Globbing problem

I'm new to 3D printing and have scanned most of the forum threads. I have spent quite a bit of time getting my Z-axis set up and can usually get the first layer printed correctly (using PLA on an ABS printer with the bed heater off w/blue tape and hair spray).

The problem comes on the later layers. Sometimes on the 2nd or 3rd but more often (probably since it is more frustrating) after 1 or 2 hundred layers. The filiment forms a big blob (white PLA from Robo3D) and starts dragging the print around (breaking it lose from the bed) and, of course, totally hosing the print.

This happens in different areas of the bed so my assumption is that not caused by a non-level bed.

My guess it may have something to do with extruder temperature or feeding problem. I'm using the values reccomended in the setup guide.

Any suggestions about what to try next? I'm tired of throwing away printer after they get screwed up following an hour or two of printing!

Thanks!

 

I had the same with the higher layers making a blob. What worked for me was reducing the extrusion temperature (by 5-10 degrees) and using the fan. This reduced the 'liquidity' of the already printed layers enough so that they would stay in place.

 

Thanks JohnUSA. What you said makes sense because a Z-axis problem is unlikely to start causing problems with layer 238 of a 380 layer print. Ditto with a layer height problem (especially when I'm using the 0.3mm recommended setting).

I did try lowering the 2nd+ layers temp a few degrees. I'll try lowering it some more and try turning on the fan.