Support sticking together too well like some melting goo

Too hot? I print at 230c then to 215c doesn improve. Is is print head nozzle too large?

It sounds as though you may have a print that has only one or two narrow columns close together - whether as part of the print or as support material. In that case the print head remains close or in contact with the top of the same small area most of the time, so the layer doesn't get a chance to cool and the whole thing melts into a shapeless blob. You need to ensure that the print head moves away from a single area of your print long enough to allow each layer to solidify before it prints the following layer. To do that, you could either add a small column that is the same height as the print some distance away from your print when you slice it, or set the skirt height to be the same number of layers as your print (so a thin wall will end up being printed all around it). Either method will force the head to move away from a single place on the print between layers, giving it time to solidify.

I noted that Cura has a "minimum layer time" that I thought would achieve the same thing - but alas all that does is slow down the print moves for the layer - which makes matters worse!

Dave
(#106)

As someone emailed me and asked what we do, here's what I suggest:

Support material is tricky, and there doesn't seem to be much definitive information about it. We try and avoid using it. When we do, we tend to reduce the extrusion width of support, to the point that it barely sticks to itself! Usually, this means setting it smaller than the width of the nozzle, ie with a 0.5mm nozzle, printing at 0.2mm layer height, make the extrusion width 0.3mm. This usually makes it much lighter, but can make it a bit too fragile. Change this in Slic3r in 'Print Settings > Advanced > Extrusion width > Support material'. Experimentation is the key!

Ian
RepRapPro tech support