Poor upper layer quality

I was working on a school project and things seemed to be going fine. The surface quality was good no skipping, over or under extrusion. However as my printer reached the top of the model the extruder started to skip. This wasn't too bad as it was only about a half inch from the end of the print. However every print afterwards was complete trash. It's as if the skipping began at the end of the first print and never left. After the first print all of my prints have had a skip somewhere during the print causing poor output.



Here you can see the print does well only until about half way through the print then begins skipping.



This was the first print in question. This is the only skipping on this print.

I think I might possibly be over-extruding but im not sure. I do not have a caliper to accurately measure my filament or my output.

Here are my print settings.

Hatchbox black PLA

210c

.2mm layer height

no retraction or lift z

E3D V6 with bowden drive

kossel mini

I also have the filament diameter at 1.75 but I think this may be a bit to high causing to much filament to get backed up in the hot end. At the same time however the first layers always come out thin and not very well adhered to the bed.

How well is your hotend cooled?

I printed and fitted this onto my hot end. [www.thingiverse.com]

I'm not sure that design would be ideal for cooling the hotend since a lot of the flow branches off towards the nozzle. You could try using the original fan bracket and see if it helps any.

I changed out the fan duct so that it didn't point at the nozzle and I cleaned out the nozzle with some high heat. I think cooling the nozzle put a clog in it and caused the poor performance.

So did switching the fan duct solve your problem?

No not really. I think the real problem here is that my heater just can't keep up the temperature. While keeping airflow off of the nozzle surely helped it's not the whole story. I recently tried some trouble shooting and the only solution I've come up with is to use a higher temperature. Maybe my thermistor is a bit off. I have the printer set to 235 degrees, where it seems to work, but it doesn't stay there. After the first of the filament goes through the temperature drops down to about 223 degrees and stays there. I'm now crawling along at about 10 mm/s and it seems to do ok. I don't know what happened between printing smoothly and what i'm getting now.

Could be some problem with the filament feed.

I hope it is, i'm out of ideas by now. I tried putting the spool on a film canister and then onto a screw to keep it in place.

I made u an arrrrrrt.



The inside hole on the spool sits on the lip of the film canister. The whole canister then spins on the screw. Before I just had the spool sitting on top of the printer on a piece of plastic. I'm going to switch back and see how things go.

Did you tension the x belt recently? When the z gets higher the smoothrods could bend inwards and bind up. I don't know what printer you have but with my prusa i3 the x motor and x idler also shifted inwards making the binding permanent. I could go on tensioning but it kept shifting, the tension on the belt remained the same. Something similar can happen to yours.

Make sure your max PWM value for the hotend is 255, in the firmware settings.

Sorry I already solved this same problem in another thread.[forums.reprap.org]