. I was thinking that retraction might need to be increased under these conditions also.

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I try to write with consideration for all nationalities. Please let me know if something is unclear.
Printing with Mendel90 from fedora 25 using Cura, FreeCAD, MeshLab, OpenSCAD, Skeinforge and Slic3r tools.

With the addition of self fusing silicone tape around the heater block you can print PLA at lower temperatures which greatly reduces the ooze.

Edited 1 time(s). Last edit at 10/16/2013 06:39PM by nophead.

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[www.hydraraptor.blogspot.com]

I have mine on order but could only find a USA supplier so I guess it'll be 10 days or so.

I'm printing ABS at 230C so I'm not sure if I can lower the temperature anymore. But I'll give retraction speed a shot. What value would you guys recommend for the 90 (I'm at 20 mm/s right now)? The wiki says it should be 3 times your feed rate, assuming the stepper can handle it. And the imperfections look like small waves going out and in on the surface. They stop once the printer gets high enough that its only printing one object.

With ABS you should not have any problems with ooze. Many of the parts of your kit were printed on a kit version Mendel90 with lots of parts on the bed at one time.

Don't change the retraction speed, just increase the distance a little if it is oozing. That leads to blobs on parts and bits missing.

Waves going in an out near the bottom sound like z wobble, nothing to do with multiple parts. A photo would help.

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[www.hydraraptor.blogspot.com]

It's really not that bad, it's just that I'm planning to sell what I printed so I'd like it to be as perfect as possible. I'll try changing the distance. Doesn't z wobble make waves going up? The waves are in the xy plane. I've tried taking several pictures, but I can't get the picture good enough to the point where it's visible (it's not that hard to see, I'm just bad with a camera). I guess I can't say for sure that it's because of multiple objects, but I've never seen it before I tried.

That sounds more like ringing on long moves. Check the belts are tight and try reducing the travel speed.

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[www.hydraraptor.blogspot.com]

So reducing travel speed down to 40mm/s seemed to help, but didn't remove the problem, and I'd really rather not go any lower due to time constraints. I did finally get a good enough picture though, in the upper left corned of print 1 is what I'm talking about. But there's also other imperfections...both attached prints were printed with the same settings and print 2 is about 2 times larger than print 1, so that's what I meant by the prints get a little messy when I try to print multiple objects.

And this is off topic, but Chris have you considered writing an ebook of some sort about a physics/mathematics approach to the theory and operation of reprap printers? You seem to be able to troubleshoot all of these issues without photos a lot of the time and you already do it in your blog posts I'd personally be interested in a copy.

BrianC,
Take a look here : [garyhodgson.com]

Alan

Edited 1 time(s). Last edit at 10/19/2013 11:25AM by Alzibiff.

Wow I didn't realize the blog was so extensive, I didn't see too many recent posts so I assumed that was always the pattern. Looks like I've got a lot of reading to do...about 3000 pages worth , thanks Alan

There seems to be something loose on your printer. The corners shouldn't look like that even with travels speeds of 200mm/s. Also the rings on your cylinder look like some sort of periodic flow problem or Z wobble.

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[www.hydraraptor.blogspot.com]

I checked all the fasteners and two of the hex pillars were loose. That made the print a little neater but I still saw the waves on all sharp corners. Which made me realize I had sharpest angle set to 60 instead of 90 up until now, Changing that has fixed it for the most part, it's still slightly visible. The rings on the cylinder are actually inner threads, the light makes it look like there's something wrong. On the outside, there actually is something wrong, I think it's the infill perimeter overlap ratio set too low, because looking at the gcode analyzer, it's leaving holes when the thread thickness becomes too thin. Increasing it improved it, so I guess I'll play around with those two values until I get it right. What I'm confused about though is why the corner thing didn't happen with PLA. I printed corners much sharper than 60, but never had to change the setting until I started printing in ABS.

EDIT: just looked up sharpest angle on the skeinforge wiki and it seems like increasing it to 90 should have made it even worse. So now I'm just confused on how it made it better.

Edited 1 time(s). Last edit at 10/19/2013 04:04PM by BrianC.