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melvincator

UM3 Support Structure Printing

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Hi,

Just acquired UM3 Extended and trying some test prints. I am using Cura 2.3.0.

Problem I have is when printing support structures in PVA (Primary structure in PLA). The raft gets printed OK. When the main body of the part is printed, no support structure is laid down - the PVA extrudes from the nozzle and just hangs there in a curly mess. I have noticed that, even though I have disabled the prime tower option, the print head dives over to where the prime tower would be on the plate (approximately) and again tries to lay down some material but just creates the same curly mess. I have now seen on Cura that when layer mode is switched on and I travel through the layers, there are some "random" tracks which show this strange printhead travel

Any ideas?

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Try exiting and restarting cura. It has weird bugs. Also use cura 2.3.1 but that's not much improved.

Look at it in layer view before printing. Cura 2.3.1 is frustrating - I typically need a damn hour to slice something that will have support. Crazy. :( Hopefully it will get better some day.

However I'm wondering if part of your problem might also be that you never did the "z offset" thing in the menu items? or if you did there was some solid pva on the end of the right nozzle such that you leveled it too high. If the nozzle is just .2mm too high the pva won't stick to the glass.

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If the problem is visible in layer view, please show it there.  Note that it shows PVA brighter in layer view if that is selected and PLA brighter in layer view if *that* nozzle is seleccted.

OK - I have redone the Z calibration and I no longer get the curly mess. The support structure now gets laid down OK but doesn't stick to the raft (both raft and support structure are PVA) I haven't adjusted any temperatures from the defaults anywhere. Could this be the problem?

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Strange! I never touched the default PVA printing temp of 215C on my UM3. I haven't had this problem. Try it without raft. I don't use raft. Has your PVA absorbed so much water that you can hear the water sizzling and boiling as it prints PVA? If so then that's probably the problem. But the raft looks pretty good so maybe it's just printing the PVA too fast? Did you mess with the printing speeds for PVA? Note that I believe the printing speeds for each material are different - you have to select in cura which nozzle (left/right) before checking/changing settings in cura. I know - it's confusing.

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I have abandoned the idea of a raft and gone with a brim. Seems to be a lot better but still not acceptable. I haven't changed any temp or speed settings from default but what I have done in CURA , on the advice of Ultimaker UK, is to change infill pattern to tetrahedral, support pattern and interface pattern to Triangles, the support interface thickness to 1.5 and the brim width to 7. New testing is underway. (soon going to need some more material)

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Don't set the support interface pattern to triangles, that's a really bad idea if your interface is 100% full.

The problem of support on the raft is that the raft introduces a z gap, which also applied to the support in cura 2.3.

This is solved in cura 2.4. The support is also printed on layers in between the raft and the model.

If you print the raft with PVA you should set the z gap to zero and the initial layer overlap to zero.

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